JP2015058677A - Ink jet recorder and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder and an image processing method capable of reducing color shift generated by deviation of attachment of a recording head from a nozzle arrangement direction.SOLUTION: A control part 30 makes each of plural recording head units 10, 12, 14, 16 form a line image respectively, based on line chart image data for forming the line-state line image extending in a direction vertical to a nozzle row direction on predetermined pixel positions, where are determined for each of the plural recording heads in advance. The control part 30 specifies an error of image formation positions among the recording head units 10, 12, 14, 16 specified from the line images formed by the plural recording units 10, 12, 14, 16 respectively for each of the recording heads. Then the control part 30 decides a correction position of a discharge image data for each of the recording head, based on the specified error for each of the recording heads, and inserts or deletes a pixel to the decided correction positions, for correcting discharge image data.

Description

  The present invention relates to an ink jet recording apparatus and an image processing method.

  Conventionally, in image formation in an ink jet recording apparatus, there has been a strong demand for higher definition of images and higher recording speed. In order to solve this problem, there is known an ink jet recording apparatus including a recording head unit in which a plurality of recording heads each having a nozzle row in which a plurality of nozzles are arranged in rows at predetermined intervals are arranged in a staggered manner. Therefore, it is possible to perform image formation by a so-called one-pass method (line head method) in which image formation is performed only by conveying a recording medium.

  In addition, such an ink jet recording apparatus is known in which a recording head unit as described above is provided for each color of YMCK. The ink jet recording apparatus configured as described above converts the input image data into discharge image data for each color of YMCK, and assigns these discharge image data to the recording head units of each color. Each color recording head unit forms an image on a recording medium by ejecting ink droplets from each nozzle based on the assigned ejection image data, thereby enabling color image formation.

  By the way, the conventional ink jet recording apparatus has a problem that the recording head is displaced due to the mechanical structure.

  If an image is formed in such a state, the ink droplet does not land at the assumed position on the recording medium, and the displacement of the ink droplet landing position occurs between the recording head units, causing image degradation such as color misregistration. End up.

In view of such a situation, in a conventional ink jet recording apparatus, a position correction mark is printed on a sheet and detected by a mark sensor, and the positional deviation of the head unit is determined from the detection result, so that the head unit is parallel to the transport surface. There is one in which the displacement is corrected by moving in any direction (for example, Patent Document 1).
In addition, there is a type in which the inclination information of the line head is stored in advance, and the ink ejection timing is controlled based on the information (for example, Patent Document 2).

JP 2010-162724 A JP 2006-15590 A

  By the way, the above-described ink jet recording apparatus using the line head method has an advantage that it can be replaced in units of recording heads and is excellent in maintenance cost. However, in the line head system in which a plurality of heads are arranged, the number of pixels that do not require correction between the two heads when the recording heads are replaced due to the configuration in which the recording heads are arranged in a line. However, there is a problem that a large deviation occurs as an accumulated error when viewed with a plurality of heads. For example, as shown in FIG. 20A, recording heads 1101C, 1102C, 1103C, 1104C... That discharge cyan ink and recording heads 1101M, 1102M, 1103M, 1104M. In the ink jet recording apparatus, when the recording heads 1102M, 1103M, 1104M... Are displaced from the recording heads 1102C, 1103C, 1104C..., One end side is an image as shown in FIG. Even if they match, color misregistration occurs in the image formed on the recording medium on the other end side.

  However, none of the inventions described in the above-mentioned patent documents can cope with the positional deviation caused by the replacement of the recording head.

  An object of the present invention is to provide an ink jet recording apparatus and an image processing method that can reduce color misregistration caused by being displaced in the nozzle arrangement direction when the recording head is replaced.

In order to solve the above problems, the invention according to claim 1 is characterized in that a plurality of recording heads having nozzle rows in which a plurality of nozzles are arranged at predetermined intervals are arranged in a staggered manner along the nozzle row direction, A plurality of recording head units in which a plurality of nozzles arranged at respective end portions of the adjacent recording heads overlap each other in a direction perpendicular to the nozzle row direction are arranged in a direction perpendicular to the nozzle row direction. The input image data is converted into ejection image data for each recording head unit, and ink is ejected from each nozzle of the plurality of recording heads according to the ejection image data while the recording medium is conveyed to the recording medium. In an inkjet recording apparatus for forming an image,
Each of the plurality of recording head units forms the measurement image based on measurement image data for forming a predetermined measurement image at a predetermined pixel position for each recording head, and the plurality of recordings An error of the image forming position between the recording head units specified from the measurement image formed by each of the head units is specified for each recording head, and the ejection image data is determined from the error for each specified recording head. And a control unit that determines a correction position corresponding to each recording head, and corrects the ejection image data by inserting or deleting a pixel at the determined correction position.

According to a second aspect of the present invention, in the ink jet recording apparatus according to the first aspect,
The control unit is characterized in that a pixel is inserted or deleted with a position corresponding to the connecting portion of the ejection image data as the correction position.

The invention according to claim 3 is the ink jet recording apparatus according to claim 1 or 2,
The control unit determines the correction position so that the position differs for each recording head unit.

The invention according to claim 4 is the ink jet recording apparatus according to any one of claims 1 to 3,
The control unit determines the correction position so that the ejection image data does not continue in a direction perpendicular to the nozzle row direction.

The invention according to claim 5 is the ink jet recording apparatus according to claim 4,
The control unit includes a plurality of pixels in the nozzle row direction and a direction perpendicular to the nozzle row direction, each of which is formed in a matrix and uses the mask data in which the correction position is defined. The correction position is determined by performing mask processing on the image data.

A sixth aspect of the present invention is the ink jet recording apparatus according to the fifth aspect,
The mask data is defined such that only one correction position is defined in the nozzle row direction, and the correction positions have a substantially uniform interval without a period in the entire mask data. It is pattern data.

The invention according to claim 7 is the inkjet recording apparatus according to any one of claims 1 to 6,
An image reading unit for reading the measurement image;
The control unit specifies an error in an image forming position between the recording head units from the position of the measurement image read by the image reading unit.

According to an eighth aspect of the present invention, a plurality of recording heads each having a nozzle row in which a plurality of nozzles are arranged at predetermined intervals are arranged in a staggered manner along the nozzle row direction, and adjacent recording heads are arranged. A plurality of recording head units each having a connecting portion in which a plurality of nozzles formed at each end overlap each other in a direction perpendicular to the nozzle row direction are arranged in a direction perpendicular to the nozzle row direction, and input image data An ink jet recording apparatus for converting an image into ejection image data for each recording head unit and ejecting ink from each nozzle of the plurality of recording heads according to the ejection image data while conveying the recording medium An image processing method using
Each of the plurality of recording head units is based on measurement image data for forming a line-shaped measurement image extending in a direction perpendicular to the nozzle row direction at a predetermined pixel position for each recording head. A measurement image forming step for forming the measurement image on
An error measurement step of measuring, for each recording head, an error in the image forming position between the recording head units from the formed measurement image;
A correction position determining step for determining the correction position of the ejection image data corresponding to each recording head from the measured error for each recording head;
A correction step of correcting the ejection image data by inserting or deleting a pixel at the determined correction position;
It is characterized by including.

  According to the present invention, it is possible to reduce color misregistration caused by being displaced in the nozzle arrangement direction when the recording head is replaced.

1 is a perspective view illustrating a schematic configuration of an ink jet recording apparatus. FIG. 3 is a plan view for schematically explaining an arrangement state of recording heads. It is an enlarged view for demonstrating a connection part roughly. It is a block diagram which shows the functional structure of an inkjet recording device. It is a schematic block diagram explaining image formation. It is a flowchart explaining a correction determination table creation process. It is a figure explaining line chart image data. It is a figure explaining an example of an error determination table. It is a figure explaining an example of a correction determination table. It is a figure explaining the other example of a correction | amendment determination table. It is a flowchart explaining a distortion correction process. It is a flowchart explaining a correction process. It is a figure explaining a mask pattern. It is a figure explaining the arrangement position of a mask pattern. It is a figure explaining insertion of a pixel. It is a figure explaining deletion of a pixel. It is a figure explaining the example of application of this invention. It is a figure explaining the example of application of this invention. It is a perspective view which shows the other example of the inkjet recording device which concerns on this Embodiment. FIG. 6 is a diagram illustrating a problem caused by a recording head position shift.

  Hereinafter, an ink jet recording apparatus according to an embodiment of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In addition, in the following description, what has the same function and structure attaches | subjects the same code | symbol, and abbreviate | omits the description. Further, in the following description, “image data” refers to, for example, data of an entire image formed on one recording medium, and “pixel” refers to one dot constituting “image data”. Data.

As shown in FIG. 1, the ink jet recording apparatus 2 has a platen 6 that supports a recording medium 4. A transport roller 8 for transporting the recording medium 4 is provided before and after the platen 6. When the transport roller 8 is driven, the recording medium 4 is transported from the rear to the front while being supported by the platen 6.
In the following description, the conveyance direction of the recording medium 4 is referred to as “Y direction”, and the direction orthogonal to the conveyance direction is referred to as “X direction”. The Y direction and the X direction are directions on the horizontal plane.

  Above the platen 6, recording head units 10, 12, 14, and 16 are provided from the upstream side to the downstream side in the Y direction. Each recording head unit 10, 12, 14, 16 extends in the X direction. For example, the recording head unit 10 ejects cyan (C) ink toward the recording medium 4. Further, the recording head unit 12 ejects magenta (M) ink toward the recording medium 4. The recording head unit 14 ejects yellow (Y) ink toward the recording medium 4. The recording head unit 16 ejects black (K) ink toward the recording medium 4. The arrangement order of the recording head units 10, 12, 14, and 16 can be arbitrarily set.

  Further, a line sensor 18 as an image reading unit is provided on the downstream side of the recording head unit 16 above the platen 6. The line sensor 18 extends in the X direction, and can read an image formed on the recording medium 4 and specify a position where the image is formed.

When the recording head unit 10 is viewed in plan from below, as shown in FIG. 2, six recording heads 101 to 106 are arranged in a staggered pattern on the substrate 100 along the X direction. The number of recording heads is not limited to this, and can be set as appropriate. In each of the recording heads 101 to 106, a large number of nozzles N are formed in rows at predetermined intervals. That is, each of the recording heads 101 to 106 has a nozzle row. The number of nozzles N can be set arbitrarily. Further, the number of nozzle rows is not limited to one, and may be two or more rows. Each of the recording heads 101 to 106 includes, for example, an ejection unit such as a piezo element (piezoelectric element) inside, and the ejection of each ink droplet from each nozzle N can be controlled independently by the operation of the ejection unit. it can.
The ink used in the present embodiment is four colors of cyan (C), magenta (M), yellow (Y), and black (K), but is not limited to this. For example, light cyan (LC), light cyan Other colors such as magenta (LM) and light yellow (LY) can also be used. In this case, a recording head unit corresponding to each color is further provided.
Since the recording head units 12, 14, and 16 have the same configuration as the recording head unit 10, only the recording head unit 10 will be described in the following description, and the recording head units 12, 14, and 16 will be described. The same reference numerals are used and the description thereof is omitted.

The recording head unit 10 includes a first connecting portion 111 to a fifth connecting portion 115 in which a plurality of nozzles N formed at respective end portions of the adjacent recording heads 101 to 106 overlap each other in the Y direction. Yes. FIG. 3 is an enlarged view of the second connecting portion 112 where the recording heads 102 and 103 overlap each other in the Y direction. As shown in FIG. 3, each of the recording heads 102 and 103 has n nozzles N. The joining portion 112 includes 32 ((n−31) th to nth) nozzles N at the right end of the nozzle row of the recording head 102 and 32 at the left end of the nozzle row of the recording head 103. The nozzles N (1st to 32nd) overlap each other in the Y direction. However, in practice, since the mounting error of the recording heads 102 and 103 occurs, the number of overlapping nozzles N is not necessarily 32. For this reason, at the time of product shipment, the overlapping position of the nozzles N is confirmed and registered in advance, thereby preventing the ink droplet ejection position from deviating during image formation.
In the present embodiment, for ease of explanation, an example in which 32 nozzles N are overlapped is shown and described. However, the number of overlapping nozzles is not limited to the above, and is arbitrarily set. Can do.

  The nozzles N that eject ink droplets at the connecting portions 111 to 115 are either one of the two. Which nozzle N ejects ink droplets can be appropriately set according to the characteristics of the nozzle and ink.

Next, the functional configuration of the inkjet recording apparatus 2 will be described with reference to FIG.
The ink jet recording apparatus 2 includes a transport unit 20 and a control unit 30 in addition to the recording head units 10, 12, 14, 16 and the line sensor 18 described above.

  The transport unit 20 includes a transport roller 8 and a transport motor 20 a that rotates the transport roller 8. The transport motor 20a is driven and controlled by the control unit 30, and is configured to transport the recording medium 4 in the Y direction (see FIG. 1) by rotating the transport roller 8 in a predetermined direction.

  The control unit 30 controls each unit of the inkjet recording apparatus 2, and includes a CPU (Central Processing Unit) 31, a RAM (Random Access Memory) 32, a ROM (Read Only Memory) 33, and the like.

  The CPU 31 reads out various application programs related to various functions as the ink jet recording apparatus 2 stored in the ROM 33, develops them in a work area in the RAM 32, and comprehensively controls the ink jet recording apparatus 2 according to the program.

  The RAM 32 includes, for example, a program storage area for expanding a processing program executed by the CPU 31, a data storage area for storing input data, a processing result generated when the processing program is executed, and the like.

  The ROM 33 stores a system program that can be executed by the inkjet recording apparatus 2, various processing programs that can be executed by the system program, various data that are used when the various processing programs are executed, and the like.

Next, a processing procedure for executing image formation performed in the ink jet recording apparatus 2 configured as described above will be described with reference to FIG. The image formation in the present embodiment is realized by functions of each unit as shown in FIG.
In the present embodiment, the control unit 30 is configured to realize the functions of the following units by software processing. However, the control unit 30 may be implemented by including a circuit for causing these units to function, a dedicated processor, and the like. Good.

  As shown in FIG. 5, the control unit 30 includes an ink amount limiting unit 301, an edge detection unit 302, a distortion correction unit 303, a shading correction unit 304, a primary gamma correction unit 305, a halftone processing unit 306, and a joint correction unit 307. , A nozzle missing correction unit 308, a conveyance direction correction unit 309, and an image formation processing unit 310. The control unit 30 converts the input image data into ejection image data that is image data for each of the recording head units 10, 12, 14, and 16, and then the ink amount limiting unit 301 and the edge detection unit for each ejection image data. 302, distortion correction unit 303, shading correction unit 304, primary gamma correction unit 305, halftone processing unit 306, splice correction unit 307, nozzle missing correction unit 308, and conveyance direction correction unit 309 are used for correction. Thereafter, an image forming process by the image forming processing unit 310 is executed.

  The ink amount restriction unit 301 restricts the amount of ink of each color of YMCK. Specifically, for example, the ink amount restriction unit 301 sets the amount of ink of each color to a maximum of 400%, while maintaining the color reproduction accuracy to increase the amount of ink of each color to, for example, a maximum of 320%. Make corrections such as limiting. The degree of restriction of the amount of ink of each color can be arbitrarily set.

  The edge detection unit 302 generates Tag information for storing an edge part when performing halftone processing.

  The distortion correction unit 303 corrects image distortion caused by the positional deviation of the recording heads 101 to 106. Details will be described later.

  The shading correction unit 304 corrects non-uniformity in density caused by a difference in ink discharge amount for each recording head, a bent flight of ink, a variation in ink discharge amount for each nozzle, and the like.

  The primary gamma correction unit 305 performs gamma correction for suppressing dot gain that occurs when halftone processing is performed.

  The halftone processing unit 306 performs halftone processing using an AM screen or FM screen.

  The splice correction unit 307 sets the correspondence relationship of the nozzles N between the recording heads 101 to 106 in the splice portions 111 to 115.

  The nozzle missing correction unit 308 detects the ejection failure of the nozzle N, and performs image data interpolation based on this.

  The transport direction correction unit 309 corrects landing deviation due to variations in ink ejection speed for each nozzle N.

  The image forming processing unit 310 controls the recording head units 10, 12, 14, and 16 to form an image on the recording medium 4 based on the image data that has been subjected to various corrections as described above.

  Next, a correction determination table creation process executed by the control unit 30 of the inkjet recording apparatus 2 configured as described above will be described with reference to FIG.

  First, the control unit 30 generates line chart image data as measurement image data (step S101).

  Specifically, the control unit 30 generates line chart image data CH as shown in FIG. In the line chart image data CH, line-shaped images (line images) extending in the Y direction, which is a direction perpendicular to the X direction that is the nozzle row direction, form the recording head units 10, 12, 14, and 16 of the respective colors. The image data is formed at a predetermined pixel position for each of the recording heads 101 to 106. That is, the line chart image data CH forms a cyan line chart CC by the recording head unit 10, forms a magenta line chart CM by the recording head unit 12, and forms a yellow line chart CY by the recording head unit 14. The data for forming a black line chart CK by the recording head unit 16. The line chart CC is composed of cyan line images C1 to C6. The line chart CM is composed of magenta line images M1 to M6. The line chart CY is composed of yellow line images Y1 to Y6. The line chart CK is composed of black line images K1 to K6.

  The line images C1, M1, Y1, and K1 are respectively the recording head 101 of the cyan recording head unit 10, the recording head 101 of the magenta recording head unit 12, the recording head 101 of the yellow recording head unit 14, and the black recording head unit. The nozzles N that eject ink are assigned to be images formed by 16 recording heads 101 and formed at the same position on the X axis.

  The line images C2, M2, Y2, and K2 are respectively the recording head 102 of the cyan recording head unit 10, the recording head 102 of the magenta recording head unit 12, the recording head 102 of the yellow recording head unit 14, and the black recording head unit. The nozzles N that eject ink are assigned to be images formed by 16 recording heads 102 and formed at the same position on the X axis.

  The line images C3, M3, Y3, and K3 are respectively the recording head 103 of the cyan recording head unit 10, the recording head 103 of the magenta recording head unit 12, the recording head 103 of the yellow recording head unit 14, and the black recording head unit. Nozzles N that eject ink are assigned to be images formed by 16 recording heads 103 and formed at the same position on the X axis.

  The line images C4, M4, Y4, and K4 are respectively the recording head 104 of the cyan recording head unit 10, the recording head 104 of the magenta recording head unit 12, the recording head 104 of the yellow recording head unit 14, and the black recording head unit. Nozzles N that eject ink are assigned so as to be formed at the same position on the X axis.

  The line images C5, M5, Y5, and K5 are respectively the recording head 105 of the cyan recording head unit 10, the recording head 105 of the magenta recording head unit 12, the recording head 105 of the yellow recording head unit 14, and the black recording head unit. Nozzles N that eject ink are assigned to be images formed by 16 recording heads 105 and formed at the same position on the X axis.

  The line images C6, M6, Y6, and K6 are respectively the recording head 106 of the cyan recording head unit 10, the recording head 106 of the magenta recording head unit 12, the recording head 106 of the yellow recording head unit 14, and the black recording head unit. The nozzles N that eject ink are assigned to be images formed by 16 recording heads 106 and formed at the same position on the X axis.

  The line images C1, M1, Y1, K1 to C6, M6, Y6, and K6 are respectively generated by nozzles N other than the nozzles N related to the connecting portions 111 to 115, that is, the nozzles N that are not included in the connecting portions 111 to 115. It is comprised so that it may be formed. In addition, you may make it form a line image with the nozzle N which concerns on the connection parts 111-115.

  After generating the line chart image data CH as described above, the control unit 30 controls the recording head units 10, 12, 14, 16 and outputs the line chart to the recording medium 4 (step S102).

  Subsequently, the control unit 30 reads a line chart formed on the recording medium 4 by the line sensor 18 (step S103).

  The control unit 30 determines the position error of the line chart between colors from the read line chart (step S104). Then, based on the determination result, for example, an error determination table as shown in FIG. 8 is generated.

  The error determination table shown in FIG. 8 indicates how much position error exists in the image forming area corresponding to the connecting portions 111 to 115 in the unit of pixel in the relationship between each color of CMY and K color. Specifically, the error of the image forming position between the recording head units 10, 12, 14, and 16 specified from the above-described line chart is specified for each recording head 101 to 106, and for each specified recording head 101 to 106. The error in the connecting portions 111 to 115 can be specified from the error. For example, according to the error determination table shown in FIG. 8, there is a positional error of 0.5 pixels on the left side of the cyan image with respect to the black image in the image forming area corresponding to the first connecting portion 111. Further, in the image forming area corresponding to the second joint portion 112, there is a positional error of one pixel on the left side of the cyan image with respect to the black image. That is, since the cyan recording head 103 has a positional error of 0.5 pixels to the left of the cyan recording head 102, the cyan recording head 103 is accumulated with respect to the black recording head 103. This is because an error of one pixel occurs. Further, in the image forming area corresponding to the third joint portion 113, there is a position error of 1.5 pixels on the left of the cyan pixel with respect to the black pixel. That is, since the cyan recording head 104 has a positional error of 0.5 pixels to the left of the cyan recording head 103, the cyan recording head 104 is accumulated with respect to the black recording head 104. This is because an error of 1.5 pixels occurs. Similarly, in the image forming area corresponding to the fourth connecting portion 114, there is a positional error of two pixels on the left of the cyan pixel with respect to the black pixel, and in the image forming region corresponding to the fifth connecting portion 115. , There is a position error of 2.5 pixels on the left side of the black pixel of cyan. Further, in the image forming area corresponding to the third connecting portion 113, the yellow image has a positional error of 0.5 pixels to the right of the black image. Further, in the image forming area corresponding to the fourth connecting portion 114, the yellow image has a position error of one pixel on the right side with respect to the black image. That is, since the yellow recording head 105 has a positional error of 0.5 pixels to the right of the yellow recording head 104, the yellow recording head 105 accumulates with respect to the black recording head 105. This is because an error of one pixel occurs. Similarly, in the image forming area corresponding to the fifth joint 115, the yellow image has a position error of 1.5 pixels to the right of the black image. In the above-described embodiment, for convenience of explanation, an example in which a position error of 0.5 pixels occurs in one joint is shown as an example of the position error. However, the position error is not limited to 0.5 pixels, and one joint is shown. Needless to say, it is possible to apply in the range of 0 <X <1, where X is the position error.

  Next, the control unit 30 creates a correction determination table based on the error determination table generated as described above (step S105), and ends this process. Specifically, for example, the control unit 30 creates a correction determination table as shown in FIG. 9 based on the error determination table shown in FIG. The correction determination table shown in FIG. 9 is created as follows. That is, first, a pixel for one pixel is inserted into an area corresponding to the second connecting portion 112 and an area corresponding to the fourth connecting portion 114 of cyan image data (discharged image data). In addition, a pixel corresponding to one pixel is deleted from an area corresponding to the fourth connecting portion 114 of the yellow ejection image data. The correction determination table shown in FIG. 9 is a table for instructing the above-described distortion correction unit 303 to insert and delete pixels as described above. In the present embodiment, when correction of ejection image data of each color is performed using the correction determination table created in this way, and image formation is performed based on this correction, an image having no positional error (color misregistration) is obtained for each color. Can be formed.

Further, the control unit 30 can create and use a correction determination table as shown in FIG. 10 instead of the correction determination table shown in FIG. In the correction determination table shown in FIG. 10, instead of deleting pixels for one pixel in an area corresponding to the fourth connecting portion 114 of yellow discharge image data, cyan discharge image data and magenta discharge are used. One pixel is inserted into a region corresponding to the fourth connecting portion 114 of the image data and the black ejection image data. Therefore, it is only necessary to insert two pixels into a region corresponding to the fourth connecting portion 114 of the cyan ejection image data. Even in this case, similar results can be obtained.
In addition, as described above, the example in which the pixel is inserted or deleted when the cumulative error becomes one pixel has been described. However, the pixel range is not limited to one pixel and the cumulative error is 0.5 to 1.5 The position error can be reduced by inserting or deleting pixels. For example, in the case where a position error of 0.6 pixels has occurred, if a pixel is inserted or deleted, the position error can be reduced to 0.4 pixels, and from the viewpoint of further reducing the accumulated position error. preferable.

  Next, the distortion correction process will be described with reference to FIG. The distortion correction process is a process executed by the distortion correction unit 303 in the control unit 30 functioning. This distortion correction processing is executed for each color of ejection image data.

  First, the control unit 30 determines whether or not the coordinates of a target pixel for determining whether or not to correct image data (hereinafter, may be referred to as a target pixel) is equal to or less than the maximum value in the Y direction (Y axis). Is determined (step S201). When the control unit 30 determines that the coordinate of the pixel of interest is less than or equal to the maximum value in the Y axis (step S201: Y), whether or not the coordinate of the pixel of interest is less than or equal to the maximum value in the X direction (X axis). Is determined (step S202). When the control unit 30 determines that the coordinate of the target pixel is equal to or less than the maximum value on the X axis (step S202: Y), the control unit 30 determines whether the target pixel is an area corresponding to the connecting units 111 to 115. (Step S203).

  When the control unit 30 determines that the pixel of interest is a region corresponding to the connecting portions 111 to 115 (step S203: Y), whether the target pixel is a region corresponding to the connecting portions 111 to 115, and Then, it is determined which color of the ejection image data is used (step S204).

  The control unit 30 refers to the correction determination table created as described above, and collates with the determination result in step S204 (step S205).

  As a result of the collation in step S205, the control unit 30 determines whether or not the pixel of interest is an area corresponding to a joint unit that performs correction processing (step S206). That is, the control unit 30 determines whether or not the value in the reference destination field of the correction determination table is a value other than “0”, which is a value indicating that correction processing is not performed. When the control unit 30 determines that the pixel of interest is a region corresponding to a connecting portion that performs correction processing (step S206: Y), the control unit 30 determines whether or not the pixel of interest is a region that performs correction processing (step S206). S207). Specifically, the control unit 30 determines whether or not the region corresponding to the joint portion is a region where mask processing using a mask pattern described later is performed. When the control unit 30 determines that the target pixel is a region to be corrected (step S207: Y), the control unit 30 performs the correction process for inserting or deleting the pixel in the target pixel (step S208), and then the target pixel. Is incremented by 1 (step S209), and the process of step S202 is executed. Details of the correction process will be described later. On the other hand, when the control unit 30 does not determine that the target pixel is an area to be corrected (step S207: N), the control unit 30 executes the process of step S209 without executing the process of step S208. In addition, when the control unit 30 does not determine in step S206 that the target pixel is an area corresponding to a joint portion for performing correction processing, that is, the value in the reference destination field of the correction determination table performs correction processing. If it is determined that the value is “0”, which is not present (step S206: N), the process of step S209 is executed without executing the processes of steps S207 and S208.

  Further, when the control unit 30 does not determine in step S203 that the target pixel is an area corresponding to the connection units 111 to 115 (step S203: N), the control unit 30 does not execute the processing of step S204 to step S208. The process of step S209 is executed.

  In addition, when the control unit 30 does not determine in step S202 that the coordinate of the target pixel is equal to or less than the maximum value on the X axis (step S202: N), the control unit 30 increments the Y axis coordinate of the target pixel by 1, After the X-axis coordinate is set to the origin position (step S210), the process of step S201 is executed.

  If the control unit 30 does not determine that the coordinate of the pixel of interest is equal to or less than the maximum value on the Y axis in step S201 after repeatedly executing the above-described processing (step S201: N), the control unit 30 ends this processing.

  In the present embodiment, as described above, pixels can be inserted or deleted at positions corresponding to the connecting portions 111 to 115 of the ejection image data.

  Next, the correction process executed in step S207 of the distortion correction process will be described with reference to FIG.

First, the control unit 30 performs a mask process for applying a mask pattern to the ejection image data (step S301). This masking process is a process for determining a pixel correction position, which will be described later. Here, the “correction position” refers to the position of the pixel where the pixel is inserted or deleted. Specifically, the control unit 30 applies the mask pattern P as shown in FIG. 13 to a predetermined coordinate on the X axis, as shown in FIG. They are arranged side by side in a continuous manner in the Y direction. As shown in FIG. 13, the mask pattern P is pattern data formed in a matrix with 16 × 32 pixels as one unit, and only one dot indicating the correction position in the nozzle row direction (X direction). The pattern data is defined so that the correction positions thereof have substantially equal intervals without having a cycle (in the entire mask pattern P) in 16 × 32 pixels. In other words, the mask pattern is formed in a matrix having a plurality of pixels in the nozzle row direction and a direction perpendicular to the nozzle row direction, and the correction positions are defined. The mask pattern P is pattern data that approximates a blue noise pattern. Thus, in the present embodiment, the correction position can be determined so that the position differs in the direction (Y direction) perpendicular to the nozzle row direction (X direction) of the ejection image data. In the present embodiment, the pattern of the mask pattern P is different for each color of CMYK. For example, if the cyan mask pattern is as shown in FIG. 13, the magenta mask pattern is shifted by 4 pixels in the X direction, and the yellow mask pattern is shifted by 8 pixels in the X direction. Suppose that the black mask pattern is shifted by 12 pixels in the X direction. Thus, in the present embodiment, the correction position can be determined so that the position differs for each ejection image data.
In the present embodiment, it is possible to suppress the occurrence of moire patterns due to periodicity by configuring the mask pattern P as described above.
The mask pattern applicable in the present embodiment may be pattern data that approximates noise of other colors such as white noise, as long as only one dot is formed in the X direction. Further, it may be pattern data having regularity.
In addition, the size of the mask pattern applicable in this embodiment is not limited to the 16 × 32 pixels described above, but if the size is too large in the X direction, the area where the pixels are inserted and the pixels are shifted becomes large. On the other hand, if the size is too small in the X direction, regularity occurs at the positions where the pixels are inserted, and an undesirable pattern appears. It is preferable to do this. A preferable mask pattern size is 16 × 64 pixels or the like in addition to the 16 × 32 pixels described above.

  Next, the control unit 30 determines whether or not the coordinate of the target pixel is a position where a dot is made in the mask pattern P (step S302). When the control unit 30 determines that the coordinate of the target pixel is a position where a dot is made in the mask pattern P (step S302: Y), the control unit 30 refers to the correction determination table to determine whether or not to insert the pixel. Is determined (step S303). That is, the control unit 30 determines to insert a pixel when the value in the field corresponding to the connection portion in the correction determination table is a value indicating that the pixel is to be inserted.

When it is determined that the pixel is to be inserted (step S303: Y), the control unit 30 executes a pixel insertion process (step S304). Specifically, the control unit 30 shifts each pixel on the right side in the X direction from the coordinate of the target pixel by one pixel to the right, and inserts the pixel into the coordinate of the target pixel. As a pixel to be inserted, a pixel adjacent to the left side in the X direction is applied as it is (nearest neighbor). For example, as shown in FIG. 15A, it is determined that the 18th pixel in the fourth connecting portion 114 configured by the cyan recording head 104 and the cyan recording head 105 is inserted by the above-described processing. If it is, the pixels on the right side in the X direction from the 18th pixel are shifted one pixel in the right direction. Then, as shown in FIG. 15B, a new pixel is inserted between the 17th pixel and the shifted 18th pixel. This new pixel becomes the same pixel as the 17th pixel by the nearest neighbor method. Thereby, the discharge image data of cyan can be enlarged by one nozzle on the right side. As described above, when inserting the 18th pixel, each pixel on the right side in the X direction from the 18th pixel is shifted by one pixel to the right, so that FIG. As a result, the number of nozzles is insufficient for the pixels. Therefore, from the viewpoint of forming an image by making all the pixels correspond to the nozzles, for example, it is preferable to reduce the number of nozzles for forming an image by giving pixels to the total number of nozzles. Further, as will be described later, even when pixels are deleted, from the viewpoint of forming an image by making all pixels correspond to nozzles, for example, the number of nozzles for forming an image by providing pixels is made smaller than the total number of nozzles. It is preferable.
Note that the method of generating a pixel to be inserted is not limited to the nearest neighbor described above, and various methods such as obtaining a pixel value by a bilinear method, a bicubic method, or the like can be applied.

  The control unit 30 determines whether or not the target pixel is an edge portion (step S305). When the control unit 30 determines that the target pixel is an edge portion (step S305: Y), the control unit 30 performs a filtering process for smoothing the pixel (step S306), and then ends this process. For example, a median filter is suitable for the filter processing, but is not limited thereto. On the other hand, when the control unit 30 does not determine that the pixel of interest is an edge portion (step S305: N), the process ends without executing the process of step S306.

  Further, when it is not determined in step S303 that a pixel is to be inserted (step S303: N), the control unit 30 executes the pixel deletion process (step S307), and then ends this process. Specifically, the control unit 30 deletes the pixel at the coordinate of the target pixel, and shifts each pixel on the right side in the X direction from the coordinate of the target pixel by one pixel to the left. For example, as shown in FIG. 16A, it is determined that the 18th pixel in the fourth connecting portion 114 configured by the yellow recording head 104 and the yellow recording head 105 is deleted by the above-described processing. In such a case, as shown in FIG. 16B, after removing the 18th pixel, each pixel on the right side in the X direction from the 19th pixel is shifted by one pixel to the left. Thereby, the yellow discharge image data can be reduced by one nozzle on the left side.

  Further, when the control unit 30 does not determine in step S302 that the coordinate of the target pixel is the position where the hit point is performed in the mask pattern P (step S302: N), the process ends.

  Next, an application example of this embodiment will be described. FIG. 17A shows, for example, cyan discharge image data.

  When pixels are inserted in the discharge image data shown in FIG. 17A as described above, one pixel is inserted in each column in the Y direction as shown in FIG. 17B. It becomes. Then, when an adjacent pixel is applied to the inserted pixel position by the nearest neighbor method, a corrected image as shown in FIG. 17C is formed.

  In the present embodiment, correction is performed to enlarge or reduce the ejection image data in the X direction by inserting or deleting pixels in this way, thereby reducing the position error with other color images and thereby preventing color misregistration. It becomes possible to suppress.

  FIG. 18A shows, for example, an image formed by superimposing an image formed by cyan discharge image data and an image formed by magenta discharge image data.

  When the pixels are inserted as described above into the ejection image data of the magenta image shown in FIG. 18A, one pixel is placed in each column in the Y direction as shown in FIG. 18B. It will be inserted. Then, when an adjacent pixel is applied to the inserted pixel position by the nearest neighbor method and a median filter is applied to the edge portion, a corrected image as shown in FIG. 18C is formed.

  As described above, in the present embodiment, when the portion into which the pixel is inserted is an edge portion, the filtering process is performed, so that it is possible to satisfactorily correct both the edge portion and the non-edge portion.

  As described above, according to the present embodiment, the inkjet recording apparatus 2 includes the recording heads 101 to 106 having nozzle rows in which a plurality of nozzles N are arranged at predetermined intervals in a staggered manner along the nozzle row direction. A plurality of recording head units 10 having a plurality of nozzles N arranged at the respective ends of the recording heads 101 to 106 that are arranged adjacent to each other and overlap each other in a direction perpendicular to the nozzle row direction. , 12, 14, and 16 are arranged side by side in a direction perpendicular to the nozzle row direction, and the input image data is converted into ejection image data for each of the recording head units 10, 12, 14, and 16, and the recording medium 4 is conveyed. Then, ink is ejected from each nozzle N of the plurality of recording heads 101 to 106 according to the ejection image data, and an image is formed on the recording medium. The control unit 30 includes a plurality of line-based line images extending in a direction perpendicular to the nozzle row direction, based on line chart image data CH for forming each of the recording heads 101 to 106 at a predetermined pixel position. The recording head units 10, 12, 14, 16 are each formed with a line image, and the recording head unit 10, identified from the line images formed by each of the recording head units 10, 12, 14, 16 An error in the image forming position between 12, 14, and 16 is specified for each of the recording heads 101 to 106. The control unit 30 determines the correction position of the ejection image data corresponding to each of the recording heads 101 to 106 based on the specified error of each of the recording heads 101 to 106. The control unit 30 corrects the ejection image data by inserting or deleting pixels at the determined correction position. As a result, it is possible to reduce the color misregistration caused by the recording head being deviated in the nozzle arrangement direction.

  Further, according to the present embodiment, the control unit 30 inserts or deletes a pixel with the positions corresponding to the connecting portions 111 to 115 of the ejection image data as correction positions. As a result, an error in the image forming position between the recording head units can be effectively absorbed, and color misregistration can be further reduced.

  Further, according to the present embodiment, the control unit 30 determines the correction position so that the position differs for each of the recording head units 10, 12, 14, and 16. As a result, it is possible to suppress deterioration in image quality caused by the correction positions matching between colors.

  Further, according to the present embodiment, the control unit 30 determines the correction position so as not to be continuous in a direction perpendicular to the nozzle row direction of the ejection image data. As a result, it is possible to reduce deterioration in image quality due to the appearance of a regular image in the corrected ejection image data.

  Further, according to the present embodiment, the control unit 30 is formed in a matrix having a plurality of pixels in the nozzle row direction and a direction perpendicular to the nozzle row direction, and the correction position is defined. The correction position is determined by masking the ejection image data using the mask pattern. As a result, the correction position can be easily determined, so that the processing efficiency is improved.

  In addition, according to the present embodiment, only one correction position is defined for the mask pattern in the noise column direction, and the correction position does not have a period in the entire mask pattern, and the mask pattern has a substantially equal feeling. Since the pattern data is formed in this way, the dot positions of the mask pattern are evenly distributed, so that correction positions in the discharge image data can be distributed well and correction can be performed satisfactorily.

  Further, according to the present embodiment, the line sensor 18 reads a line image. The control unit 30 specifies an error in the image forming position between the recording head units 10, 12, 14, and 16 from the position of the line image read by the line sensor 18. As a result, an error in the image forming position can be easily specified.

  The description in the embodiment of the present invention is an example of the ink jet recording apparatus according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of each functional unit constituting the ink jet recording apparatus can be appropriately changed.

  In the present embodiment, an example of an ink jet recording apparatus capable of performing image formation by a so-called line head method in which image formation is performed only by conveying a recording medium has been described. For example, as illustrated in FIG. The above-described recording head unit for each color is mounted on the recording medium, and while the recording medium is conveyed in the Y direction, the carriage 504 is conveyed along the direction perpendicular to the conveying direction of the recording medium (X direction), while It can also be employed in the ink jet recording apparatus 2A that ejects ink. In the recording head unit in this case, a plurality of recording heads are arranged in a staggered manner along the conveyance direction of the recording medium. The recording head has a nozzle row in which a plurality of nozzles are arranged at predetermined intervals, and the nozzle row direction is parallel to the conveyance direction of the recording medium.

  In the present embodiment, one pixel is inserted and deleted for each connecting portion 111 to 115, but two or more pixels are inserted and deleted for each connecting portion 111 to 115. You may do it.

  In the present embodiment, the pixels are inserted and deleted in the region corresponding to the ejection image data connecting portions 111 to 115. However, the region other than the region corresponding to the ejection image data connecting portions 111 to 115 is used. The pixel may be inserted and deleted in step.

  In the present embodiment, pixels are inserted and deleted from the ejection image data. However, only one of pixel insertion and deletion may be performed.

  In this embodiment, the pixel correction position is determined so that the position is different for each ejection image data (color). However, the pixel correction position may be the same among the ejection image data.

  In this embodiment, the correction position is determined so that the position is different in the direction (Y direction) perpendicular to the nozzle row direction of the ejection image data. However, the correction position is the same in the Y direction. It may be.

  In this embodiment, the correction position is determined using the mask pattern. However, the correction position may be determined by performing a predetermined calculation, for example, without using the mask pattern.

  In the present embodiment, a line sensor 18 is provided to read a line image formed by the recording head units 10, 12, 14, and 16, and based on the line image, the space between the recording head units 10, 12, 14, and 16 is read. The error in the image forming position is specified, but the line sensor is not provided, and the line image is read by a reading device separate from the ink jet recording apparatus 2, and the image forming position between the recording head units 10, 12, 14, and 16 is determined. The error may be specified and the result may be input to the inkjet recording apparatus 2.

  In the present embodiment, an example in which a hard disk, a semiconductor nonvolatile memory, or the like is used as a computer-readable medium of the program according to the present invention is disclosed, but the present invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. A carrier wave is also used as a medium for providing program data according to the present invention via a communication line.

2 Inkjet recording device 4 Recording medium 10, 12, 14, 16 Recording head unit 18 Line sensor (image reading unit)
101 to 106 Recording heads 111 to 115 Connecting unit 30 Control unit 303 Distortion correcting unit D Discharged image data N Nozzle P Mask pattern

Claims (8)

A plurality of recording heads having a nozzle row in which a plurality of nozzles are arranged at predetermined intervals are arranged in a staggered manner along the nozzle row direction, and a plurality of nozzles arranged at each end of the recording heads arranged adjacent to each other Are provided with a plurality of recording head units having connecting portions that overlap each other in a direction perpendicular to the nozzle row direction, and the input image data is ejected image data for each recording head unit. In an inkjet recording apparatus for forming an image on a recording medium by discharging ink from each nozzle of the plurality of recording heads according to the discharge image data while converting the recording medium to
Each of the plurality of recording head units forms the measurement image based on measurement image data for forming a predetermined measurement image at a predetermined pixel position for each recording head, and the plurality of recordings An error of the image forming position between the recording head units specified from the measurement image formed by each of the head units is specified for each recording head, and the ejection image data is determined from the error for each specified recording head. An ink jet recording apparatus comprising: a control unit that determines a correction position corresponding to each recording head, and corrects the ejection image data by inserting or deleting a pixel at the determined correction position.   2. The inkjet recording apparatus according to claim 1, wherein the control unit inserts or deletes a pixel with the position corresponding to the connecting portion of the ejection image data as the correction position.   3. The ink jet recording apparatus according to claim 1, wherein the control unit determines the correction position so that the position differs for each recording head unit.   4. The inkjet recording according to claim 1, wherein the control unit determines the correction position so that the ejection image data does not continue in a direction perpendicular to the nozzle row direction. 5. apparatus.   The control unit includes a plurality of pixels in the nozzle row direction and a direction perpendicular to the nozzle row direction, each of which is formed in a matrix and uses the mask data in which the correction position is defined. The inkjet recording apparatus according to claim 4, wherein the correction position is determined by performing mask processing on image data.   The mask data is defined such that only one correction position is defined in the nozzle row direction, and the correction positions have a substantially uniform interval without a period in the entire mask data. 6. The ink jet recording apparatus according to claim 5, wherein the ink jet recording apparatus is pattern data. An image reading unit for reading the measurement image;
The said control part specifies the error of the image formation position between the said recording head units from the position of the said image for a measurement read by the said image reading part, The any one of Claims 1-6 characterized by the above-mentioned. Inkjet recording apparatus. A plurality of recording heads having a nozzle row in which a plurality of nozzles are arranged at predetermined intervals are arranged in a staggered manner along the nozzle row direction, and a plurality of recording heads formed at each end of the adjacent recording heads A plurality of recording head units each having a connecting portion in which nozzles overlap with each other in a direction perpendicular to the nozzle row direction are arranged in a direction perpendicular to the nozzle row direction, and input image data is ejected from each recording head unit. An image processing method using an inkjet recording apparatus that converts data into data and ejects ink from each nozzle of the plurality of recording heads according to the ejection image data while conveying the recording medium to form an image on the recording medium. ,
Each of the plurality of recording head units is based on measurement image data for forming a line-shaped measurement image extending in a direction perpendicular to the nozzle row direction at a predetermined pixel position for each recording head. A measurement image forming step for forming the measurement image on
An error measurement step of measuring, for each recording head, an error in the image forming position between the recording head units from the formed measurement image;
A correction position determining step for determining the correction position of the ejection image data corresponding to each recording head from the measured error for each recording head;
A correction step of correcting the ejection image data by inserting or deleting a pixel at the determined correction position;
An image processing method comprising: