JP2016147420A - Print control apparatus and print control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration in image quality caused by a poor nozzle.SOLUTION: The printing control device comprises: a poor nozzle detecting portion that detects a poor nozzle; a complementary processing portion that performs complementary processing by which dots are given to adjacent pixels with respect to a pixel array in which pixels corresponding to the poor nozzle in printing data are continuous or the size of dots that the adjacent pixels have is increased; and a data shift processing portion that performs data shift processing by which ink amounts by the dots that the pixels corresponding to the poor nozzle have in the printing data or missing ink amounts are aggregated and an allocation relation between pixels and nozzles is changed so that the missing ink amounts are reduced. When the poor nozzles are not continuous in a predetermined direction, the complementary processing portion performs complementary processing to the printing data, and when the complementary processing portion does not perform the complementary processing, the data shift processing portion performs data shift processing to the printing data.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a print control apparatus and a print control method.

  In an ink jet printer that performs printing by discharging ink from a plurality of nozzles onto a print medium, the nozzles may be clogged. For example, such clogging occurs when the ink dries in the vicinity of the nozzle opening or paper dust or dust adheres to the nozzle. Clogging of the nozzles causes ink ejection failure. Due to the ejection failure of the nozzle (defective nozzle), missing dots (also referred to as missing dots) on the print medium occur due to the fact that the ink that should be ejected is not ejected.

  Here, based on the image data, for each pixel group assigned to the same nozzle, the number of liquid ejecting pixels, which is the number of pixels to which liquid should be ejected, is calculated, and defective nozzles in which ejection defects occur from a plurality of nozzles A liquid ejecting method is known in which the position of an image formed on a medium is adjusted by ejecting liquid from a plurality of nozzles based on the number of liquid ejecting pixels and the position of a defective nozzle (Patent). Reference 1).

JP 2010-684 A

  By adjusting the position of the image as in Document 1, it is possible to reduce the number of liquid ejecting pixels assigned to the defective nozzle, that is, the number of missing dots. However, even if the number of missing dots is reduced, some missing dots can still occur. In such a situation, further improvement for suppressing missing dots has been demanded.

  SUMMARY An advantage of some aspects of the invention is that it provides a print control apparatus and a print control method that can more accurately suppress image quality deterioration caused by a defective nozzle.

  One aspect of the present invention is a print control apparatus that controls the ejection of ink by a nozzle row having a plurality of nozzles arranged at predetermined intervals in a predetermined direction based on print data expressing a dot pattern by a plurality of pixels. A pixel array in which a defective nozzle detection unit that detects a defective nozzle that causes an ink ejection defect from the plurality of nozzles and a defective nozzle corresponding pixel that is a pixel that is assigned to the defective nozzle in the print data. A complementary processing unit for applying a complementary process to the print data to add a dot to a neighboring pixel or increasing a dot size of the neighboring pixel, and a dot of the defective nozzle corresponding pixel in the print data The amount of missing ink, which is the amount of ink, is totaled, and the pixel and the nozzle are reduced so that the amount of missing ink is reduced. A data shift processing unit for subjecting the print data to a data shift process for changing the allocation relationship, and when the defective nozzle is not continuous in the predetermined direction, the complementary processing unit adds the print data to the print data. When the complement processing is performed and the complement processing unit does not execute the complement processing, the data shift processing unit performs the data shift processing on the print data.

  According to another aspect of the present invention, there is provided a printing control apparatus for controlling ink ejection by a nozzle row having a plurality of nozzles arranged at predetermined intervals in a predetermined direction based on print data expressing a dot pattern with a plurality of pixels. A defective nozzle detection unit that detects a defective nozzle that causes an ink ejection defect from the plurality of nozzles, and a dot among defective pixel corresponding pixels that are pixels assigned to the defective nozzle in the print data. A complementary processing unit for executing a complementary process for causing ink to be ejected to a normal nozzle in which the ejection failure does not occur in correspondence with the dot-missing pixel having the same position in the predetermined direction as the defective nozzle; and the print data The amount of missing ink, which is the amount of ink due to the dots of the defective nozzle corresponding pixel, is tabulated, and the missing ink amount A data shift processing unit for applying to the print data a data shift process that changes the allocation relationship between the pixels and the nozzles so as to decrease, and when the normal nozzle exists, the complement processing unit Executes the complement processing, and when the complement processing unit does not execute the complement processing, the data shift processing unit performs the data shift processing on the print data.

  According to these configurations, when the defective nozzle is included in the nozzle row, the complementary processing unit can execute the complementary processing as in the case where the defective nozzle does not continue in the predetermined direction or the normal nozzle exists. In such a situation, the complementary process is preferentially executed. On the other hand, if a defective nozzle continues in the predetermined direction or if the complementary processing unit cannot execute the complementary processing, such as when the normal nozzle does not exist, the data shift processing is executed. Therefore, compared to the conventional case, dot omission (image quality degradation) caused by a defective nozzle is more easily suppressed, and high image quality can be provided in the printing result.

One aspect of the present invention is that the complementary processing unit is disposed on the normal nozzle that ejects ink of the same color as that of the ink to be ejected by the defective nozzle, the position in the predetermined direction being the same as the defective nozzle. The complementary process for ejecting ink may be executed.
According to this configuration, it is possible to compensate for missing dots caused by defective nozzles by ejecting ink from normal nozzles corresponding to ink of the same color as the defective nozzles.

One aspect of the present invention is that the ink to be ejected by the defective nozzle is achromatic, and the complementary processing unit uses different chromatic inks whose positions in the predetermined direction are the same as the defective nozzle. The complementing process for causing ink to be ejected to the plurality of normal nozzles to be ejected may be executed.
According to this configuration, it is possible to compensate for missing dots caused by defective nozzles by mixing a plurality of chromatic inks ejected from a plurality of normal nozzles.

One aspect of the present invention is that, when the complement processing unit does not execute the complement processing, the data shift processing unit is ejected corresponding to a predetermined area including the defective nozzle corresponding pixel in the print data. The data shift process may be performed on the print data when the amount of ink to be printed is equal to or greater than the first threshold and equal to or less than the second threshold greater than the first threshold.
According to this configuration, such dot missing can be reduced by data shift processing when dot missing due to a defective nozzle is easily noticeable (easily visible).

One aspect of the present invention is that when the complement processing unit does not execute the complement processing, the data shift processing unit shifts the data shift from the missing ink amount before the data shift processing is performed on the print data. The data shift process may be performed on the print data when a value obtained by subtracting the missing ink amount after the process is equal to or greater than a third threshold value.
According to this configuration, when the effect of reducing the missing dots due to the defective nozzle is recognized to some extent, such missing dots can be reduced by the data shift processing.

According to one aspect of the present invention, when the complement processing unit does not execute the complement processing, the data shift processing unit has a fourth ink loss amount before the data shift processing is performed on the print data. When the value is equal to or greater than the threshold value, the data shift processing may be performed on the print data.
According to this configuration, when dot missing due to a defective nozzle can occur to some extent, such dot missing can be reduced by data shift processing.

  The technical idea of the present invention is also realized by a device other than a printing control device. For example, the present invention relates to a method (printing control method) including each step executed by each unit of the printing control apparatus, a computer program for causing a computer to execute the method, and a computer-readable storage medium storing the program It may be realized in various categories taken.

  A printing control apparatus that controls ink ejection by a nozzle array having a plurality of nozzles arranged at predetermined intervals in a predetermined direction based on print data expressing a dot pattern with a plurality of pixels, the plurality of nozzles A defective nozzle detection unit that detects a defective nozzle in which an ink ejection defect occurs, and a missing ink amount that is an ink amount by a dot included in a defective nozzle corresponding pixel that is a pixel assigned to the defective nozzle in the print data ( The first missing ink amount) and the missing ink amount (second ink amount) that is the ink amount due to the dots of the defective nozzle corresponding pixel that is the pixel assigned to the defective nozzle in the rotated print data obtained by rotating the print data by 180 degrees. If the second missing ink amount is smaller, the print data after the rotation is compared. It controls the discharge of the ink on the basis of, being able to grasp the structure.

The block diagram which illustrates the device composition concerning this embodiment. FIG. 3 is a diagram illustrating a configuration of a print head. 6 is a flowchart showing print control processing. The figure for demonstrating an example of a complementation process (vicinity complement). The flowchart which shows a data shift process. The figure for demonstrating an example of a data shift process. The figure for demonstrating anti-nozzle complementation and color mixture complement. 10 is a flowchart illustrating print control processing according to a fourth embodiment. The flowchart which shows the data shift process concerning 5th Embodiment.

1. Outline of device configuration:
FIG. 1 is a block diagram illustrating functions of the print control apparatus 10 and the like according to the present embodiment. The print control apparatus 10 is grasped as a product such as a printer or a multifunction peripheral including a printer function. The print control apparatus 10 is configured to include a printing unit 30 that actually performs printing on a print medium and a partial configuration (for example, a control unit 11 described later) for controlling the behavior of the printing unit 30. In this case, a part of the configuration may be referred to as the print control apparatus 10. The print control apparatus 10 may be called a printing apparatus, an image processing apparatus, or the like. Each configuration shown in FIG. 1 is not limited to a single location or a case where the configurations are aggregated in a single case, but a single system is constructed by the presence of these configurations in locations away from each other and being communicable. It may be. For example, the print control apparatus 10 includes a printer that actually prints on a print medium and a computer program (printer driver) for controlling the behavior of the printer to control the printer (such as a personal computer). And may be configured to include.

  In FIG. 1, the print control apparatus 10 includes a control unit 11, an operation input unit 16, a display unit 17, a communication interface (I / F) 18, a slot unit 19, a defective nozzle detection unit 20, a printing unit 30, and the like. As an example. The control unit 11 includes, for example, an IC having a CPU, a ROM, a RAM, and other storage media. In the control unit 11, various functions (for example, a complementary processing unit 12, a data shift processing unit, etc.) are executed by the CPU executing arithmetic processing according to a program stored in a ROM or the like using a RAM or the like as a work area. 13).

  The operation input unit 16 includes various buttons and keys for accepting an operation by the user. The display unit 17 is a part for displaying various information related to the print control apparatus 10 and is configured by, for example, a liquid crystal display (LCD). A part of the operation input unit 16 may be realized as a touch panel displayed on the display unit 17.

  The printing unit 30 is a mechanism for printing an image on a print medium. When the printing method employed by the printing unit 30 is an inkjet method, the printing unit 30 has a configuration such as a print head 31 (see FIG. 2), a conveyance unit 36 that conveys a print medium along a predetermined conveyance direction, and the like. Have. When the printing unit 30 (or the print control apparatus 10) is a product corresponding to a so-called line printer, the print head 31 as a line head basically does not move, and therefore the carriage 35 indicated by the broken line in FIG. Become.

  The print head 31 supplies various inks from ink cartridges (not shown) for each of a plurality of types of ink (for example, cyan (C) ink, magenta (M) ink, yellow (Y) ink, black (K) ink, etc.). Receive. The print head 31 can eject (eject) ink (ink droplets) from a plurality of nozzles provided corresponding to various inks. When the ejected ink lands on the print medium, dots are formed on the print medium and printing is realized. “Dot” basically refers to an ink droplet that has landed on a print medium, but the expression “dot” is also used as appropriate in the description of the process before the ink droplet has landed on the print medium. The specific types and number of liquids used by the printing unit 30 are not limited to those described above. For example, various inks and liquids such as light cyan, light magenta, orange, green, gray, light gray, white, metallic ... It can be used.

  The transport unit 36 includes a roller for supporting and transporting the print medium, a motor for rotating the roller (all not shown), and the like. The print medium is typically paper. However, in the present embodiment, materials other than paper are included in the concept of the printing medium as long as the material can record the liquid and can be transported by the transport unit 36.

The communication I / F 18 is a generic name for interfaces for connecting the print control apparatus 10 to the external device 100 by wire or wirelessly. Examples of the external device 100 include various devices that are input sources of image data for the print control apparatus 10 such as a smartphone, a tablet terminal, a digital still camera, and a personal computer (PC). The print control apparatus 10 can be connected to the external device 100 via the communication I / F 18 by various means and communication standards such as a USB cable, a wired network, a wireless LAN, and e-mail communication.
The slot part 19 is a part for inserting an external storage medium such as a memory card. That is, the print control apparatus 10 can also input image data stored in the storage medium from an external storage medium such as a memory card inserted in the slot unit 19.

  The control unit 11 can execute image processing for generating print data from the input image data. Various formats of image data can be considered. For example, the image data is data expressed by gradation in RGB (red, green, blue) for each pixel. The control unit 11 appropriately performs known image processing such as resolution conversion processing, color (color system) conversion processing, and halftone processing on the image data, so that an image to be printed is formed with a plurality of pixels. Print data expressed by a pattern is generated. Of course, the control unit 11 may input such print data from the external device 100 or the like.

  A dot pattern (dot pattern) is an array of dots on (dot formation or ink ejection) and off (dot non-formation or ink non-ejection). It also defines dot on / off for each pixel. I can say that. For example, when the print head 31 ejects CMYK ink, the print data includes data defining dot on / off for each pixel for each CMYK. Also, the print data is simply binary data indicating dot on / off, and is also referred to as a plurality of dots having different volumes per droplet (for example, large dots, medium dots, small dots, etc.). Multi-value (four-valued) data indicating ON or OFF of any of a plurality of size dots). Large dots, medium dots, and small dots are just names according to the relative size difference between the dots. Here, the smallest size dot among the multiple size dots that can be formed by the nozzle is small. A dot, a dot of the maximum size is called a large dot, and a dot larger than a small dot and smaller than a large dot is called a medium dot. Of course, the nozzle may be capable of forming dots of many different sizes.

  The print head 31 drives each nozzle based on such print data. For example, it is assumed that a drive signal (a kind of pulse) for driving each nozzle is given to the print head 31. Although detailed explanation is omitted, in the print head 31, according to dot on / off information (or information of large dot on, medium dot on, small dot on, dot off) for each pixel represented by the print data. By switching the application of the drive signal to the drive element provided for each nozzle, ink ejection / non-ejection from each nozzle based on the print data is realized.

  The defective nozzle detection unit 20 is means for detecting defective nozzles from a plurality of nozzles of the print head 31. The defective nozzle is a generic term for nozzles that cannot eject ink droplets normally (ie, ejection failure occurs) even though the ink ejection operation is performed by applying the drive signal. Causes of ejection failure include air bubbles in the nozzle and the ink flow path communicating with the nozzle, drying and thickening (adhering) of ink near the nozzle, and paper dust adhering to the vicinity of the nozzle opening, etc. Is mentioned. When an ejection failure occurs, typically, ink is not ejected from the nozzle, resulting in a phenomenon in which dots that should be originally formed on the printing medium are missing (dot missing). Also, in the case of ejection failure, even if ink is ejected from the nozzle, the amount of liquid is too small or the flight direction (ballistic) of the ink is misaligned so that it does not land properly. Cheap.

  In the present embodiment, the defective nozzle detection unit 20 notifies the control unit 11 of nozzle information. The nozzle information is information indicating the presence or absence of ejection failure for each nozzle of the print head 31, that is, information indicating whether each nozzle is a defective nozzle. The nozzle information may be anything as long as it is information that can directly or indirectly determine whether each nozzle is a defective nozzle. In this embodiment, the process for generating nozzle information is not particularly limited, and any technique for determining and detecting a defective nozzle can be employed. For example, the defective nozzle detection unit 20 detects the presence or absence of ejection failure for each nozzle using the method disclosed in Japanese Patent Application Laid-Open No. 2013-12676, and notifies the control unit 11 of the result as nozzle information. Can do. Specifically, a waveform (period, etc.) of residual vibration such as a so-called diaphragm (a part of elements constituting the print head 31) that bends as the driving element (piezoelectric element) is deformed by application of the driving signal. By measuring, it is detected whether the ink is normally ejected from each nozzle or whether there is an ejection failure. Alternatively, the defective nozzle detection unit 20 discharges each nozzle by obtaining an evaluation (artificial or mechanical evaluation) of dot missing in a test pattern printed by discharging ink from each nozzle of the print head 31. The presence or absence of a defect may be detected to generate nozzle information.

  FIG. 2 simply illustrates the configuration of the print head 31 as a line head. The upper part of FIG. 2 illustrates the arrangement of the nozzles 34 on the ink ejection surface 31 a of the print head 31. The ink ejection surface 31 a is a surface where the nozzles 34 are opened, and is a surface facing the print medium S conveyed by the conveyance unit 36. In FIG. 2, a direction D2 corresponds to the transport direction. The direction D1 is a direction orthogonal to the direction D2, and corresponds to a predetermined direction in the claims. In FIG. 2, each nozzle 34 is indicated by a black dot in the head 32.

  In the example of FIG. 2, the print head 31 is configured by connecting a plurality of heads 32 along the direction D <b> 1 (unitized). Each head 32 has the same configuration, and all have nozzle rows 33C, 33M, 33Y, and 33K for each ink color. The nozzle row 33C is a nozzle row in which nozzles 34 for discharging C ink are arranged at predetermined intervals, and the nozzle row 33M is a nozzle row in which nozzles 34 for discharging M ink are arranged at predetermined intervals. Yes, the nozzle row 33Y is a nozzle row in which nozzles 34 for discharging Y ink are arranged at a predetermined interval, and the nozzle row 33K is a nozzle in which nozzles 34 for discharging K ink are arranged at a predetermined interval. Is a column. The nozzle rows 33C, 33M, 33Y, and 33K are parallel to each other, and in the example of FIG. 2, are also parallel to the direction D1.

  When viewed from the entirety of such a print head 31 (a set of a plurality of heads 32), the print head 31 has a predetermined interval (predetermined nozzle pitch) over a range in which the width of the print medium S can be covered in the direction D1. It can be said that a nozzle row having a plurality of nozzles 34 arranged for each ink color (for example, CMYK) is provided. All the nozzle rows 33C for each head 32 are collectively referred to as a nozzle row CNL. That is, the nozzle row CNL is a nozzle row for discharging the C ink that the print head 31 has. Similarly, all the nozzle rows 33M for each head 32 are collectively represented as a nozzle row MNL, all the nozzle rows 33Y for each head 32 are collectively represented as a nozzle row YNL, and all the nozzle rows 33K for each head 32 are collectively represented as a nozzle row KNL. To do.

As can be seen from FIG. 2, the individual heads 32 are displaced in the direction D <b> 2. Accordingly, the nozzles 34 constituting the nozzle row (nozzle row CNL) for discharging one color ink (for example, C ink) are not necessarily arranged on the same straight line, and may be shifted in the direction D2. Further, the nozzles 34 constituting the nozzle row (nozzle row CNL) for discharging one color ink (for example, C ink) may be arranged at predetermined intervals (equal intervals) as a result. Therefore, the directions of the nozzle rows 33C, 33M, 33Y, and 33K may be oblique to the direction D1.
According to such a configuration, the print control apparatus 10 uses a nozzle row having a plurality of nozzles 34 arranged at predetermined intervals in a predetermined direction (direction D1) based on print data expressing a dot pattern with a plurality of pixels. It can be said that ink ejection is controlled.

  Further, as can be seen from FIG. 2, the head 32 overlaps with the other head 32 in the direction D1. In such an overlapping range (overlapping range OL), the overlapping nozzles 34 in one head 32 and the overlapping nozzles 34 in the other head 32 exist at the same position in the direction D1. That is, in the overlapping range OL, nozzles 34 for ejecting ink of one color (for example, C ink) corresponding to a certain position in the direction D1 are present in each head 32 sharing the overlapping range OL. . The two nozzles 34 for ejecting the same color ink with different heads 32 having the same position in the direction D1 are referred to as “nozzles”. In this specification, even if the directions and positions of each component are expressed as parallel, orthogonal, equally spaced, identical, etc., they mean only strictly parallel, orthogonal, equally spaced, identical, etc. It does not mean that it includes errors that are acceptable in terms of product performance and errors that may occur during product manufacturing.

2. Print control processing:
FIG. 3 is a flowchart showing a print control process executed by the control unit 11.
In step S <b> 100, the control unit 11 refers to the latest nozzle information notified from the defective nozzle detection unit 20, and branches the process depending on whether there is a defective nozzle. Here, when the nozzle information indicates that there is a defective nozzle among the plurality of nozzles 34 of the print head 31, the process proceeds to step S120. On the other hand, if the nozzle information indicates that there is no defective nozzle among the plurality of nozzles 34 of the print head 31, the process proceeds to step S110. In step S110, the control unit 11 executes normal printing processing based on the print data. That is, the behavior of the printing unit 30 including the print head 31 is controlled based on the print data to print an image on the print medium. Since the normal printing process has no features, further explanation is omitted.

  In step S120, the control unit 11 determines whether or not the complement processing unit 12 can execute the complement processing for complementing the missing dot due to the defective nozzle indicated by the nozzle information, and can perform the complement processing. If so, the process proceeds to step S130, and if the supplement processing cannot be performed, the process proceeds to step S140. Here, it is determined whether or not “neighboring complementing” as a complementing process is feasible.

  First, neighborhood complementing is a process in which dots are added to neighboring pixels for a pixel row in which defective nozzle corresponding pixels that are pixels assigned to defective nozzles in print data are continuous, or the size of the dots of the neighboring pixels is increased. Is applied to the print data. The neighborhood pixel mentioned here includes a pixel printed by a nozzle adjacent to the defective nozzle (first defective nozzle) in the direction D1. If the nozzle for printing the neighboring pixel (the nozzle adjacent to the first defective nozzle in the direction D1) is also a defective nozzle (second defective nozzle), naturally, the second missing dot is caused by the first defective nozzle. It cannot be complemented by ink ejection from the defective nozzle, and similarly, missing dots from the second defective nozzle cannot be complemented by ink ejection from the first defective nozzle. Therefore, if the defective nozzle indicated by the nozzle information is not continuous in the direction D1, the control unit 11 determines that proximity complement is possible (“Yes” in step S120), and proceeds to step S130. On the other hand, if the defective nozzle indicated by the nozzle information is continuous in the direction D1, it is determined that the vicinity cannot be complemented (“No” in step S120), and the process proceeds to step S140.

In step S <b> 130, a printing process involving a complementing process (neighboring complementing) by the complementing processing unit 12 is executed.
FIG. 4 is a diagram for explaining an example of neighborhood complement. The upper part of FIG. 4 illustrates a correspondence relationship between a part of the nozzle row KNL including a plurality of nozzles 34 (white circles) for ejecting one color ink (for example, K ink) and the print data DB before processing. doing. Here, “before processing” means a state in which neither the complementary processing nor the data shift processing described later is performed. The lower part of FIG. 4 illustrates print data DAC after complement processing. Each rectangle constituting the print data DB and DAC represents a pixel. The print data DB and DAC shown in FIG. 4 are print data representing a K ink dot pattern. It is assumed that the nozzle indicated by reference numeral 34N among the nozzles 34 included in the nozzle row KNL is a defective nozzle (a defective nozzle detected by the defective nozzle detection unit 20).

  The print data DB and DAC are composed of a plurality of pixels arranged corresponding to the direction D1 and the direction D2, respectively. In the following, the orientation of the arrangement of the pixels constituting the print data may be expressed by the direction D1 or the direction D2, but this is only the relationship between the orientation of the image and the directions D1 and D2 when the printing is performed by the print head 31. Based on correspondence relationship. The complement processing unit 12 generates print data DAC that complements the dots to be formed by the defective nozzles 34N based on the print data DB.

  The pixel row NPL shown in FIG. 4 is an area where pixels (defective nozzle corresponding pixels NP) assigned to the defective nozzle 34N are connected in the direction D2, and is also referred to as a defective nozzle corresponding pixel row NPL. Pixels on both sides of the defective nozzle corresponding pixel NP in the direction D1 are referred to as primary neighboring pixels, and pixels on the opposite side of the primary neighboring pixels from the defective nozzle corresponding pixels NP are referred to as secondary neighboring pixels. In addition, the nozzles 34 that are adjacent to the defective nozzle 34N in the nozzle row KNL in the direction D1 are called primary neighboring nozzles, and the nozzles 34 on the opposite side of the nozzles KNL from the primary neighboring nozzles to the defective nozzle 34N are in the secondary neighborhood. This is called a nozzle. Dots are formed corresponding to the primary neighboring pixels by the ink ejected from the primary neighboring nozzles, and dots are formed corresponding to the secondary neighboring pixels by the ink ejected from the secondary neighboring nozzles.

  In the proximity complementing by the complementing processing unit 12, dots are added to at least the primary neighboring pixels, or the size of the dots of the primary neighboring pixels is increased. In FIG. 4, “0”, “S”, “M”, and “L” shown in the pixels of the print data DB and DAC indicate the sizes of dots that the pixels have. That is, 0 indicates dot off, S indicates small dot on, M indicates medium dot on, and L indicates large dot on. For example, when the print processing data DB is used, the complement processing unit 12 applies to “a pixel having a dot among the defective nozzle corresponding pixels NP (that is, a pixel in which a missing dot is generated; hereinafter referred to as“ dot missing pixel ”)”. For the primary neighboring pixels adjacent to the direction D1, if the dot is off, it is converted to small dot on (dot addition), and the complement processing unit 12 applies the dot missing pixel to the dot missing pixel, for example, according to the print data DB. On the other hand, the primary neighboring pixels adjacent in the direction D1 are converted to medium dot on if small dots are on, and are converted to large dots on if medium dots are on (increase in dot size). Is the data after such conversion (neighbor interpolation) is performed on the print data DB.The print data DAC of FIG. It is indicated by a bold frame for primary neighboring pixels increased's were made.

  The specific method of neighborhood complement is not limited to the above-described method. For example, the complement processing unit 12 calculates the dot size calculated from the dot size of the dot missing pixel according to the print data DB and the dot size of the primary neighboring pixel adjacent to the dot missing pixel in the direction D1. Is the dot size after conversion for the primary neighboring pixels (dot size in the print data DAC). For example, the dot size is defined as dot off = 0, small dot = 1, medium dot = 2, large dot = 3, and the like, and the dot size (1, 2, 2) of the dot missing pixel according to the print data DB 3) and the dot size (any one of 0, 1, 2, and 3) of the primary neighboring pixel adjacent to the dot missing pixel in the direction D1 with respect to the primary neighboring pixel. The dot size after conversion of. However, a dot size of 4 or more by such calculation is regarded as 3, that is, a large dot. The process of converting the dot size by such calculation may be performed on the primary neighboring pixels on both sides of the dot-missing pixel when following the print data DB, or may be performed only on one primary neighboring pixel. .

  When the print data DB is binary data that simply indicates on / off of dots for each pixel, neighborhood complementation is a simple process of whether or not to add dots to the primary neighborhood pixels. . The complement processing unit 12 may generate the print data DAC by changing dots (any one of dot addition, deletion, size increase, and size decrease) for the secondary neighboring pixels.

  In the printing process (step S130) accompanied by the complementing process (neighboring complementing) by the complementing process unit 12, the behavior of the printing unit 30 including the print head 31 is controlled based on the print data DAC after the complementing process, and an image is printed on the print medium. Let it print. Accordingly, an image in which dot missing due to the defective nozzle 34N (dot missing corresponding to the dot missing pixel) is complemented by increased ink ejection for neighboring pixels, that is, an image in which dot missing due to the defective nozzle 34N is eliminated or suppressed is obtained. Obtained as a print result.

On the other hand, in step S140, a printing process involving a data shift process by the data shift processing unit 13 is executed. Data shift processing is processing that aggregates the missing ink amount, which is the amount of ink due to dots of defective nozzle-corresponding pixels in the print data, and changes the relationship between pixels and nozzles so that the missing ink amount decreases. is there.
FIG. 5 is a flowchart showing the data shift process.
FIG. 6 is a diagram for explaining an example of the data shift processing.

  The upper part of FIG. 6 illustrates the correspondence relationship between the print data DB and the nozzle row KNL including a plurality of nozzles 34 for ejecting one color ink (for example, K ink). The lower part of FIG. 6 illustrates print data DAS after the data shift process. However, in FIG. 6, unlike in FIG. 4, the individual pixels constituting the print data are not represented by rectangles. In FIG. 6, it is assumed that there are a total of 29 nozzles 34 having nozzle numbers 1 to 29 constituting the nozzle row KNL. Of course, the number of nozzles 34 constituting the nozzle row KNL is actually larger, and not all of them are on the same straight line.

  In FIG. 6, the print data DB and DAS are data having 25 pixels along the direction D1. A region where pixels having the same position in the direction D1 are connected in the direction D2 is simply referred to as a pixel column. The above-described defective nozzle corresponding pixel row NPL is also one of such pixel rows. In FIG. 6, for convenience, pixel column numbers 1 to 25 are assigned to these pixel columns. All the pixels in the same pixel row are assigned to the same nozzle 34. In such a configuration, in this embodiment, when data shift processing is not executed, print data is printed by a total of 25 nozzles 34 having nozzle numbers 3 to 27. That is, the nozzles 34 having nozzle numbers 1, 2, 28, and 29 are not normally used. The nozzle 34 that is not normally used in this way is called a spare nozzle. In other words, the print head 31 has spare nozzles that are not normally used in the nozzle rows CNL, MNL, YNL, and KNL for each ink color.

  In step S200 of FIG. 5, the data shift processing unit 13 adds up the missing ink amount (missed ink amount A1 before shift) in the print data DB. As an example, when the nozzle information is referred to, it is assumed that two consecutive nozzles having nozzle numbers 12 and 13 among the nozzle numbers 1 to 29 shown in the upper part of FIG. 6 are defective nozzles. For reference, FIG. 6 shows the ink amount in the pixel column for each pixel column of pixel column numbers 1 to 25. This is the ink amount for each pixel column necessary for printing an image (character string “1PE”) as exemplified in the print data DB and DAS of FIG.

  However, in the present embodiment, the amount of ink in the pixel array is represented by the number of dots instead. When the print data DB is binary data that simply indicates ON / OFF of dots for each pixel, the number of pixels having dots in the pixel column, that is, the number of dots in the pixel column is the ink amount in the pixel column. On the other hand, when the print data DB is quaternary data indicating on or off of any one of large dots, medium dots, and small dots for each pixel, for example, one large dot is 1 dot, and one medium dot is 0. The number of dots in the pixel row obtained by performing conversion according to the difference in ink amount per one dot, such as 5 dots, 1 small dot is 0.25 dots, etc., is the ink amount in the pixel row.

  As described above, the nozzle 34 with the nozzle number 12 is a defective nozzle. In the example of FIG. 6, the ink amount in the pixel row of the pixel row number 10 in the print data DB assigned to the nozzle 34 with the nozzle number 12 is 12. . Further, as described above, the nozzle 34 with the nozzle number 13 is a defective nozzle, and in the example of FIG. 6, the ink amount in the pixel row of the pixel row number 11 in the print data DB assigned to the nozzle 34 with the nozzle number 13 is 12. It is. Accordingly, the sum (12 + 12 = 24) of the ink amounts in the pixel columns of the pixel column numbers 10 and 11 in the print data DB is the missing ink amount A1 before the shift.

  In step S210, the data shift processing unit 13 sets the number of shift nozzles for data shift. Data shift is a process of moving the positional relationship between the print data DB and the nozzles in the direction D1 by the number of shift nozzles. In the example of FIG. 6, since there are two spare nozzles on both sides of the normally used nozzle numbers 3 to 27, the value that can be set as the number of shift nozzles is either -2, -1, +1, or +2. It is. Of course, the more spare nozzles, the more types of shift nozzles that can be set. Here, the negative shift nozzle number indicates that the nozzle number assigned when attention is paid to one pixel row is shifted to a number smaller than the normally used nozzle number, and the positive shift nozzle number is one pixel row. This means that the assigned nozzle number shifts to a larger number than the normally used nozzle number. Here, for example, it is assumed that the number of shift nozzles is set to −2.

  In step S220, the data shift processing unit 13 totals the missing ink amount (shifted missing ink amount A2) when the data is shifted according to the number of shift nozzles set in step S210. As described above, when the number of shift nozzles is set to −2, nozzles 34 having nozzle numbers 1 to 25 including spare nozzles having nozzle numbers 1 and 2 are used for printing pixel numbers 1 to 25. Become. In this case, the amount of ink in the pixel row of the pixel row number 12 assigned to the nozzle 34 (defective nozzle) of the nozzle number 12 is 4, and the pixel of the pixel row number 13 assigned to the nozzle 34 (defective nozzle) of the nozzle number 13 Since the ink amount in the column is 4, the sum (4 + 4 = 8) of the ink amounts in the pixel columns of the pixel column numbers 12 and 13 becomes the missing ink amount A2 after the shift.

  In step S230, the data shift processing unit 13 determines whether or not all the settable shift nozzle numbers (−2, −1, +1, +2 in the above example) derived from the number of spare nozzles have been set. To do. If the number of unset shift nozzles remains, the process returns to step S210. In step S210, after setting one of the number of unset shift nozzles, the process proceeds to step S220. If there is no unset shift nozzle number, the process proceeds to step S240.

  In step S240, the data shift processing unit 13 sets the number of shift nozzles (optimum shift nozzle number) when the value obtained by subtracting the missing ink amount A2 after shifting from the missing ink amount A1 before shifting (dot missing reduction amount) becomes the maximum. The data shift process is executed accordingly. In the above example, each of the missing ink amount A1 before shifting and the four after-shifting missing ink amounts A2 counted in step S220 according to the number of shift nozzles -2, -1, +1, +2 respectively. The difference (dot missing reduction amount) is calculated, and the number of shift nozzles when the maximum dot missing reduction amount is obtained is the optimum number of shift nozzles.

Incidentally, when the number of shift nozzles is −1, the nozzles 34 having the nozzle numbers 2 to 26 are used for printing the pixel row numbers 1 to 25 and are assigned to the nozzles 34 having the nozzle number 12 (defective nozzles). Since the ink amount in the pixel row of the pixel row number 11 is 12, and the ink amount in the pixel row of the pixel row number 12 assigned to the nozzle 34 (defective nozzle) of the nozzle number 13 is 4, the post-shift missing ink amount A2 = 16 It becomes.
When the number of shift nozzles is +1, the nozzles 34 having nozzle numbers 4 to 28 are used for printing pixel numbers 1 to 25, and the pixels assigned to the nozzle 34 having nozzle number 12 (defective nozzle). Since the ink amount in the pixel row of the column number 9 is 0 and the ink amount in the pixel row of the pixel row number 10 assigned to the nozzle 34 (defective nozzle) of the nozzle number 13 is 12, the post-shift missing ink amount A2 = 12. Become.
When the number of shift nozzles is +2, the nozzles 34 having nozzle numbers 5 to 29 are used for printing pixel numbers 1 to 25, and the pixels assigned to the nozzles 34 having nozzle numbers 12 (defective nozzles). Since the ink amount in the pixel row of the column number 8 is 0 and the ink amount in the pixel row of the pixel row number 9 assigned to the nozzle 34 (defective nozzle) of the nozzle number 13 is 0, the missing ink amount A2 = 0 after the shift. Become.

  According to such an example, the optimum number of shift nozzles for obtaining the maximum dot drop reduction amount is +2. Therefore, the data shift processing unit 13 executes data shift processing according to the optimal number of shift nozzles = + 2 for the print data DB. The lower part of FIG. 6 illustrates a correspondence relationship between the print data DAS after such data shift processing and the nozzle row KNL. That is, when the correspondence relationship between the print data DB and the nozzle row KNL is used as a reference, all the pixels constituting the print data DAS are assigned to the previous nozzle 34 shifted in the direction D1 by the shift nozzle number = + 2. In the printing process (step S140) accompanied by the data shift process by the data shift processing unit 13, the behavior of the printing unit 30 including the print head 31 is controlled based on the print data DAS after the data shift process to print an image on the print medium. Let Therefore, an image in which dot missing due to the defective nozzle 34N is reduced is obtained as a printing result.

  Naturally, the post-shift missing ink amount A2 that gives the optimum number of shift nozzles is a smaller number than the pre-shift missing ink amount A1. If all the after-shift missing ink amounts A2 calculated in step S220, which are repeatedly executed while changing the number of shift nozzles, are greater than or equal to the missing ink amount A1 before shifting, dot missing is reduced by data shift processing. I can't. In this case, the data shift processing unit 13 does not execute step S240 because it does not make sense, and as a result, printing based on the print data DB (normal printing processing) is executed.

  According to such an embodiment, when the defective nozzle 34N is included in the nozzle row of the print head 31, the defective nozzle 34N is not continuous in the direction D1, that is, the complement processing unit 12 performs the complement processing (neighbor complement). If it is possible to execute, neighborhood complement is preferentially executed and dot missing is complemented. On the other hand, if the defective nozzles 34N are continuous in the direction D1, that is, if the complement processing unit 12 cannot perform the complement processing (neighbor complementing), the data shift processing by the data shift processing unit 13 is executed and dot missing is detected. Decrease. Therefore, compared to the conventional case, dot omission (deterioration in image quality) caused by a defective nozzle is more accurately suppressed, and high image quality can be provided in the printing result.

  Further, the data shift process has the following effects. The controller 11 counts ink consumption in an ink cartridge (not shown) that supplies ink for each color to the print head 31 as needed. Such a count is executed by calculating (estimating) the amount of ink for each color ejected by the print head 31 according to the dot pattern in the print data given to the print head 31. That is, instead of whether or not ink is actually ejected, if the print data defines dot-on, the current ink consumption is updated assuming that ink corresponding to the dot has been ejected. In such a counting method, when there is a defective nozzle 34N, it is counted as a part of the ink consumption amount that ink that is not actually ejected is ejected. Therefore, the actual ink consumption and the ink consumption grasped by the control unit 11 based on the count deviate. According to the data shift processing, the actual dot missing caused by the defective nozzle 34N can be reduced. Therefore, it can be said that the data shift process also has the effect of suppressing the divergence (improving ink consumption counting accuracy).

3. Other embodiments:
The present invention is not limited to the above-described embodiment (referred to as the first embodiment for the sake of convenience), and can be carried out in various modes without departing from the gist thereof. A form can be adopted. A configuration in which each embodiment is appropriately combined also falls within the disclosure scope of the present invention. In the following description of the embodiment, the description of matters common to the first embodiment will be omitted as appropriate.

(Second Embodiment)
The description of the second embodiment will also refer to the flowchart of FIG.
In step S120, the control unit 11 determines whether or not the complement processing unit 12 can execute the complement processing for complementing the missing dot due to the defective nozzle indicated by the nozzle information, and can perform the complement processing. If so, the process proceeds to step S130, and if the supplement processing cannot be performed, the process proceeds to step S140. However, in the second embodiment, it is determined whether or not “complementation with position-corresponding nozzles” can be executed as the complement processing.

Complementation with position-corresponding nozzles corresponds to the dot-missing pixels in the print data DB, and causes ink to be ejected to normal nozzles (position-corresponding nozzles) that have the same position in the direction D1 as the defective nozzles 34N and do not cause defective ejection Complementary processing. The concept of complementation by position-corresponding nozzles includes “nozzle complementation” and “color mixture complementation”. Here, first, the second embodiment will be described on the assumption that the complement processing unit 12 can execute the nozzle compensation.
Compensation for nozzles is a process in which the complement processing unit 12 ejects ink to a normal nozzle that ejects the same color as the color of the ink to be ejected by the defective nozzle 34N whose position in the direction D1 is the same as that of the defective nozzle 34N. It is.

  FIG. 7A is a diagram for explaining an example of complementary nozzles. FIG. 7A shows a part of a nozzle row KNL including a plurality of nozzles 34 for ejecting ink of one color (for example, K ink), including an overlapping range OL, and a print data DB (for K ink). The correspondence relationship with print data expressing a dot pattern is illustrated. In FIG. 7A, the defective nozzle 34N (the defective nozzle detected by the defective nozzle detection unit 20) is included in the overlapping range OL.

  In step S120, the control unit 11 determines whether or not the defective nozzle 34N indicated by the nozzle information corresponds to a nozzle constituting the counter nozzle. The definition of the nozzle is as already described. In the first place, when the defective nozzle 34N does not correspond to the nozzle constituting the counter nozzle, the position corresponding nozzle does not exist and the counter nozzle complement is impossible, and therefore the control unit 11 cannot execute the complement processing. (Proceed to step S140). Further, even if the defective nozzle 34N corresponds to the nozzle constituting the counter nozzle, if the other nozzle constituting the counter nozzle is also a defective nozzle in relation to the defective nozzle 34N, the counter nozzle complement is impossible. (There is no position-corresponding nozzle), so the control unit 11 determines that the supplement processing cannot be performed (proceeds to step S140).

  The defective nozzle 34N and the nozzle 34P surrounded by a broken line in FIG. 7A constitute a pair of nozzles. The nozzle 34P is not a defective nozzle (that is, a normal nozzle). Therefore, the nozzle 34P corresponds to an example of the position corresponding nozzle. In such a case, in step S120, the control unit 11 determines that the supplement processing (for nozzle complement) is feasible, and proceeds to step S130.

  In step S <b> 130, a printing process involving a complement process (for nozzle complement) by the complement processing unit 12 is executed. In the printing process with counter-nozzle complementation, for the pixels having dots in the pixel array (pixel array NPL illustrated in FIG. 7A) allocated to the counter-nozzle including the defective nozzle 34N, the defective nozzle included in the counter-nozzle is assigned. The nozzle 34 is not 34N (the nozzle 34P in the example of FIG. 7A). In the normal printing process based on the print data DB, with respect to the pixel row corresponding to the overlap range OL, the pixel in which frequency (ratio) of which of the two nozzles 34 constituting the counter nozzle corresponding to the position in the direction D1 corresponds. There is an arrangement to assign In the nozzle-to-nozzle interpolation, such a rule is ignored, and a dot having a dot in the pixel row NLP is assigned to the nozzle 34 that is not the defective nozzle 34N included in the nozzle-to-nozzle. It is ensured that dots are formed corresponding to the pixel positions that have been present. As a result, dot omission due to the defective nozzle 34N does not occur.

  Next, the second embodiment will be described on the assumption that the complement processing unit 12 can execute color mixture complement. The color mixture complementing means that when the ink to be ejected by the defective nozzle 34N is achromatic, the complement processing unit 12 ejects a plurality of different chromatic color inks whose positions in the direction D1 are the same as the defective nozzle 34N. In this process, ink is ejected to the normal nozzle.

  FIG. 7B is a diagram for explaining an example of color mixture complementation. FIG. 7B illustrates a correspondence relationship between a part of each of the nozzle arrays KNL, CNL, MNL, and YNL and the print data DB (print data that represents a K ink dot pattern). In FIG. 7B, the defective nozzle 34N (the defective nozzle detected by the defective nozzle detection unit 20) is included in the nozzle row KNL.

  In step S120, the control unit 11 determines whether or not the defective nozzle 34N indicated by the nozzle information corresponds to a nozzle for discharging achromatic ink. When the print head 31 ejects CMYK ink, the K ink corresponds to achromatic ink. In the first place, missing dots of chromatic color ink cannot be eliminated by color mixture complementation. Therefore, when the defective nozzle 34N indicated by the nozzle information is a nozzle for ejecting chromatic color ink such as CMY ink (nozzle belonging to any one of the nozzle rows CNL, MNL, YNL), color mixture complementation is impossible. Since the position corresponding nozzle does not exist, the control unit 11 determines that the supplement processing cannot be performed (proceeds to step S140). In addition, even if the defective nozzle 34N corresponds to a nozzle for ejecting achromatic ink, if the nozzle of each chromatic ink whose position in the direction D1 is the same as that of the defective nozzle 34N includes a defective nozzle, color mixing is performed. Since the complement is impossible (the position-corresponding nozzle does not exist), the control unit 11 determines that the complement process cannot be performed (proceeds to step S140).

  The defective nozzle 34N surrounded by a broken line in FIG. 7B, the nozzle 34C in the nozzle row CNL, the nozzle 34M in the nozzle row MNL, and the nozzle 34Y in the nozzle row YNL constitute a set of nozzles having the same position in the direction D1. To do. Further, it is assumed that the nozzles 34C, 34M, and 34Y are not defective nozzles (that is, normal nozzles). Accordingly, the nozzles 34C, 34M, and 34Y correspond to an example of the position corresponding nozzle. In such a case, in step S120, the control unit 11 determines that the supplement processing (color mixture complement) is executable, and the process proceeds to step S130.

  In step S <b> 130, a printing process involving a complementing process (color mixture complementing) by the complementing processing unit 12 is executed. In the printing process with color mixture complement, the nozzles 34C and 34M are associated with pixels (dot missing pixels) having dots among the defective nozzle corresponding pixels NP (see the pixel row NPL illustrated in FIG. 7B) assigned to the defective nozzle 34N. , 34Y to discharge ink. As a result of such processing, CMY ink dots are formed in an overlapping manner corresponding to the pixel positions where the K ink dots are present in the print data DB (the pixel positions at which K ink dots are missing by the defective nozzle 34N). The mixed color of these dots complements the missing dot of K ink by the defective nozzle 34N. It should be noted that color mixture complementation can also be performed for achromatic inks that are lighter than K ink, such as gray (light black), light gray, and the like. For example, when the print head 31 ejects ink such as gray, light cyan, light magenta, yellow, etc., it is possible to compensate for the missing color of the gray ink with three colors of ink such as light cyan, light magenta, yellow. Is possible.

  According to the second embodiment, when the nozzle row of the print head 31 includes the defective nozzle 34N, if the position-corresponding nozzle exists, that is, the complement processing unit 12 performs the complement processing (position-corresponding nozzle). If the situation is such that it is possible to execute (completion by), complementation by the position-corresponding nozzle is preferentially executed and dot missing is complemented. On the other hand, if the position-corresponding nozzle does not exist, that is, if the complementing processing unit 12 cannot execute the complementing process (complementing with the position-corresponding nozzle), the data shift processing by the data shift processing unit 13 is executed and the missing dot is detected. Decrease. Therefore, compared to the conventional case, dot omission (deterioration in image quality) caused by a defective nozzle is more accurately suppressed, and high image quality can be provided in the printing result.

(Third embodiment)
In step S120 of FIG. 3, the control unit 11 is capable of executing at least one complementing process among a plurality of types of complementing processes so that the complementing process unit 12 can execute the dot missing due to the defective nozzle indicated by the nozzle information. It may be determined whether or not there is. Then, if at least one of the multiple types of complementary processing can be executed, the process proceeds to step S130, where the complementary processing unit 12 executes the complementary processing, and all of the multiple types of complementary processing cannot be executed. If so, the process proceeds to step S140, and the data shift processing unit 13 executes the data shift process. For example, when the controller 11 recognizes a defective nozzle based on the nozzle information (step S100), any one of the above-described proximity complement, counter-nozzle complement, and color mixture complement is used to complement the missing dot due to the defective nozzle. If even one situation can be executed, the complement processing unit 12 is caused to execute one of such executable complement processes (steps S120 and S130). In this case, if the defective nozzle is continuous in the direction D1 and does not belong to the overlapping range OL and is a nozzle for discharging chromatic color ink, proximity complement, counter-nozzle complement, and color mixture Since all of the complements cannot be executed, a data shift process is executed (step S140).

  In the third embodiment, priority can be given to the complementary processing. It can be said that the best complement result is easily obtained in the vicinity complement, the nozzle complement, and the color mixture complement. Therefore, in order to complement the missing dot due to the defective nozzle indicated by the nozzle information, the control unit 11 first determines whether or not the nozzle complement can be performed (step S120), and the nozzle complement can be performed. For example, the complement processing unit 12 performs nozzle compensation (step S130). If the control unit 11 determines that the complementary to the nozzle cannot be performed in order to complement the missing dot due to the defective nozzle indicated by the nozzle information, whether or not the proximity complement or the color mixture complement can be performed. If it is determined (step S120) and either of the neighborhood complement and the color mixture complement can be executed, the complement processing unit 12 is caused to execute either the neighborhood complement or the color mixture complement (step S130).

  The control unit 11 may or may not give priority to the neighborhood complement and the color mixture complement. In the case where priorities are assigned to the proximity complement and the color mixture complement, the control unit 11 can assign priorities according to the characteristics of the print medium used for printing, for example. The characteristics of the print medium referred to here are the ease of bleeding of ink and the difficulty of bleeding. Neighborhood complement is a technique that makes it difficult to see missing dots due to defective nozzles by increasing the amount of ink ejected from the primary neighborhood nozzles, etc., so that the ink ejected by the primary neighborhood nozzles spreads in print media that are difficult to bleed ink. The effect (the effect of filling in missing dots) is small. On the other hand, in the neighborhood complement, the color to be complemented is not limited like the color mixture complement. Therefore, when the setting of the print medium used by the printing unit 30 is a predetermined first print medium that is relatively hard to bleed, such as glossy paper, the control unit 11 compares the proximity complement and the color mixture complement. , The complement processing unit 12 is controlled so as to execute color mixture complementing with priority. On the other hand, when the setting of the printing medium used by the printing unit 30 is a predetermined second printing medium that is relatively easy to bleed ink, such as plain paper, the control unit 11 performs the proximity complement and the color mixture complement. In the comparison, the complement processing unit 12 is controlled so that neighborhood complement is executed with priority.

(Fourth embodiment)
FIG. 8 is a flowchart showing print control processing executed by the control unit 11 in the fourth embodiment, which is an example different from FIG. FIG. 8 differs from FIG. 3 in that it has the determination of step S135. When it is determined in step S120 that the complement processing for complementing the missing dot due to the defective nozzle indicated by the nozzle information is not executable by the complement processing unit 12 (“No” in step S120), the control unit 11 performs step S135. Proceed to

  In step S135, the control unit 11 determines whether or not a condition for executing the data shift process (data shift execution condition) is satisfied. If the data shift execution condition is satisfied, step S140 (data shift The process proceeds to (printing process with processing). On the other hand, if the data shift execution condition is not satisfied, the process proceeds to step S110 (normal printing process).

  The control unit 11 performs a second process in which the amount of ink to be ejected corresponding to a predetermined area including the defective nozzle corresponding pixel NP in the print data DB is greater than or equal to the first threshold and greater than the first threshold. When the threshold value is not more than the threshold value, the data shift execution condition is satisfied. The predetermined area including the defective nozzle corresponding pixel NP is, for example, an area formed by a plurality of pixel arrays that are continuous in the direction D1 with the defective nozzle corresponding pixel array NPL substantially at the center in the print data DB. Further, the ink amount to be ejected corresponding to the predetermined area can be grasped, for example, by a ratio with respect to the ink amount (maximum ink amount: duty 100%) when all the pixels in the predetermined area have a large tod.

  The control unit 11 sums up the ink amounts by the dots of the pixels in the predetermined area when the print data DB is followed. For example, when Q is the number of pixels in the predetermined area, a value obtained by multiplying the number q of dots defined in the predetermined area by 100 / Q [%] according to the print data DB is the predetermined area. As the amount of ink to be ejected. Even in this case, when the print data DB is simply binary data indicating ON / OFF of the dot for each pixel, the number of dots defined in the predetermined area is set as the number of dots q. On the other hand, when the print data DB is quaternary data indicating on or off of any one of large dots, medium dots, and small dots for each pixel, for example, one large dot is 1 dot, and one medium dot is 0. The number of dots in the predetermined area obtained by performing conversion according to the difference in the amount of ink per drop, such as 5 dots, 1 small dot, 0.25 dots, etc., is the dot number q.

  Here, dot missing due to the defective nozzle 34N appears as a streak (color streak of the print medium) on the print medium corresponding to the defective nozzle corresponding pixel row NPL. However, when the amount of ink to be ejected in a region having a certain area including the defective nozzle corresponding pixel row NPL is small in the first place, such a streak is hardly noticeable. In addition, when the amount of ink to be ejected in such a region is a relatively large amount that is close to the maximum ink amount, the missing dots are substantially filled with erosion by neighboring dots, and such a streak Is hardly noticeable. In other words, the streaks due to missing dots are easily noticeable when the amount of ink to be ejected in a region having a certain area including the defective nozzle corresponding pixel row NPL is not too small and not too large. When the condition is met, a measure (data shift processing) for reducing missing dots is executed.

  Various specific numerical values of the first threshold value and the second threshold value are conceivable. In view of such circumstances, for example, the first threshold value = 30% and the second threshold value = 70% or so. That is, when the ink amount to be ejected corresponding to the predetermined area including the defective nozzle corresponding pixel NP in the print data DB is about 50% (about 30% to 70%) with respect to the maximum ink amount, the dot missing is caused. Since the line is easily noticeable, the data shift execution condition is satisfied. According to the fourth embodiment, the data shift process is executed when it is recognized that an appropriate effect is generated by the data shift process. Is avoided.

(Fifth embodiment)
FIG. 9 is a flowchart showing data shift processing in the fifth embodiment, which is an example different from FIG. FIG. 9 differs from FIG. 5 in that it has the determinations of steps S205 and S235. However, the determinations in steps S205 and S235 are not mandatory determinations, and only one of the determinations may be added to the flowchart of FIG.

  In step S205, the data shift processing unit 13 determines whether or not the missing ink amount A1 before shifting calculated in step S200 is equal to or greater than a predetermined threshold (“fourth threshold” in the claims). To do. The data shift processing unit 13 proceeds to step S210 when the missing ink amount A1 before shifting is equal to or larger than the predetermined fourth threshold value, and the missing ink amount A1 before shifting becomes the fourth threshold value. If not, the flowchart (FIG. 9) ends.

  Further, in step S235, the data shift processing unit 13 counts the missing ink after shift calculated in step S220 according to the missing ink amount A1 before shift calculated in step S200 and the number of shift nozzles that can be set in step S210. It is determined whether or not the maximum dot drop reduction amount of each difference (dot drop reduction amount) from the amount A2 is equal to or greater than a predetermined threshold value (“third threshold value” in the claims). . The data shift processing unit 13 proceeds to step S240 when the maximum dot drop reduction amount is equal to or larger than the predetermined third threshold, and the maximum dot drop reduction amount is the third threshold value. When it is less than the value, the flowchart (FIG. 9) is terminated.

  The data shift process (step S240) is executed both when the flowchart (FIG. 9) is directly terminated after the determination in step S205 and when the flowchart (FIG. 9) is terminated directly after the determination in step S235. Instead, step S140 (FIGS. 3 and 8) is substantially the same as the normal printing process (step S110). When the missing ink amount A1 before shifting is small, dot missing is not noticeable in the first place, and the effect of executing the data shift process is weak (it is difficult for the user to recognize that the image quality has been improved by the data shift process). The maximum dot drop reduction amount is the amount of dot drop reduced by the data shift process. However, even when this amount is small in the first place, it is not meaningful to execute the data shift process. Therefore, in the fifth embodiment, when the missing ink amount A1 before shift is greater than or equal to the fourth threshold value, or when the maximum dot drop reduction amount is greater than or equal to the third threshold value, that is, data shift processing. The data shift process is executed when the image quality improvement effect is substantially recognized.

(Sixth embodiment)
The control unit 11 may cause the print head 31 to perform nozzle cleaning. The nozzle cleaning is a process for forcibly discharging ink from each nozzle 34 of the print head 31 to eliminate clogging of the nozzle 34 that occurs at that time and to return the defective nozzle 34 to a normal nozzle. is there. For example, the control unit 11 causes the print head 31 to perform nozzle cleaning after finishing Step S130 and Step S140 (FIGS. 3 and 8). In addition, the control unit 11 may cause the print head 31 to perform nozzle cleaning when the complement process is not performed and the data shift process is not performed in a situation where there is a defective nozzle. That is, when it is determined in step S135 (FIG. 8) that the data shift execution condition is not satisfied, when the flowchart of FIG. 9 is directly terminated from the determination of step S205, or directly after the determination of step S235 is terminated. In this case, the print head 31 may perform nozzle cleaning.

(Seventh embodiment)
The control unit 11 sets the missing ink amount (the missing ink amount before rotation (= the missing ink amount A1 before shifting)) that is the ink amount due to the dots of the defective nozzle corresponding pixel NL in the print data DB and the print data DB by 180 degrees. When the amount of missing ink (amount of missing ink after rotation), which is the amount of ink by the dots of the defective nozzle corresponding pixel NL in the rotated print data after rotation, is compared, and the amount of missing ink after rotation is smaller The print head 31 may perform printing based on the rotated print data.

  The print data DB shown in the upper part of FIG. 6 will be described as an example. The missing ink amount before rotation in the print data DB is the pixel of the pixel column of pixel column number 10 assigned to the nozzle 34 of nozzle number 12 (defective nozzle 34N). The sum of the in-column ink amount (12) and the in-pixel ink amount (12) of the pixel column of the pixel column number 11 assigned to the nozzle 34 (defective nozzle 34N) of the nozzle number 13 is 24. On the other hand, when the print data DB is rotated by 180 degrees, the pixel row having the pixel row number 16 before the rotation is assigned to the nozzle 34 (defective nozzle 34N) with the nozzle number 12, and the pixel row number before the rotation is assigned. The pixel row that was 15 is assigned to the nozzle 34 (defective nozzle 34N) with nozzle number 13. Accordingly, the missing ink amount after rotation is the ink amount (0) in the pixel column that was the pixel column number 16 before the rotation, and the pixel column number 15 that was the pixel column number before the rotation. It is 3 which is the sum of the ink amount (3).

  In this example, since the missing ink amount after rotation is smaller than the missing ink amount before rotation, the control unit 11 causes the print head 31 to execute printing based on the print data after rotation. Rotating the print data by 180 degrees does not change the printed matter obtained by the user (it does not change the correspondence between the long side / short side of the print medium and the long side / short side of the print data). There is no penalty for the user. Further, by rotating the print data by 180 degrees in this manner, dot omission can be reduced and image quality is improved.

(Eighth embodiment)
Until now, the case where the print head 31 is a line head has been described as an example. However, the print head 31 is of course a type mounted on a so-called serial painter and moved in a predetermined main scanning direction by a carriage 35. The print head may be used. Referring to FIG. 2, assuming that the print head 31 is a print head mounted on a serial painter, the print medium S is transported by the transport unit 36 in a direction parallel to the direction D1, not the direction D2. It will be. The print head 31 is moved along a direction (main scanning direction) parallel to the direction D2 by the carriage 35. That is, the ink ejection (pass) accompanying the movement of the print head 31 and the conveyance (paper feed) of the print medium S at a certain distance are alternately repeated, so that the band unit image is printed on the print medium S. Is repeated.

  In this case, in the print data, a region where pixels having the same position in the direction D1 are connected along the direction D2 (connected along the main scanning direction) corresponds to the pixel row used in the above description. That is, the relationship between the conveyance direction of the print medium S and the direction in which the pixel row faces differs between the line printer and the serial printer. Even in such a serial printer, the description of the complementary processing and data shift processing up to now is similarly applied. However, when the data shift process is executed, that is, when the range of nozzle numbers used for each pass is changed, the image (band image) printed in the previous pass to the print medium S and the next pass to the print medium S The control unit 11 needs to adjust the paper feed distance for each paper feed so that the image (band image) printed in step S1 is connected in the direction D1.

DESCRIPTION OF SYMBOLS 10 ... Print control apparatus, 11 ... Control part, 12 ... Complement processing part, 13 ... Data shift processing part, 20 ... Defective nozzle detection part, 30 ... Printing part, 31 ... Print head, 32 ... Head, 34 ... Nozzle, 34N ... Defective nozzle, 35 ... Carriage, 36 ... Conveying unit, 100 ... External device, S ... Print medium, KNL, CNL, MNL, YNL ... Nozzle array

Claims (9)

A print control apparatus that controls ejection of ink by a nozzle row having a plurality of nozzles arranged in a predetermined direction at a predetermined interval based on print data expressing a dot pattern by a plurality of pixels,
A defective nozzle detection unit for detecting a defective nozzle in which an ink ejection defect occurs from the plurality of nozzles;
Complement processing for adding dots to neighboring pixels with respect to a pixel row in which defective nozzle corresponding pixels, which are pixels assigned to the defective nozzle in the print data, are continuous or increasing the size of the dots of the neighboring pixels is performed on the print data A complementary processing unit for applying to,
Data shift processing is performed in which the amount of missing ink, which is the amount of ink due to dots of the defective nozzle corresponding pixel in the print data, is aggregated and the allocation relationship between the pixel and the nozzle is changed so that the amount of missing ink is reduced. A data shift processing unit for applying to the print data,
When the defective nozzle is not continuous in the predetermined direction, the complement processing unit performs the complement processing on the print data,
The print control apparatus, wherein the data shift processing unit performs the data shift processing on the print data when the complement processing unit does not execute the complement processing. A print control apparatus that controls ejection of ink by a nozzle row having a plurality of nozzles arranged in a predetermined direction at a predetermined interval based on print data expressing a dot pattern by a plurality of pixels,
A defective nozzle detection unit for detecting a defective nozzle in which an ink ejection defect occurs from the plurality of nozzles;
Corresponding to a defective pixel corresponding to a defective nozzle corresponding to a defective nozzle corresponding to the defective nozzle in the print data, the position in the predetermined direction is the same as the defective nozzle, and the ejection failure does not occur A complementary processing unit for executing a complementary process for causing the nozzles to eject ink;
Data shift processing is performed in which the amount of missing ink, which is the amount of ink due to dots of the defective nozzle corresponding pixel in the print data, is aggregated and the allocation relationship between the pixel and the nozzle is changed so that the amount of missing ink is reduced. A data shift processing unit for applying to the print data,
When the normal nozzle is present, the complement processing unit executes the complement processing,
The print control apparatus, wherein the data shift processing unit performs the data shift processing on the print data when the complement processing unit does not execute the complement processing.   The complement processing unit performs the complement processing for ejecting ink to the normal nozzle that ejects ink of the same color as that of the ink to be ejected by the defective nozzle, the position in the predetermined direction being the same as the defective nozzle. The printing control apparatus according to claim 2, wherein the printing control apparatus is a printing control apparatus. The ink to be ejected by the defective nozzle is achromatic,
The complement processing unit performs the complement processing for ejecting ink to a plurality of normal nozzles that eject different chromatic color inks whose positions in the predetermined direction are the same as those of the defective nozzle. The printing control apparatus according to claim 2.   When the complementary processing unit does not execute the complementary processing, the data shift processing unit determines that the amount of ink to be ejected corresponding to a predetermined area including the defective nozzle corresponding pixel in the print data is a first threshold. The data shift process is performed on the print data when the print data is equal to or greater than a value and equal to or less than a second threshold value greater than the first threshold value. The printing control apparatus described.   When the complement processing unit does not execute the complement processing, the data shift processing unit performs the data shift processing from the missing ink amount before performing the data shift processing on the print data. 6. The print control apparatus according to claim 1, wherein when the value obtained by subtracting the amount is equal to or greater than a third threshold value, the data shift process is performed on the print data.   When the complement processing unit does not execute the complement processing, the data shift processing unit, when the amount of missing ink before performing the data shift processing on the print data is greater than or equal to a fourth threshold, The print control apparatus according to claim 1, wherein the data shift process is performed on the print data. A print control method for controlling ejection of ink by a nozzle row having a plurality of nozzles arranged in a predetermined direction at a predetermined interval based on print data expressing a dot pattern by a plurality of pixels,
A defective nozzle detecting step for detecting a defective nozzle in which defective ink ejection occurs from the plurality of nozzles;
When the defective nozzle is not continuous in the predetermined direction, a dot is given to a neighboring pixel for a pixel row in which defective nozzle corresponding pixels that are pixels assigned to the defective nozzle in the print data are continuous, or the neighboring pixel is A complementing step for performing a complementing process for increasing the size of the dots on the print data;
When the complementing step is not executed, the missing ink amount that is the ink amount due to the dots of the defective nozzle corresponding pixel in the print data is totaled, and the pixel and the nozzle are assigned so that the missing ink amount is reduced. And a data shift process for performing a data shift process for changing the relationship on the print data. A print control method for controlling ejection of ink by a nozzle row having a plurality of nozzles arranged in a predetermined direction at a predetermined interval based on print data expressing a dot pattern by a plurality of pixels,
A defective nozzle detecting step for detecting a defective nozzle in which defective ink ejection occurs from the plurality of nozzles;
A dot having a dot among defective nozzle corresponding pixels which are pixels assigned to the defective nozzle in the print data when there is a normal nozzle in which the position in the predetermined direction is the same as that of the defective nozzle and the ejection failure does not occur A complementing step for performing a complementing process for causing the normal nozzle to eject ink in correspondence with the missing pixel;
When the complementing step is not executed, the missing ink amount that is the ink amount due to the dots of the defective nozzle corresponding pixel in the print data is totaled, and the pixel and the nozzle are assigned so that the missing ink amount is reduced. And a data shift process for performing a data shift process for changing the relationship on the print data.

Images