JP2016185608A - Assignment mask and how to generate assignment mask - Google Patents

Abstract

Generation of image unevenness in an overlapping print region is suppressed. A plurality of print heads each having a plurality of nozzle rows arranged in parallel to each other include nozzles having the same coordinate in the nozzle row direction along the plurality of nozzle rows in two adjacent print heads. When printing is performed by a printing apparatus arranged to have an overlapping nozzle area at the end of each print head, each dot in the overlapping printing area in a print medium on which dots are formed by the nozzles in the overlapping nozzle area is 2 In the allocation mask in which the allocation information for determining which of the two print heads is formed is set, the allocation information is the nozzle array of each print head in the image of the overlapping print area obtained by applying the allocation mask. Is set so that the spatial frequency of the dots formed by the above has blue noise characteristics or green noise characteristics. [Selection] Figure 1

Description

  The present invention relates to an allocation mask for determining which nozzle forms a dot in a region where nozzles overlap in a predetermined direction.

  In an ink jet line printer, printing is performed by ejecting ink from nozzles of a line head provided over the entire sheet width in a direction intersecting the sheet feeding direction while feeding a printing sheet. The line head is generally configured by arranging a plurality of print heads each having a length in the longitudinal direction smaller than the paper width in a staggered manner in the paper width direction. Further, in these print heads, for example, as described in Patent Document 1, there is an overlapping region where the ends of adjacent print heads partially overlap in the arrangement direction. Of the two nozzles having the same coordinate along the arrangement direction in the overlapping region, which nozzle forms the dot is determined by mask processing using a predetermined mask (hereinafter referred to as “assignment mask”). Is done. The allocation mask of Patent Document 1 is a mask in which a value of “0” or “1” is set for each dot position. In the mask processing, an allocation mask is applied to the image data after halftone processing, and when the value set at the same dot position is “1”, dot formation is permitted to one print head and the other printing is performed. When dot formation is not allowed for the head and this value is “0”, dot formation is not allowed for one print head and dot formation is allowed for the other print head.

JP 2011-76156 A

  In printing using an allocation mask described in Patent Document 1, dot dispersibility is relatively good in a print region (hereinafter referred to as “overlap print region”) formed by the nozzles of the above-described overlap region. However, the print head of Patent Document 1 has one nozzle row, and dot dispersibility in the case of having a plurality of nozzle rows has not been considered. In recent years, due to demands for high resolution and high-speed printing, each print head may include a plurality of nozzle rows arranged slightly shifted from each other in the nozzle row direction. As described above, when the print head includes a plurality of nozzle arrays, the plurality of nozzle arrays form dots at different raster positions (print positions in the paper feed direction). However, if the landing position of the ink ejected from at least one nozzle row is deviated due to manufacturing errors such as the orientation and position of the nozzle, and meandering or lifting of the paper when feeding the paper, it is formed by the nozzle row. Since the dot row to be shifted is out of the planned position, image unevenness may occur. In particular, in the overlap region, since dots are formed by two print heads, such image unevenness is more noticeable.

  Such a problem may occur not only in a line head printer but also in the case of generating printing data used in a printer that performs printing by scanning a head in the paper width direction, so-called a serial head printer. In a serial head printer, image unevenness may occur in an area where all dots are formed by a plurality of scans, as in the above-described overlapping print area. Therefore, a technique capable of reducing image unevenness in the overlapping print area has been desired.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to the first aspect of the present invention, a plurality of print heads each having a plurality of nozzle rows arranged in parallel to each other are arranged in two adjacent print heads along the plurality of nozzle rows. When printing is performed by a printing apparatus in which overlapping nozzle regions having nozzles having the same direction coordinates exist at the end of each print head, dots are formed by the nozzles in the overlapping nozzle region. An allocation mask in which allocation information for determining which of the two print heads is used to form each dot in the overlapping print area on the print medium is provided. In this allocation mask, the allocation information indicates that a spatial frequency of dots formed by each nozzle row of each print head in the image of the overlapping print region obtained by applying the allocation mask has a blue noise characteristic or a green noise characteristic. It may be set to have.
According to the allocation mask of this aspect, in the allocation mask, the allocation information includes a blue noise characteristic in which the spatial frequency of dots formed by each nozzle row of each print head in the image of the overlapping print area obtained by applying the allocation mask Or it is set to have green noise characteristics. For this reason, in the overlapping print region obtained by applying such an assignment mask, the dispersibility of the dots formed by each nozzle row can be improved, so the dot position (liquid level) by at least one nozzle row of the two nozzle rows can be improved. Even if the droplet landing position is deviated, it is possible to suppress the occurrence of dot density (image unevenness) in the overlapping print region.

(2) According to the second aspect of the present invention, a print head having a plurality of nozzle rows arranged in parallel to each other is placed on a print medium in a crossing direction that intersects the nozzle row direction along the plurality of nozzle rows. When printing is performed by a printing apparatus that forms a dot on the print medium by performing a main scan that moves relative to each other, each dot in the overlapping print area in which an image is formed by a plurality of times of the main scan An allocation mask in which allocation information for determining which of the main scans is to be formed is set. In this allocation mask, the allocation information indicates that a spatial frequency of dots formed by each nozzle row of each print head in the image of the overlapping print region obtained by applying the allocation mask has a blue noise characteristic or a green noise characteristic. Is set to have.
According to the allocation mask of this form, the allocation information includes a blue noise characteristic or a green noise characteristic in which the spatial frequency of dots formed by each nozzle row of each print head in the image of the overlapping print region obtained by applying the allocation mask Is set to have For this reason, since the dispersibility of the dots formed by each nozzle row can be improved in the overlapping print region obtained by applying such an allocation mask, the dots formed by at least one of the two main scans Even if the position (droplet landing position) is deviated, it is possible to suppress the occurrence of dot density (image unevenness) in the overlapping print region.

(3) According to the third aspect of the present invention, a plurality of print heads each having a plurality of nozzle rows arranged in parallel to each other are arranged in two adjacent print heads along the plurality of nozzle rows. When printing is performed by a printing apparatus in which overlapping nozzle areas having overlapping nozzles, which are nozzles whose direction coordinates are the same, exist at the end of each print head, dots are generated by the nozzles in the overlapping nozzle area. An assignment mask generation method is provided in which assignment information for determining which of the two print heads is used to form each dot in an overlapping print region in a print medium on which is formed. This assignment mask generation method includes (a) a step of preparing a binarization mask having a first feature and a second feature, and (b) the same size as the assignment mask, which is determined in advance. A step of preparing for each print head a mask original image that can be printed with a duty ratio corresponding to the dot formation ratio of each nozzle in the overlapping nozzles, and (c) applying the binarized mask to each mask original image And a step of obtaining a mask binarized image for each print head, and (d) generating the assigned mask for each print head based on the mask binarized image. In the entire image obtained by applying the binarization mask as a dither mask used for halftone processing for generating dot data representing the presence or absence of dot formation based on input image data, The spatial frequency of the image has a blue noise characteristic or a green noise characteristic, and the second feature is an image obtained by applying the binarization mask as a dither mask used in the halftone process. The spatial frequency of the dots formed by each nozzle row included in each print head has blue noise characteristics or green noise characteristics.
According to the allocation mask generation method of this aspect, the binarization mask used when generating the allocation mask for each head is applied to each print head in an image obtained by applying the binarization mask. Since the spatial frequency of the dots formed by each included nozzle row is set to have a blue noise characteristic or a green noise characteristic, it is formed by each nozzle row in the overlapping print area obtained by applying the allocation mask. The dispersibility of the formed dots can be improved. For this reason, even if the dot position (droplet landing position) of at least one of the two nozzle arrays is shifted, the occurrence of dot density (image unevenness) in the overlapping print region can be suppressed.

(4) According to the fourth aspect of the present invention, a print head having a plurality of nozzle rows arranged in parallel to each other is placed on a print medium in a crossing direction intersecting with the nozzle row direction along the plurality of nozzle rows. When printing is performed by a printing apparatus that forms a dot on the print medium by performing a main scan that moves relative to each other, each dot in the overlapping print area in which an image is formed by a plurality of times of the main scan An allocation mask generation method in which allocation information for determining which of the main scans is to be formed is set. In this allocation mask generation method, each nozzle row includes at least two different nozzles in the nozzle row and scans the same coordinates in the intersecting direction of the print medium by the main scanning a different number of times. There are overlapping nozzles. This assignment mask generation method includes (a) a step of preparing a binarization mask having a first feature and a second feature, and (b) the same size as the assignment mask, which is determined in advance. A step of preparing for each print head a mask original image that can be printed with a duty ratio corresponding to the dot formation ratio of each nozzle in the overlapping nozzles, and (c) applying the binarized mask to each mask original image And a step of obtaining a mask binarized image for each print head, and (d) generating the assigned mask for each print head based on the mask binarized image. In the entire image obtained by applying the binarization mask as a dither mask used for halftone processing for generating dot data representing the presence or absence of dot formation based on input image data, The second feature is that an image obtained by applying the valuation mask as a dither mask used in the halftone process has a spatial noise frequency of blue noise or green noise characteristics. The spatial frequency of dots formed by each nozzle row included in each print head has blue noise characteristics or green noise characteristics.
According to the allocation mask generation method of this aspect, the binarization mask used when generating the allocation mask for each head is applied to each print head in an image obtained by applying the binarization mask. Since the spatial frequency of the dots formed by each included nozzle row is set to have a blue noise characteristic or a green noise characteristic, it is formed by each nozzle row in the overlapping print area obtained by applying the allocation mask. The dispersibility of the formed dots can be improved. For this reason, even if the dot position (droplet landing position) formed by at least one of the two main scans is shifted, the occurrence of dot density (image unevenness) in the overlapping print region can be suppressed.

(5) In the allocation mask generation method according to the third aspect or the fourth aspect, the size of the mask original image in the intersecting direction intersecting the nozzle array direction along the plurality of nozzle arrays is in the intersecting direction. It may be equal to the size of the binarization mask. Since the size of the mask original image in the intersecting direction is equal to the size of the binarized mask in the intersecting direction, when the assignment mask is tiled and assignment is performed for each nozzle of the overlapping nozzles, Dispersibility can be smoothed and image unevenness can be reduced.

  A plurality of constituent elements of each embodiment of the present invention described above are not essential, and some or all of the effects described in the present specification are to be solved to solve part or all of the above-described problems. In order to achieve the above, it is possible to appropriately change, delete, replace with a new component, and partially delete the limited contents of some of the plurality of components. In order to solve part or all of the above-described problems or to achieve part or all of the effects described in this specification, technical features included in one embodiment of the present invention described above. A part or all of the technical features included in the other aspects of the present invention described above may be combined to form an independent form of the present invention.

  The present invention can be realized in various forms. For example, a printing data generating device, a printing device, a liquid ejecting device, a printing data generating method, a printing method, a liquid ejecting method, and a computer program that realizes at least one of these methods, The present invention can be realized in the form of a non-temporary recording medium on which a computer program is recorded.

FIG. 2 is a block diagram illustrating a configuration of a printer including an assignment mask as an embodiment of the present invention. 4 is an explanatory diagram showing a detailed configuration of a line head 60. FIG. It is explanatory drawing which shows the detailed structure of the nozzle row group shown in FIG. 3 is a flowchart illustrating a procedure of print processing executed in the printer. It is explanatory drawing which illustrates the noise characteristic with which the dither mask 51 is provided. It is explanatory drawing which shows the content of the allocation process typically. It is a flowchart which shows the procedure of the production | generation process of the two allocation masks 52 and 53 used in an allocation process. It is explanatory drawing which shows an example of the binarized image obtained by step S230 based on the mask image 55 for back heads. It is explanatory drawing which shows an example of the image obtained by applying the allocation mask obtained by the allocation mask process of this embodiment. It is explanatory drawing which shows an example of the image obtained by applying the allocation mask of a comparative example. It is explanatory drawing which shows schematic structure of the printer in 2nd Embodiment. It is explanatory drawing which shows typically the relationship between the scanning of the printing head 130 in 2nd Embodiment, and a printing range.

A. First embodiment:
A1. Printer configuration:
FIG. 1 is a block diagram illustrating a configuration of a printer including an assignment mask according to an embodiment of the present invention. The printer 10 is an ink jet line printer, and includes a control unit 20, a line head 60, an ink supply mechanism 70, a paper feed mechanism 80, an operation panel 91, and a memory card slot 92.

  The control unit 20 controls the entire printer 10. The control unit 20 is electrically connected to the line head 60, the paper feed mechanism 80, the operation panel 91, and the memory card slot 92. The control unit 20 includes a CPU (Central Processing Unit) 30, a ROM (Read Only Memory) 41, a RAM (Random Access Memory) 42, and an EEPROM (Electrically Erasable Programmable Read-Only Memory) 50. All of these components included in the control unit 20 are connected to the internal bus. The CPU 30 functions as the input unit 31, halftone processing unit 32, allocation processing unit 33, and print control unit 34 by expanding and executing the control program stored in the ROM 41 on the RAM 42. The processing content of each of these functional units will be described in print processing and assignment mask generation processing described later.

  The EEPROM 50 stores a dither mask 51, a preceding head assignment mask 52, a following head assignment mask 53, a preceding head mask original image 54, and a following head mask original image 55. Of these, the dither mask 51, the leading head mask original image 54, and the trailing head mask original image 55 are stored in the EEPROM 50 in advance. The preceding head assignment mask 52 and the succeeding head assignment mask 53 are stored in the EEPROM 50 after an assignment mask generation process described later is executed. The dither mask 51 is used for halftone processing by a systematic dither method, and includes a plurality of threshold values. The dither mask 51 is used for a printing process to be described later and also used in an assignment mask generation process. The dither mask 51 corresponds to a subordinate concept of the binarization mask in the claims. The leading head allocation mask 52 and the trailing head allocation mask 53 are used in a printing process described later. The leading head mask original image 54 and the trailing head mask original image 55 are used in an assignment mask generation process described later. Details of the dither mask 51, the two assignment masks 52 and 53, and the two mask original images 54 and 55 will be described later.

  The line head 60 has a plate-like appearance and has a number of nozzles that open vertically downward in the mounted state. By ejecting ink droplets from these nozzles, a large number of ink dots are formed on the printing paper P, and an image is printed. The detailed configuration of the line head 60 will be described later.

  The ink supply mechanism 70 includes a cartridge holder 71, an ink cartridge 72, and an ink supply path 73. An ink cartridge 72 is detachably attached to the cartridge holder 71. In the present embodiment, four ink cartridges 72 corresponding to the ink colors discharged from the printer 10 are mounted on the cartridge holder 71. Specifically, four ink cartridges 72 corresponding to four colors of cyan (C), magenta (M), yellow (Y), and black (K) are mounted on the cartridge holder 71. The ink supply path 73 connects the cartridge holder 71 and the line head 60, and supplies ink of each color from the cartridge holder 71 to the line head 60. Thus, the printer 10 corresponds to a so-called off-carriage type printer.

  The paper feed mechanism 80 includes a paper feed motor 81 and a paper feed roller 82 driven by the paper feed motor 81. The paper feed mechanism 80 conveys the printing paper P from a paper supply unit (for example, a paper tray) in the printer 10 to a paper discharge unit (for example, a discharge tray). A platen (not shown) is disposed at a position facing the line head 60 with the printing paper P in between.

  The operation panel 91 allows the user to perform various settings and menu selections in the printer 10. The operation panel 91 may be constituted by, for example, a plurality of physical button groups, a touch panel, or the like. The memory card slot 92 is detachably loaded with a memory card MC storing image data. The CPU 30 can read image data from the memory card MC installed in the memory card slot 92 and write image data to the memory card MC. In the present embodiment, the image data stored in the memory card MC is RGB (Red, Green, Blue) color system image data.

A2. Detailed printhead configuration:
FIG. 2 is an explanatory diagram showing a detailed configuration of the line head 60. FIG. 2 shows the configuration of the line head 60 on the surface facing the printing paper P. Note that a part of the configuration of the line head 60 is omitted for convenience of illustration.

  In the line head 60, a plurality of print heads in which nozzle row groups 61 to 64 for ejecting inks of colors C, M, Y, and K are formed are arranged in a staggered manner over the printing range of the printing paper P. Composed. The reason why the print heads are arranged in a staggered manner as described above is to solve the problem of the strength of the end of the print head and the problem of the installation space of the attached device. Each print head has the same configuration. Note that the number of print heads constituting the line head 60 may be two or more. Further, the method for arranging the print heads is not particularly limited, and may be, for example, stepped. Similarly, in the present embodiment, the nozzles constituting the nozzle row groups 61 to 64 are formed in a straight line in the print head arrangement direction, but the nozzle arrangement method is not particularly limited. For example, they may be arranged in a staggered pattern.

  Among these print heads, the one disposed on the upstream side in the transport direction of the printing paper P is referred to as a preceding head PH, and the one disposed on the downstream side is referred to as a trailing head FH hereinafter. The leading head PH and the trailing head FH each have an area overlapping with another adjacent print head (hereinafter also referred to as an overlapping nozzle area ORA) and an area without the overlapping (hereinafter referred to as a single nozzle area). (Also referred to as SA). As will be described later, in the overlapping nozzle area ORA, the leading head PH and the trailing head FH have nozzles having the same coordinate in the nozzle row direction. The reason why the overlapping nozzle area ORA is provided in this way is to suppress the occurrence of banding in the portion corresponding to the joint between the print heads in the print image due to the difference in the characteristics of each print head. .

  The leading head PH and the trailing head FH form one dot row on the printing paper P along the arrangement direction of the print heads, that is, the nozzle row direction by adjusting the paper feed and ink ejection timing. A dot row of an area of the printing paper P (hereinafter referred to as “single print area”) where dots are formed by the nozzles of the single nozzle area SA is formed by either the preceding head PH or the trailing head FH. On the other hand, the dot row of the area of the printing paper P (hereinafter referred to as “overlapping printing area”) formed by the nozzles of the overlapping nozzle area ORA is formed by both the preceding head PH and the following head FH. .

  By continuously performing the dot row forming operation along the nozzle row direction, dot rows (also referred to as rasters in this embodiment) are also formed in the transport direction of the printing paper P. Of the print areas printed in this way, areas corresponding to the respective print heads are also referred to as bands. In the present embodiment, for convenience of explanation, as shown in FIG. 2, the overlapping print areas are separated by a central portion and numbered (J in the figure is a positive integer) to identify the band. To do.

  FIG. 3 is an explanatory diagram illustrating a detailed configuration of the nozzle array group illustrated in FIG. 2. FIG. 3 shows a detailed configuration of two nozzle row groups 61 included in the same overlapping nozzle area ORA. In FIG. 3, one nozzle row group 61 is the nozzle row group 61 of the preceding head PH, and the other nozzle row group 61 is the nozzle row group 61 of the trailing head FH.

  The nozzle row group 61 of each head PH and FH has two nozzle rows that are parallel to each other. Specifically, the nozzle row group 61 of the preceding head PH has a nozzle row LpA and a nozzle row LpB. The nozzle row group 61 of the trailing head FH has a nozzle row LfA and a nozzle row LfB. The two nozzle rows constituting each nozzle row group 61 include the same number of nozzles as each other, and are shifted from each other in the nozzle row direction. More specifically, if the distance (nozzle pitch) along the nozzle row direction between nozzles adjacent to each other in the nozzle row direction in each nozzle row is 2k, the two nozzle rows are shifted in the nozzle row direction by half k. Is arranged. With such a configuration, the nozzle pitch k of each nozzle row group 61 as a whole when viewed from the paper feed direction is relatively small, and high-resolution printing and high-speed printing are realized. The paper feed direction in the present embodiment corresponds to the subordinate concept of the cross direction in the claims.

  The leading head PH includes eight nozzles np1 to np8 at the upper end of FIG. 3 as nozzles included in the overlapping nozzle area ORA. Similarly, the trailing head FH includes eight nozzles nf1 to nf8 at the lower end of FIG. 3 as nozzles included in the overlapping nozzle area ORA. In the overlapping nozzle area ORA, the leading head PH and the trailing head FH have nozzles having the same coordinate in the nozzle row direction. In other words, the leading head PH and the trailing head FH each have nozzles that form the same raster. Specifically, the nozzle np1 of the leading head PH and the nozzle nf1 of the trailing head FH have the same coordinate in the nozzle row direction. Similarly, the nozzle np2 of the preceding head PH and the nozzle nf2 of the following head FH, the nozzle np3 of the preceding head PH and the nozzle nf3 of the following head FH, the nozzle np4 of the preceding head PH and the nozzle nf4 of the following head FH, the preceding head Nozzle np5 of PH and nozzle nf5 of trailing head FH, nozzle np6 of leading head PH and nozzle nf6 of trailing head FH, nozzle np7 of leading head PH and nozzle nf7 of trailing head FH, nozzle np8 of leading head PH and The nozzles nf8 of the trailing head FH have the same coordinate in the nozzle row direction. Therefore, for example, among the two nozzles np1 and nf1 forming the same raster, the dot at the same position is formed by any one of the nozzles. In FIG. 3, the ratio (%) associated with each of the nozzles np1 to np8 and nf1 to nf8 will be described later.

A3. Printing process:
FIG. 4 is a flowchart illustrating a procedure of print processing executed in the printer 10. When the user performs a print instruction operation for an image stored in the memory card MC using the operation panel 91 or the like, a print process is executed in the printer 10. The input unit 31 reads and inputs image data to be printed from the memory card MC via the memory card slot 92 (step S110). The CPU 30 refers to a lookup table (not shown) stored in the EEPROM 50 and performs color conversion from RGB format to CMYK format for the input image data (step S120).

  The halftone processing unit 32 performs halftone processing for converting the image data after color conversion into bitmap data represented by ON and OFF of each color dot (step S130). In the halftone processing in this embodiment, the input data is compared with the threshold value of the dither mask 51 by a systematic dither method using the dither mask 51. If the input data is equal to or greater than the threshold value, it is determined that the dot is on. Is less than the threshold value, it is determined that the dot is off. The halftone process is not limited to the binarization process of turning dots on and off, but may be a multi-value process such as turning on and off large dots and small dots. Further, the image data to be processed in step S130 may be data after various image processing such as resolution conversion processing and smoothing processing is performed as well as color conversion processing.

  Here, in this embodiment, the dither mask 51 is set in advance so that the dispersibility of dots in the entire bitmap data obtained by applying the dither mask is excellent. In addition, a raster group (hereinafter referred to as “Group A”) formed by the nozzle array on the left side of each print head (for example, the nozzle array LpA of the preceding head PH and the nozzle array LfA of the succeeding head FH shown in FIG. 3). In addition, the dispersibility of the dots constituting each of the print heads is excellent, and the nozzle array on the right side of each print head (for example, the nozzle array LpB of the preceding head PH and the nozzle array LfB of the succeeding head FH shown in FIG. 3) is formed. It is set in advance so that the dispersibility of the dots constituting the raster group (hereinafter also referred to as “B group”) is excellent. More specifically, the spatial frequency of the A group dots and the spatial frequency of the B group dots in the bitmap data obtained by applying the dither mask 51 are both so-called blue noise characteristics or so-called green noise characteristics. Is set in advance so that

  FIG. 5 is an explanatory diagram illustrating the noise characteristics provided in the dither mask 51. FIG. 5 conceptually illustrates the threshold spatial frequency characteristics set for each pixel of the dither mask 51 having the blue noise characteristics and the green noise characteristics for the dots of the A group and the B group. The blue noise characteristic in the dither mask 51 has the largest frequency component in a high frequency region in which the length of one cycle is near 2 pixels. This means that the storage position of the threshold is adjusted so that the largest frequency component is generated in the high frequency region in consideration of the human visual characteristic that the sensitivity is low in the high frequency region. When dots are generated using the dither mask 51 having such blue noise characteristics, an image having excellent dot dispersibility can be obtained.

  FIG. 5 further illustrates the green noise characteristic as a dashed curve. As shown in the figure, the green noise characteristic has the largest frequency component slightly on the low frequency side than the brie noise characteristic, and if the pixel size is sufficiently small, a good image that does not feel grainy even with the green noise characteristic. Is obtained. The dither mask 51 is preset so as to have a predetermined spatial frequency characteristic such as a blue noise characteristic or a green noise characteristic. The dither mask 51 having such a predetermined spatial frequency characteristic may be generated by, for example, a generation method described in JP 2007-116432 A.

  As shown in FIG. 4, the allocation processing unit 33 performs allocation processing for allocating which of the leading head PH and the trailing head FH forms dots at each dot formation position in the overlapping print region (step S140).

  FIG. 6 is an explanatory diagram schematically showing the contents of the allocation process. The leftmost part of FIG. 6 shows the final dot array DA, which is the result of the halftone process (step S130) for the overlapping print area. The lattice of the final dot array DA indicates the pixels of the image data. A grid displayed by hatching indicates pixels determined to be dot-on in the halftone process, and a grid displayed in white indicates pixels determined to be dot-off in the halftone process.

  In the preceding head assignment mask 52, the positions of pixels in which dots are formed by the preceding head PH among the pixels in the overlapping print area are recorded. Of the grids shown in the figure, hatched grids indicate pixels that form dots with the leading head PH (dots on), and pixels displayed in white do not form dots with the leading head PH. The pixel which forms a dot with the head FH is shown. By masking the final dot array DA using such a preceding head assignment mask 52, it is possible to determine the pixels on which dots are to be formed by the preceding head PH in the final dot array DA. Specifically, an overlapping portion between the dot-on pixel of the final dot array DA and the dot-on pixel of the preceding head allocation mask 52 is a dot arrangement DA1 in which dots are formed by the preceding head PH.

  The succeeding head assignment mask 53 records the positions of pixels in which dots are formed by the succeeding head FH among the pixels in the overlapping print area. The dot arrangement DA2 in which dots are formed by the succeeding head FH can be determined by masking the final dot array DA using such a succeeding head assignment mask 53. Note that the dot arrangement DA2 can be determined as an overlapping portion between the dot-on pixel of the final dot array DA and the dot-off pixel of the preceding head allocation mask 52. In the following description, information that assigns each dot forming position (pixel) to each dot forming position (pixel) as to which dot of the preceding head PH or the following head FH is used to form each dot constituting the overlapping print area is also referred to as allocation result information. Say. In the allocation masks 52 and 53, information (“0” and “1” described later) indicating whether or not to form dots for each pixel corresponds to a subordinate concept of the allocation information in the claims.

  As shown in FIG. 4, when the assignment process is completed, the print control unit 34 controls the line head 60, the motor 81, and the like based on the bitmap data obtained in step S130 and the assignment result information obtained in step S140. It is driven to execute printing (step S150). Thus, the printing process ends.

  Here, in the overlapping print region of the image obtained by the above-described printing process, the dispersibility of the dots formed by each nozzle row is very excellent. Specifically, the spatial frequency of dots formed in each nozzle row has a so-called blue noise characteristic or green noise characteristic. Such characteristics are obtained by the preceding head allocation mask 52 and the trailing head allocation mask 53 used for the allocation process. Processing for generating these two allocation masks 52 and 53 will be described below.

A4. Assignment mask generation processing:
FIG. 7 is a flowchart showing a procedure for generating two allocation masks 52 and 53 used in the allocation process. In the printer 10, when the user operates the operation panel 91 to select an allocation mask generation menu and inputs an execution instruction, an allocation mask generation process is executed. Note that the user sets the print ratio in the printer 10 before starting the allocation mask generation process. Therefore, information indicating the print ratio is stored in the EEPROM 50. Further, the user stores the preceding head mask original image 54 and the subsequent head mask original image 55 in the EEPROM 50 before the start of the allocation mask generation processing. As will be described later, these two mask original images 54 and 55 are generated as images that can be printed at a duty ratio in accordance with the print ratio set by the user. In other words, the user generates the leading head mask original image 54 and the trailing head mask original image 55 according to the print ratio to be set, and stores them in the EEPROM 50.

  The above-described print ratio is set for each nozzle included in the overlapping nozzle area ORA. The print ratio means a duty ratio in the same raster of pixels in which dots are formed by the corresponding nozzles for each of two nozzles having the same coordinate in the nozzle row direction in the preceding head PH and the following head FH. Specifically, for example, as shown in FIG. 3, 10% is set for the nozzle np1 of the preceding head PH. This means that the number of pixels in which dots are formed by the nozzle np1 is set to 10 when all the pixels of the raster formed by the nozzles np1 and nf1 are 100. Further, 90% is set as the printing ratio for the nozzle nf1 of the succeeding head FH that forms part of the same raster. As shown in FIG. 3, the eight nozzles np1 to np8 included in the overlapping nozzle area ORA in the preceding head PH are respectively 10% (nozzle np1), 20 in the order from top to bottom along the nozzle row direction. % (Nozzle np2), 30% (nozzle np3), 40% (nozzle np4), 50% (nozzle np5), 60% (nozzle np6), 70% (nozzle np7), and 80% (nozzle np8) are set. ing. That is, the preceding head PH is set with a duty ratio that gradually increases in the order from top to bottom along the nozzle row direction as the print ratio. On the other hand, the duty ratio that gradually decreases in the order from top to bottom along the nozzle row direction is set as the print ratio for the eight nozzles nf1 to nf8 included in the overlapping nozzle area ORA in the trailing head FH. ing. Specifically, the eight nozzles nf1 to nf8 are respectively 90% (nozzle nf1), 80% (nozzle nf2), 70% (nozzle nf3) in the order from top to bottom along the nozzle row direction. 60% (nozzle nf4), 50% (nozzle nf5), 40% (nozzle nf6), 30% (nozzle nf7), and 20% (nozzle nf8) are set.

As shown in FIG. 7, first, the CPU 30 prepares a dither mask having the following two features (feature 1 and feature 2) (step S210).
[Characteristic 1]: When the halftone process of step 130 is performed on a flat (constant gradation value) image using the dither mask, the entire halftone process result (bitmap data) Good dot dispersibility.
[Characteristic 2]: The same halftone processing result (bitmap data) obtained by performing the halftone processing of Step 130 on a flat (constant gradation value) image using the dither mask. When grouping is performed for each of a plurality of nozzle rows assigned to the ink color and dots belonging to each group are extracted, the dispersibility of the extracted dots of each group is good.
In the above features 1 and 2, “good dot dispersion” means having blue noise characteristics or green noise characteristics. The “grouping for each of a plurality of nozzle rows assigned to the same ink color” in the above feature 2 is assigned to the nozzle row LpA of the preceding head PH in the example of the nozzle row group shown in FIG. 3, for example. Grouping into a total of four groups: a group, a group assigned to the nozzle row LpB of the preceding head PH, a group assigned to the nozzle row LfA of the following head FH, and a group assigned to the nozzle row LfB of the following head FH. means. Such a dither mask having the two features 1 and 2 may be generated by, for example, a generation method described in Japanese Patent Application Laid-Open No. 2007-116432.

  The CPU 30 prepares a mask original image for each of the preceding head and the succeeding head (step S220). In the present embodiment, the mask original image means an image that can be printed with a duty ratio in accordance with the print ratio set for each of the preceding head and the succeeding head. As described above, the preceding head mask original image 54 and the subsequent head mask original image 55 stored in the EEPROM 50 by the user before the start of the allocation mask generation process correspond to the mask original image. Therefore, in this embodiment, CPU30 prepares a mask original image by specifying the two mask original images 55 and 54 stored in EEPROM50 as step S220. In step S220, a message prompting the user to store the two mask original images 55 and 54 is displayed on the operation panel 91 or the like, and the user stores the two mask original images 54 and 55 in the EEPROM 50 based on the message. Then, the two stored mask original images 55 and 54 may be specified.

  The CPU 30 applies the dither mask prepared in step S210 to each mask original image prepared in step S220 to obtain a binarized image (step S230).

  FIG. 8 is an explanatory diagram showing an example of a binarized image obtained in step S230 based on the succeeding head mask original image 55. As shown in FIG. FIG. 8A shows the trailing head mask original image 55, and FIG. 8B shows the binarized image 55 h obtained in step S 230 based on the trailing head mask original image 55.

  As described above, the duty ratio that gradually decreases in the order from top to bottom along the nozzle row direction is set as the print ratio for the eight nozzles nf1 to nf8 included in the overlapping nozzle area ORA in the trailing head FH. ing. Therefore, as shown in FIG. 8A, the mask image 55 for the trailing head is generated as an image (gradation image) whose density gradually decreases in the order from top to bottom along the nozzle row direction. Yes. When such an image is printed on the printing paper P, in the obtained image, the duty ratio gradually decreases in the order from top to bottom along the nozzle row direction. The duty ratio at this time corresponds to the positions of the eight nozzles nf1 to nf8 and the set duty ratio. Although not shown, the preceding head mask original image 54 is an image that approximates an image obtained by inverting the succeeding head mask original image 55 shown in FIG. Such two mask original images 55 and 54 may be created by, for example, known image processing software.

  Since the binarized image 55h shown in FIG. 8B is generated based on the dither mask prepared in step S210, the raster group formed by the nozzle row LpA of the preceding head PH shown in FIG. A position (raster) corresponding to any of a raster group formed by the nozzle row LfA of the head FH, a raster group formed by the nozzle row LpB of the preceding head PH, and a raster group formed by the nozzle row LfB of the subsequent head FH The dispersibility of the dots is also very good.

  In the present embodiment, the size of the preceding head allocation masks 52 and 53 in the nozzle row direction is equal to the size of the overlapping nozzle region ORA in the nozzle row direction. Further, the size of the preceding head allocation masks 52 and 53 in the paper feeding direction is equal to the size of the dither mask 51 in the paper feeding direction. By making the size of each allocation mask 52, 53 in the paper feeding direction equal to the size of the dither mask 51 in the paper feeding direction, the two allocation masks 52, 53 are tiled so that all the nozzles in the overlapping nozzle area ORA. This is because the dot dispersibility at the tiling boundary becomes smooth and the printing unevenness becomes inconspicuous when assigning (assigning which nozzles form dots). In the dither mask prepared in step S210, the threshold value is set in advance so that the dispersibility of the dots at the tiling boundary becomes smooth when tiling is performed to determine the on / off of the dots. Because it is. Note that the size of each allocation mask 52, 53 in the paper feeding direction may be different from the size of the dither mask prepared in step S210.

  The CPU 30 sets the dot-on to “1” and the dot-off to “0” in the binarized image for the preceding head PH and the binarized image of the succeeding head FH obtained in step S230, respectively. Head assignment masks (leading head assignment mask 52 and following head assignment mask 53) are obtained and stored in the EEPROM 50 (step S240).

  FIG. 9 is an explanatory diagram showing an example of an image obtained by applying the assignment mask obtained by the assignment mask process of the present embodiment. FIG. 10 is an explanatory diagram illustrating an example of an image obtained by applying the assignment mask of the comparative example. In FIG. 10, printing is performed with the same configuration as the embodiment except for the assignment mask. That is, in the assignment mask of the comparative example, the dispersibility of the dots formed in each nozzle row respectively included in the preceding head PH and the succeeding head FH is not considered as in the assignment masks 52 and 53 of the present embodiment.

  In FIG. 9, the image Fp1 showing the dots of the overlapping print area formed by the preceding head PH, the image Ff1 showing the dots of the overlapping printing area formed by the succeeding head FH, and the nozzle array LpA of the preceding head PH. The image Fp1a showing the dots of the overlapped print area and the image Ff1a showing the dots of the overlap print area formed by the nozzle row LfA of the succeeding head FH are shown. These images represent printing results for the same input image. Such an input image is an image in which dots are to be formed with a high duty ratio, that is, an image in which one side is represented by high gradation pixels. Specifically, an image having a duty ratio of approximately 100% when the image Fp1 and the image Ff1 are combined is used. As shown in the figure, both the image Fp1 formed by the preceding head PH and the image Ff1 formed by the following head FH are excellent in dot dispersibility (granularity). In addition, the image Fp1a formed by the nozzle row LpA of the preceding head PH and the image Ff1a formed by the nozzle row LfA of the subsequent head FH are also excellent in dot dispersibility. Although illustration is omitted, the image formed by the nozzle row LpB of the preceding head PH and the image formed by the nozzle row LfB of the subsequent head FH are also excellent in dot dispersibility.

  In FIG. 10, as in FIG. 9, the image Fp2 showing the dots of the overlapping print area formed by the preceding head PH, the image Ff2 showing the dots of the overlapping printing area formed by the succeeding head FH, and the preceding head PH The image Fp2a which shows the dot of the duplication print area | region formed with the nozzle row LpA of this, and the image Ff2a which shows the dot of the duplication print area | region formed with the nozzle row LfA of the succeeding head FH are represented. The input image that is the basis of the image shown in FIG. 10 is the same as the input image when each image shown in FIG. 9 is formed. Both the image Fp2 formed with the preceding head PH and the image Ff2 formed with the following head FH are relatively excellent in dot dispersibility (granularity). However, in the image Fp2a formed by the nozzle row LpA of the preceding head PH and the image Ff2a formed by the nozzle row LfA of the succeeding head FH, the sparse and dense portions extending vertically in FIG. Are generated, and the dispersibility (granularity) of the dots is poor. For this reason, for example, due to a manufacturing error of the nozzle row LpA of the preceding head PH, a paper feed error, or the like, the landing position of the ink droplet ejected from at least one of the two nozzle rows in each head When the deviation occurs, color unevenness (dot density) in the overlapping print region may become more conspicuous. Here, in the halftone process of the printing process, that is, the halftone process using the dither mask 51, the bitmap data is set so as to improve the dispersibility of the corresponding dots mainly for the pixels of the intermediate gradation. The dispersibility of dots corresponding to high gradation pixels cannot be improved. In addition, in the assignment mask of the comparative example, the dispersibility of the dots formed in each nozzle row included in the preceding head PH and the following head FH is not considered. Due to these reasons, in the comparative example, the dot dispersibility of the overlapping print region is lowered particularly when a high gradation image is printed.

  On the other hand, when the allocation mask of the present embodiment (the preceding head allocation mask 52 and the following head allocation mask 53) is used, the dispersibility of dots formed by each nozzle row of each head is excellent as described above. In other words, since the assignment masks 52 and 53 that can obtain such excellent dispersibility are set in advance, the overlapping is performed regardless of whether the image to be printed is a high-gradation image or not. The dispersibility of dots in the printing area can be improved. For this reason, even if the landing positions of the ink droplets ejected from at least one of the two nozzle rows are shifted in each head, the occurrence of color unevenness (dot density) in the overlapping print region is suppressed. .

  In the printer 10 according to the first embodiment described above, which nozzle is used to form dots in the overlapping print region among the nozzles of the preceding head PH and the nozzles of the succeeding head FH included in the overlapping nozzle region ORA. Is determined using the preceding head allocation mask 52 and the succeeding head allocation mask 53. For this reason, it is possible to improve the dispersibility of the dots formed by each nozzle row of each print head in the overlapping print region, and in either print head, the ink is ejected from at least one of the two nozzle rows. Even if the landing positions of the ink droplets are deviated, the occurrence of color unevenness (dot density) in the overlapping print region can be suppressed. This is because the spatial frequency of the dots formed by each nozzle row of each print head in the image of the overlapping print region obtained by applying the allocation masks 53 and 54 to each of the allocation masks 53 and 54 is blue noise characteristics. Alternatively, it is set to have green noise characteristics. In particular, even when a high gradation image is printed, the dispersibility of the dots in the overlapping print region is suppressed. In such a case, even if the landing positions of the ink droplets are shifted, color unevenness (dot dot The occurrence of (dense / dense) can be suppressed.

  Each of the preceding head assignment mask 52 and the succeeding head assignment mask 53 uses an image that can be printed at a duty ratio according to a print ratio set by the user as a mask original image, and applies to the mask original image. It is generated based on an image obtained by performing halftone processing. For this reason, it is possible to generate allocation result information in which dot on / off is controlled in accordance with the printing ratio.

  Further, since the size of each allocation mask 52, 53 in the paper feeding direction is made equal to the size of the dither mask 51 in the paper feeding direction, the two allocation masks 52, 53 are tiled so that all the allocation nozzles in the overlapping nozzle area ORA are all tiled. When assigning nozzles, the dot dispersibility at the tiling boundary can be made smooth and printing unevenness can be made inconspicuous.

  Further, the succeeding head mask original image 55 is generated as an image (gradation image) whose density gradually decreases in the order from the top to the bottom along the nozzle row direction. It is generated as an image (gradation image) whose density gradually decreases in the order from bottom to top along the direction. For this reason, for example, even when the landing position of the dot formed by the trailing head FH is shifted in the nozzle row direction (downward in FIG. 3), the print ratio is a low value ( Since the low duty is set, it is possible to suppress the duty from being extremely increased at the shifted portion. For this reason, even in this case, color unevenness (dot density) can be suppressed.

B. Second embodiment:
FIG. 11 is an explanatory diagram illustrating a schematic configuration of a printer according to the second embodiment. The printer 10a includes the carriage motor 141, the drive belt 142, the pulley 143, the sliding shaft 144, the carriage 110, and the ink cartridge 120 in place of the line head 60 and the ink supply mechanism 70. Different from 10. Since other configurations of the printer 10a of the second embodiment are the same as those of the printer 10 of the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof is omitted. The printer 10a corresponds to a so-called on-carriage type printer.

  The carriage motor 141 drives the carriage 110 in the main scanning direction via the drive belt 142. The drive belt 142 is an endless belt spanned between the carriage motor 141 and the pulley 143, and is connected to the carriage 110. The sliding shaft 144 supports the carriage 110 so as to be slidable. On the carriage 110, ink cartridges 120 of C, M, Y, and K are detachably mounted. The carriage 110 includes a print head 130 that faces the print paper P, and ejects ink droplets from the print head 130. Both the carriage motor 141 and the carriage 110 are connected to the control unit 20. The control unit 20 drives the carriage motor 141 to reciprocate the print head 130 in the main scanning direction, and drives the paper feed motor 141 to move the printing paper P in the sub scanning direction. The control unit 20 drives the nozzles of the print head 130 at an appropriate timing based on the print data in accordance with the movement of the carriage 110 that reciprocates (main scan) and the conveyance of the print paper P (sub scan). As a result, dots of appropriate colors are formed at appropriate positions on the printing paper P.

  FIG. 12 is an explanatory diagram schematically showing the relationship between the scan of the print head 130 and the print range in the second embodiment. As shown in FIG. 12, the print head 130 has nozzle row groups 131, 132, 133, and 134 for each color. Each of the nozzle row groups 131 to 134 has two nozzle rows. The print head 130 forms a dot group (dots in a band K) corresponding to the position in the K-th (K is a positive integer) main scan. Further, after the K-th main scan, the print head P is transported by a predetermined amount in the sub-scanning direction, and when the print head 130 and the print paper P move relative to each other, A dot group (band K + 1 dots) corresponding to the position of the print head 130 at this time is formed. The same applies to the K + 2th main scan. In the figure, for convenience of display, the print head 130 is displayed so as to be displaced in the main scanning direction for each main scanning, but in reality, the printing paper P moves in the sub scanning direction. ing.

  The relative position of the print head 130 with respect to the print paper P in the continuous K-th and K + 1-th main scans is set so that some of the nozzle row groups 131 to 134 overlap in the sub-scanning direction (nozzle row direction). In the figure, the upper end nozzle row UN arranged at the front end portion in the sub-scanning direction of the nozzle row groups 131 to 134 overlaps with the lower end nozzle row LN arranged at the front end portion on the opposite side. Show. The upper end nozzle row UN and the lower end nozzle row LN are composed of nozzles that scan the same coordinates in the sub-scanning direction (nozzle row direction) by different times of main scanning. Such upper end nozzle row UN and lower end nozzle row LN correspond to the overlapping nozzle area ORA in the first embodiment described above.

  Each dot in the print area formed by the upper end nozzle row UN and the lower end nozzle row LN is formed by one of the nozzle rows. That is, the printing area formed by the upper nozzle array UN and the lower nozzle array LN corresponds to the overlapping printing area of the first embodiment described above. Such a print area is formed by two consecutive main scans. On the other hand, in each nozzle row group 131 to 134 of the print head 130, the print region formed by the other nozzles excluding the upper end nozzle row UN and the lower end nozzle row LN is the single print region of the first embodiment described above. It corresponds to. That is, such a print area is formed by one main scan.

  In the printer 10a of the second embodiment, which dot array forms each dot in the print area formed by the upper end nozzle array UN and the lower end nozzle array LN, in other words, out of two consecutive main scans. Which main scan is used for the determination is determined using the two allocation masks 52 and 53. In the printer 10a of the second embodiment, the assignment mask generation process is executed in the same manner as the printer 10 of the first embodiment.

  The printer 10a of the second embodiment having the above configuration has the same effect as the printer 10 of the first embodiment.

C. Variations:
C1. Modification 1:
In each embodiment, the succeeding head mask original image 55 is generated as an image (gradation image) whose density gradually decreases in the order from top to bottom along the nozzle row direction. Although an image (gradation image) whose density gradually decreases in the order from bottom to top along the nozzle row direction is generated, the present invention is not limited to this. For example, two mask original images may be used interchangeably. Further, for example, these two mask original images may be images printed at the same duty ratio (for example, 50%) in any print head and any raster. The print ratio is set by the user before the start of the allocation mask generation process, but may be set in advance in the printers 10 and 10a instead.

C2. Modification 2:
In the first embodiment, each of the nozzle row groups 61 to 64 included in the leading head PH and the trailing head FH is constituted by two nozzle rows, but may be constituted by an arbitrary number of nozzle rows of three or more. Good. Similarly, in the second embodiment, each of the nozzle row groups 131 to 134 included in the print head 130 may also be configured by an arbitrary number of nozzle rows of 3 or more.

C3. Modification 3:
In each embodiment, the allocation mask generation processing is executed in the printers 10 and 10a, but the present invention is not limited to this. For example, it may be executed on a computer different from the printers 10 and 10a. In this configuration, the assignment mask obtained as a result of the assignment mask process executed by the computer may be transmitted to the printers 10 and 10a via the memory card MC and the network, for example, and stored in the EEPROM 50. In addition, steps S110 to S140 of the printing processing procedures may be executed by the above-described computer instead of the printers 10 and 10a. In such a configuration, the bitmap data obtained in step S130 and the allocation result information obtained in step S140 are transmitted to the printer 10, 10a via, for example, the memory card MC and the network, and the printer 10, 10a. Step S150 may be executed.

C4. Modification 4:
The printers 10 and 10a are ink jet printers, but any liquid ejecting apparatus that ejects liquid other than ink may be used. For example, the following various liquid ejecting apparatuses are applicable.
(1) Image recording device such as facsimile device (2) Color material injection device used for manufacturing color filter for image display device such as liquid crystal display (3) Organic EL (Electro Luminescence) display and surface emitting display (Field Electrode material injection device used for electrode formation such as Emission Display (FED), etc. (4) Liquid injection device for injecting liquid containing biological organic material used for biochip manufacturing (5) Sample injection device as a precision pipette (6) Lubrication Oil injection device (7) Resin liquid injection device (8) Liquid injection device for injecting lubricating oil pinpoint to precision machines such as watches and cameras (9) Micro hemispherical lenses (optical lenses) used in optical communication elements, etc. ), Etc., to inject a transparent resin liquid such as an ultraviolet curable resin liquid onto the substrate (10) Acid or to etch the substrate A liquid ejecting apparatus that ejects alkaline of the etching solution (11) any other liquid ejecting apparatus including a liquid ejecting head ejecting a minute amount of liquid droplet

  The “droplet” described above refers to the state of the liquid ejected from the liquid ejecting apparatus, and includes those that have a tail in the form of particles, tears, or threads. The “liquid” here may be any material that can be ejected by the liquid ejecting apparatus. For example, the “liquid” may be a material in a state in which the substance is in a liquid phase, such as a material in a liquid state having high or low viscosity, and sol, gel water, other inorganic solvents, organic solvents, solutions, Liquid materials such as liquid resins and liquid metals (metal melts) are also included in the “liquid”. Further, “liquid” includes not only a liquid as one state of a substance but also a liquid obtained by dissolving, dispersing or mixing particles of a functional material made of a solid such as a pigment or metal particles in a solvent. Further, representative examples of the liquid include ink and liquid crystal as described in the above embodiment. Here, the ink includes various liquid compositions such as general water-based ink and oil-based ink, gel ink, and hot-melt ink.

C5. Modification 5:
In each embodiment and modification, a part of the configuration realized by hardware may be replaced with software. Conversely, a part of the configuration realized by software may be replaced with hardware. May be. When a part or all of the functions of the present invention are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. In the present invention, the “computer-readable recording medium” is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but an internal storage device in a computer such as various RAMs and ROMs, a hard disk, etc. It also includes an external storage device fixed to the computer. That is, the “computer-readable recording medium” has a broad meaning including an arbitrary recording medium in which data can be fixed instead of temporarily.

  The present invention is not limited to the above-described embodiments and modifications, and can be realized with various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments and the modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Printer 10a ... Printer 20 ... Control unit 30 ... CPU
31 ... Input unit 32 ... Halftone processing unit 33 ... Allocation processing unit 41 ... ROM
42 ... RAM
44 ... Print control unit 50 ... EEPROM
DESCRIPTION OF SYMBOLS 51 ... Dither mask 52 ... Leading head allocation mask 53 ... Subsequent head allocation mask 54 ... Leading head mask original image 55 ... Subsequent head mask original image 55h ... Binary image 60 ... Line head 61-64 ... Nozzle row Group 70 ... Ink supply mechanism 71 ... Cartridge holder 72 ... Ink cartridge 73 ... Ink supply path 80 ... Paper feed mechanism 81 ... Paper feed motor 82 ... Paper feed roller 91 ... Operation panel 92 ... Memory card slot 110 ... Carriage 120 ... Ink cartridge DESCRIPTION OF SYMBOLS 130 ... Print head 131-134 ... Nozzle row group 141 ... Carriage motor 142 ... Drive belt 143 ... Pulley 144 ... Sliding shaft DA ... Final dot arrangement DA1 ... Dot arrangement DA2 ... Dot arrangement FH ... Subsequent head Ff1 ... Image Ff1a ... Image Ff2 ... Image Ff2a ... Image Fp1 ... Image Fp1a ... Image Fp2 ... Image Fp2a ... Image LN ... Lower Nozzle Row LfA ... Nozzle Row LfB ... Nozzle Row LpA ... Nozzle Row LpB ... Nozzle Row MC ... Memory Card ORA ... Overlapping Nozzle Region P ... Printing Paper PH ... Leading head SA ... Single nozzle area UN ... Top nozzle row k ... Nozzle pitch nf1 to nf8 ... Nozzle np1 to np8 ... Nozzle

Claims (5)

A plurality of print heads each having a plurality of nozzle rows arranged in parallel to each other, and overlapping nozzles in which two adjacent print heads have nozzles having the same coordinate in the nozzle row direction along the plurality of nozzle rows. When printing is performed by a printing apparatus arranged to have an area at the end of each print head, each dot in the overlapping print area in the print medium in which dots are formed by the nozzles in the overlapping nozzle area is An assignment mask in which assignment information for determining which of the print heads is formed is set,
The allocation information is set so that a spatial frequency of dots formed by each nozzle row of each print head has a blue noise characteristic or a green noise characteristic in the image of the overlapping print region obtained by applying the allocation mask. Assigned mask. Dots are formed on the print medium by performing a main scan in which a print head having a plurality of nozzle rows arranged in parallel to each other is moved relative to the print medium in a crossing direction intersecting the nozzle row direction along the plurality of nozzle rows. When printing is performed by a printing apparatus that forms the image, which of the plurality of main scans is used to form each dot in the overlapping print region in which an image is formed by a plurality of times of the main scan. An allocation mask in which allocation information for determination is set,
The allocation information is set so that the spatial frequency of dots formed by each nozzle row in each main scan has a blue noise characteristic or a green noise characteristic in the image of the overlapping print region obtained by applying the allocation mask. Assigned mask. A plurality of print heads each having a plurality of nozzle rows arranged in parallel to each other includes overlapping nozzles that are nozzles having the same coordinate in the nozzle row direction along the plurality of nozzle rows in two adjacent print heads. When printing is performed by a printing apparatus arranged so as to have an existing overlapping nozzle area at the end of each print head, each dot in the overlapping print area in a print medium on which dots are formed by the nozzles in the overlapping nozzle area An allocation mask generation method in which allocation information for determining which of the two print heads is used is set,
(A) preparing a binarization mask having a first feature and a second feature;
(B) preparing a mask original image that is the same size as the assigned mask and that can be printed with a duty ratio corresponding to a dot formation ratio of each nozzle in the overlapping nozzles determined in advance for each print head; ,
(C) applying the binarization mask to each mask original image to obtain a mask binarized image for each print head;
(D) generating the allocation mask for each print head based on the mask binarized image;
With
The first feature is that an image obtained by applying the binarization mask as a dither mask used in halftone processing for generating dot data indicating the presence or absence of dot formation based on input image data Overall, the spatial frequency of the dots has blue noise characteristics or green noise characteristics,
The second feature is that, in an image obtained by applying the binarization mask as a dither mask used for the halftone process, the spatial frequency of dots formed by each nozzle row included in each print head Each of which has a blue noise characteristic or a green noise characteristic. Dots are formed on the print medium by performing a main scan in which a print head having a plurality of nozzle rows arranged in parallel to each other is moved relative to the print medium in a crossing direction intersecting the nozzle row direction along the plurality of nozzle rows. When printing is performed by a printing apparatus that forms the image, which of the plurality of main scans is used to form each dot in the overlapping print region in which an image is formed by a plurality of times of the main scan. An allocation mask generation method in which allocation information for determination is set,
Each nozzle row includes at least two nozzles different from each other in the nozzle row, and there are overlapping nozzles that scan the same coordinates in the intersecting direction on the print medium by different times of the main scanning,
(A) preparing a binarization mask having a first feature and a second feature;
(B) preparing a mask original image that is the same size as the assigned mask and that can be printed with a duty ratio corresponding to a dot formation ratio of each nozzle in the overlapping nozzles determined in advance for each print head; ,
(C) applying the binarization mask to each mask original image to obtain a mask binarized image for each print head;
(D) generating the allocation mask for each print head based on the mask binarized image;
With
The first feature is that an image obtained by applying the binarization mask as a dither mask used in halftone processing for generating dot data indicating the presence or absence of dot formation based on input image data Overall, the spatial frequency of the dots has blue noise characteristics or green noise characteristics,
The second feature is that, in an image obtained by applying the binarization mask as a dither mask used for the halftone process, the spatial frequency of dots formed by each nozzle row in each main scan is respectively An allocation mask generation method having a blue noise characteristic or a green noise characteristic. In the generation method of the allocation mask according to claim 3 or 4,
The allocation mask generation method, wherein a size of the mask original image in a crossing direction intersecting a nozzle row direction along the plurality of nozzle rows is equal to a size of the binarized mask in the crossing direction.