JP5906630B2 - Image processing apparatus, image processing method, and liquid ejection apparatus - Google Patents

Description

  The present invention relates to an image processing apparatus or the like for a liquid ejection apparatus, and more particularly to an image processing apparatus or the like that can appropriately perform correction processing for each nozzle when nozzles that eject liquid are arranged at high density.

  Conventionally, a liquid ejection apparatus such as an ink jet printer has been used. In the ink jet printer, printing is executed by ejecting ink of each color as a color material from a plurality of nozzles provided in the head onto a print medium such as paper.

  In such an ink jet printer, it is known that defects occur in printed matter such as density unevenness due to the characteristics of each nozzle (ink discharge amount, ink discharge direction, etc.).

  In order to eliminate such problems due to the nozzle characteristics, it has been proposed to perform correction processing on image data for printing.

  Regarding the correction process, for example, Patent Document 1 below shows that the density characteristics due to the landing position error are corrected by measuring the density characteristics of the print area corresponding to each nozzle using a test pattern.

JP 2006-264069 A

  However, in recent years, the resolution of printers has increased, and the number of nozzles that eject ink has increased dramatically, resulting in higher nozzle density. As a result, in grasping the characteristics of each nozzle necessary for performing the correction processing related to each nozzle described above, dots that have landed from adjacent nozzles on the output test pattern are likely to overlap, and the output result for each nozzle is accurately grasped. It became difficult to do. Thereby, the correction information (correction value) generated based on the characteristics may be inaccurate. Also, considering human visual ability, correction processing in units that are too fine is meaningless. Further, the data amount of the correction information (correction value) increases as the number of nozzles increases, and this imposes pressure on the data storage capacity of the printer and its control device.

  Further, when dealing with these problems, each situation that affects the printing result, such as the type of printing medium (paper) and the location of the nozzles, should be considered. In particular, in a line head type ink jet printer in which the head is fixed, the line head is divided into a plurality of units, and these units have an overlap portion in the paper width direction, the overlap portion Since the behavior of the printing process is more complicated than other parts, special handling is desired for the nozzles arranged in the part.

  SUMMARY OF THE INVENTION An object of the present invention is an image processing apparatus for a liquid ejection apparatus, which can appropriately perform correction processing for each nozzle when nozzles that eject liquid are arranged at high density. , Etc. is to provide.

  In order to achieve the above object, one aspect of the present invention is an image processing apparatus for a liquid ejecting apparatus that is connectable to a liquid ejecting apparatus and that ejects liquid from a plurality of nozzles to a medium to be ejected according to image data. Comprises a control unit that corrects the image data according to a predetermined correction value and executes a correction process for adjusting the ink discharge amount from each nozzle, and the correction value is a predetermined number of nozzles of 2 or more. One value is set every time.

  Further, in the above invention, a preferred aspect is characterized in that one value set as the correction value is a value obtained by averaging correction values in the predetermined number of nozzles.

  Furthermore, in the above invention, a preferable aspect thereof is that the correction value is set for each type of the ejection target medium, and the predetermined number of the nozzles for which the correction value is set is different for each type of the ejection target medium. It is characterized by that.

  Furthermore, in the above invention, a preferable aspect is that the predetermined number of nozzles to which the correction value is set is larger as the type of the medium to be ejected has a larger area of dots formed when the same amount of the liquid is ejected. It is characterized by that.

Furthermore, in the above-described invention, a preferred aspect is that the liquid ejection device includes a plurality of head units that eject the liquid at fixed positions with respect to the ejection target medium that includes the nozzle and moves between the head units. In a case where there is an overlap portion where the positions of the nozzles overlap in the direction intersecting with the movement of the discharge target medium, the predetermined number of nozzles in which the correction value is set in the overlap portion is different from other portions. It is characterized by.

Furthermore, in the above-mentioned invention, a preferred aspect is characterized in that the predetermined number in the overlap portion is smaller than other portions.

  In order to achieve the above object, another aspect of the present invention is an image process for the liquid ejection apparatus that can be connected to a liquid ejection apparatus and that ejects liquid from a plurality of nozzles to an ejection medium according to image data. In the image processing method to be executed, the image data is corrected according to a predetermined correction value, and a correction process for adjusting the ink discharge amount from each nozzle is executed. The correction value is a predetermined number of 2 or more. One value is set for each nozzle.

  In order to achieve the above object, according to still another aspect of the present invention, a liquid that can be connected to an image processing apparatus and that discharges liquid from a plurality of nozzles to an ejection medium in accordance with image data received from the image processing apparatus. The discharge device includes a control unit that corrects the image data according to a predetermined correction value and executes a correction process for adjusting an ink discharge amount from each nozzle, and the correction value is a predetermined number of two or more. One value is set for each nozzle.

Furthermore, in the above-described invention, one aspect includes a transport unit that transports the ejection target medium and a plurality of nozzles that eject the liquid at fixed positions with respect to the ejection target medium that is moved by the transport unit. A head unit, and between the head units, there is an overlap part in which the position of the nozzle overlaps in a direction intersecting the movement of the ejection target medium, and the control unit is configured to correct the correction in the overlap part. The predetermined number of nozzles for which values are set is set to be different from those of other portions.

  Further objects and features of the present invention will become apparent from the embodiments of the invention described below.

1 is a configuration diagram according to an embodiment of an image processing apparatus to which the present invention is applied. FIG. 2 is a diagram illustrating a schematic arrangement of a head unit of a printer. It is the figure which illustrated the correction table 128. 3 is a flowchart illustrating a procedure of processing performed by a driver 12. FIG. 10 is a diagram exemplifying a test pattern printing result in generation of a correction table 128. It is the figure which illustrated the condition of the dot of the printed test pattern. It is a figure explaining the relationship between a density gradation value and measured density value. It is a figure for demonstrating the production | generation of the correction table.

  Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention. In the drawings, the same or similar elements are denoted by the same reference numerals or reference symbols.

  FIG. 1 is a configuration diagram according to an embodiment of an image processing apparatus to which the present invention is applied. A driver 12 shown in FIG. 1 is an image processing apparatus to which the present invention is applied, and executes a process of correcting the characteristics of each nozzle provided in the printer 2 after the color conversion process to the color space of the ink color used in the printer 2. The correction processing is executed based on correction information (correction table 128) in which one correction value is set for each of two or more adjacent nozzles. In addition, the number of nozzles for which one correction value is set is changed according to the type of paper to be printed (discharged medium), and the number of nozzles in the above-described overlap portion is set to a value different from the other portions. Due to these characteristics, in the image processing apparatus according to the present embodiment, the above correction processing in the case of a printer in which nozzles are arranged at high density is executed appropriately and with a reduced data storage capacity. Can do.

  FIG. 1 functionally shows the apparatus configuration in the present embodiment. The host computer 1 (image processing apparatus) is a host apparatus of the printer 2 that gives a print instruction to the printer 2, and is configured by a personal computer, for example. Therefore, although not shown, the host computer 1 includes a CPU (control unit of the image processing apparatus), a RAM, a ROM, an HDD, a display, an operation device, and the like.

  The application 11 is a print request source, and there may be applications having various functions such as a text creation application and a graphic creation application. The application 11 includes a program that instructs processing contents, the CPU that executes processing according to the programs, the RAM, and the like, and outputs image data representing the printing contents when a print request is made.

  The driver 12 is a driver for the printer 2 that is executed by the CPU of the host computer 1. The driver 12 performs image processing on the image data output from the application 11 to obtain image data (print data) for the printer 2. This is a part that sends data to the printer 2 and issues a print instruction for printing requested by the application 11.

  The driver 12 includes a driver program for instructing processing contents, the CPU for executing processing according to the program, various data used for processing, the RAM, and the like. The specific functional configuration and processing contents will be described later. . The driver program is stored in the HDD of the host computer 1 by being copied from a storage medium such as a CD to the host computer 1 or downloaded to the host computer 1 via a network such as the Internet. The

  The printer 2 (liquid ejection device) is, for example, a line head inkjet printer that executes a printing process in accordance with a printing instruction from the host computer 1. As shown in FIG. 1, the printer 2 includes a controller 13 and a print execution unit 14.

  The controller 13 (the control unit of the liquid ejection device) is a part that receives print data according to the print instruction and causes the print execution unit 14 to execute print processing according to the print data. Specifically, it is configured by a program describing processing contents, a CPU that executes processing according to the program, a RAM, a ROM that stores the program, an ASIC, and the like.

  The print execution unit 14 is a part that actually executes print processing on a print medium such as paper in accordance with an instruction from the controller 13. Here, a line head including a plurality of nozzles that discharge ink (liquid) that is a color material to the print medium, a conveyance device that conveys the print medium at a predetermined speed, and the like are provided. Here, as an example, CMYK (cyan, magenta, yellow, black) four-color ink is used. Further, as an example, the line head is divided into a plurality of head units, and these are arranged in a staggered manner.

  FIG. 2 is a diagram illustrating a schematic arrangement of the head portion of the printer 2. Here, the head 141 is divided into three head units 141a, 141b, and 141c, and as shown in FIG. 2 with respect to the conveyance direction (arrow a in the figure) of the paper 143 that is the printing medium, Arranged in a staggered pattern.

  Each head unit includes four nozzle rows 141, and each nozzle row 141 includes a plurality of (here, 360) nozzles. The nozzle rows 142 are configured to eject CMYK inks in order from the left in each nozzle unit. That is, the leftmost nozzle row 142 ejects C-color ink from the nozzles, the right-side nozzle row 142 ejects M-color ink from the nozzles, and the right-next nozzle row 142 ejects Y-color ink from the nozzles. In the rightmost nozzle row 142, K-color ink is ejected from the nozzles.

  Accordingly, 1080 nozzles are provided for each color in this example. Then, as shown in FIG. 2, the adjacent head units are arranged so as to partially overlap in the width direction of the paper 143. In the overlap portion indicated by b in FIG. Two nozzles are arranged at the same position (can eject ink with two nozzles).

  At the time of printing, ink of each color is ejected from each nozzle of such an arrangement provided in the fixed head unit to the paper 143 moving in the transport direction.

  Next, the functional configuration of the driver 12 shown in the lower part of FIG. 1 will be described. The rasterization unit 121 is a part that performs rasterization processing on the image data output from the application 11 and generates bitmap data expressed in, for example, an RGB (red, green, blue) color space.

  The color conversion unit 122 is a part that converts the bitmap data into data expressed in the color space of CMYK, which is the color of the color material, according to the color conversion table 127. The color conversion table 127 is an LUT (look-up table) prepared in advance, and is a table in which each density gradation value of CMYK corresponding to each density gradation value of RGB is stored. The color conversion table 127 is designed for each paper type because the color actually printed varies with the same density gradation value depending on the type of printing medium (paper type). Stored. For example, LUTs are stored for plain paper and fine paper, respectively.

  Also, in the color conversion table 127, for each color in the RGB color space (first color space), the density gradation value thereof is expressed by 8 bits (256 gradations) as an example, and each color has a value of 0 to 255. Has a value. Similarly, each color in the CMYK color space (second color space) is designed to have values of 0 to 255 for each color. Each color conversion table 127 generated in advance is stored in the HDD or the like in the same manner as the driver program described above.

  Next, the nozzle characteristic correction unit 123 is a part that corrects the bitmap data after the color conversion according to the correction table 128. Here, the correction process for the nozzle characteristics described above, that is, the correction process for suppressing a printing defect that appears due to the characteristics of each nozzle provided in the line head is executed. By the correction process, the amount of ink ejected from each nozzle is corrected appropriately.

  The correction table 128 is a table in which the density gradation value before correction is associated with the density gradation value after correction for each nozzle, and is prepared in advance and stored in the HDD or the like. The storage method is the same as that of the driver program described above.

  FIG. 3 is a diagram illustrating the correction table 128. In the table shown in FIG. 3, one nozzle row 142 (one color) is shown, and there is a nozzle number (here, nozzles # 0 to # 1079) indicating each nozzle in the vertical column. The later density gradation value is stored.

  As shown by 128A in FIG. 3, in this table, one correction value (corrected density gradation value) is given for every three nozzles. That is, a correction value common to the three nozzles is set.

  For example, in the 128A table, when the input gradation value is “200” for the three nozzles “Nozzle # 0, 1, 2”, the value should be corrected to “190”. Is set, and in the bitmap data after the color conversion, if the value of the pixel ejecting ink from these nozzles is “200”, the value is corrected to “190” by the nozzle characteristic correcting unit 123. become.

  As shown in FIG. 3, a plurality of correction tables 128 are prepared for each type of printing medium (paper type) (128A, B, C, D,...). Here, for example, the correction table 128A is for plain paper, and the correction table 128B is for fine paper. As described above, the correction value is set for each of the three nozzles in the plain paper table, but the correction value is set for every two nozzles in the fine paper table as shown in the lower part of FIG. The For example, a correction value of “189” is set for the input gradation value “200” for the two nozzles “Nozzle # 0, 1”.

  Thus, in the correction table 128 of the image processing apparatus, correction values are set for each of the plurality of nozzles, and the number of nozzles for which the correction values are set differs depending on the paper type. Then, the number of papers with less ink bleeding (the smaller the area of dots formed with the same ink amount) is, the smaller the number is. Therefore, as described above, a correction value is set for every two nozzles for fine paper with little bleeding, and a correction value is set for every three nozzles for plain paper with more bleeding.

  Further, in the present embodiment, as described above, the three head units arranged in a staggered manner are provided, and there are overlap portions in the width direction of the paper 143 between the head units, and 2 at the same position in the direction. Since a set of nozzles is provided, in other words, two nozzles of the same color exist in the same raster and the situation is different from the other parts, so the nozzles in the overlapping part are treated differently.

  Specifically, here, the correction values are set for each raster (two nozzles at the same position) without collecting the correction values by a plurality of nozzles as in the other portions. In other words, in other portions, correction values are set for each of a plurality of nozzles arranged continuously in the width direction of the paper 143 (the direction orthogonal to the conveyance direction of the paper 143). A correction value is set for each nozzle.

  In the example shown in FIG. 3, the correction value of the overlap portion is stored in the correction table 128 like the part indicated by b in FIG. 3. In the example shown here, the nozzle of nozzle # 350 located at the lower part of head unit 141a and the nozzle of nozzle # 360 located at the upper part of head unit 141b exist on the same raster (at the same position in the width direction of paper 143). The same correction value is given. The correction values are not set together with the nozzles (for example, nozzles # 349 and # 351) adjacent in the width direction of the paper 143. Similarly, correction values are stored for other nozzles located in the overlap portion. In the example shown here, 10 nozzles overlap.

  A method for generating these correction tables 128 will be described later. Similar correction tables 128 are prepared and stored for the other three colors.

  Next, the dot separation unit 124 is a part that converts the corrected bitmap data into data expressed by the dot generation rate according to the dot generation amount table 129. Here, as an example, there are three sizes of small dots (S), medium dots (M), and large dots (L) that can be hit with each nozzle, and the density gradation value (0-255) before processing is set. These are converted into data of the occurrence rates of these three dots. The occurrence rate of each dot can be indicated by a value of 0-4096, for example.

  The dot generation amount table 129 is a table in which the generation rates of the three dots are associated with the CMYK density gradation values (0 to 255). The dot generation amount table 129 is prepared in advance for each paper type and is stored in the HDD or the like. Stored. The storage method is the same as that of the driver program described above.

  Next, the halftone processing unit 125 is a part that executes so-called halftone processing and converts the data converted into the dot occurrence rate into data representing the presence or absence of each dot. As a processing method, a conventional dither method, an error diffusion method, or the like can be used.

  Next, the print data conversion unit 126 is a part that converts the data after the halftone process into the print data expressed by a command for the printer 2.

  In the driver 12 in the present embodiment having the configuration as described above, image processing is executed as follows. FIG. 4 is a flowchart illustrating a procedure of processing performed by the driver 12. Hereinafter, specific contents of the image processing will be described with reference to FIG.

  First, as described above, when the application 11 issues a print request, the image data is received by the driver 12 (step S1). At this stage, the received image data is usually in a data format expressed in units of objects such as text, graphics, and images. Therefore, the rasterizing unit 121 executes rasterization processing and converts the image data into Conversion into bitmap data (step S2). Specifically, each pixel is converted into data having density gradation values (0-255) for each color of RGB. A conventional method can be used for rasterization.

  Next, the generated bitmap data is transferred to the color conversion unit 122, and color conversion processing using the color conversion table 127 described above is executed (step S3). Specifically, the user of the host computer 1 selects the color conversion table 127 corresponding to the paper repair according to the information indicating the paper type selected by the operation device or determined as the default value, Data expressed by (R, G, B) of each pixel is sequentially converted into data expressed by (C, M, Y, K). Then, bitmap data in which each pixel is expressed by a density gradation value of each color of CMYK is generated.

  For the image data in the CMYK color space generated in this way, that is, for the image data expressed by the density gradation value of the ink color used in the printer 2, the correction processing related to the nozzle characteristics described above. Is executed (step S4). First, the nozzle characteristic correcting unit 123 selects a correction table 128 corresponding to the paper type according to the information indicating the paper type. After that, for each color data (density gradation value) of each pixel, it is determined which nozzle is used to strike, and the corrected density gradation value corresponding to the determined nozzle is the correction table 128 selected above. And processing to change the data to the extracted value. Therefore, the data expressed by (C, M, Y, K) is corrected and converted into data expressed by (C ′, M ′, Y ′, K ′). That is, appropriate image data reflecting the characteristics of each nozzle is generated.

  The determination of which nozzle to hit is performed using the processing result of a portion (not shown in FIG. 1) of the driver 12 that executes the processing.

  Next, a decomposition process for each dot is performed on the corrected data (step S5). This process is performed by the dot separation unit 124 using the dot generation amount table 129 as described above. Specifically, according to the information indicating the paper type, a dot generation amount table 129 corresponding to the paper type is selected, and (C ′, M ′, Y ′, K) is selected for each pixel with reference to the selected table. The density gradation value of ') is converted into the generated amount data (S, M, L) for each dot.

  Thereafter, the converted data is transferred to the halftone processing unit 125, where halftone processing is executed (step S6). The image data is converted into data representing the presence / absence of small, medium and large dots.

  The halftone processed data is converted into print data for the printer 2 by the print data conversion unit 126 (step S7) and transmitted to the printer 2 (step S8). Thereafter, the transmitted print data is received by the controller 13 and a printing process according to the print data is executed. That is, ink is ejected from each nozzle according to print data, and small, medium, and large dots are formed on the print medium.

  Next, generation of the correction table 128 described above will be described. The correction table 128 is generated for each individual printer 2. In the following, a description will be given of nozzle arrays that eject ink of the same color for each paper type.

  First, a test pattern printing process is actually executed in the apparatus. The printing process is executed with respect to a plurality of density gradation values (for example, five levels obtained by equally dividing 0-255) from low density to high density, respectively, for all nozzles of that color. FIG. 5 is a diagram illustrating the printing result. The test pattern shown in FIG. 5 is a printing result from density (1) to density (5) corresponding to the plurality of density gradation values, and is printed so as to become darker sequentially toward the right. The vertical length of the test pattern (A in FIG. 5) corresponds to the printable width of the head 141, that is, the print width of all nozzles of that color arranged in the width direction of the paper 143. The density width (B in FIG. 5) of the test pattern is set to a length (number of dots, for example, 200 dots) appropriate for determining the density of the printing result. Accordingly, each density ((1)-(5)) region is generated as a result of performing ink ejection from all nozzles for the same density gradation value by the width (B in FIG. 5). .

  Thereafter, the actual density value of the printed test pattern is measured using a scanner or the like.

  Next, the measurement result is input to a computer having a function of generating a correction table, and the correction table 128 is generated by the computer as follows.

  FIG. 6 is a diagram exemplifying the dot state of the printed test pattern. FIG. 6 is an enlarged view of part C in FIG. 5, and as an example, formed dots (D in the figure) in the density (3) region are shown. Further, on the left side, nozzles that eject ink of those dots are shown.

  First, an actual density value (actual density value) at each density ((1)-(5)) of the test pattern described above is determined for each nozzle (each raster for the overlap portion). Specifically, an average of measured density values of each dot (for example, 200 dots) discharged between the widths of the density areas (B in FIGS. 5 and 6) is used as an actually measured density value for the density. decide.

  Next, for each nozzle (each raster for the overlap portion), a plurality of (here, 5 points) actually measured density values obtained in this way and the density gradation values of the image data based on them. Thus, the actually measured density values for all density gradation values are obtained by interpolation processing.

  FIG. 7 is a diagram for explaining the relationship between the density gradation value and the actually measured density value. In the graph showing the relationship between the density gradation value and the actually measured density value in FIG. 7, each solid line represents the total density gradation value obtained by the interpolation processing of each nozzle (each raster for the overlap portion). Measured concentration value for. For example, in the curve of B, the actually measured density value obtained for the density gradation value corresponding to each density ((1)-(5)) of the test pattern is represented by a black circle in the figure, and the interval between them is It is obtained by interpolation. Similarly, a curve is obtained for the other nozzles. In this example, a curve of (1080−overlap portion) is generated.

  Next, an average measured density curve (broken line A in FIG. 7) of all nozzles is obtained. That is, the average measured density value of all nozzles for all density gradation values is obtained. Specifically, in each of the densities ((1) to (5)), an average value of all the nozzles of the actually measured density value obtained for each of the nozzles can be obtained and interpolated between them.

  Thereafter, the correction value is generated so that the output result from each nozzle becomes the obtained average measured density, that is, the output density unevenness from each nozzle is eliminated. Specifically, for each density tone value for each nozzle (for each raster for the overlap portion), the density tone value for obtaining the average measured density for the density tone value is calculated as the density tone value after correction. The base of the correction table 128 described above is generated. In the example shown in FIG. 7, for example, for the density gradation value g1 of the nozzle represented by the solid line B, the density gradation value g2 of the solid line B that becomes the actually measured density value of the broken line A corresponding to the density gradation value is The density gradation value after correction is determined. That is, correction of g1 to g2 is stored in the correction table 128.

  In this way, a correction table (based on the correction table 128) in which one correction value is set for each nozzle (each raster for the overlap portion) is generated. Such a correction table is similarly generated for nozzle rows of other colors (the other three colors). Similarly, for other sheet types, a correction table in which one correction value is set for each nozzle (each raster for the overlap portion) is generated.

  Next, for each of the generated correction tables, a process for collecting correction values with a plurality of nozzles is executed. Specifically, for each nozzle of the number determined for each paper type adjacent in the width direction of the paper 143, the average value of the correction values stored for each density gradation value is calculated for each nozzle. A process is performed in which the average value is used as a correction value for the nozzles. Then, the plurality of nozzles and the correction value obtained from the average value are stored in the table in association with each other, and the correction table 128 is generated.

  FIG. 8 is a diagram for explaining the generated contents. FIG. 8A illustrates the base of the correction table 128 described above, and one correction value is set for each nozzle as shown in the figure. From this state, as described above, the average value of the correction values is obtained for each density gradation value for each of a plurality of nozzles, here, for each of the three nozzles, and the final value is obtained as shown in FIG. Is stored as a typical correction table 128. FIG. 8 shows a table for plain paper. In FIG. 6, one correction value is set for each of three adjacent nozzles indicated by E.

  In this manner, the correction table 128 is similarly generated for other paper types. For example, in the case of fine paper, correction values for two adjacent nozzles are collected (averaged) to generate a correction table 128B.

  In addition, the correction value of the overlap portion is left as the basis of the correction table 128 without performing the process of collecting the plurality of nozzles. That is, as described with reference to FIG. 3, one correction value is set for one raster in the final correction table 128.

  Although the generation method of the correction table 128 has been described above, the number of nozzles for collecting correction values is an example, and an appropriate value of 2 or more can be selected as appropriate. Further, although correction values may be collected by a plurality of rasters even in the overlap portion, since the printing behavior is different from other portions, it is preferable that the number of nozzles is different from the other portions.

  In addition, the correction of the ink ejection amount due to the nozzle characteristics by the correction table 128 is expressed not only by the method for the image data expressed by the density gradation values of CMYK but also by the SML after the dot decomposition. You may perform with respect to data, and you may perform with respect to the voltage used for the ink discharge in the printer 2. FIG. Also in these cases, the method of generating and holding the correction table 128 is the same except that the unit of the correction value is different.

  Further, the processing performed by the driver 12 in the above description may be executed on the printer 2 side or divided into the host computer 1 and the printer 2.

  As described above, the image processing apparatus according to this embodiment has correction information (correction value) for adjusting the amount of ink ejected from each nozzle of the printer 2 for each of a plurality of adjacent nozzles. Even when a large number of nozzles are provided at high density, the data volume of the correction information can be kept small. In addition, since there is no problem in integrating the correction values within a range that exceeds the resolution capability of human vision, the number of nozzles having the correction value (the number of nozzles for which one correction value is set) is appropriately set. By selecting, the quality of the printed output is not degraded. In addition, when nozzles are arranged at high density, errors due to overlapping dots are included in the measured density value of each nozzle described above, which is the basis of correction information. Therefore, correction information may be provided for each nozzle. Proper correction is not always possible, and such waste can be eliminated.

  Also, in the case of a paper type with a large amount of blur, finely setting correction information has no precision and is equally meaningless. As described above, the nozzle that sets correction information more than a paper type with less blur By increasing the number, waste can be eliminated. Therefore, appropriate correction can be performed without waste by appropriately changing the number of nozzles for which correction information is set according to the paper type.

  In addition, in the overlap part where dots are formed at the same place by two nozzles, there are more factors affecting the printing result than in other parts, and the variation in output density is large, so more accurate correction is desired. As described above, this portion is treated differently from the other portions with respect to the number of nozzles for which correction information is set. Specifically, the number of nozzles for which correction information is set is set to be smaller than that in other portions, and finer correction is executed. In the overlap area, two nozzles form one dot in the other part, so the size of one dot is smaller than the other part, and there is less bleeding, so set a finer correction value. However, the relative error does not increase.

  Further, the present invention can be applied not only to a printer but also to a similar liquid ejection apparatus.

  The protection scope of the present invention is not limited to the above-described embodiment, but covers the invention described in the claims and equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 Host computer, 2 Printer, 11 Application, 12 Driver, 13 Controller, 14 Print execution part, 121 Rasterization part, 122 Color conversion part, 123 Nozzle characteristic correction part, 124 Dot separation part, 125 Halftone processing part, 126 Print data Conversion unit, 127 color conversion table, 128 correction table, 129 dot generation amount table, 141 head, 141a-c head unit, 142 nozzle row, 143 paper

Claims (6)

An image processing apparatus for the liquid ejection apparatus that is connectable to a liquid ejection apparatus and that ejects liquid from a plurality of nozzles to a medium to be ejected according to image data,
A controller that corrects the image data according to a predetermined correction value and executes a correction process for adjusting an ink discharge amount from each nozzle;
The liquid ejection device includes a plurality of head units that eject the liquid at fixed positions with respect to the ejection target medium provided with the nozzles, and a direction intersecting the movement of the ejection target medium between the head units. When there is an overlap part where the position of the nozzle overlaps,
For each head unit,
In a portion other than the overlap portion, the correction value is set to one value for each of a predetermined number of nozzles of 2 or more ,
In the overlap portion, the correction value is set to one value for each of the nozzles whose number is smaller than the predetermined number . In claim 1,
One value set as the correction value is a value obtained by averaging the correction values for the predetermined number of nozzles. In claim 1 or 2,
The correction value is set for each type of the ejection target medium,
The image processing apparatus according to claim 1, wherein the predetermined number of the nozzles for which the correction value is set is different for each type of the ejection target medium. In claim 3,
The image processing apparatus, wherein the predetermined number of nozzles to which the correction value is set is larger as the type of the medium to be ejected has a larger area of dots formed when the same amount of the liquid is ejected. An image processing method for performing image processing for discharging that liquid material discharge device liquid toward the discharge medium from the plurality of nozzles according to image picture data,
Correcting the image data according to a predetermined correction value, and executing a correction process for adjusting the ink discharge amount from each nozzle;
The liquid ejection device includes a plurality of head units that eject the liquid at fixed positions with respect to the ejection target medium provided with the nozzles, and a direction intersecting the movement of the ejection target medium between the head units. When there is an overlap part where the position of the nozzle overlaps,
For each head unit,
In a portion other than the overlap portion, the correction value is set to one value for each of a predetermined number of nozzles of 2 or more ,
In the overlap portion, the correction value is set to one value for each of the nozzles whose number is smaller than the predetermined number . A liquid ejection apparatus that is connectable to an image processing apparatus and that ejects liquid from a plurality of nozzles to a medium to be ejected according to image data received from the image processing apparatus,
The image data is corrected in accordance with a predetermined correction value, and the control unit that performs a correction process of adjusting the amount of ink discharged from each nozzle,
A transport unit for transporting the discharged medium;
A plurality of head units having the nozzles and ejecting the liquid at fixed positions with respect to the ejection target medium moved by the transport unit;
Between the head units, there is an overlap portion where the positions of the nozzles overlap in the direction intersecting with the movement of the discharged medium,
For each head unit,
In a portion other than the overlap portion, the correction value is set to one value for each of a predetermined number of nozzles of 2 or more ,
In the overlap portion, the correction value is set to one value for each of the nozzles whose number is smaller than the predetermined number .