JP2013067033A - Image processor, image processing method, and liquid ejection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor for a liquid ejection device such as a printer, which appropriately corrects failures caused by characteristics of respective nozzles for ejecting liquid, and easily generates information for the correction.SOLUTION: The image processor for the liquid ejection device that ejects the liquid from the nozzles according to image data has a nozzle characteristic correction part that corrects the image data based on correction information generated in advance concerning a first type of medium to be ejected which corrects the image data for the nozzles, wherein the nozzle characteristic correction part uses the correction information when ejecting the liquid to a second type of medium to be ejected that has larger area thereon where the liquid is ejected relative to the same value of the image data than the first type of medium to be ejected.

Description

  The present invention relates to an image processing apparatus or the like for a liquid ejection apparatus such as a printer, and in particular, can appropriately correct a defect caused by the characteristics of each nozzle that ejects liquid, and easily generates information for that purpose. It is related with the image processing apparatus etc. which can be used.

  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 processing, for example, Patent Document 1 below discloses a technique for correcting the ejection ink amount of each nozzle from the output result of an unevenness detection pattern or the like.

Japanese Patent Laid-Open No. 2004-174751

  However, when generating correction data for performing the above-described correction processing, a test pattern is output and its density is actually measured using a sheet with large ink bleeding, and the correction data is determined based on the result. There is a possibility that the adjacent dots overlap each other and the characteristics of each nozzle cannot be accurately grasped, and accurate correction data cannot be determined. Also, since the degree of bleeding varies depending on the location, it is difficult to grasp the tendency. Therefore, there is a possibility that processing with inaccurate correction data may be performed, which may promote density unevenness.

  In addition, in a line head type ink jet printer in which the head is fixed and 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 is used. The behavior of the printing process is more complicated than the other parts, and therefore there are many causes of density unevenness in the part printed at the overlap part. For this reason, even when printing is performed with the same nozzle, the output density may change depending on the type of paper that is the printing medium, and the determination of correction data using the test pattern described above is not appropriate. The wrapping portion must be performed for each type of paper, and therefore requires a lot of man-hours.

  Accordingly, an object of the present invention is an image processing apparatus for a liquid discharge apparatus such as a printer, which can appropriately correct a defect caused by the characteristics of each nozzle that discharges liquid, and easily provides information for that purpose. It is an object to provide an image processing apparatus and the like that can be generated.

  In order to achieve the above object, one aspect of the present invention provides a first type in which an image processing apparatus for a liquid ejection apparatus that ejects liquid from a nozzle according to image data corrects the image data for the nozzle. A nozzle characteristic correction unit that corrects the image data based on correction information generated in advance for the target ejection medium, and the nozzle characteristic correction unit discharges the liquid that is ejected with respect to the same value of the image data. The correction information is used when the liquid is ejected to the second type of target medium having a larger area on the target medium than the first type of target medium.

  Furthermore, in the above-described invention, a preferable aspect includes an ejection medium information input unit to which information on a type of an ejection medium to which liquid is ejected is input, and the first type of ejection medium is the ejection medium information input. The type of discharged medium having the smallest area on the discharged medium of the liquid to be discharged among the types of discharged medium input to the section, or the discharged medium input to the discharged medium information input section The type of the medium to be ejected is smaller in the area of the liquid ejected on the medium to be ejected than the type of the medium to be ejected.

  Furthermore, in the above-described invention, a preferable aspect is that the liquid ejection device includes a plurality of head units that eject the liquid at positions where the nozzles are fixed with respect to the moving ejection target medium, and between the head units, When there is an overhead portion in which the position of the nozzle overlaps in a direction crossing the movement of the ejection target medium, the nozzle characteristic correction unit corrects when the liquid is ejected to the second type ejection target medium. When performing the above, using a value obtained as a result of processing the correction value of the correction information based on a function prepared in advance for the second type of ejection target medium for the nozzle located in the overhead portion. It is characterized by.

  Furthermore, in the above-described invention, a preferable aspect is characterized in that the correction by the nozzle characteristic correction unit is a process of making the color density uniform on the discharge target medium onto which the liquid has been discharged.

  In order to achieve the above object, according to another aspect of the present invention, in the image processing method of a liquid ejection apparatus that ejects liquid from a nozzle according to image data, when the liquid is ejected to a first type of ejection medium, The image data is corrected in accordance with correction information generated in advance for the first type of discharge medium for correcting the image data for the nozzle, and the liquid target discharged for the same value of the image data is corrected. When the liquid is ejected to the second type of ejection medium having an area on the ejection medium larger than that of the first type of ejection medium, the correction generated in advance for the first type of ejection medium Correcting the image data in accordance with the information.

  In order to achieve the above object, according to still another aspect of the present invention, there is provided a liquid ejecting apparatus that ejects liquid from a nozzle according to image data, a head unit including a plurality of nozzles that eject the liquid, and the nozzle. A nozzle characteristic correction unit that corrects the image data in accordance with correction information generated in advance for the first type of ejection target medium that corrects the image data, and the nozzle characteristic correction unit is the same as the image data. In the case where the liquid is ejected to a second type of ejection target medium in which the area of the liquid ejected with respect to the value is larger than the first type of ejection target medium, the first type The correction information generated in advance for the target ejection medium is used.

  Furthermore, in the above invention, a preferred aspect is characterized in that the liquid is ink, and the head portion executes printing on the ejection target medium.

  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 the figure which illustrated the result of having compared the correction value of plain paper and fine paper.

  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 processing for correcting the characteristics of each nozzle provided in the printer 2 after color conversion processing into the color space of ink colors used in the printer 2. Regardless of which type of paper (discharged medium) is used for the correction process, fine paper such as fine paper (such as fine paper, which has a small area of dots generated on the paper for the same image data) Processing is performed using the correction information generated for the (paper). Further, in the correction processing in the overlap portion of the head unit including the nozzle, the correction information generated for the paper with small bleeding is a function predetermined for each paper type, for example, a printer model Each time processing is performed with information processed by a fixed function. Therefore, in the image processing apparatus according to the present embodiment, an appropriate correction process is executed based on the correction information generated by a sheet with small blur, and if the above function is determined once, for each individual printer. It is only necessary to generate the correction information including the output of the test pattern for one type of paper, and the number of preparation work can be reduced.

  FIG. 1 functionally shows the apparatus configuration in the present embodiment. The host computer 1 is a host device 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, RAM, ROM, HDD, display, 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, performs image processing on the image data output from the application 11 to obtain image data (print data) for the printer 2, sends the print data to the printer 2, and This is a part that 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 is, for example, a line head ink jet printer that executes print processing in accordance with the print instruction of 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 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 exemplifying a schematic arrangement of a head portion which is an embodiment 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.

  Therefore, for each color, 1080 nozzles are provided 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 printing condition because the color actually printed varies depending on the printing conditions such as the type of printing medium (paper type) and resolution, even with the same density gradation value. And stored in the HDD or the like. For example, LUTs for predetermined high resolution and predetermined low resolution are prepared for plain paper and fine paper, and a total of four LUTs are stored.

  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.

  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.

  For example, in the nozzle of “Nozzle # 0”, when the input gradation value is “200”, it is indicated that the value should be corrected to “190”, and the bitmap after the color conversion is performed. In the data, if the value of the pixel ejecting ink from the nozzle is “200”, the value is corrected to “190” by the nozzle characteristic correcting unit 123.

  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. A set of nozzles will be provided. In other words, since there are two nozzles of the same color in the same raster, the correction values for the nozzles in the overlapped portion are stored together in the correction table 128 as indicated by b in FIG. Yes. 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. Similarly, correction values are stored for other nozzles located in the overlap portion. In the example shown here, 10 nozzles overlap.

  In addition, as shown in FIG. 3, a plurality of correction tables 128 are prepared for each type of printing medium (128A, B, C, D,...). The same correction value (corrected density gradation value) is stored for the nozzles other than the printing section, and the correction value corresponding to the printing medium type (paper type) is stored for each nozzle of the overlapping section. More specifically, the portions other than the overlap portion are the types with the least blur among the print media used in the printer 2 (the type is input to the driver 12) (with the same density gradation value). The correction value generated for the type with the smallest dot area to be generated) or the type with less blur than the printing medium used in the printer 2 (the type is input to the driver 12) is used. For the overlap portion, a value obtained by converting the correction value generated for the portion other than the overlap portion as described above with a predetermined function is used.

  The correction table 128 and the function generation method 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 of the printing conditions, and includes the HDD and the like. Stored in 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 color conversion corresponding to the printing condition is selected according to the information indicating the printing condition such as the paper type and resolution selected by the user of the host computer 1 using the operation device or determined as a default value. The table 127 is selected, and data represented by (R, G, B) of each pixel is sequentially converted into data represented 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. Although not shown, the driver 12 includes an ejection medium information input unit to which information indicating printing conditions including the paper type is input.

  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 of the printing condition according to the information indicating the printing condition. 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 printing conditions, a dot generation amount table 129 corresponding to the printing conditions 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. First, an arbitrary device (individual) is selected for the model of the target printer 2, and a correction table for each paper type is generated for the device by the same method. Specifically, it is generated as follows.

  Here, as an example, it is assumed that two types of paper, fine paper and plain paper, can be used in the printer 2 model. Further, it is assumed that the fine paper is of a paper type in which bleeding is smaller than that of the plain paper (the area on the same dot paper is small). In the following, one color is described, and the other three colors are generated in the same manner.

  First, the printing process is actually executed for both sheets in the selected 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 following processing is similarly performed on both sheets.

  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 example in which the portion C in FIG. 5 is enlarged. FIGS. 6A and 6B show the printing results of plain paper and fine paper, respectively, and P in the drawing shows the nozzle pitch. ing. Since plain paper has greater bleeding than fine paper, adjacent dots (Da) overlap vertically and horizontally as shown in FIG. 6A, and the actual density value obtained by measuring this print result is The print density by each nozzle may not be shown accurately. On the other hand, in the fine paper shown in FIG. 6B, the dots (Db) hit by the respective nozzles do not overlap each other, and the actual density value obtained by measuring the printing result is suitable for the printing density by each nozzle. It can be said that it is shown.

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

  Next, for each nozzle, a plurality of (here, 5 points) measured density values obtained in this way and the relationship between the density gradation values of the image data based on them are interpolated. The actually measured density value for all density gradation values is obtained.

  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 actually measured density value with respect to all the density gradation values obtained by the interpolation processing of each nozzle. 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, a process is performed in which the density tone value for obtaining the average measured density for the density tone value is used as the density tone value after correction, and the above-described correction is performed. A table 128 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, the correction table 128 stores the correction of g1 to g2.

  Next, since the correction table for the color is generated for both plain paper and fine paper, the function in the overlap portion described above is determined. First, with respect to a predetermined density gradation value, for example, a density gradation value corresponding to each density ((1)-(5)) of the test pattern, the density gradation values (correction values) after correction for both sheets. Are compared at the overlap.

  FIG. 8 is a diagram illustrating the comparison result. In the graph, the horizontal axis represents nozzle #, and the vertical axis represents the density gradation value after correction of the generated correction table. The portion indicated by OL in the figure indicates the density gradation value after correction of the nozzle in the overlap portion. As described above, the correction value for the overlap portion is given one value for two nozzles having the same position. The solid line in FIG. 8 indicates the correction value for fine paper, and the dotted line indicates the correction value for plain paper.

  Next, a function for obtaining the correction value of the plain paper in the overlap portion is obtained from the correction value of the fine paper in the overlap portion. That is, a function for superimposing the solid line in the OL of FIG. 7 on the dotted line is obtained. This processing can be performed by various conventional mathematical methods. The function is obtained for each overlap portion, and the ratio of the correction value of the plain paper to the correction value of the fine paper (the input) is the position of the nozzle from the end (for example, the upper end) of the overlap portion (input). A function that represents (returns) the magnification.

  In this way, a function is obtained for each of the compared density gradation values, and thereafter, interpolation processing is performed between these density gradation values to obtain a function for all density gradation values.

  Thus, the operation for obtaining the function in the overlap portion described above is completed. Here, the description has been made assuming that there are two types of paper. However, if there are more types, the above function for fine paper (in this case, the fine paper is minimally blurred) is also displayed for each type. Desired.

  Next, for each printer 2 (each individual) of the model for which the function is determined, the above-described correction table 128 is generated before use. First, a correction table is generated for fine paper in the same manner as the function determination described above. That is, the test pattern shown in FIG. 5 is printed by the printer 2, the actually measured density value is obtained by a scanner or the like, and the density gradation value after correction is obtained by the method described with reference to FIG.

  Thereafter, a correction table for plain paper is generated, and the density gradation value after correction for the nozzles other than the overlap portion is copied and stored as it is as the value of the generated correction table for fine paper. Further, the corrected density gradation value for the overlap portion is stored in a table by obtaining the corrected density correction value for each gradation value by the function determined above. Specifically, when the density correction value after each correction is obtained, the position of the nozzle is given to the corresponding function, and the obtained magnification is obtained by multiplying the value in the corresponding fine paper correction table.

  If there are more paper types that can be used by the printer 2, a correction table is created in the same manner using the determined function for the paper.

  Here, the correction table for the other paper types is generated by the above-described function based on the correction table for fine paper having the smallest bleeding among the paper types used by the printer 2. It is also possible to replace the paper type with less blur than the paper with fine paper and determine the above functions and generate a correction table using these functions by the same operation.

  Before use, a correction table based on the fine paper or the like and the above function for each paper type are prepared, and density gradation values corrected using these are used during image processing by the driver 12. May be requested. The calculation method is the same as that in the case where the table is generated in advance.

  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, in the image processing apparatus according to the present embodiment, the paper type with the smallest bleeding of ink ejected (area of dots formed) among the paper types used in the printer 2 or the printer Based on the correction value of the correction table 128 generated for the paper type in which the ink bleeding (area of formed dots) is smaller than the paper type used in No. 2, the correction process for each paper type is executed. In the paper type for which the correction table 128 is generated, in the output of the test pattern when generating the correction value, there is little blur and adjacent dots do not overlap, so an accurate measured value is obtained, and therefore the correct correction value Therefore, the appropriate correction process can be executed based on the correction value. Thereby, image processing reflecting the nozzle characteristics is performed, and the print quality can be improved. For example, density unevenness due to nozzle characteristics can be suppressed.

  Further, as described above, the correction value is determined by a function that reflects the characteristics of the paper type for the overlap portion that should be considered for the paper type in the correction processing for the nozzle characteristics. Correction can be performed.

  Further, as described above, once a function corresponding to each paper type is generated for each model of the printer 2, the above-described correction table 128 generation process with test pattern output is performed for each apparatus (for each individual). Therefore, it is only necessary to perform the above-described basic paper type with less blurring, and the number of steps for generating the correction table 128 that requires a relatively long time can be reduced.

  Although a so-called line head is used as the ink jet head, the image processing apparatus according to the present invention can be used when a so-called serial head is used.

  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 (7)

An image processing apparatus for a liquid ejection apparatus that ejects liquid from a nozzle according to image data,
A nozzle characteristic correcting unit that corrects the image data based on correction information generated in advance for the first type of ejection target medium that corrects the image data for the nozzle;
The nozzle characteristic correction unit applies to the second type of discharged medium, the area of the liquid discharged on the discharged medium with respect to the same value of the image data being larger than the first type of discharged medium. The correction information is used when the liquid is discharged. In claim 1,
An ejection medium information input unit for inputting information on the type of ejection target medium from which the liquid is ejected;
The first type of discharged medium is a type of discharged medium having the smallest area on the discharged medium of the liquid to be discharged among the types of discharged medium input to the discharge medium information input unit, Alternatively, the image processing apparatus is a type of discharged medium in which the area of the liquid to be discharged on the discharged medium is smaller than the type of discharged medium input to the discharge medium information input unit. In claim 1 or 2,
The liquid ejecting apparatus includes a plurality of head units that eject the liquid at positions where the nozzles are fixed with respect to the ejected medium to be moved, and a direction intersecting the movement of the ejected medium between the head units. If there is an overhead part where the nozzle position overlaps,
When the nozzle characteristic correction unit performs correction when discharging the liquid to the second type of target medium, the nozzle characteristic correction unit applies the second type of target medium to the nozzle located in the overhead unit. An image processing apparatus using a value obtained by processing a correction value of the correction information based on a function prepared in advance. In any one of Claims 1 thru | or 3,
The correction by the nozzle characteristic correction unit is a process for making the color density uniform on the target medium onto which the liquid has been discharged. An image processing method of a liquid ejection apparatus that ejects liquid from a nozzle according to image data,
When ejecting the liquid to the first type of ejection medium, the image data is corrected according to correction information generated in advance for the first type of ejection target medium for correcting the image data for the nozzle,
In the case where the liquid is ejected to the second type of ejection target medium in which the area of the liquid ejected with respect to the same value of the image data is larger than the first type of ejection target medium An image processing method comprising: correcting the image data according to the correction information generated in advance for the first type of ejection target medium. A liquid ejection device that ejects liquid from a nozzle according to image data,
A head portion having a plurality of nozzles for discharging the liquid;
A nozzle characteristic correction unit that corrects the image data according to correction information generated in advance for the first type of ejection target medium that corrects the image data for the nozzle, and
The nozzle characteristic correction unit is configured for a second type of discharged medium in which the area of the liquid to be discharged with respect to the same value of the image data is larger than the first type of discharged medium. When the liquid is ejected, the correction information generated in advance for the first type of medium to be ejected is used. In claim 6,
The liquid is an ink, and the head unit performs printing on the ejection target medium.