JP2019018433A - Printing system, printing method, and printer - Google Patents

Abstract

To perform printing more properly even in the case where an abnormal nozzle exists.SOLUTION: A printing system 10 performing printing in an ink jet system includes an ink jet head 102 having a plurality of nozzles manages the plurality of nozzles in the ink jet head 102 by classifying them into a plurality of groups, divides a region to which ink is discharged by the plurality of nozzles included in the respective groups into preset scanning direction unit regions, manages the unit region density being the density of the ink in each scanning direction unit region, and brings the unit region density closer to the normal-time region density by increasing a discharge amount of the ink discharged to the scanning direction unit region by a normal nozzle included in the group including the abnormal nozzle when any nozzle is an abnormal nozzle.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printing system, a printing method, and a printing apparatus.

  2. Description of the Related Art Conventionally, an ink jet printer that is a printing apparatus that performs printing by an ink jet method has been widely used (see, for example, Patent Document 1). An ink jet printer performs printing on a medium by ejecting ink (ink droplets) from fine nozzles in an ink jet head.

Japanese Patent Application Laid-Open No. 2006-334979

  In an ink jet printer, due to the structure in which ink is ejected from fine nozzles, the ejection characteristics of the nozzles affect the quality of printing. In addition, when abnormal nozzles (defective nozzles) whose ejection characteristics deviate from the normal range occur, printing may not be performed properly. Therefore, conventionally, various methods for performing printing even when there are abnormal nozzles have been studied. For example, when performing multi-pass printing in which printing is performed by performing a plurality of main scanning operations for each position on the medium, using the features of the multi-pass operation, instead of abnormal nozzles For example, a method for setting an alternative nozzle (alternative nozzle) for discharging ink is known.

  However, depending on the configuration of the ink jet printer, it may not be possible to set an alternative nozzle using the characteristics of the operation in the multi-pass method. Therefore, conventionally, a more appropriate configuration or the like is desired for a configuration or the like that performs printing when there is an abnormal nozzle.

  Here, Patent Document 1 discloses a discharge failure as a method that makes it difficult to see white streaks generated by discharge means with discharge failure without requiring special and complicated processing, and simplifies discharge failure inspection. A method of generating recording data so that the discharge density of the head unit determined to include the nozzle is lower than the arrangement density of the nozzles, and driving the nozzles based on the generated recording data to form an image. It is disclosed. Such a method can be executed without using the characteristics of the operation in the multipath method. However, when compensation of ejection characteristics is performed when there is an abnormal nozzle, it is desirable to use a configuration that makes the result of the operation performed for compensation less noticeable. Therefore, conventionally, a more appropriate configuration or the like is desired for a configuration or the like that performs printing when there is an abnormal nozzle. Therefore, an object of the present invention is to provide a printing system, a printing method, and a printing apparatus that can solve the above-described problems.

  The inventor of the present application has earnestly studied a configuration that can perform printing more appropriately even when an abnormal nozzle is present. First, a plurality of nozzles included in the inkjet head are divided into a plurality of groups and managed, and the ejection characteristics of abnormal nozzles are compensated between the plurality of nozzles included in each group. In this case, for example, it may be possible to compensate for the ejection characteristics of the abnormal nozzle by increasing the ejection amount of ink ejected to the nozzles included in the same group as the abnormal nozzle.

  In this regard, when the ejection characteristics are simply divided into groups, depending on the compensation method, for example, a portion where ink is ejected by a nozzle with an increased ejection amount becomes conspicuous, and print quality is appropriately increased. May be difficult. More specifically, for example, when performing solid color painting with a certain density of a certain level of darkness or more, an abnormal nozzle can be obtained simply by increasing the ink discharge amount of the normal nozzle in the group. It is considered that the discharge characteristics can be appropriately compensated.

  However, an inkjet printer usually prints various images and the like as well as performing solid color painting at a constant density. In this case, for example, printing is performed so that the color and the color density differ depending on the position on the medium. In such a case, for example, simply increasing the ink discharge amount of the normal nozzle in the group may cause a portion where ink is discharged by the nozzle having the increased discharge amount to be noticeable. As a result, printing with high quality may be difficult.

  In contrast, the inventors of the present application have not only simply increased the amount of ink ejected from normal nozzles within a group, but also ejected ink from a plurality of nozzles included in each group during a scanning operation. It was considered to divide the area to be divided into a plurality of areas (scanning direction unit areas) with a predetermined width in the scanning direction, and to adjust the ink density in each area. In this case, the scanning operation is, for example, an operation of ejecting ink to the inkjet head while moving the medium relative to the inkjet head.

  Further, through further earnest research, the inventors have found characteristics necessary for obtaining such an effect and have reached the present invention. In order to solve the above-described problems, the present invention provides a printing system that performs printing by an inkjet method, and an inkjet head that ejects ink onto a medium, and the inkjet head in a preset scanning direction. A scanning drive unit that drives a scanning operation for ejecting ink to the inkjet head while relatively moving the medium; and a print control unit that controls the operations of the inkjet head and the scanning drive unit. The head has a plurality of nozzles arranged at different positions in the nozzle row direction orthogonal to the scanning direction, and during the scanning operation, each of the nozzles performs a preset printing on the medium. The ink dot is a dot interval in the scanning direction that is a dot interval in the scanning direction corresponding to the resolution. The print control unit manages the plurality of nozzles in the inkjet head by dividing the plurality of nozzles continuously arranged in the nozzle row direction into a plurality of groups each including the nozzles, and A scanning direction unit area that is a width area including a plurality of ink dots arranged in the scanning direction at the scanning direction dot interval with respect to an area in which ink is ejected by the plurality of nozzles included in the group at the time of the scanning operation. The unit area density, which is the density of the ink in each scanning direction unit area, is managed, and a nozzle within the normal range in which the ejection characteristics of the nozzle are set in advance is defined as a normal nozzle. Are defined as abnormal nozzles, and all the nozzles in the group are normal nozzles. In the case where the unit area density is defined as a normal area density, if any of the nozzles included in any of the groups is the abnormal nozzle, the print control unit includes the group including the abnormal nozzle. The amount of ink discharged to at least one of the normal nozzles included in the unit in the scanning direction unit region is made larger than the amount of ink discharged when all the nozzles in the group are the normal nozzles. Thus, the unit region density corresponding to the group is brought close to the normal region density.

  With this configuration, for example, even when an abnormal nozzle is present in the inkjet head, it is possible to appropriately secure the necessary ink discharge amount. Thereby, for example, the ejection characteristics of the abnormal nozzle can be appropriately compensated. Also, in this case, the ink density (unit area density) for each unit area in the scanning direction is adjusted to be close to the normal density (normal area density), so that each position on the medium has higher accuracy. It becomes possible to compensate for the ejection characteristics of the abnormal nozzle. In addition, for example, even when printing an image whose color or color density differs depending on the position on the medium, it is possible to appropriately prevent the portion where ink is ejected from the nozzle with the increased ejection amount from being noticeable. Can do. Therefore, if constituted in this way, for example, even when an abnormal nozzle exists, printing can be performed more appropriately.

  Here, to make the unit area density close to the normal area density, for example, by adjusting so that the ink discharge amount of the normal nozzle is increased, the unit area density and the normal area density are made higher than when the adjustment is not performed. The difference from the time domain density is to be reduced. Regarding the difference between the unit region density and the normal region density, for example, it is conceivable to adjust so as to be within a preset allowable range. In this configuration, the amount of ink discharged from the ink is, for example, the amount discharged per unit area on the medium. In this configuration, the ink jet head may be a composite head (for example, a staggered head) in which a plurality of ink jet heads are combined.

  In this configuration, the volume of ink ejected by each nozzle may be variable in a plurality of stages. In this case, making the ink volume variable in a plurality of stages means that, for example, in the operation of ejecting ink to the ejection position set according to the printing resolution, the capacity of the ink ejected to one ejection position is different from each other. It is to be able to set multiple types of capacity. In this case, the normal nozzles that increase the ink discharge amount are larger than the capacity when all the nozzles in the same group are normal nozzles, for example, at least at any timing when ink is discharged during the scanning operation. It may be possible to do so. If comprised in this way, the discharge amount of the ink of a normal nozzle can be adjusted appropriately, for example.

  Further, in this configuration, the compensation of the ejection characteristics of the abnormal nozzle as described above can be performed without using, for example, the characteristics of the operation in the multi-pass method. Therefore, in this configuration, the printing system uses an inkjet head only once at each position on the medium, such as a line-type inkjet printer or a serial-type inkjet printer that performs printing with 1 pass. The printing may be performed with a configuration in which the scanning operation is performed so as to pass. In this case, the interval in the nozzle row direction of the plurality of nozzles in the inkjet head is equal to, for example, the dot interval in the nozzle row direction corresponding to the resolution of printing performed in the printing system.

  Further, in this configuration, for example, in addition to the general printing resolution, for example, the corresponding resolution (unit area resolution) of the scanning direction unit area which becomes a reference for managing the density of ink can be considered. . In this case, the general resolution is, for example, a printing resolution corresponding to a minimum interval between dots of ink formed on a medium. The ejection characteristic compensation performed in such a configuration is more effective, for example, when the resolution of the unit region is sufficiently high. Therefore, in this case, it is preferable that the resolution of the unit region is about 300 dpi or more. In this case, for example, if attention is focused on the resolution in the scanning direction and the number of nozzles included in one group is n, the printing resolution is n times the resolution of the unit area. Therefore, it is preferable to set the printing resolution to, for example, about n × 300 dpi or more. The resolution of the unit area is more preferably about 600 dpi or more.

  In this printing system, for example, color printing may be performed by using a plurality of inkjet heads that eject inks of different colors. In this case, it is conceivable to manage a plurality of nozzles in each color ink-jet head by dividing them into a plurality of groups. In this case, for example, the density of the ink in the region to be printed in the scanning operation is managed in association with each group.

  Also, in this case, the position of the group boundary in the nozzle row direction is not the same for all color ink-jet heads, but the group boundary position in some color ink-jet heads is different. You may make it different from the inkjet head for colors. When configured in this way, for example, it is possible to set the position where ink dots are formed under different conditions for each color. In this case, for example, when expressing bright colors, it is possible to prevent multiple color inks from overlapping at the same position. Thereby, for example, it is possible to more appropriately perform printing while suppressing graininess.

  In this case, it is more preferable that the position of the group boundary is different between the magenta inkjet head and the cyan inkjet head. In this case, not only the group boundary but also the boundary position of the scanning direction unit area in the scanning direction, the boundary position in some colors may be different from the boundary position in other colors. If comprised in this way, high quality printing can be performed more appropriately, for example.

  The configuration of the printing system according to the present invention can also be considered by paying attention to the relationship between the printing resolution and the area resolution described above, for example. In addition, as a configuration of the present invention, it is conceivable to use a printing method, a printing apparatus, or the like having the same characteristics as described above. In these cases, for example, the same effects as described above can be obtained.

  According to the present invention, for example, even when an abnormal nozzle exists, printing can be performed more appropriately.

1 is a diagram illustrating an example of a printing system 10 according to an embodiment of the present invention. FIG. 1A shows an example of the configuration of the printing system 10. FIG. 1B shows an example of the configuration of the main part of the printing apparatus 12 in this example. FIG. 1C shows an example of the configuration of the inkjet head 102 in the printing apparatus 12. FIG. 5 is a diagram for explaining how to arrange ink dots 202 formed on a medium 50 by a scanning operation. FIG. 2A schematically shows an example of how the dots 202 are formed by the scanning operation. FIG. 2B is a diagram schematically showing the influence of the abnormal nozzle. It is a figure explaining management of the density of ink performed in this example. FIG. 3A shows an example of the relationship between the arrangement of the dots 202 formed on the medium 50 and the unit area. FIG. 3B shows an example of the unit area 212 set in this example. FIG. 6 is a diagram for explaining the ink density in a unit region 212 in more detail. 4A to 4E show examples of how to form the ink dots 202 in the unit region 212 when the ink density set in the unit region 212 is changed variously. It is a figure explaining in more detail about compensation of the discharge characteristic performed in this example. FIG. 5A shows an example of the volume of ink ejected from one nozzle to one ejection position. FIGS. 5B and 5C show examples of how to form dots when the ink density of the unit region 212 is increased. It is a figure explaining the structure of the printing apparatus 12, the printing operation | movement, etc. in the case of printing using the ink of several colors. FIG. 6A shows an example of the arrangement of a plurality of ink jet heads 102 y to 102 k used in the printing apparatus 12. FIG. 6B shows an example of how to divide the group 302 in each of the inkjet heads 102y to 102k. It is a figure explaining the structure of the printing apparatus 12, the printing operation | movement, etc. in the case of printing using the ink of several colors. FIG. 7A shows an example of how to set the position of the boundary of the unit area. FIG. 7B shows an example of the difference in position where the unit area of each color is set. It is a figure explaining the further modification regarding printing operation | movement etc. FIG. FIGS. 8A and 8B are diagrams for explaining the case where the setting of the ink capacity is made variable in a plurality of stages. FIG. 8C shows a modified example of the configuration of the unit region 212. It is a figure which shows an example of a detailed structure of the RIP apparatus 14, and divides the structure of the RIP apparatus 14 into a some functional block about the case where the printing apparatus 12 is considered as a multi-value printer which prints with the resolution of the unit area | region 212. Show.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of a printing system 10 according to an embodiment of the present invention. FIG. 1A shows an example of the configuration of the printing system 10. Except as described below, the printing system 10 may have the same or similar features as a known printing system that performs printing by an inkjet method. Further, the printing system 10 may further include various configurations necessary for a printing operation, for example, in addition to the illustrated configuration.

  In this example, the printing system 10 is a printing system that performs printing by an inkjet method, and includes a printing device 12 and a RIP device 14. The printing apparatus 12 is an ink jet printer that performs a printing operation, and ejects ink (ink droplets) to a medium (medium) to be printed based on ejection position data received from the RIP apparatus 14. In this case, the ejection position data is data indicating a position at which the ink jet head in the printing apparatus 12 ejects ink. More specifically, in this example, the ejection position data is data generated by RIP processing or the like performed in the RIP device 14.

  The RIP device 14 is a data processing device that generates discharge position data to be supplied to the printing device 12, and generates discharge position data based on an input image input as an image to be printed. More specifically, the RIP device 14 generates ejection position data by performing, for example, RIP processing that develops an input image into a raster image of a predetermined format. In this example, the RIP device 14 further generates ejection position data in consideration of the presence of abnormal nozzles in the printing device 12. The abnormal nozzle is, for example, a nozzle other than the normal nozzle among the nozzles of the inkjet head of the printing apparatus 12. The normal nozzle is, for example, a nozzle within a normal range in which ejection characteristics are set in advance. An abnormal nozzle can also be considered as a nozzle whose ejection characteristics are out of a preset normal range. The operation for generating the discharge position data in consideration of the presence of the abnormal nozzle will be described in more detail later. Further, in this example, the RIP device 14 generates ejection position data and supplies it to the printing device 12 to control the printing operation in the printing system 10. Accordingly, the RIP device 14 functions as a print control unit that controls a printing operation in the printing system 10.

  Next, the configuration of the printing apparatus 12 in this example will be described in more detail. FIG. 1B shows an example of the configuration of the main part of the printing apparatus 12 in this example. FIG. 1C shows an example of the configuration of the inkjet head 102 in the printing apparatus 12. In this example, the printing apparatus 12 is a line-type inkjet printer, and includes an inkjet head 102, a scanning drive unit 104, a fixing unit 106, and a control unit 120. In this case, the line-type inkjet printer is, for example, an inkjet printer that performs printing by a single-pass method using the inkjet head 102 having a length in the longitudinal direction that is longer than the width of a printing area that performs printing on the medium 50. That is. Further, the width of the print area is, for example, a width in a direction (Y direction in the drawing) orthogonal to the transport direction (X direction in the drawing) in which the medium 50 is moved relative to the inkjet head 102. is there. Further, the printing by the single pass method is, for example, that printing is performed such that each position of the printing area on the medium 50 and the inkjet head 102 face each other only once.

  For convenience of illustration, FIG. 1B shows only one ink jet head 102 in the printing apparatus 12. However, when printing is performed using, for example, a plurality of colors of ink in the actual printing apparatus 12, the printing apparatus 12 may include a plurality of inkjet heads 102 corresponding to a plurality of colors. In this case, the fact that each position of the print area and the ink jet head 102 face each other only means that, for example, the relationship between each position of each ink jet head 102 and the print area faces only once. . In the following, the Y direction in the figure is referred to as the width direction of the medium 50.

  The ink jet head 102 is a print head that ejects ink by an ink jet method, and is disposed at a predetermined position of the printing apparatus 12 so as to face the medium 50, and ejects ink toward the medium 50. In this case, ejecting ink means ejecting ink droplets from the nozzles 112 of the inkjet head 102. Further, in this example, the inkjet head 102 includes a plurality of nozzles 112 arranged at different positions in the width direction of the medium 50 as shown in FIG. 1C, for example. In this case, arranging the positions in the width direction of the medium 50 different from each other means, for example, that the position in the direction orthogonal to the width direction of the medium 50 (the conveyance direction of the medium 50) is not taken into consideration. When focusing only on the position, the positions are arranged differently. Therefore, the positions of the nozzles 112 in the conveyance direction of the medium 50 do not necessarily have to be aligned.

  As described above, in this example, the inkjet head 102 having a longer length in the longitudinal direction than the width of the print region is used. In such a case, as the ink jet head 102, for example, a composite head (for example, a stagger head or the like) in which a plurality of physically independent ink jet heads is combined may be considered. In this case, the inkjet heads constituting the inkjet head 102 may be arranged side by side in the width direction of the medium 50 by shifting the position in the transport direction.

  Further, in this example, the width direction of the medium 50 can be considered as the nozzle row direction in which the plurality of nozzles 112 in the inkjet head 102 are arranged. In this case, the plurality of nozzles 112 in the inkjet head 102 are arranged at a constant interval py as shown in the drawing. In this case, the fact that the nozzles 112 are arranged at a constant interval in the nozzle row direction is constant when only the position of each nozzle in the nozzle row direction is considered without considering the position difference in the direction orthogonal to the nozzle row direction. It is to line up at intervals. As described above, in this example, the printing apparatus 12 is a line-type inkjet printer, and performs printing by a single pass method. In this case, in the arrangement of the ink dots formed on the medium 50, the minimum dot interval in the width direction of the medium 50 is equal to the interval py of the nozzles 112 in the inkjet head 102. That is, in this case, the printing resolution in the width direction of the medium 50 is equal to the resolution corresponding to the nozzle interval py.

  The scanning drive unit 104 is a drive unit that drives a scanning operation. In this case, the scanning operation is, for example, an operation of ejecting ink to the inkjet head 102 while moving the medium 50 relative to the inkjet head 102 in a preset scanning direction. More specifically, in this example, the scanning direction is a direction parallel to the conveyance direction of the medium 50. The scan driving unit 104 drives the scanning operation by causing the inkjet head 102 to eject ink while transporting the medium 50. Accordingly, the scanning drive unit 104 drives the scanning operation so that the inkjet head 102 passes only once over each position on the medium 50. In this example, the scan driving unit 104 also functions as an ejection driving unit that causes the inkjet head 102 to eject ink.

  The fixing unit 106 is configured to fix the ink ejected onto the medium 50 by the ink jet head 102 onto the medium 50. As the fixing unit 106, it is conceivable to use a unit according to the characteristics of the ink to be used. More specifically, in this example, the inkjet head 102 ejects evaporative drying type ink (for example, solvent ink, water-based ink, etc.) fixed to the medium 50 by evaporating the solvent, for example. In this case, as the fixing unit 106, for example, a heater for heating the medium 50 may be used. Further, as the ink, for example, it is conceivable to use ink (for example, ultraviolet curable ink) that is fixed to the medium 50 by irradiation of ultraviolet rays. In this case, for example, an ultraviolet light source may be used as the fixing unit 106.

  The control unit 120 is, for example, a CPU of the printing apparatus 12 and controls the operation of each unit of the printing apparatus 12. In this example, the control unit 120 controls the operation of each unit of the printing apparatus 12 based on, for example, discharge position data received from the RIP device 14. Thereby, for example, ink is ejected to the inkjet head 102 based on the input image to be printed. According to this example, it is possible to appropriately print on the medium 50.

  As described above, in this example, the RIP device 14 functions as a print control unit in the printing system 10. Further, depending on the configuration of the printing system 10, for example, a configuration in which the control unit 120 in the printing device 12 and the RIP device 14 are combined can be considered as a printing control unit in the printing system 10. Further, in a modified example of the configuration of the printing system 10, for example, some of the functions of the RIP device 14 described above may be executed by the control unit 120 in the printing device 12. Conversely, some of the functions of the control unit 120 may be executed by the RIP device 14. In this example, the printing system 10 includes a printing device 12 and a RIP device 14 which are a plurality of devices. Further, in a modified example of the configuration of the printing system 10, for example, the printing system 10 may be configured with only one device. In this case, for example, it is conceivable to configure the printing system 10 by the printing apparatus 12 further having the function of the RIP apparatus.

  Next, the printing operation performed in the printing system 10 will be described in more detail. As described above, when printing is performed by the printing apparatus 12 of this example, the minimum dot interval in the width direction of the medium 50 in the arrangement of the ink dots formed on the medium 50 is the inkjet head 102. Is equal to the interval py of the nozzles 112 at As a result, the printing resolution in the width direction of the medium 50 is equal to the resolution corresponding to the nozzle interval py.

  In this case, the printing resolution in the scanning direction (the conveyance direction of the medium 50) is a resolution corresponding to the minimum interval (dot interval) of ink dots formed on the medium 50 by one nozzle 112. More specifically, in the printing apparatus 12 of this example, the scan driving unit 104 supplies, for example, a drive signal that changes at a preset ejection cycle to each nozzle 112 of the inkjet head 102. In this case, the drive signal is a signal for causing each nozzle 112 to eject ink. Further, in this case, at each timing during the scanning operation, the scan driving unit 104 supplies a drive signal to the nozzle 112 selected based on the ejection position data, and causes the nozzle 112 to eject ink. With this configuration, for example, ink can be appropriately ejected to each position of the medium 50 according to the image to be printed.

  In this case, the minimum period when ink is continuously ejected from each nozzle 112 in the inkjet head 102 is equal to the period of the drive signal. Further, the ink ejected at the minimum cycle lands on the medium 50 at a position separated by a distance corresponding to the transport amount of the medium 50 between them. Therefore, the dot interval of the ink formed on the medium 50 is equal to the conveyance amount of the medium 50 in the period corresponding to the cycle of the drive signal.

  FIG. 2 is a diagram for explaining the arrangement of the ink dots 202 formed on the medium 50 by the scanning operation. FIG. 2A schematically shows an example of how the dots 202 are formed by the scanning operation.

  In FIG. 2, for convenience of explanation, an example of the arrangement of ink dots formed on the medium is illustrated for the case where 100% solid printing set in advance on the medium is performed. On the other hand, at the time of actual printing, for example, it is conceivable to form ink dots only at positions necessary for expressing an image to be printed without necessarily forming ink dots at all positions. In FIG. 2, for convenience of illustration, a state in which the ink dots 202 are accurately formed at the designed ejection positions set in accordance with the printing resolution is schematically shown. However, during actual printing, the landing position where the ink lands may be deviated from the designed position within an allowable range corresponding to the accuracy required for printing. In FIG. 2, each ink dot 202 is illustrated in a size that does not contact the adjacent dot 202. However, at the time of actual printing, the size (diameter) of the dots 202 may be a size that contacts the adjacent dots 202. In addition, the manner of illustration of the arrangement of the ink dots as described above is the same or similar in other drawings that will be described in detail later. 2A shows an example of how the dots 202 are arranged when all the nozzles 112 (see FIG. 1) in the inkjet head 102 (see FIG. 1) are normal nozzles.

  As described above, in this example, the printing apparatus 12 (see FIG. 1) performs printing by the single pass method while moving the medium 50 in the transport direction. In this case, the printing resolution in the width direction of the medium 50 is equal to the resolution corresponding to the nozzle interval py. Therefore, for example, when performing solid printing that ejects ink to all ejection positions on the medium 50, the ink dots 202 on the medium 50 are equal to the nozzle interval py in the width direction of the medium 50. They will be lined up at regular intervals.

  In this case, the printing resolution in the scanning direction is determined according to the period of the drive signal and the conveyance speed of the medium 50 as described above. In this case, the resolution in the scanning direction is determined according to the cycle of the drive signal and the conveyance speed. For example, when performing solid printing or the like, the dot in the scanning direction is arranged for the arrangement of the ink dots 202 formed on the medium 50. The interval 202 is determined accordingly. More specifically, in this example, the interval (minimum interval) between the dots 202 in the scanning direction is a predetermined interval px. The interval px is an example of a scanning direction dot interval that is a dot interval in the scanning direction corresponding to the printing resolution. Further, in this case, with respect to the operation of each nozzle 112, for example, it can be considered that a plurality of dots 202 can be formed side by side in the scanning direction at an interval px.

  When all the nozzles 112 in the inkjet head 102 are normal nozzles, dots 202 arranged at a minimum interval corresponding to the printing resolution can be formed on the medium 50 as shown in the drawing. However, when any one of the nozzles 112 in the inkjet head 102 is an abnormal nozzle, the dot 202 is not formed at a position where ink should be ejected from the nozzle 112, and the printing result is affected.

  FIG. 2B is a diagram schematically showing the influence of abnormal nozzles, and shows an example of how the ink dots 202 are formed when a scanning operation is performed in a state where there are abnormal nozzles in the nozzle row. . More specifically, in FIG. 2B, in the case where the nozzle 112 shown as an abnormal nozzle in the drawing is a non-ejection nozzle, the inkjet is set with the same setting as that shown in FIG. An example of the result of ejecting ink to each nozzle 112 of the head 102 is shown. In this case, each nozzle 112 other than the abnormal nozzles forms a plurality of dots 202 in the transport direction at the same position as that shown in FIG.

  However, when a non-ejection abnormal nozzle is included in the nozzle row of the inkjet head 102, ink is not ejected to the ejection position corresponding to the abnormal nozzle. As a result, white stripes having different states from the surroundings are formed at the discharge positions corresponding to the abnormal nozzles. In this case, the ejection position corresponding to the abnormal nozzle is a position where ink should be ejected from that nozzle. Further, the white stripe is, for example, a stripe that discharges the background color of the medium 50 by being not covered with ink. In this case, the print quality deteriorates due to the influence of the abnormal nozzle.

  In this regard, when there is a discharge characteristic of a non-discharge abnormal nozzle, it is conceivable to compensate (recover) the discharge characteristic of the abnormal nozzle, for example, using another normal nozzle. In this case, for example, the amount of ink ejected onto the medium 50 may be adjusted by increasing the amount of ink ejected from normal nozzles adjacent to abnormal nozzles in the nozzle row. In this case, the ink discharge amount is, for example, a discharge amount per unit area on the medium. Further, in this case, for example, when performing solid printing at a high density as in the case of performing solid printing shown in FIG. 2, it is possible to increase only the discharge amount of the normal nozzle adjacent to the abnormal nozzle. It is considered that compensation for the ejection characteristics of the abnormal nozzle can be performed with a certain degree of accuracy.

  However, in actual printing, it is necessary to perform printing at various densities in addition to solid printing. In this case, for example, simply increasing the discharge amount of the normal nozzle may make the influence of the compensation operation conspicuous, making it impossible to appropriately compensate the discharge characteristics. On the other hand, in this example, with regard to the density of the ink ejected to each position of the medium 50, the density of the ink is adjusted by paying attention to the density for each predetermined unit area set in advance. This also compensates for the ejection characteristics of the abnormal nozzle. Therefore, the compensation of the ejection characteristics of the abnormal nozzle performed in this example will be described in more detail below. First, for convenience of explanation, setting of unit areas and ink density for each unit area will be described.

  FIG. 3 is a diagram for explaining the ink density management performed in this example. FIG. 3A shows an example of the relationship between the arrangement of the dots 202 formed on the medium 50 and the unit area. FIG. 3B is a diagram showing an example of the unit region 212 set in this example, and shows a range of the unit region 212 by enlarging a part of the arrangement of the dots 202 shown in FIG. Shown with a dashed line. In this case, the unit region 212 is an example of a unit region in the scanning direction.

  In this example, the RIP device 14 (see FIG. 1) generates ejection position data in accordance with the position of each nozzle 112 in the inkjet head 102 (see FIG. 1) of the printing device 12. In this case, the RIP device 14 manages the plurality of nozzles 112 in the inkjet head 102 by dividing them into a plurality of groups 302. In this case, each of the plurality of nozzles 112 is included in any one group 302. Each of the plurality of groups 302 includes a plurality of nozzles 112 that are continuously arranged in the nozzle row direction. More specifically, in the case shown in the figure, each group 302 includes two nozzles 112 arranged adjacent to each other so that two nozzles 112 form a set. Thereby, the RIP device 14 handles, for example, a plurality of nozzles 112 (two nozzles arranged adjacent to each other) continuously arranged in the nozzle row direction as one set (lumb).

  Further, the RIP device 14 further divides a region where ink is ejected by the plurality of nozzles 112 included in the group 302 during the scanning operation into a plurality of regions for each predetermined unit width range 304, and manages the region. To do. In this case, the unit width range 304 is a width range including a plurality of ink dots 202 arranged in the scanning direction at an interval px (scanning direction dot interval) of the dots 202 in the scanning direction. More specifically, as shown in the figure, the unit width range 304 is a width range including two dots 202 arranged in the scanning direction at an interval px.

  Also, in this case, among the ink dots 202 formed by the plurality of nozzles 112 included in one group 302, each region including the dots 202 included in the width of the unit width range 304 is the ink density management. It becomes a unit area 212 used for. More specifically, in this case, for example, as shown in FIG. 3B, two dots 202 are arranged in the width direction (Y direction) of the medium 50, and two in the scanning direction (X direction). A range where the dots 202 are arranged is a unit region 212. Then, the RIP device 14 sets the amount of ink ejected to each position of the medium 50 by managing the unit area density which is the ink density of each unit area 212.

  Here, when printing is performed by the inkjet method, the resolution corresponding to the minimum interval of the ink dots 202 formed on the medium 50 is usually considered as the printing resolution. Therefore, the resolution of printing performed in this example is a resolution in which the resolution in the width direction of the medium 50 corresponds to the interval py of the nozzles 112, and the resolution in the scanning direction is the interval px (dot interval in the scanning direction dot interval) in the scanning direction. ).

  In this example, by setting the unit area 212 as described above, in addition to the general printing resolution, the corresponding resolution of the unit area 212 (the resolution of the unit area) can also be considered. More specifically, for example, when attention is paid to the arrangement of the plurality of unit areas 212 set on the medium 50, the interval between the unit areas 212 in the width direction and the scanning direction of the medium 50 is the unit area 212 in each direction. Is determined according to the number of dots 202 included. For example, in the drawing, since each group 302 includes two nozzles 112, the interval Dy of the unit regions 212 in the width direction of the medium 50 is twice the nozzle interval py. As a result, the resolution of the unit area in the width direction of the medium 50 is ½ of the printing resolution considered in dot units. Similarly, since the unit width range 304 is a width including two dots 202, the interval Dx between the unit regions 212 in the scanning direction is twice the dot interval px in the scanning direction. As a result, the resolution of the unit area in the scanning direction is ½ of the printing resolution considered in dot units.

  Further, as described above, in this example, each unit region 212 is a region where a plurality of dots 202 can be formed. In this case, the fact that a plurality of dots 202 can be formed in the unit region 212 means that a plurality of dots 202 can be formed in accordance with, for example, the ink density set in the unit region 212. In this case, for example, the ink density in the unit region 212 can be changed by changing the number of ink dots 202 formed in one unit region 212.

  FIG. 4 is a diagram for explaining the ink density in the unit region 212 in more detail. 4A to 4E show examples of how to form the ink dots 202 in the unit region 212 when the ink density set in the unit region 212 is changed variously. FIG. 4 shows an example in which only one type of ink volume (volume) is discharged from one nozzle to one discharge position for convenience of illustration and description. In this case, regarding the density of the ink in the unit area 212, the density when the ink dots 202 are formed at all the ejection positions in the unit area 212 is considered to be 100%. Further, the case where the volume of ink discharged from one nozzle to one discharge position is made variable in a plurality of stages will be described in more detail later.

  More specifically, FIGS. 4A to 4E show examples of how the dots 202 are formed when the number of ink dots 202 formed in the unit region 212 is 0 to 4. FIG. For example, FIG. 4A shows how to form the dots 202 when the number of dots 202 in the unit region 212 is zero. In this case, since the ink dots 202 are not formed in the unit region 212, the ink density in the unit region 212 is 0%. Further, in this case, since the state of all the ejection positions in the unit region 212 is the same, the method of forming the dots 202 for setting the ink density to 0% is as shown in FIG. There is only one type (state in which the dots 202 are not formed).

  FIG. 4B shows how the dots 202 are formed when the number of dots 202 in the unit area 212 is one. In this case, since one ink dot 202 is formed in the unit region 212, the ink density in the unit region 212 is 25%. In this case, the ink dot 202 may be formed by selecting one of the four ejection positions. Therefore, there are four types of dot 202 formation methods for setting the ink density to 25%, as shown in FIG.

  FIG. 4C shows how the dots 202 are formed when the number of dots 202 in the unit area 212 is two. In this case, since the two ink dots 202 are formed in the unit region 212, the ink density in the unit region 212 is 50%. In this case, the ink dots 202 may be formed by selecting any two of the four ejection positions. Therefore, there are six ways of forming the dots 202 for setting the ink density to 50%, as shown in FIG.

  FIG. 4C shows how the dots 202 are formed when the number of dots 202 in the unit area 212 is three. In this case, since the three ink dots 202 are formed in the unit area 212, the ink density in the unit area 212 is 75%. In this case, the ink dot 202 may be formed by selecting any three of the four ejection positions. Therefore, there are four types of dot 202 formation methods for setting the ink density to 75%, as shown in FIG.

  FIG. 4D shows how the dots 202 are formed when the number of dots 202 in the unit area 212 is four. In this case, since the four ink dots 202 are formed in the unit region 212, the density of the ink in the unit region 212 is 100%. In this case, it is necessary to form all the dots 202 among the four ejection positions. Therefore, as shown in FIG. 4D, only one type of dot 202 is formed to make the ink density 100%.

  Here, when printing is performed by an inkjet method, an observer who observes a printed image does not normally recognize individual ink dots 202, but a plurality of images within a range determined according to human visual sensitivity. The state averaged among the dots 202 is visually recognized. For example, when the printing resolution (resolution corresponding to the minimum interval of the dots 202) is about 600 dpi or more, the state of the individual ink dots 202 is usually only observed by a normal observation method. It is difficult to recognize. Therefore, in this case, for example, even if the arrangement of the dots 202 in the unit region 212 is different, it is generally considered that the same state is recognized if the ink density in the unit region 212 is the same. In particular, when the resolution of the unit area 212 described above is about 300 dpi or more, even if the arrangement of the dots 202 in the unit area 212 is different, the influence on the print quality is considered to be small. In this example, the discharge characteristics of the abnormal nozzle are compensated using such characteristics. More specifically, in this case, regarding the ink density in each unit region 212 determined according to the image to be printed, for example, it is necessary to eject ink using only normal nozzles without using abnormal nozzles. To achieve the correct density.

  Further, for such a compensation operation, for example, for the unit region density which is the density of the ink in the unit region 212, a nozzle 302 for ejecting ink to each unit region 212 is included in the group 302 (see FIG. 3). The unit region density when all the nozzles are normal nozzles is defined as a normal region density, and can be considered as an operation of adjusting the unit region density to be close to the normal region density. In this case, for example, when any nozzle included in any group 302 is an abnormal nozzle, at least one normal nozzle included in the group 302 including the abnormal nozzle causes ink to be ejected into the unit region 212. By increasing the ejection amount, the ink density in the unit area 212 corresponding to the group 302 is brought close to the normal area density. Further, in this case, increasing the amount of ink ejected by the normal nozzles into the unit region 212 means, for example, that the amount of ink ejected is greater than the amount of ink ejected when all the nozzles in the group 302 are normal nozzles. To make it bigger. Further, in this example, such a compensation operation is performed by generating the discharge position data so that the discharge amount is as described above when generating the discharge position data in the RIP device 14 (see FIG. 1).

  In this case, increasing the amount of ink ejected by the normal nozzles into the unit region 212 means, for example, increasing the total amount of ink ejected into the unit region 212 by one normal nozzle. For this reason, when there is a margin in the discharge position set in the unit region 212, it is conceivable to increase the discharge amount by increasing the discharge positions for discharging ink from one normal nozzle. More specifically, when the ink density of the unit region 212 is set to a relatively low density (for example, 50% or less) as shown in FIGS. 4B and 4C, for example, the group 302 corresponding to the unit region 212 is used. Among these nozzles, only a part of the nozzles can be used to ensure the necessary ink density. Therefore, in such a case, ink can be ejected into the unit region 212 using only normal nozzles without using abnormal nozzles included in the group 302. In this case, the operation of such a normal nozzle can be considered as an example of an operation for increasing the amount of ink ejected into the unit region 212, for example.

  On the other hand, for example, as shown in FIGS. 4D and 4E, when the ink density in the unit region 212 is increased, in order to ensure the necessary ink density, It will be necessary to use a nozzle. In this case, considering only the method of forming the dots 202 shown in FIG. 4, for example, when any nozzle in the group 302 is an abnormal nozzle, the necessary ink density is obtained only with other normal nozzles. It cannot be secured.

  In this regard, from the viewpoint of reducing the influence of the abnormal nozzle, even if the ink density in the unit area 212 is not completely matched with the normal area density, if it is close to the normal area density, a certain amount It is also possible to compensate for the ejection characteristics of the abnormal nozzle with accuracy. Therefore, also in this case, it is possible to compensate for the ejection characteristics of the abnormal nozzles by performing adjustment so that the ejection positions for ejecting ink with normal nozzles are as large as possible. However, in order to compensate for the ejection characteristics of the abnormal nozzle with higher accuracy, it is preferable that the ink density in the unit area 212 is made closer to the normal area density. Therefore, in this example, by further changing the volume (volume) of ink ejected from one normal nozzle to one ejection position, the ejection characteristics of the abnormal nozzle can be compensated with higher accuracy.

  FIG. 5 is a diagram for explaining the ejection characteristic compensation performed in this example in more detail. FIG. 5A shows an example of the volume of ink ejected from one nozzle to one ejection position. In this case, the capacity of ink ejected from one nozzle to one ejection position is the designed ink capacity when the nozzle is a normal nozzle.

  In this example, each nozzle in the inkjet head 102 (see FIG. 1) discharges ink to a discharge position set according to the printing resolution. In this case, as for the volume of ink ejected to one ejection position, a plurality of different types of volumes can be set. More specifically, in this example, each nozzle can eject ink with at least two types of capacities. One of these two types of capacities is a preset standard capacity. In this case, the standard capacity is a capacity when forming dots of a predetermined normal size (N size) ink. Also, the normal size dots are, for example, dots of ink formed other than when the ejection amount is increased to compensate for ejection characteristics.

  The other of the two types of capacities is a capacity when forming dots of L size ink larger than the normal size. The L-sized dots are ink dots that are formed when the ejection amount is increased to compensate for ejection characteristics. In this example, the capacity of the ink corresponding to the L size dot is about twice the capacity of the ink corresponding to the normal size (N size) dot. In this case, the L-size dots can be considered as large-size dots (compensation large balls) for compensating the ejection characteristics.

  When configured in this manner, for example, the amount of ink ejected into the unit region 212 by the normal nozzle can be increased without increasing the ejection position at which ink is ejected by the normal nozzle in the unit region 212. More specifically, in this case, for example, all the nozzles in the same group 302 (see FIG. 3) at least at any timing when ink is ejected during the scanning operation for normal nozzles that increase the ink ejection amount. It is conceivable that the capacity is larger than the capacity when the nozzle is a normal nozzle. With this configuration, for example, even when the ink density of the unit region 212 is increased, the ejection characteristics of the abnormal nozzle can be compensated more appropriately.

  More specifically, in this case, for example, by setting some of the ink dots formed in the unit region 212 to L size dots, only the part of the nozzles in the group 302 is used. It becomes possible to increase the density of the ink. FIGS. 5B and 5C show examples of how to form dots when the ink density of the unit region 212 is increased. FIG. 5B shows an example of how to form dots when the ink density in the unit region 212 is 75%. In this case, only one of the two nozzles in the group 302 used for forming one unit region 212 is used. In this case, by forming one normal size dot 202 and one L size dot 202, an amount of ink corresponding to three normal size dots 202 is formed in the unit region 212. To discharge.

  FIG. 5C shows an example of how dots are formed when the ink density in the unit region 212 is 100%. Also in this case, only one of the two nozzles in the group 302 used for forming one unit region 212 is used. In this case, by forming two L-size dots 202, an amount of ink corresponding to four normal-size dots 202 is ejected into the unit region 212.

  According to this example, for example, when the ink density of the unit region 212 is increased, even if any nozzle in the group 302 is an abnormal nozzle, the ink ejection amount required only by other normal nozzles Can be secured appropriately. Thereby, for example, the ejection characteristics of the abnormal nozzle can be compensated more appropriately with higher accuracy.

  Here, as described above, in this example, the capacity of the ink corresponding to the L size dots is about twice the capacity of the ink corresponding to the normal size dots. However, the relationship between the ink capacities does not necessarily have to be strictly doubled, and may be close to double as long as necessary print quality can be ensured. More specifically, the capacity of the ink corresponding to the L size dots is, for example, about 1.5 to 2.5 times, preferably 1.8 to 2 times the capacity of the ink corresponding to the normal size dots. It is conceivable to make it about 2 times. In this case, for example, in consideration of how the ink spreads on the medium 50, it is preferable that the area of the L-sized dots is about twice that of the normal-sized dots.

  In this case, the adjustment for bringing the unit region density close to the normal region density is not necessarily made to coincide with each other, but may be made sufficiently close within a range in which necessary printing quality can be ensured. Therefore, for the adjustment to bring the unit area density closer to the normal area density, for example, by adjusting the ink discharge amount of the normal nozzle to be larger, the unit area density and the normal area density than when the adjustment is not performed. It can also be considered to reduce the difference from the time-domain density. In this case, it is preferable to adjust the difference between the unit region density and the normal region density so as to fall within a preset allowable range, for example.

  As described above, according to this example, for example, it is possible to appropriately compensate for the ejection characteristics of the abnormal nozzle. In this case, the ink density (unit area density) for each unit area 212 is adjusted so as to be close to the normal density (normal area density). It becomes possible to compensate for the ejection characteristics of the nozzle. In addition, for example, when printing an image including a halftone portion with various gradations, for example, instead of simply performing solid printing, a portion where ink is discharged by a nozzle with an increased discharge amount is conspicuous. This can be prevented appropriately. In this case, an image including a halftone portion of various gradations is an image having different colors and color densities depending on the position on the medium, for example. Therefore, according to this example, for example, even when there is an abnormal nozzle, printing can be performed more appropriately.

  Here, in the above, for convenience of explanation, with regard to the configuration of the printing apparatus 12 (see FIG. 1), focusing on only one inkjet head 102 (see FIG. 1) corresponding to one color ink, the configuration and operation I explained. However, in the actual printing apparatus 12, it is conceivable to perform color printing using different colors of ink. In this case, the printing apparatus 12 includes a plurality of inkjet heads 102 corresponding to a plurality of colors of ink. Therefore, the configuration of the printing apparatus 12 and the printing operation when performing printing using a plurality of colors of ink will be described in more detail below.

  6 and 7 are diagrams illustrating the configuration of the printing apparatus 12 and the printing operation when printing is performed using a plurality of colors of ink. FIG. 6A shows an example of the arrangement of a plurality of ink jet heads 102 y to 102 k used in the printing apparatus 12. In FIG. 6A, only the arrangement of the inkjet heads 102y to 102k is illustrated for the configuration of the printing apparatus 12 for convenience of illustration. Also in this case, the printing apparatus 12 further includes a configuration necessary for a printing operation, for example. More specifically, the printing apparatus 12 may further include various configurations that are the same as or similar to the configuration illustrated in FIG. In the configuration shown in FIG. 6A, as each of the inkjet heads 102y to 102k, for example, an inkjet head that is the same as or similar to the inkjet head 102 in the configuration shown in FIG.

  When performing printing (color printing) using a plurality of colors of ink in the printing apparatus 12, printing is performed using a plurality of inkjet heads 102y to 102k as shown in the drawing. More specifically, for example, when printing in full color, Y (yellow) ink jet heads 102y and C (cyan) are used as ink jet heads that eject inks of basic colors (process colors) of color expression. It is conceivable to use the inkjet head 102c for color, the inkjet head 102m for M (magenta) color, and the inkjet head 102k for K (black) color. In this case, these inkjet heads 102y-k are arranged with their positions in the transport direction being shifted from each other along the transport direction of the medium 50, as shown in the figure. If comprised in this way, the ink of each color can be appropriately discharged with the inkjet heads 102y-k with respect to each position of the conveyed medium 50, for example. Thereby, color printing on the medium 50 can be appropriately performed.

  In this case, it is preferable to set the arrangement order of the inkjet heads 102y to 102k according to, for example, the characteristics of the ink to be used. More specifically, when evaporating and drying ink such as solvent ink is used, for example, as described with reference to FIG. 1, from the upstream side to the downstream side in the conveyance direction of the medium 50, FIG. As shown, the inkjet head 102y, the inkjet head 102c, the inkjet head 102m, and the inkjet head 102k are preferably arranged in this order. Further, for example, when ultraviolet curable ink (UV ink) or the like is used, the inkjet head 102k, the inkjet head 102m, the inkjet head 102c, the inkjet head from the upstream side to the downstream side in the conveyance direction of the medium 50, contrary to the above. It is preferable to arrange them in the order of 102y.

  Also in this case, when there is an abnormal nozzle among the nozzles of each of the ink jet heads 102y to 102k, the ejection characteristics of the abnormal nozzle are the same as or similar to those described with reference to FIGS. Can be compensated for. More specifically, in this case, it can be considered that the plurality of nozzles in each of the inkjet heads 102y to 102k are divided into a plurality of groups 302 and managed. Further, in this case, for example, the ink density in the area printed by each of the inkjet heads 102y to 102k in the scanning operation is managed in association with each group 302 or unit area. With this configuration, for example, even when an abnormal nozzle is present in any of the inkjet heads 102y to 102k, the ejection characteristics of the abnormal nozzle can be appropriately compensated.

  In addition, when printing is performed using a plurality of inkjet heads 102y to 102k, it is preferable that the method of dividing the unit area used as a reference for managing the ink density is different for each inkjet head. With this configuration, for example, the position of the unit region can be appropriately changed depending on the color of the ink. In this case, for example, it is possible to make a difference for each ink color with respect to the result of halftone processing performed in the RIP processing (for example, designation of a position where dots are formed). Therefore, with this configuration, for example, the method of forming ink dots on the medium can be made different for each ink color.

  Also, more specifically, when the unit area division method is the same for all colors, for example, when expressing a bright color, designation of a position for forming an ink dot (or a position for not forming a dot) It tends to be the same for all colors. In this case, for example, dots of a plurality of colors are overlapped in a state where dots of other surrounding ink are not formed, and it is considered that graininess is likely to occur in the printing result. On the other hand, when configured as described above, differences in color are likely to occur at positions where ink dots are formed. Therefore, if comprised in this way, the printing which suppressed the granular feeling can be performed more appropriately, for example. Thereby, for example, printing with higher quality can be performed. In this case, the position of the unit for compensating the ejection characteristics of the abnormal nozzle can also be shifted for each ink color. Therefore, with this configuration, it is possible to more appropriately prevent the printing result from being affected by the compensation of the ejection characteristics, for example.

  Further, in this case, for example, the position of the group 302 to be set and the position of the boundary of the unit region in the scanning direction between a part of the ink jet heads 102y to 102k and the other ink jet heads are shown in FIG. As shown in FIG. 7B and FIG. FIG. 6B shows an example of how to divide the group 302 in each of the inkjet heads 102y to 102k. FIG. 7A shows an example of how to set the position of the boundary of the unit area.

  More specifically, in this case, the group 302 is divided in the same way for Y-color and M-color inkjet heads as shown in FIG. 6B, for example. Also, the same separation is used for the C-color and K-color inkjet heads. Then, the position of the boundary of the group 302 in the nozzle row direction is made different for the Y color and M color division methods and the C and K color division methods.

  In addition, as to how to divide the area where ink is ejected from a plurality of nozzles included in one group 302 into a plurality of unit areas 212, for example, as shown in FIG. By dividing, the same separation method is used for the Y-color and C-color inkjet heads. Further, the same division is used for the M-color and K-color inkjet heads. Then, the positions of the boundaries of the unit areas in the scanning direction are made different for the Y color and C color division methods and the M and K color division methods.

  When the boundary of the group 302 and the boundary of the unit area in the scanning direction are set in this way, the position of the unit area set for each color is, for example, as shown in FIG. Everything will be different. FIG. 7B is a diagram illustrating an example of a difference in position where the unit areas of each color are set. The area where nine dots 202 are formed on the medium 50 and the unit area set for each color. An example of the relationship is shown. Further, the four diagrams in FIG. 7B show unit regions for each color formed in the range by paying attention to nine dots 202 at the same position. For the unit areas for each color, one unit area set so as to be completely included in this range is shown. More specifically, the upper left diagram in FIG. 7B shows an example of the unit region 212y for Y color. The figure on the upper right side shows a unit area 212c for C color. The lower left diagram shows an example of the unit area 212m for M color. The lower right diagram shows a unit area 212k for K color. If comprised in this way, the position of the unit area | region for each color can be appropriately varied depending on the color of the ink.

  In the configuration shown in FIG. 7B, among the overlapping of the unit areas between the colors used for printing, the overlapping of the C-color unit area 212c and the M-color unit area 212m is the smallest. Is set to In this case, the overlap of unit areas between colors overlaps when focusing on one unit area for a certain color and one unit area for another color that partially overlaps the unit area. It is a part.

  Here, when printing is performed using YMCK inks, the Y ink is brighter than the other colors. For this reason, it is considered that the Y-color ink dots are unlikely to change in brightness even if they overlap with the other color ink dots. Further, the K color ink is a dark color by itself. For this reason, in the case of K ink dots, even if they overlap with other color ink dots, it is considered that the change in brightness hardly occurs. On the other hand, for example, in the case of a combination of C color ink and M color ink, it is considered that the change in brightness caused by the ink dots being formed in the same ejection position is increased. As a result, when the C ink dots and the M ink dots overlap at the same ejection position, it is considered that the influence on the graininess is particularly large.

  On the other hand, when configured as described above, the C-color unit region 212c and the M-color unit region 212m are shifted in the diagonal direction of the unit region, so that the C-color unit region 212c. And the unit area 212m for M color can be reduced. Therefore, if comprised in this way, a granular feeling etc. can be suppressed more appropriately and high quality printing can be performed more appropriately, for example.

  As can be seen from the above description, when generating the ejection position data, it is preferable to generate the data so that the C color ink and the M color ink do not overlap as much as possible at the same ejection position. In this case, for example, at the time of binarization processing for determining the ejection position, it is conceivable to perform processing by designating the position selection method in each of the width direction and the scanning direction of the medium. If comprised in this way, a granular feeling can be suppressed more appropriately, for example. Depending on the quality required for printing, the unit area 212 may be set at the same position on the medium for all colors used for printing. If constituted in this way, management of unit field 212 can be performed more easily, for example.

  Next, a modified example of the printing operation performed in the printing system 10 will be described. In the above, with respect to the configuration in which the volume (volume) of ink ejected to one ejection position by one normal nozzle is variable, the case where two types of capacities can be set using FIG. I explained. However, in a modified example of the printing operation performed in the printing system 10, it is also conceivable to change the ink capacity in more stages.

  FIG. 8 is a diagram for explaining a further modification example regarding the printing operation and the like. FIGS. 8A and 8B are diagrams for explaining the case where the setting of the ink capacity is made variable in a plurality of stages. FIG. 8A shows an example of the capacity of ink ejected from one nozzle to one ejection position when the ink capacity setting is variable in three stages. In this case, each nozzle in the ink jet head can eject ink with three types of capacities S, M, and L as shown in the drawing. Further, in this case, each nozzle in the inkjet head 102 forms ink dots of three types of sizes on the medium 50 according to the respective capacities of the ink. More specifically, among these three types of capacities, the smallest capacity is a capacity in the case where dots of small size (S size) ink are formed on the medium 50. The second smallest capacity is a capacity when forming medium-sized (M size) ink dots on the medium 50. The largest capacity is a capacity when forming a large size (L size) ink dot on the medium 50. In this case, the capacities of these three types of inks may be capacities used for purposes other than the compensation of the ejection characteristics. When configured in this way, for example, the ink density for each unit region can be set in more detail. Even when there are abnormal nozzles, the ink density in the unit area can be adjusted appropriately by increasing the discharge amount of other normal nozzles. This also makes it possible to perform high-quality printing more appropriately.

  In order to compensate the ejection characteristics with higher accuracy, it may be possible to form dots of a larger size (compensation large balls) for compensating the ejection characteristics. In this case, for example, in addition to the three types of capacities shown in FIG. 8A, it may be possible to further set the ink capacities for forming such large-sized dots. FIG. 8B shows an example of the capacity of ink ejected from one nozzle to one ejection position when forming a large-sized dot for compensating the ejection characteristics. In this case, each nozzle in the ink jet head 102 can eject ink with a larger capacity indicated by LL in the drawing in addition to the three types of capacity shown in FIG. The large capacity is a capacity when forming an extra large size (LL size) dot larger than a large size (L size) ink dot. If constituted in this way, it becomes possible to form dots of ink of more various sizes, for example. Thereby, for example, the discharge characteristics can be compensated more appropriately with higher accuracy.

  In the above description, the size of the unit area has been described mainly in the case where two ink dots in the width direction and the scanning direction of the medium 50 are arranged to include a total of four dots. . However, the size of the unit area is not limited to the above, and may be changed according to the required print quality.

  FIG. 8C shows a modified example of the configuration of the unit region 212. In this case, the unit region 212 is set to a size including four dots 202 in total, in which four ink dots 202 in the width direction and the scanning direction of the medium 50 are arranged. Even in such a configuration, for example, the same or similar to the case described above, the ink density is adjusted by paying attention to the ink density in the unit region 212 unit. If an abnormal nozzle exists, the ink density in the unit area 212 is brought close to the normal area density by increasing the ejection amount of the normal nozzle included in the same group as the abnormal nozzle. This also compensates for the ejection characteristics of the abnormal nozzle, for example.

  Further, for example, as shown in FIG. 8C, when a unit region 212 having a size including many ink dots 202 is used, a normal nozzle that increases the ejection amount is selected according to the position of the abnormal nozzle. It is preferable to More specifically, for example, when a larger ink dot 202 is formed by increasing the discharge amount of a normal nozzle, if a large dot is formed in a portion away from the position where the dot 202 should originally be formed by an abnormal nozzle. In some cases, an unintended bias occurs in the ink density distribution in the unit region 212, and the influence of compensation may be noticeable. In addition, for example, if the ink density near the boundary with the adjacent unit region 212 is increased, the boundary portion may be conspicuous. Therefore, when compensating the ejection characteristics of the abnormal nozzle, the ejection amount is set when the dot 202 is formed by the normal nozzle at a position close to the position where the dot 202 should originally be formed by the abnormal nozzle (for example, the adjacent ejection position). It is preferable to enlarge it. In addition, when the unit region 212 having a size including many ink dots 202 is used, for example, when ink is ejected to a plurality of ejection positions in the unit region 212, the ink ejection amount by the normal nozzle is increased. Etc. are also conceivable. In this case, for example, it is preferable to adjust the ejection amount so that the density of the ink near the position where the dot 202 should originally be formed by the abnormal nozzle is higher.

  When setting the unit areas 212 of various sizes, the number of dots 202 arranged in the width direction of the medium 50 is determined by the number of nozzles included in each group set in the inkjet head. Further, the number of dots 202 arranged in the scanning direction is determined according to a preset unit width range. In this case, for example, the unit width range may be set to a width in which the same number of dots 202 as the number of nozzles included in one group are arranged in the scanning direction. Further, according to the required printing quality, the setting of the operation of the printing apparatus 12 (see FIG. 1), etc., for the unit width range, for example, a number of dots 202 different from the number of nozzles included in one group are scanned. You may set to the width | variety arranged in a direction.

  Further, the size of the unit area 212 is preferably determined according to the resolution of printing performed in the printing apparatus 12, for example. In this case, the printing resolution is a resolution corresponding to the minimum interval of the ink dots 202 formed on the medium, as described above. Further, as described above, when the ink density is adjusted using the unit region 212, the resolution of the unit region 212 can be considered in addition to the resolution of the printing. In this case, it is preferable to set the resolution of the unit area 212 to a certain level (for example, 300 dpi or more) in order to make the influence of the compensation of the ejection characteristics inconspicuous.

  In this case, for example, the number of nozzles included in each group set in the inkjet head is n (n is an integer of 2 or more), and the printing resolution in the width direction of the medium 50 is Ay (dpi). Then, the resolution By of the unit region 212 in the width direction of the medium 50 is Ay / n (dpi). In this case, in order to set the resolution By of the unit region 212 to 300 dpi or more, it is necessary to set the printing resolution Ay in the width direction of the medium 50 to n × 300 dpi or more. More specifically, for example, when n = 2, the printing resolution is preferably 2 × 300 = 600 dpi or more. If comprised in this way, printing with high quality can be performed more appropriately, for example.

  Further, as described above, the ink density in the unit region 212 can be adjusted in a plurality of steps by changing the number of ink dots 202 formed in the unit region 212. . Therefore, the unit region 212 can be considered as a unit capable of expressing gradations with multiple values. In this case, considering the resolution of the unit region 212 as described above, for example, the printing operation performed in the printing apparatus 12 is not configured to express gradation in dot units, but is multi-valued in unit units 212 units. It can also be considered as an operation for expressing the gradation. In this case, the printing apparatus 12 can be considered as a multi-value printer that performs printing at the resolution of the unit area 212, for example. When the operation of the printing apparatus 12 is considered in this way, it is conceivable that the generation of the ejection position data performed in the RIP apparatus 14 (see FIG. 1) is performed in accordance with the operation of the printing apparatus 12.

  Therefore, an example of processing performed by the RIP device 14 when the printing device 12 is considered as a multi-value printer that performs printing at the resolution of the unit area 212 will be described below. FIG. 9 is a diagram illustrating an example of a detailed configuration of the RIP device 14. When the printing device 12 is considered as a multi-value printer that performs printing at the resolution of the unit area 212, the configuration of the RIP device 14 has a plurality of functions. Shown in blocks. In this case, the RIP device 14 first forms a set gradation image that is a multi-gradation image in accordance with the resolution of the unit region 212, and then generates ejection position data based on the set gradation image. . In addition, as a configuration for performing such an operation, the RIP device 14 includes a gradation image generation unit 152, an ejection position data generation unit 154, a nozzle information storage unit 156, and a pattern storage unit 158.

  Except as described below, the RIP device 14 may have the same or similar characteristics as a known device that performs RIP processing or the like. In the following description, for the sake of convenience of explanation, the printing resolution described above as the general printing resolution is defined as dot resolution. This dot resolution is a resolution corresponding to the minimum interval between dots of ink formed on the medium. Further, the ink ejection position set on the medium according to the dot resolution is defined as a dot position.

  The gradation image generation unit 152 is a processing unit that generates a set gradation image based on the input image. More specifically, in this configuration, the gradation image generation unit 152 generates an image having the same resolution as the resolution of the unit region 212 and a number of gradations larger than 2 as the set gradation image. As the number of gradations, the number of gradations corresponding to the type of ink density that can be adjusted in the unit region 212 is used.

  Here, the type of ink density that can be adjusted in the unit region 212 is, for example, the type of ink density that can be expressed by the difference in the way ink dots are formed in the unit region 212. More specifically, for example, when the number of dots formed in the unit area 212 is variable in the range of 0 to 4 as described above with reference to FIG. Depending on, five types of density can be expressed. For example, when the volume of ink ejected by each nozzle is made variable in a plurality of stages, the density that can be expressed increases depending on the number of stages to be made variable. In this case, the number of gradations corresponding to the type of ink density that can be adjusted in the unit region 212 is not necessarily the same as the number of types of ink density that can be adjusted. It may be less than the number of. More specifically, as the number of gradations, for example, it is conceivable to use a number (for example, a power of 2) that is equal to or less than the number of types of ink density that can be adjusted and that can be easily handled by a computer.

  In this case, the set gradation image can be considered as an image indicating the input image with a resolution lower than the dot resolution, for example. More specifically, for example, an image obtained by converting an input image into a raster image of a predetermined format can be used as the set gradation image. In this case, as the raster image, an image having the resolution of the unit region 212 and the number of gradations is used. Further, as the set gradation image, for example, an image obtained by further performing color separation processing according to the color used for printing may be considered. In this case, the gradation image generation unit 152 generates, for example, a plurality of grayscale images each corresponding to each color used for printing as the set gradation image. Further, as described above, the resolution of the set gradation image is equal to the resolution of the unit region 212. Therefore, each pixel of the set gradation image is associated with one of the unit areas 212. As a result, each pixel of the set gradation image is associated with a plurality of dot positions set in the corresponding unit region 212.

  In this configuration, the discharge position data generation unit 154 generates discharge position data based on the set gradation image. In this case, as the ejection position data, for example, data indicating at least a dot position that causes the inkjet head to eject ink at the time of printing corresponding to the input image is generated. Further, in this case, the discharge position data generation unit 154 generates discharge position data based on the information stored in the nozzle information storage unit 156 so as to compensate the discharge characteristics of the abnormal nozzle. Further, based on the information stored in the pattern storage unit 158, the dot position where ink is to be ejected is determined.

  The nozzle information storage unit 156 is a storage unit that stores information indicating an abnormal nozzle, and stores, for example, the position of the abnormal nozzle in the inkjet head as information indicating the abnormal nozzle. The nozzle information storage unit 156 may further store information indicating a group including the abnormal nozzle in association with the abnormal nozzle. The pattern storage unit 158 is a storage unit that stores a dot selection pattern that is a pattern for selecting a dot position in the unit region 212. In this case, the dot selection pattern is, for example, a pattern that selects at least some dot positions from among a plurality of dot positions associated with the pixels of the set gradation image. Further, the pattern storage unit 158 stores, for example, a dot selection pattern associated with each gradation value included in the number of gradations of the set gradation image. In this case, a plurality of types of dot selection patterns are stored as dot selection patterns corresponding to at least some of the gradation values. More specifically, the pattern storage unit 158 stores, for example, dot selection patterns corresponding to various ink dot formation methods as shown in FIG. In this case, a plurality of patterns corresponding to the same ink density are stored as a plurality of dot selection patterns corresponding to the same gradation value for at least some of the gradation values.

  Also in this case, the pattern storage unit 158 further stores a compensation pattern as a dot selection pattern in order to compensate for the ejection characteristics of the abnormal nozzle. As such a compensation pattern, for example, when any nozzle in the group is an abnormal nozzle, it is conceivable to use a pattern that realizes a predetermined ink density without using the nozzle. In this case, a pattern for increasing the discharge amount of any normal nozzle other than the abnormal nozzle can be suitably used.

  In this case, the ejection position data generation unit 154 selects, for example, one of the dot selection patterns corresponding to the gradation value of each pixel of the set gradation image, and based on the gradation value of each pixel. At least some dot positions are selected from a plurality of dot positions associated with each pixel. Then, by setting the selected dot position as a dot position for causing the inkjet head to eject ink, ejection position data is generated. If comprised in this way, discharge position data can be produced | generated appropriately based on a setting gradation image, for example. In the operation of generating the discharge position data in this way, for example, when any nozzle in the ink jet head is an abnormal nozzle, the discharge position data generation unit 154, for example, applies to the unit region 212 corresponding to the abnormal nozzle. In the processing, a compensation pattern that does not use an abnormal nozzle is selected as a dot selection pattern. And the dot position which makes an inkjet head discharge an ink is selected using the dot selection pattern. If comprised in this way, the compensation of the discharge characteristic of an abnormal nozzle can be performed appropriately, for example.

  In this case, the RIP device 14 supplies the generated ejection position data to the printing device 12. In the printing apparatus 12, the control unit 120 (see FIG. 1) controls the operation of the scanning drive unit 104 (see FIG. 1) based on the ejection position data received from the RIP device 14. Accordingly, the scan driving unit 104 causes the ink jet head 102 (see FIG. 1 to eject ink) based on the ejection position data. With this configuration, for example, the printing operation corresponding to the input image is appropriately performed. Can be executed.

  Further, when the ejection position data is generated in this way, for example, the processing amount of the processing performed by the RIP device 14 is reduced as compared with the case where the RIP processing or the like is performed by a normal method (a known general method). Is also possible. More specifically, when generating the ejection position data as described above, an image having a resolution lower than the dot resolution is generated as the set gradation image generated before the generation of the ejection position data. For example, in this case, as described above, the gradation image generation unit 152 generates an image having a resolution that matches the resolution of the unit region 212 as the set gradation image. Further, the discharge position data generation unit 154 generates dot position discharge position data based on such a set gradation image of resolution.

  In this case, for example, the resolution of the set gradation image in the scanning direction is Bx, and the resolution of the set gradation image in the width direction of the medium is By. When the number of dots arranged in a line is m and the number of dots arranged in the width direction of the medium is n, the resolution Ax of the ejection position data in the scanning direction is m · Bx, and the resolution Ay of the ejection position data in the width direction of the medium Becomes n · By. As described above, the resolution of the set gradation image is lower than the resolution of the ejection position data.

  In this regard, for example, when RIP processing or the like is performed by a normal method, halftone processing or the like is performed at the resolution of the ejection position data. In this case, a process for handling a large number of pixels is required, and thus the required processing amount may be enormous. More specifically, for example, when performing RIP processing at a high resolution (for example, 600 dpi or more), an increase in time required for processing may be a problem.

  On the other hand, when the set gradation image as described above is used, since the resolution is lower than that of the ejection position data, the processing amount necessary for the halftone process or the like can be significantly reduced. In this case, the process of generating the discharge position data in the discharge position data generation unit 154 can be executed by, for example, selecting a dot selection pattern prepared in advance. In this case, it is considered that a large amount of processing is not necessary, for example, when the RIP processing is performed by a normal method. Therefore, with this configuration, for example, the amount of data processing required to generate the ejection position data can be significantly reduced. Thereby, for example, high quality printing can be performed more appropriately.

  Subsequently, supplementary explanations and the like regarding each configuration described above will be given. As described above, the printing apparatus 12 used in the printing system 10 can be considered as, for example, a multi-value printer that performs printing at the resolution of the unit area. In this case, if considered simply, it seems that the print quality is affected by using the resolution of the unit region 212 lower than the dot resolution.

  However, as described in FIGS. 3 and 4 on page 39 of “Practical digital color image design and evaluation” which is a book published by Trikeps, for example, when using a multi-value printer, Can be printed with a gradation reproduction capability equivalent to or higher than that of a binary printer having a higher resolution. When adjusting the ink density in the unit area as described above, for example, a unit area having a size in which two ink dots in the width direction and the scanning direction of the medium are arranged (a unit area having a size of 2 × 2). However, it is possible to express gradations of three or more gradations. Therefore, even when printing is performed as described above, high-quality printing can be appropriately performed if the resolution of the unit region 212 is sufficiently high. The resolution of the unit region 212 is, for example, 300 dpi or more, preferably 600 dpi or more in each of the width direction and the scanning direction of the medium.

  In the above description, the case where a line-type inkjet printer is used as the printing apparatus 12 has been described. However, as the printing device 12, for example, a serial ink jet printer that performs printing with the number of passes set to 1 may be used. Also in this case, high quality printing can be appropriately performed in the same or similar manner as described above.

  Further, the process of generating the ejection position data in the RIP device 14 is not limited to the process described with reference to FIG. 9, and may be performed by the same or similar method as the RIP process of the normal method, for example. In this case, for example, without generating a set gradation image in the middle, for example, halftone processing at dot resolution is performed, and the ejection position data is generated directly from the input image. In this case, for example, a unit region is set for the result of the halftone process, and the ejection characteristics of the abnormal nozzle are compensated. More specifically, in this case, ejection position data that takes into account abnormal nozzles is generated by changing the positions at which ink dots are formed, the dot size, and the like in the unit area corresponding to the abnormal nozzles. In this case, for example, the unit area may be set before the halftone process. In this case, for example, the halftone process is performed under the condition that the abnormal nozzle is not used while compensating the ejection characteristics in the unit region.

  The present invention can be suitably used for a printing system, for example.

DESCRIPTION OF SYMBOLS 10 ... Printing system, 12 ... Printing apparatus, 14 ... RIP apparatus, 50 ... Medium, 102 ... Inkjet head, 104 ... Scanning drive part, 106 ... Fixing means, 112 ... Nozzle, 120 ... Control unit, 152 ... Gradation image generation unit, 154 ... Discharge position data generation unit, 156 ... Nozzle information storage unit, 158 ... Pattern storage unit, 202 ... dot, 212 ... unit area, 302 ... group, 304 ... unit width range

Claims (16)

A printing system that performs printing by an inkjet method,
An inkjet head that ejects ink to a medium;
A scanning drive unit that drives a scanning operation for ejecting ink to the inkjet head while moving the medium relative to the inkjet head in a preset scanning direction, and operations of the inkjet head and the scan driving unit A print control unit for controlling
The inkjet head has a plurality of nozzles arranged at different positions in a nozzle row direction orthogonal to the scanning direction,
During the scanning operation, each of the nozzles can form ink dots on the medium at a scanning direction dot interval that is a dot interval in the scanning direction corresponding to a preset printing resolution,
The print control unit manages the plurality of nozzles in the inkjet head by dividing them into a plurality of groups each including a plurality of the nozzles continuously arranged in the nozzle row direction, and each of the nozzles during the scanning operation. The areas in which ink is ejected by the plurality of nozzles included in the group are divided into scanning direction unit areas each having a width including a plurality of ink dots arranged in the scanning direction at the scanning direction dot interval. Manage the unit area density, which is the density of ink in the scanning direction unit area,
A nozzle within a normal range in which the ejection characteristics of the nozzle are set in advance is defined as a normal nozzle, a nozzle other than the normal nozzle is defined as an abnormal nozzle, and all the nozzles in the group are the normal nozzles. In the case where the unit region density in the case is defined as a normal region density, if any of the nozzles included in any of the groups is the abnormal nozzle, the print control unit includes the abnormal nozzle. The amount of ink discharged by at least one of the normal nozzles included in the group into the scanning direction unit region is set larger than the amount of ink discharged when all the nozzles in the group are the normal nozzles. Thus, the unit area density corresponding to the group is made closer to the normal area density. Stem.   When any of the nozzles included in any of the groups is the abnormal nozzle, the print control unit is preset with a difference between the unit region density corresponding to the group and the normal region density The printing system according to claim 1, wherein the unit region density corresponding to the group is adjusted so as to be within an allowable range. Each nozzle in the inkjet head ejects ink to an ejection position set according to the printing resolution, and a plurality of different types of capacity can be set for the volume of ink ejected to one ejection position. And
When any one of the nozzles included in any of the groups is the abnormal nozzle, the print control unit applies the ink to the group including the abnormal nozzle at least at any timing when ink is ejected during the scanning operation. 3. The volume of ink ejected to at least one of the normal nozzles included is greater than the capacity when all the nozzles in the group are the normal nozzles. Printing system. The interval in the nozzle row direction of the plurality of nozzles in the inkjet head is equal to the dot interval in the nozzle row direction corresponding to the resolution of printing performed in the printing system,
4. The scanning operation according to claim 1, wherein the scanning driving unit drives the scanning operation so that the ink-jet head passes only once over each position on the medium. 5. Printing system. Each of the groups includes n nozzles (n is an integer of 2 or more), which is a preset number,
The printing system according to claim 1, wherein a resolution of printing performed in the printing system is n × 300 dpi or more. A plurality of the inkjet heads that eject inks of different colors;
The print control unit manages the plurality of nozzles in the ink jet head for each color by dividing the plurality of nozzles into groups, and for each ink density in a region to be printed in the scanning operation. Manage in association with the group,
Regarding the position of the group boundary in the nozzle row direction, the position of the group boundary in the inkjet head for any color and the boundary of the group in the inkjet head for any other color The printing system according to claim 1, wherein the position is made different. As the plurality of inkjet heads, the inkjet heads for yellow, magenta, cyan, and black colors are provided,
The position of the group boundary in the magenta inkjet head is different from the position of the group boundary in the cyan inkjet head for the position of the group boundary in the nozzle row direction. The printing system according to claim 6.   In the scanning operation, any one of the boundaries in the scanning direction unit region in the scanning direction when dividing the region in which ink is ejected by the plurality of nozzles included in one group into the plurality of scanning direction unit regions The position of the boundary of the scanning direction unit region corresponding to the ink jet head for the other color is further made different from the position of the boundary of the scanning direction unit region corresponding to the ink jet head for any one of the other colors The printing system according to claim 6 or 7, wherein A printing method for performing printing by an inkjet method,
Using an inkjet head that ejects ink to a medium,
Driving a scanning operation for ejecting ink to the inkjet head while moving the medium relative to the inkjet head in a preset scanning direction;
The inkjet head has a plurality of nozzles arranged at different positions in a nozzle row direction orthogonal to the scanning direction,
During the scanning operation, each of the nozzles can form ink dots on the medium at a scanning direction dot interval that is a dot interval in the scanning direction corresponding to a preset printing resolution,
For the plurality of nozzles in the inkjet head, a plurality of the nozzles arranged continuously in the nozzle row direction are managed by being divided into a plurality of groups, and each of the plurality of nozzles included in the group at the time of the scanning operation. The areas where ink is ejected by the nozzles are divided into scanning direction unit areas that are width areas including a plurality of ink dots arranged in the scanning direction at intervals of the scanning direction dots, and ink in each scanning direction unit area Unit area density, which is the density of
A nozzle within a normal range in which the ejection characteristics of the nozzle are set in advance is defined as a normal nozzle, a nozzle other than the normal nozzle is defined as an abnormal nozzle, and all the nozzles in the group are the normal nozzles. In the case where the unit region density in the case is defined as a normal region density, if any of the nozzles included in any of the groups is the abnormal nozzle, at least any of the groups including the abnormal nozzle By making the amount of ink discharged by the normal nozzle into the unit region in the scanning direction larger than the amount of ink discharged when all the nozzles in the group are the normal nozzles, A printing method, wherein the corresponding unit area density is brought close to the normal area density. A printing apparatus that performs printing by an inkjet method,
An inkjet head that ejects ink to a medium;
A scanning drive unit that drives a scanning operation for ejecting ink to the inkjet head while moving the medium relative to the inkjet head in a preset scanning direction, and operations of the inkjet head and the scan driving unit A print control unit for controlling
The inkjet head has a plurality of nozzles arranged at different positions in a nozzle row direction orthogonal to the scanning direction,
During the scanning operation, each of the nozzles can form ink dots on the medium at a scanning direction dot interval that is a dot interval in the scanning direction corresponding to a preset printing resolution,
The print control unit manages the plurality of nozzles in the inkjet head by dividing them into a plurality of groups each including a plurality of the nozzles continuously arranged in the nozzle row direction, and each of the nozzles during the scanning operation. The areas in which ink is ejected by the plurality of nozzles included in the group are divided into scanning direction unit areas each having a width including a plurality of ink dots arranged in the scanning direction at the scanning direction dot interval. Manage the unit area density, which is the density of ink in the scanning direction unit area,
A nozzle within a normal range in which the ejection characteristics of the nozzle are set in advance is defined as a normal nozzle, a nozzle other than the normal nozzle is defined as an abnormal nozzle, and all the nozzles in the group are the normal nozzles. In the case where the unit region density in the case is defined as a normal region density, if any of the nozzles included in any of the groups is the abnormal nozzle, the print control unit includes the abnormal nozzle. The amount of ink discharged by at least one of the normal nozzles included in the group into the scanning direction unit region is set larger than the amount of ink discharged when all the nozzles in the group are the normal nozzles. Thus, the unit area density corresponding to the group is made closer to the normal area density. Location. A printing system that performs printing by an inkjet method,
An inkjet head that ejects ink to a medium;
An ejection drive unit for ejecting ink to the inkjet head;
A printing control unit that controls operations of the inkjet head and the ejection driving unit;
The print control unit
A processing unit that generates a set gradation image that is an image having a larger number of gradations than 2 that is set in advance, and that generates the set gradation image based on an input image that is input as an image to be printed An image generator;
An ejection position data generating unit that generates ejection position data indicating a position at which the inkjet head ejects ink based on the set gradation data;
The ejection drive unit causes the inkjet head to eject ink based on the ejection position data,
The resolution corresponding to the minimum dot interval in the arrangement of the ink dots formed on the medium by the inkjet head is defined as the dot resolution, and the ink ejection position set on the medium according to the dot resolution When defined as a position, the ejection position data generation unit generates, as the ejection position data, data indicating at least the dot position that causes the inkjet head to eject ink during printing corresponding to the input image,
The gradation image generation unit generates an image indicating the input image at a resolution lower than the dot resolution as the set gradation image,
Each pixel of the set gradation image is associated with a plurality of the dot positions,
The ejection position data generation unit selects at least some of the dot positions from the plurality of dot positions associated with each pixel based on a gradation value of each pixel of the set gradation image. Then, the ejection position data is generated by setting the selected dot position as the dot position that causes the inkjet head to eject ink. A pattern storage unit that stores a dot selection pattern that is a pattern for selecting at least some of the dot positions from the plurality of dot positions associated with the pixels of the set gradation image;
The pattern storage unit stores the dot selection pattern associated with each gradation value included in the number of gradations of the set gradation image,
The printing according to claim 11, wherein the ejection position data generation unit selects the dot position that causes the inkjet head to eject ink based on the dot selection pattern stored in the pattern storage unit. system. The pattern storage unit includes a plurality of types of dot selection patterns as the dot selection patterns corresponding to at least some of the plurality of gradation values included in the number of gradations of the set gradation image. Remember,
For the pixels of the set gradation image having gradation values that are associated with a plurality of types of dot selection patterns, the ejection position data generation unit selects one of the plurality of types of dot selection patterns. The printing system according to claim 12, wherein the printing system selects and selects the dot positions that cause the inkjet head to eject ink based on the selected dot selection pattern. The inkjet head has a plurality of nozzles that discharge the ink,
When the nozzles whose discharge characteristics are out of the preset normal range are defined as abnormal nozzles, and any of the nozzles is the abnormal nozzle, the discharge position data generation unit uses the abnormal nozzle. The printing system according to claim 12 or 13, wherein the dot selection pattern that is not to be selected is selected, and the dot position that causes the inkjet head to eject ink is selected based on the selected dot selection pattern. A printing method for performing printing by an inkjet method,
Using an inkjet head that ejects ink to a medium,
Causing the inkjet head to eject ink based on ejection position data indicating a position at which the inkjet head ejects ink;
In the operation of generating the discharge position data,
A gradation image that is a process for generating a set gradation image that is an image having a gradation number greater than 2 that is set in advance, and that generates the set gradation image based on an input image that is input as an image to be printed Generation process,
A discharge position data generating process for generating the discharge position data based on the set gradation data;
The resolution corresponding to the minimum dot interval in the arrangement of the ink dots formed on the medium by the inkjet head is defined as the dot resolution, and the ink ejection position set on the medium according to the dot resolution When defined as a position, in the ejection position data generation process, as the ejection position data, generate data indicating at least the dot position that causes the inkjet head to eject ink during printing corresponding to the input image,
In the gradation image generation processing, as the set gradation image, an image indicating the input image is generated at a resolution lower than the dot resolution,
Each pixel of the set gradation image is associated with a plurality of the dot positions,
In the ejection position data generation process, at least a part of the dot positions is selected from the plurality of dot positions associated with each pixel based on a gradation value of each pixel of the set gradation image. Then, the ejection position data is generated by setting the selected dot position as the dot position that causes the inkjet head to eject ink. A printing apparatus that performs printing by an inkjet method,
An inkjet head that ejects ink to a medium;
An ejection drive unit for ejecting ink to the inkjet head;
A printing control unit that controls operations of the inkjet head and the ejection driving unit;
The print control unit
A processing unit that generates a set gradation image that is an image having a larger number of gradations than 2 that is set in advance, and that generates the set gradation image based on an input image that is input as an image to be printed An image generator;
An ejection position data generating unit that generates ejection position data indicating a position at which the inkjet head ejects ink based on the set gradation data;
The ejection drive unit causes the inkjet head to eject ink based on the ejection position data,
The resolution corresponding to the minimum dot interval in the arrangement of the ink dots formed on the medium by the inkjet head is defined as the dot resolution, and the ink ejection position set on the medium according to the dot resolution When defined as a position, the ejection position data generation unit generates, as the ejection position data, data indicating at least the dot position that causes the inkjet head to eject ink during printing corresponding to the input image,
The gradation image generation unit generates an image indicating the input image at a resolution lower than the dot resolution as the set gradation image,
Each pixel of the set gradation image is associated with a plurality of the dot positions,
The ejection position data generation unit selects at least some of the dot positions from the plurality of dot positions associated with each pixel based on a gradation value of each pixel of the set gradation image. Then, the ejection position data is generated by setting the selected dot position as the dot position that causes the inkjet head to eject ink.

Images