JP2012144024A - Printer and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent density unevenness, while reducing time and effort.SOLUTION: This printer includes: a dot forming section that is provided with a nozzle row having a plurality of nozzles arranged in a predetermined direction and causes the nozzle row to eject ink while relatively moving the nozzle row and a medium in a relative movement direction intersecting with the predetermined direction so as to form, in the predetermined direction, a plurality of dot lines each having a plurality of dots arranged in the relative movement direction; a storage section that stores a plurality of correction tables which are formed for each dot width and have density correction values associated with the dot lines; and a detection section that detects a dot width of a dot formed on the medium by the dot forming section. The printer forms a correction table for a certain medium on the basis of a result obtained by the detection section when the certain medium is used and the plurality of correction tables stored in the storage section.

Description

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

  For example, when an image is formed on a medium (for example, paper) by a printing apparatus such as an ink jet printer, streaky density unevenness may occur in the image. Therefore, the correction pattern is printed for each ink color by using the printing apparatus, the correction pattern is read by a scanner or the like, and the density correction value is calculated based on the obtained color information to correct the density. Things have been done. As such correction, for example, a correction table using a correction table in which density correction values are associated with a row of dots (a raster line to be described later) aligned in the direction in which the head and the medium move relative to each other has been proposed (for example, a patent Reference 1).

JP 2005-206991 A

Depending on the printing conditions, the density unevenness may vary. For example, if the type of medium is different, the size (dot width) of the dots formed may be different even if the ink discharge amount is the same. In this case, the density unevenness is different, and there is a possibility that the density unevenness cannot be suppressed even if the correction table described above is used. Although it is conceivable to prepare a correction table for each medium, it takes time and labor to create a correction table for each medium.
Accordingly, an object of the present invention is to suppress density unevenness while reducing time and labor.

A main invention for achieving the above object has a nozzle row in which a plurality of nozzles are arranged in a predetermined direction, and ink is ejected from the nozzle row while relatively moving the nozzle row and the medium in a relative movement direction intersecting the predetermined direction. And a plurality of correction tables created for each dot width, each of which includes a dot forming unit that forms a plurality of dot lines in which the plurality of dots are arranged in the relative movement direction. A storage unit that stores a plurality of correction tables associated with density correction values and a detection unit that detects a dot width of dots formed on the medium by the dot forming unit, and uses a certain medium. Generating a correction table for the certain medium based on the detection result of the detection unit at the time and the plurality of correction tables stored in the storage unit. A printing apparatus for the butterflies.
Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

1 is a block diagram illustrating a configuration of a printing system. It is a schematic block diagram around a printing area. It is explanatory drawing of the arrangement | sequence of the some head in the lower surface of a head unit. It is explanatory drawing of the head arrangement | positioning for simplified description, and the mode of dot formation. FIG. 8 is an explanatory diagram of processing by a printer driver. FIG. 6A is an explanatory diagram of a state when an ideal raster line is formed. FIG. 6B is an explanatory diagram when density unevenness occurs. FIG. 6C is a diagram illustrating a state where the occurrence of density unevenness is suppressed. It is a figure which shows the flow of a correction value acquisition process. It is explanatory drawing of correction pattern CP. It is a graph which shows the calculation density | concentration for every raster line about sub pattern CSP. FIG. 10A is an explanatory diagram of a procedure for calculating a density correction value Hb for correcting the command gradation value Sb for the i-th raster line. FIG. 10B is an explanatory diagram of a procedure for calculating a density correction value Hb for correcting the command gradation value Sb for the j-th raster line. It is a figure which shows a BRS correction table. It is a figure which shows an example of the evaluation pattern of BRS correction | amendment. It is a figure for demonstrating the concept of color difference type | formula (DELTA) E94. It is a figure which shows the measurement result of (DELTA) E94 for every sub pattern of an evaluation pattern. It is a figure for demonstrating a some BRS correction table. It is the schematic for demonstrating the tendency of dot size and BRS correction data. It is a flowchart which shows the BRS correction table creation process in 1st Embodiment. It is explanatory drawing of the preservation | save BRS correction table in 1st Embodiment. It is explanatory drawing of the BRS correction data produced with each gradation. It is a figure which shows the dot incidence in a SML table. It is explanatory drawing of the preservation | save BRS correction table in 2nd Embodiment. It is a flowchart which shows the BRS correction table creation process in 2nd Embodiment. It is a figure which shows the calculation result of the average dot size for every gradation value. It is explanatory drawing of the BRS correction data produced with each gradation. It is a figure which shows the combination of a SML table and a BRS correction table group. It is a flowchart which shows the whole process of 3rd Embodiment. It is a figure which shows the BRS correction table created with the SML table. It is a flowchart which shows the BRS correction table creation process for the production printing target media in 3rd Embodiment. It is explanatory drawing of the BRS correction data produced with each gradation.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

A nozzle row having a plurality of nozzles arranged in a predetermined direction, and ejecting ink from the nozzle row while relatively moving the nozzle row and the medium in a relative movement direction intersecting the predetermined direction, thereby moving the nozzle row in the relative movement direction. A dot forming unit that forms a plurality of dot lines in which a plurality of dots are arranged in the predetermined direction, and a plurality of correction tables created for each dot width, each of which has a plurality of density correction values associated with the dot lines A storage unit that stores a correction table; and a detection unit that detects a dot width of a dot formed on the medium by the dot formation unit, the detection result of the detection unit when using a certain medium, and Based on the plurality of correction tables stored in the storage unit, the correction table for the certain medium is created.
According to such a printing apparatus, since a correction table for each medium is automatically created using a plurality of correction tables prepared in advance, it is not necessary to create a correction table for each medium. Therefore, density unevenness can be suppressed while reducing time and labor.

In this printing apparatus, it is preferable that the dot forming unit forms a pattern with a plurality of gradations on a medium, and the detection unit detects the dot width for each gradation.
According to such a printing apparatus, correction suitable for each gradation can be performed.

In such a printing apparatus, it is desirable to calculate the density correction value corresponding to the dot width for each gradation.
According to such a printing apparatus, since the density unevenness can be suppressed regardless of the gradation, the density unevenness can be further suppressed.

In this printing apparatus, the dot forming unit may form single size dots, and the dot width may be an average value of dot widths of the single size dots.
According to such a printing apparatus, the accuracy of dot width calculation can be improved.

In this printing apparatus, the dot forming unit forms dots of a plurality of sizes, and the dot width is an average value of the dot widths of the dots of the plurality of sizes at an occurrence rate of the dots of the plurality of sizes. It may be a weighted average value.
According to such a printing apparatus, even when dots of a plurality of sizes are used, the consistency between the dot width and the density correction value can be improved.

In this printing apparatus, it is preferable that the plurality of correction tables be prepared for each dot generation table in which the generation rate of each dot of the plurality of sizes is determined.
According to such a printing apparatus, the dot generation table can be selected according to the medium, so that density unevenness can be more reliably suppressed.

It is preferable that the printing apparatus further includes a light source that irradiates light to dots formed on the medium, and the ink is an ink that is cured by light irradiation.
According to such a printing apparatus, it is possible to perform printing on a medium on which ink is difficult to fix. That is, there are many types of media to be printed. Therefore, in this case, the effect of not having to prepare a correction table for each medium (saving labor and time) becomes significant.

  Also, the relative movement is achieved by having a nozzle row in which a plurality of nozzles are arranged in a predetermined direction, and ejecting ink from the nozzle row while relatively moving the nozzle row and the medium in a relative movement direction intersecting the predetermined direction. A printing method of a printing apparatus for forming a plurality of dot lines in which a plurality of dots are arranged in a predetermined direction in a plurality of correction tables created for each dot width, each having a density correction value in each dot line Storing a plurality of associated correction tables in a storage unit, detecting a dot width of a dot formed on a certain medium, detecting a dot width detected on the certain medium, and storing in the storage unit Based on the stored correction tables, a correction table for the certain medium is created, and printing is performed on the certain medium using the created correction table. Printing method and having it and the reveals.

=== About the printing system ===
An outline of a printing system 100 for forming an image on a medium will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of the printing system 100.
As shown in FIG. 1, the printing system 100 according to the present embodiment is a system that includes a printer 1, a computer 110, and a scanner 120.

The printer 1 is a device that discharges liquid onto a medium to form dots on the medium. In the present embodiment, the printer 1 is a color inkjet printer. The printer 1 of the present embodiment is an apparatus that prints an image on a medium by ejecting ultraviolet curable ink (hereinafter referred to as UV ink) that is cured by irradiation with ultraviolet light (hereinafter referred to as UV) that is a type of light. The UV ink is an ink containing an ultraviolet curable resin, and is cured by undergoing a photopolymerization reaction in the ultraviolet curable resin when irradiated with UV. The printer 1 using such UV ink can print images on various media such as paper, cloth, and film sheets.
The configuration of the printer 1 will be described later.

  The computer 110 includes an interface 111, a CPU 112, and a memory 113. The interface 111 exchanges data between the printer 1 and the scanner 120. The CPU 112 performs overall control of the computer 110 and executes various programs installed in the computer 110. The memory 113 stores various programs and various data. Among the programs installed in the computer 110, there are a printer driver for converting image data output from the application program into print data, and a scanner driver for controlling the scanner 120. Then, the computer 110 outputs the print data generated by the printer driver to the printer 1.

  The scanner 120 (corresponding to a detection unit) includes a scanner controller 125 and a reading unit 121. The scanner controller 125 includes an interface 122, a CPU 123, and a memory 124. The interface 122 communicates with the computer 110. The CPU 123 performs overall control of the scanner 120. For example, the reading unit 121 is controlled. The memory 124 stores a computer program and the like. The reading unit 121 includes three sensors (CCD and the like) (not shown) corresponding to, for example, R (red), G (green), and B (blue).

  With the above configuration, the scanner 120 irradiates the medium on which the image is formed by the printer 1, detects the reflected light by each sensor of the reading unit 121, reads the image of the medium, and reads the color of the image Get information. Then, data indicating the color information of the image (read data) is transmitted to the scanner driver of the computer 110 via the interface 122. The scanner 120 according to the present embodiment is provided on a medium conveyance path in the printer 1, and reads an image printed on the medium when the medium is conveyed. The scanner 120 of the present embodiment also detects the dot size (dot width) of dots formed on the medium (described later).

  The “printing apparatus” means the printer 1 in a narrow sense, but means a system of the printer 1, the computer 110, and the scanner 120 in a broad sense.

<Configuration of Printer 1>
Next, the configuration of the printer 1 will be described with reference to FIGS. 1 and 2. FIG. 2 is a schematic configuration diagram around the print area.

  As shown in FIG. 1, the printer 1 includes a head unit 20, a transport unit 30, a detector group 40, a controller 50, and an irradiation unit 60. When the printer 1 receives print data from the computer 110, the controller 50 controls each unit (head unit 20, transport unit 30, irradiation unit 60) based on the print data and prints an image on a print medium. The situation in the printer 1 is monitored by the detector group 40, and the detector group 40 outputs a signal corresponding to the detection result to the controller 50. The controller 50 controls each unit based on the detection result output from the detector group 40. The head unit 20 and the transport unit 30 correspond to a dot forming unit.

The head unit 20 is for ejecting ink (in this embodiment, UV ink) onto a medium (for example, paper S). The head unit 20 prints an image by forming dots on the medium by ejecting ink onto the medium being transported. The printer 1 of this embodiment is a line printer, and the head unit 20 can form dots for the paper width at a time.
Details of the configuration of the head unit 20 will be described later.

  The transport unit 30 is for transporting the medium in the transport direction. The transport unit 30 includes an upstream roller 32 </ b> A and a downstream roller 32 </ b> B, and a belt 34. When a conveyance motor (not shown) rotates, the upstream roller 32A and the downstream roller 32B rotate, and the belt 34 rotates. The medium fed by a paper feed roller (not shown) is conveyed by the belt 34 to a printable area (area facing the head). When the belt 34 conveys the medium, the medium moves in the conveyance direction with respect to the head unit 20. Note that the medium being transported is electrostatically attracted or vacuum attracted to the belt 34.

  The detector group 40 includes a rotary encoder (not shown), a paper detection sensor (not shown), and the like. The rotary encoder detects the rotation amount of the upstream roller 32A and the downstream roller 32B. The transport amount of the medium can be detected based on the detection result of the rotary encoder. The paper detection sensor detects the position of the leading edge of the medium being fed.

  The controller 50 controls each unit of the printer 1 through the unit control circuit 54 by the CPU 52. The printer 1 also has a memory 53 (corresponding to a storage unit) having a storage element, and the memory 53 stores a correction table for correcting the density of each raster line. Details of the correction table will be described later.

  The irradiation unit 60 is for irradiating UV to the UV ink (dot) landed on the medium. In the printer 1 of the present embodiment, the irradiation unit 60 includes a UV irradiation light source (not shown) such as a lamp. The irradiation unit 60 is provided downstream of the head unit 20 in the transport direction. For this reason, dots formed on the medium (dots formed by UV ink) are cured by being irradiated with UV from the irradiation unit 60 when the medium is transported in the transport direction.

<About print processing>
In such a printer 1, when the controller 50 receives the print data, the controller 50 first rotates a paper feed roller (not shown) by the transport unit 30, and moves the medium (for example, paper S) to be printed to the belt 34. Send it up. The paper S is conveyed on the belt 34 without stopping at a constant speed, and passes under the head unit 20. While the medium passes under the head unit 20, ink is intermittently ejected from each nozzle of the head. That is, the dot formation process and the medium transport process are performed simultaneously. As a result, an image composed of a plurality of dots along the transport direction and the paper width direction is printed on the paper S. The paper S on which dots are formed then passes under the irradiation unit 60. At this time, the controller 50 irradiates UV from the light source of the irradiation unit 60. As a result, the dots formed on the paper S are cured and fixed on the medium.
Finally, the controller 50 discharges the paper S on which image printing has been completed.

=== About the head unit ===
FIG. 3 is an explanatory diagram of an arrangement of a plurality of heads on the lower surface of the head unit 20. As shown in the drawing, a plurality of heads 23 are arranged in a staggered pattern along a direction (paper width direction) intersecting the transport direction. In the present embodiment, it is assumed that the head unit 20 includes three heads (a first head 23A, a second head 23B, and a third head 23C) for simplification of description. Each head is formed with a black ink nozzle row, a cyan ink nozzle row, a magenta ink nozzle row, and a yellow ink nozzle row. Each nozzle row includes a plurality of nozzles that eject ink. The plurality of nozzles in each nozzle row are arranged at a constant nozzle pitch along the paper width direction.

  FIG. 4 is an explanatory diagram of the head arrangement and dot formation for simplified explanation. For simplification of description, only a nozzle row of a certain color (for example, a yellow ink nozzle row) of each head is shown. In order to further simplify the description, it is assumed that there are 12 nozzles provided in the nozzle row of each head. Each of these nozzles forms a row of dots (dot lines) arranged in the direction in which the head and the medium move relative to each other. This row of dots is called a “raster line”. In the case of a line printer as in this embodiment, “raster line” means a row of dots arranged in the paper transport direction. In the case of a serial printer that prints using a head mounted on a carriage, “raster line” means a row of dots arranged in the carriage movement direction. Hereinafter, as shown in the figure, the raster line at the nth position is referred to as an “nth raster line”.

  As shown in the figure, the nozzle row of each head includes a first nozzle group 231 and a second nozzle group 232. Each nozzle group is composed of, for example, six nozzles arranged in the paper width direction at an interval of 1/180 inch. The first nozzle group 411 and the second nozzle group 412 are configured to be shifted by 1/360 inch in the paper width direction. Thereby, the nozzle row of each head is a nozzle row composed of 12 nozzles arranged at intervals of 1/360 inch in the paper width direction. Numbers are assigned to the nozzle rows of each head in order from the top in the figure.

  Ink droplets are intermittently ejected from each nozzle shown in FIG. 4 onto the medium being conveyed, thereby forming 36 raster lines on the medium. For example, the nozzle # 1A of the first head 23A forms a first raster line on the medium, and the nozzle # 1B of the second head 23B forms a thirteenth raster line on the medium. The nozzle # 1C of the third head 23C forms the 25th raster line on the medium. Each raster line is formed along the transport direction. Thus, in the present embodiment, each raster line corresponds to one nozzle of each head.

  In the following description, a region (first raster line to twelfth raster line) printed by the first head 23A is also referred to as band 1. The area printed by the second head 23B (the 13th raster line to the 24th raster line) is the band 2 and the area printed by the third head 23C (the 25th raster line to the 36th raster line). This is also called Band 3. In addition, a boundary portion (for example, the vicinity of the twelfth and thirteenth raster lines) of each band (band 1, band 2, and band 3) is also called a joint.

=== Outline of processing by printer driver ===
As described above, the printing process is started when print data is transmitted from the computer 110 connected to the printer 1. The print data is generated by processing by the printer driver. Hereinafter, processing by the printer driver will be described with reference to FIG. FIG. 5 is an explanatory diagram of processing by the printer driver.

  As shown in FIG. 5, the print data is generated by executing resolution conversion processing (S011), color conversion processing (S012), halftone processing (S013), and rasterization processing (S014) by the printer driver. The

  First, in the resolution conversion process, the resolution of the RGB image data obtained by executing the application program is converted into a print resolution corresponding to the designated image quality. Next, in the color conversion process, RGB image data whose resolution has been converted is converted into CMYK image data. Here, the CMYK image data means image data for each color of cyan (C), magenta (M), yellow (Y), and black (K). A plurality of pieces of pixel data constituting the CMYK image data are each represented by 256 gradation values. This gradation value is determined based on RGB image data, and is hereinafter also referred to as a command gradation value.

  Next, in the halftone process, the multi-level gradation value indicated by the pixel data constituting the image data is converted into a small-level dot gradation value that can be expressed by the printer 1. That is, the 256-level gradation value indicated by the pixel data is converted into a 4-level dot gradation value. Specifically, no dot corresponding to the dot gradation value [00], formation of a small dot corresponding to the dot gradation value [01], formation of a medium dot corresponding to the dot gradation value [10], and The four levels of formation of large dots corresponding to the dot gradation value [11] are converted. After that, the dot generation rate (dot generation rate) is determined for each dot size, and the printer 1 uses the dither method, γ correction, error diffusion method, etc. so that the printer 1 forms the dots in a dispersed manner. Data is created.

  Next, in the rasterizing process, with respect to the image data obtained by the halftone process, the data of each dot (dot gradation value data) is changed in the order of data to be transferred to the printer 1. The rasterized data is transmitted as part of the print data.

=== Suppression of density unevenness ===
Next, density unevenness occurring in an image printed using the printer 1 and a method for suppressing the density unevenness will be described.
For the following description, “pixel region” and “column region” are set. The pixel area refers to a rectangular area virtually defined on the medium, and the size and shape are determined according to the printing resolution. One “pixel” constituting the image data corresponds to one pixel area. Further, the “row area” is an area on the medium constituted by a plurality of pixel areas arranged in the transport direction. One column region corresponds to a “pixel column” in which pixels are arranged in a direction opposite to the transport direction on the data.

<About density unevenness>
First, uneven density will be described with reference to the drawings. FIG. 6A is an explanatory diagram of a state when dots are ideally formed. The ideal formation of a dot means that an ink droplet has landed at the center position of the pixel region, the ink droplet spread on the medium, and a dot is formed in the pixel region. When each dot is accurately formed in each pixel region, a raster line (a dot row in which dots are arranged in the transport direction) is accurately formed in the row region.

  FIG. 6B is an explanatory diagram when density unevenness occurs. The raster lines formed in the second row region are formed closer to the third row region due to variations in the flight direction of the ink droplets ejected from the nozzles. As a result, the second row region is light and the third row region is dark. In addition, the ink amount of the ink droplets ejected to the fifth row region is smaller than the prescribed ink amount, and the dots formed in the fifth row region are small. As a result, the fifth row region becomes lighter.

  When a printed image composed of raster lines having different shades is viewed macroscopically, striped density unevenness along the transport direction is visually recognized. This uneven density causes a reduction in image quality of the printed image.

<About the method for suppressing uneven density>
As a measure for suppressing the density unevenness as described above, it is conceivable to correct the gradation value (command gradation value) of the pixel data. That is, it is only necessary to correct the gradation value of the pixel data corresponding to the unit area constituting the row area so that the row area is dark (light) and easily visible, so that the row area is formed light (dark). For this reason, the density correction value H for correcting the gradation value of the pixel data is calculated for each raster line. This density correction value H is a value reflecting the density unevenness characteristic of the printer 1.

  If the density correction value H for each raster line has been calculated, the printer driver performs a process for correcting the gradation value of the pixel data for each raster line based on the density correction value H when the halftone process is executed. . When each raster line is formed with the gradation value corrected by this correction processing, the density of the raster line is corrected, and as a result, the occurrence of uneven density in the printed image is suppressed as shown in FIG. 6C. become. FIG. 6C is a diagram illustrating a state where the occurrence of density unevenness is suppressed.

  For example, in FIG. 6C, the dot generation rate of the second and fifth row regions that are visually recognized lightly increases, and the dot generation rate of the third row region that is viewed darkly decreases. The gradation value of the pixel data of the corresponding pixel is corrected. In this manner, the dot generation rate of the raster line in each row area is changed, the density of the image pieces in the row area is corrected, and the density unevenness of the entire print image is suppressed.

<Calculation of density correction value H>
Next, a process for calculating the density correction value H for each raster line (hereinafter also referred to as a correction value acquisition process) will be outlined. The correction value acquisition process is performed, for example, under the correction value calculation system 200 in the inspection line of the printer 1 manufacturing factory. The correction value calculation system is a system for calculating the density correction value H corresponding to the density unevenness characteristic of the printer 1 and has a configuration substantially similar to that of the printing system 100 described above. That is, the correction value calculation system includes the printer 1, the computer 110, and the scanner 120 (for convenience, the same reference numerals as those in the printing system 100 are used).

  The printer 1 is a target device of the correction value acquisition process. In order to print an image having no density unevenness using the printer 1, the density correction value H for the printer 1 is calculated in the correction value acquisition process. It will be. The configuration of the printer 1 is omitted because it has already been described. The computer 110 placed on the inspection line is installed with a correction value calculation program for the computer 110 to execute correction value acquisition processing.

  Hereinafter, an outline procedure of the correction value acquisition process will be described with reference to FIG. FIG. 7 is a diagram showing a flow of correction value acquisition processing. When the printer 1 capable of multicolor printing is used as in the present embodiment, the correction value acquisition process for each ink color is performed in the same procedure. In the following description, correction value acquisition processing for one ink color (for example, yellow) will be described.

  First, the computer 110 transmits print data to the printer 1, and the printer 1 forms a correction pattern CP on the medium by the same procedure as the above-described printing operation (S021). As shown in FIG. 8, the correction pattern CP is formed of five types of density sub-patterns CSP. FIG. 8 is an explanatory diagram of the correction pattern CP.

  Each sub-pattern CSP is a belt-like pattern, and is configured by arranging a plurality of raster lines along the transport direction in the paper width direction. Each sub-pattern CSP is generated from image data having a constant gradation value (command gradation value), and as shown in FIG. 8, the density increases in order from the left sub-pattern CSP. Yes. The command gradation values for each sub-pattern CSP are expressed as Sa, Sb, Sc, Sd, Se (Sa <Sb <Sc <Sd <Se) in order from the left. For example, the sub-pattern CSP formed with the command gradation value Sa is expressed as CSP (1) as shown in FIG. Similarly, the sub patterns CSP formed by the command gradation values Sb, Sc, Sd, and Se are denoted as CSP (2), CSP (3), CSP (4), and CSP (5), respectively.

  Next, the computer 110 causes the scanner 120 to read the correction pattern CP and obtains the result (S022). As described above, the scanner 120 has three sensors corresponding to R (red), G (green), and B (blue). The scanner 120 irradiates the correction pattern CP with light, and reflects the reflected light to each sensor. Detect by. Note that the computer 110 has the same number of pixel columns in which pixels are arranged in the direction corresponding to the transport direction on the image data obtained by reading the correction pattern and the number of raster lines (number of column areas) constituting the correction pattern. Adjust so that In other words, the pixel rows read by the scanner 120 and the row regions are made to correspond one-to-one. Then, the average value of the read gradation values indicated by each pixel in the pixel column corresponding to a certain row region is set as the read tone value of the row region.

  Next, the computer 110 calculates the density of the raster line (in other words, the row region) of each sub-pattern CSP based on the read gradation value acquired by the scanner 120 (S023). Hereinafter, the density calculated based on the read gradation value is also referred to as calculated density.

  FIG. 9 is a graph showing the calculated density for each raster line for the sub-pattern CSP having the command gradation values Sa, Sb, and Sc. The horizontal axis in FIG. 9 indicates the position of the raster line, and the vertical axis indicates the magnitude of the calculated density. As shown in FIG. 9, the sub-patterns CSP are formed with the same command gradation value, but the raster lines are shaded. This difference in density of raster lines is a cause of uneven density in the printed image.

  Next, the computer 110 calculates a density correction value H for each raster line (S024). The density correction value H is calculated for each command gradation. Hereinafter, the density correction values H calculated for the command gradations Sa, Sb, Sc, Sd, and Se are referred to as Ha, Hb, Hc, Hd, and He, respectively. In order to explain the calculation procedure of the density correction value H, the density correction value for correcting the command gradation value Sb so that the calculated density of the raster line of the sub-pattern CSP (2) of the command gradation value Sb is constant. A procedure for calculating Hb will be described as an example. In this procedure, for example, the average value Dbt of the calculated densities of all raster lines in the sub-pattern CSP (2) of the command gradation value Sb is determined as the target density of the command gradation value Sb. In FIG. 9, for the i-th raster line whose calculated density is lighter than the target density Dbt, the command gradation value Sb may be corrected to be darker. On the other hand, for the jth raster line whose calculated density is higher than the target density Dbt, the command gradation value Sb may be corrected to be lighter.

  FIG. 10A is an explanatory diagram of a procedure for calculating a density correction value Hb for correcting the command gradation value Sb for the i-th raster line. FIG. 10B is an explanatory diagram of the procedure for calculating the density correction value Hb for correcting the command gradation value Sb for the j-th raster line. 10A and 10B, the horizontal axis indicates the magnitude of the command gradation value, and the vertical axis indicates the calculated density.

The density correction value Hb with respect to the command gradation value Sb of the i-th raster line is the calculated density Db of the i-th raster line and the command gradation value Sc in the sub-pattern CSP (2) of the command gradation value Sb shown in FIG. 10A. Is calculated based on the calculated density Dc of the i-th raster line in the sub-pattern CSP (3). More specifically, in the sub-pattern CSP (2) of the command gradation value Sb, the calculated density Db of the i-th raster line is smaller than the target density Dbt. In other words, the density of the i-th raster line is lighter than the average density. If it is desired to form the i-th raster line so that the calculated density Db of the i-th raster line is equal to the target density Dbt, the gradation value of the pixel data corresponding to the i-th raster line, that is, the command level As shown in FIG. 10A, the tone value Sb is expressed by the following equation (1) using linear approximation from the correspondence relationship (Sb, Db) and (Sc, Dc) between the command gradation value and the calculated density in the i-th raster line. It is sufficient to correct up to the target command gradation value Sbt calculated by
Sbt = Sb + (Sc−Sb) × {(Dbt−Db) / (Dc−Db)} (1)
Then, a density correction value H for correcting the command tone value Sb for the i-th raster line is obtained from the command tone value Sb and the target command tone value Sbt by the following equation (2).
Hb = ΔS / Sb = (Sbt−Sb) / Sb (2)

On the other hand, the density correction value Hb for the command gradation value Sb of the j-th raster line is the calculated density Db of the j-th raster line in the sub-pattern CSP (2) of the command gradation value Sb shown in FIG. It is calculated based on the calculated density Da of the j-th raster line in the sub-pattern CSP (1) of the value Sa. Specifically, in the sub-pattern CSP (2) of the command gradation value Sb, the calculated density Db of the jth raster line is larger than the target density Dbt. If it is desired to form the jth raster line so that the calculated density Db of the jth raster line is equal to the target density Dbt, the command gradation value Sb of the jth raster line is set as shown in FIG. 10B. From the correspondence relationship (Sa, Da), (Sb, Db) between the command gradation value and the calculated density in the jth raster line to the target command gradation value Sbt calculated by the following equation (3) using linear approximation. It may be corrected.
Sbt = Sb + (Sb−Sa) × {(Dbt−Db) / (Db−Da)} (3)
Then, the density correction value Hb for correcting the command gradation value Sb for the j-th raster line is obtained by the above equation (2).

  As described above, the computer 110 calculates the density correction value Hb for the command gradation value Sb for each raster line. Similarly, density correction values Ha, Hc, Hd, and He for the command gradation values Sa, Sc, Sd, and Se are calculated for each raster line. For other ink colors, density correction values Ha to He are calculated for each of the command gradation values Sa to Se for each raster line.

  Thereafter, the computer 110 transmits the density correction value H data to the printer 1 and stores it in the memory 53 of the printer 1 (S025). As a result, in the memory 53 of the printer 1, a correction table (hereinafter also referred to as a BRS correction table) in which the density correction values Ha to He for each of the five command gradation values Sa to Se are collected for each raster line is created. The

  FIG. 11 is a diagram showing a BRS correction table stored in the memory 53. By performing the correction value acquisition process described above for each ink color, a BRS correction table is created for each ink color as shown in FIG. As a result, a BRS correction table for four colors of CMYK is formed. This BRS correction table is referred to by the printer driver to correct the gradation value of each raster line constituting the image data of the image when the printer 1 is used to print the image.

  After the correction value acquisition process is completed, the printer 1 is packaged and shipped after passing through another inspection process. When an image is printed by the purchaser (user) of the printer 1, an image having a density corrected by the density correction value H is printed.

  For example, the printer driver of the user's computer 110 determines the gradation value of each pixel data (hereinafter, the gradation value before correction is referred to as Sin) based on the density correction value H of the raster line corresponding to the pixel data. Correction is performed (hereinafter, the corrected gradation value is referred to as Sout).

Specifically, if the gradation value Sin of a certain raster line is the same as any one of the command gradation values Sa, Sb, Sc, Sd, and Se, the density correction value H stored in the memory of the computer 110 is used as it is. Can be used. For example, if the gradation value Sin of the pixel data is Sin = Sb, the corrected gradation value Sout is obtained by the following equation.
Sout = Sb × (1 + Hb) (4)

On the other hand, when the gradation value of the pixel data is different from the command gradation values Sa, Sb, Sc, Sd, Se, the correction value is calculated based on the interpolation using the density correction values of the surrounding command gradation values. For example, when the command tone value Sin is between the command tone value Sb and the command tone value Sc, linearity using the density correction value Hb of the command tone value Sb and the density correction value Hc of the command tone value Sc. If the correction value obtained by interpolation is H ′, the gradation value Sout after the correction of the command gradation value Sin is obtained by the following equation.
Sout = Sin × (1 + H ′) (4) ′
In this way, density correction processing is performed for each raster line.

=== Example of Evaluation of Effect by BRS Correction ===
<About the evaluation pattern>
FIG. 12 is a diagram illustrating an example of an evaluation pattern for BRS correction.
This evaluation pattern is printed on the medium by the printer 1 and is formed by a plurality of strip-like sub-patterns, similar to the correction pattern CP.
Each sub-pattern is configured by arranging a plurality of raster lines along the transport direction in the paper width direction. Each sub-pattern is generated from image data having a predetermined gradation value. As shown in the figure, sub-patterns of cyan, magenta, yellow, gray, blue, green, and red are formed in order from the left.

<About evaluation index>
The computer 110 evaluates the density unevenness for each sub-pattern by causing the above-described evaluation pattern to be read by the scanner 120, for example.

In this embodiment, the color difference formula ΔE94 is used as an evaluation index for density unevenness. ΔE94 is expressed by the following equation.

ΔE94 = √ {(ΔH ^* / Sh) ² + (ΔL ^* / SL) ² + (ΔC ^* / Sc) ² } (5)

Note that L ^* , C ^* , and H ^* are the lightness, saturation, and hue of the L ^* a ^* b ^* display system, respectively. Further, SL = 1, Sc = 1 + 0.045C ^* , and Sh = 1 + 0.015C ^* .

FIG. 13 is a diagram for explaining the concept of the color difference equation ΔE94.
When printing is performed on the medium using the nozzles of each head, raster lines corresponding to the nozzles are formed in the row region of the medium as described above. By reading this with the scanner 120, an RGB value indicating the density of the pixel column corresponding to each raster line is obtained for each pixel column. In the present embodiment, RGB values are converted into L ^* a ^* b ^* display system components (hereinafter referred to as Lab values). When the average of Lab values of all raster lines is (L ^* _H , a ^* _H , b ^* _H ) and the Lab values of the nth raster line are (L ^* _n , a ^* _n , b ^* _n ), the Lab value The color difference between the average and the Lab value of the nth raster line is represented by the distance between two points in the L ^* a ^* b ^* space. For example, when the Lab value of the first raster line and _{^{(L * 1, a * 1}} , b * 1), the average value _{^{(L * H, a * H}} , b * H) color difference Delta] E ₁ with the

^{_{ΔE 1 = √ {(L *}} H -L * 1) 2 + (a * H -a * 1) 2 + (b * H -b * 1) 2} ··· (6)

It becomes. Similarly, the average value _{^{(L * H, a * H}} , b * H) and a color difference Delta] E _n the Lab values of the n raster lines respectively obtained. A value obtained by further averaging these color differences (ΔE _{1 to} ΔE _{36 in} this embodiment) corresponds to ΔE94.

  Therefore, as can be seen from the above relationship, the value of ΔE94 increases as the density unevenness increases (as the variation in the Lab value of each raster line increases). Conversely, the smaller the density unevenness (the smaller the variation in the Lab value of each raster line), the smaller the value of ΔE94.

  Note that the evaluation index is not limited to that described above. For example, instead of the average value of each raster line, an absolute value (target value) may be determined, and the color difference between the absolute value and the value of each raster line may be obtained.

<About evaluation results>
FIG. 14 is a diagram illustrating a measurement result of ΔE94 for each sub-pattern of the evaluation pattern.
The horizontal axis in FIG. 14 indicates the sub-pattern for each color. The vertical axis in FIG. 14 indicates the magnitude of ΔE94. Further, in the graph of each sub-pattern, the diagonal line (right side) indicates a case where correction is not performed, and white (left side) indicates a case where correction is performed using a correction table.

As described above, the larger the density unevenness of each raster line, the larger the value of ΔE94, and the smaller the density unevenness, the smaller the value of ΔE94. For example, it can be seen from the figure that the gray sub-pattern has a large density unevenness and the yellow sub-pattern has a small density unevenness.
In each sub-pattern, the value of ΔE94 is smaller when correction is performed than when correction is not performed. That is, it can be seen that the density unevenness is improved in each sub-pattern.
However, it is difficult from the viewpoint of cost and time to create a BRS correction table for each medium in a printer that has many types (for example, several hundred types) of print target media as in the present embodiment. On the other hand, if the BRS correction table corresponding to the medium is not used, density unevenness may occur and image quality may deteriorate.
Therefore, in the present embodiment, a plurality of BRS correction tables are created in advance, and a BRS correction table for an unknown medium is newly created using the BRS correction tables.

=== Definition of terms ===
Before describing this embodiment, definitions of terms used in the following embodiments will be described.
The correction value of each raster line at a certain gradation value (for example, each data of density correction value Ha associated with the raster line in FIG. 11) is referred to as BRS correction data.
A table in which BRS correction data for a plurality of gradation values is collected (for example, a table for cyan ink in FIG. 11) is referred to as a BRS correction table. (In this embodiment, a BRS correction table for five gradation values is created).
The BRS correction table created in advance by the correction value calculation system 200 described above and saved (stored) in the memory 53 of the printer 1 is also referred to as a saved BRS correction table (in this embodiment, as will be described later). Some have changed the dot size, some have changed the SML table).

In addition, the dot size obtained from each dot size for each dot type (for example, small dot, medium dot, large dot) and the ratio thereof is referred to as an average dot size. The average dot size dave is obtained by the following equation (7).
dave = ds × Ps + dm × Pm + dl × Pl (7)
In equation (7), ds is a small dot size, dm is a medium dot size, and dl is a large dot size (both are average values). Ps is the ratio (%) of small dots, Pm is the ratio (%) of medium dots, and Pl is the ratio (%) of large dots (Ps + Pm + Pl = 100%).

=== First Embodiment ===
In the first embodiment, only a single dot (for example, a medium dot) is used. In the present embodiment, for example, a plurality of BRS correction tables are prepared in advance for each dot size by performing the above-described correction value acquisition process by changing the type of medium.

  FIG. 15 is a diagram for explaining a plurality of BRS correction tables. In this embodiment, as shown in the figure, five types of BRS correction tables (T1 to T5) are created. Each correction table is created for each ink color, and density correction values Ha to He corresponding to the command gradation values Sa to Se are determined for each raster line. These BRS correction tables T1 to T5 are stored (stored) in the memory 53 of the printer 1.

  As described above, in these BRS correction tables T1 to T5, the dot sizes at the time of table creation are different. For example, the dot sizes when creating the BRS correction tables T1 to T5 are d1, d2, d3, d4, and d5, respectively (d1 <d2 <d3 <d4 <d5).

  FIG. 16 is a schematic diagram for explaining the tendency of the dot size and the BRS correction data. The horizontal axis in the figure is the raster number, and the vertical axis is the ink correction amount. In the figure, the BRS correction data of each raster line at a certain gradation value for a certain ink color is graphed in each of the BRS correction tables T1 to T5.

  As can be seen from the figure, the correction amount varies depending on the dot size. In particular, the difference in the correction amount due to the dot size is remarkable at the joint portion of the band. For example, it can be seen that the correction amount decreases as the dot size increases. Thus, since there is a correlation between the dot size and the correction amount, it is possible to calculate the correction amount for dot sizes other than these five dot sizes. For example, the correction data when the dot size d is d1 <d <d2 can be predicted from the correction values of the raster lines at the dot sizes d1 and d2 using spline interpolation, linear interpolation, or the like.

  Therefore, in the present embodiment, a new BRS correction table for an unknown medium is automatically created by using the above relationship. In the following embodiment, one of four ink colors will be described, but the same processing is performed for other ink colors.

  FIG. 17 is a flowchart showing BRS correction table creation processing in the first embodiment. The processing of FIG. 17 is performed, for example, so that the computer 110 controls the scanner 120 and the printer 1 via a scanner driver and printer driver of the computer 110 by one program.

  FIG. 18 is an explanatory diagram of a saved BRS correction table in the first embodiment. As shown in FIG. 18, BRS correction tables T1 to T5 respectively corresponding to five dot sizes (30 μm, 50 μm, 60 μm, 70 μm, and 90 μm) are prepared in advance. In each BRS correction table, BRS correction data (data in which raster lines and density correction values are associated) is created for each gradation value.

  First, an unknown medium (hereinafter referred to as a print target medium) is set in the printer 1, and the computer 110 causes the printer 1 to print on the print target medium. Thereafter, the dot size of the dots formed on the print target medium by the scanner 120 (specifically, the dot width in the paper width direction) is measured (FIG. 17, S101).

  Next, the computer 110 determines from the measurement result of the scanner 120 whether or not there is a saved BRS correction table (see FIG. 18) created with the same dot size (S102). If there is a stored BRS correction table having the same dot size (YES in S102), the stored BRS correction table corresponding to the dot size is set as the BRS correction table of the print target medium (S103). For example, when the dot size measurement result by the scanner 120 is 30 μm, the BRS correction table T1 corresponding to the dot size of 30 μm is set as the correction table for the medium.

On the other hand, if there is no stored BRS correction table created with the same dot size (NO in S102), in the stored BRS correction table formed with a dot size larger than the dot size formed on the print target medium. The one with the smallest dot size is selected (S104). The correction table selected here is referred to as a saved BRS table 1. Furthermore, the largest dot size is selected from the stored BRS correction tables formed with a dot size smaller than the dot width formed on the print target medium (S104). The correction table selected here is referred to as a stored BRS table 2.
For example, when the dot size measurement result by the scanner 120 is 55 μm, the BRS correction table T3 (corresponding to the dot size of 60 μm) is set in the storage BRS table 1, and the BRS correction table T2 (corresponding to the dot size of 50 μm) is stored. Set in the BRS table 2.

Then, BRS correction data for each gradation of the print target medium is created from the saved BRS table 1 and the saved BRS table 2 and set as a new BRS correction table (S106).
FIG. 19 is an explanatory diagram of an example of BRS correction data created at each gradation. As described above, when the dot size measurement result by the scanner 120 is 55 μm with respect to the stored BRS correction table of FIG. The correction table T2 is selected. Then, the computer 110 creates new BRS correction data for each gradation value by using the stored BRS table 1 (BRS correction table T3) and the stored BRS table 2 (BRS correction table T2). Specifically, as shown in FIG. 19, at a gradation value of 12%, new correction data is created by interpolation processing between the correction data Ha2 and the correction data Ha3. At a gradation value of 25%, new correction data is created by interpolation between the correction data Hb2 and the correction data Hb3. Similarly, new correction data is created for other gradation values. Then, a new BRS correction table is created by combining the correction data created for each gradation.

  As described above, in the present embodiment, five BRS correction tables are stored in the memory 53 in advance, and the dot size measurement result obtained by the scanner 120 when printing is performed using the print target medium, and the memory 53 are stored. Based on these five BRS correction tables, a new BRS correction table for the print target medium is created.

In this way, a correction table for another medium can be automatically created using a plurality of BRS correction tables prepared in advance. Therefore, since it is not necessary to prepare a BRS correction table for each medium, density unevenness can be suppressed while reducing time and labor.
In this embodiment, the dot width is obtained for each gradation, and the density correction value corresponding to the dot width is obtained for each gradation. As a result, correction suitable for each gradation can be performed, and density unevenness can be further suppressed.
In the present embodiment, since the average value of the dot sizes is used, the accuracy of dot size calculation can be improved.

  In the present embodiment, the BRS correction table is prepared for each dot size by changing the type of medium. However, the present invention is not limited to this. For example, the dot size may be changed by changing the UV irradiation conditions on the same type of medium. In this way, a plurality of BRS correction tables may be created for each dot size. In the present embodiment, the number of BRS correction tables prepared in advance is five. However, the number is not limited to this, and a plurality of BRS correction tables may be used. These are the same in the following embodiments.

=== Second Embodiment ===
In the first embodiment, the dot size is one type (for example, medium dot). In the second embodiment, dots of a plurality of types of sizes are used. Specifically, three types of dots are used: small dots (S), medium dots (M), and large dots (L). In the second embodiment, an SML table in which the occurrence rates of these small, medium, and large dots are determined for each gradation value is used.

  FIG. 20 is a diagram illustrating an example of the dot occurrence rate in the SML table. As shown in the figure, the occurrence rates of small dots, medium dots, and large dots are determined for each gradation value. The occurrence rate is the ratio of pixels that eject ink, assuming that 100% of ink is ejected to all pixels. For example, at a gradation value of 12%, small dots are formed for pixels corresponding to 30% of the whole, and medium dots and large dots are not formed. At a gradation value of 70%, small dots, medium dots, and large dots are formed in pixels corresponding to 10%, 20%, and 10%, respectively.

  FIG. 21 is an explanatory diagram of a stored BRS correction table in the second embodiment. This stored BRS correction table is created by printing using the SML table of FIG. In the first embodiment (FIG. 18), each BRS correction table corresponds to the average dot size of a single dot, whereas in the second embodiment (FIG. 21), each BRS correction table has the above three types. The difference is that it corresponds to the average dot size of the dots. Since the rest is the same as that of the first embodiment, the description thereof is omitted. Each BRS correction table shown in FIG. 21 is stored (stored) in the memory 53 of the printer 1.

FIG. 22 is a flowchart showing BRS correction table creation processing in the second embodiment.
In the second embodiment, the computer 110 causes the printer 1 to print on a print target medium using small, medium, and large dots based on the SML table. Then, the computer 110 measures each dot size (specifically, the dot width in the paper width direction) of small, medium, and large dots formed on the print target medium by the scanner 120 (S201).
Then, the computer 110 calculates the weighted average shown in Expression (7) from the detection result of each dot size of the small, medium, and large dots by the scanner 120 and the dot occurrence rate (FIG. 20) at each gradation value of the SML table. Is used to calculate the average dot size for each gradation value (S202).

  FIG. 23 is a diagram illustrating an example of the calculation result of the average dot size for each gradation value. Note that the measurement results of the dot sizes of the small dots, medium dots, and large dots in step S201 are 30 μm, 50 μm, and 70 μm, respectively. For example, since only small dots are used in FIG. 20 with a gradation value of 12%, the ratio Ps of small dots is 100% in the equation (7), and the ratio Pm of medium dots and the ratio Pl of large dots are 0%. is there. Therefore, the average dot size dave is equal to the dot size (30 μm) of the small dots from Equation (7). Further, for example, at a gradation value of 70%, the incidence of small, medium, and large dots is 10%, 20%, and 10% as compared to FIG. Are ¼, ½, and ¼, respectively. Therefore, the average dot size dave is 30 × 1/4 + 50 × 1/2 + 70 × 1/4 = 50. Similarly, the average dot size of each gradation value is obtained as shown in FIG.

  Thereafter, the computer 110 determines whether or not the BRS correction data creation process in the BRS correction table of the print target medium is completed (FIG. 22, S203). If the BRS correction data creation process has not been completed (NO in S203), the BRS correction data creation target gradation value is selected from the uncreated gradation values (S204). For example, first, 12% having the lowest gradation value is selected. Then, it is determined whether or not the selected gradation value is the same as the average dot size corresponding to the stored BRS correction data (S205).

  For example, since the average dot size is 30 μm at the gradation value of 12% in FIG. 23, the same average dot size exists in the stored BRS correction data (FIG. 21). As described above, when the stored BRS correction data has the same dot size (S205), the stored BRS correction data corresponding to the same average dot size is set as the BRS correction data of the print target medium (S206). Specifically, when the gradation value is 12% and the average dot size is 30 μm, the correction data Ha1 is selected. Then, the process returns to step S203, and it is determined whether or not the processing has been completed for all the gradation values. If processing has not been completed for all the gradation values (NO in S203), another gradation value (for example, gradation value 25%) is selected in step S204, and the average dot size of the gradation value is saved. Step S205 for determining whether there is a BRS correction data having the same average dot size is executed again.

  In step S205, when it is determined that there is no data having the same average dot size as the stored BRS correction data (NO in S205), the computer 110 includes the stored BRS correction data created with a size larger than the average dot size. The one with the smallest average dot size is selected (S207). The saved BRS correction data selected here is assumed to be saved BRS data 1. Next, the computer 110 selects the stored BRS correction data created with a size smaller than the average dot size and having the maximum average dot size (S208). The saved BRS correction data selected here is designated as saved BRS data 2.

  Then, BRS correction data of the printing target medium at the target gradation value is generated by interpolation processing from the saved BRS data 1 and the saved BRS data 2 (S209). Specifically, at a gradation value of 25%, the average dot size is 34 μm from FIG. 23, and the average dot size corresponding to the stored BRS correction data of FIG. 21 is not the same. In this case, the BRS correction data Hb2 corresponding to the minimum dot size (50 μm) among the dot sizes larger than 34 μm is selected as the stored BRS data 1 having a gradation value of 25%. Further, the BRS correction data Hb1 corresponding to the maximum dot size (30 μm) among the dot sizes smaller than 34 μm is selected as the stored BRS data 2 having a gradation value of 25%. Then, BRS correction data having a gradation value of 25% in the print target medium is created by interpolation between the stored BRS data 1 (BRS correction data Hb2) and the stored BRS data 2 (BRS correction data Hb1). Then, the process returns to step S203. The processing from step S203 to step S209 is repeated.

FIG. 24 is an explanatory diagram of BRS correction data created at each gradation. Thus, the BRS correction data used for each gradation value differs depending on the average dot size.
If it is determined in step S203 that the BRS correction data creation process for the printing target medium has been completed (YES in FIG. 22, S203), the BRS correction table creation process ends.

  In the second embodiment, even when printing is performed with a mixture of small dots, medium dots, and large dots, unknown printing is performed using a plurality of correction value tables (stored BRS correction value tables) prepared in advance. A BRS correction table for the target medium can be created. Therefore, density unevenness can be suppressed while reducing time and labor.

  In the second embodiment, three types of dots are used, but the present invention is not limited to this. For example, two types of small dots and medium dots may be used, and four or more sizes of dots may be used. In these cases, the average dot size may be obtained by a weighted average as shown in Expression (7). By doing so, the consistency between the dot size and the density correction value can be improved, and density unevenness can be suppressed even when dots having different sizes are formed.

=== Third Embodiment ===
In the second embodiment, there is one type of SML table, but in the third embodiment, a plurality of types of SML tables are prepared. A combination of BRS correction tables corresponding to each SML table (referred to as a BRS correction table group) is set.

FIG. 25 is a diagram illustrating an example of a combination of an SML table and a BRS correction table group. In each BRS correction table group, as described above, a plurality of BRS correction tables (stored BRS correction tables) are defined for each dot size. In this case, the BRS correction table group 1 is created using the SML table 1.
Each SML table and the corresponding BRS correction table group are stored in the memory 53 of the printer 1.

FIG. 26 is a flowchart showing the overall processing of the third embodiment.
First, the SML table used for the print target medium is determined as one of the SML tables (see FIG. 25) used when creating the saved BRS correction table. In the present embodiment, the SML table 1 is selected from the viewpoints of graininess, color unevenness, bleeding, etc. when printing on a print target medium (S301). In this embodiment, the SML table is selected based on graininess and color unevenness, but the present invention is not limited to this. For example, the SML table may be selected based on the dot size when a certain dot (such as a large dot) is formed.
Next, the computer 110 performs a BRS correction table creation process for the print target medium using the BRS correction table created in the SML table 1 (S302).

  FIG. 27 is a diagram showing a BRS correction table created by the SML table 1. As shown in the figure, this is the same as the second embodiment (FIG. 20).

  FIG. 28 is a flowchart showing a BRS correction table creation process for a created print target medium in the third embodiment. Note that steps S3021 to S3029 shown in FIG. 28 correspond to steps S201 to S209 of the second embodiment (FIG. 22), respectively, and thus description thereof is omitted. FIG. 29 is an explanatory diagram of BRS correction data created for each gradation. Since this is also the same as that of the second embodiment (FIG. 24), description thereof is omitted.

As described above, in the third embodiment, a plurality of SML tables are prepared, and a stored BRS correction table is defined corresponding to each SML table. A new BRS correction table for the print target medium is created using a BRS correction table corresponding to the SML table selected from, for example, graininess and color unevenness.
By doing so, density unevenness can be suppressed more reliably.

=== Other Embodiments ===
Although a printer or the like as one embodiment has been described, the above embodiment is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About the printer>
In the above-described embodiment, a line head printer in which nozzles are arranged in the paper width direction intersecting the medium conveyance direction is described as an example, but the present invention is not limited thereto. For example, while moving the head unit in the moving direction intersecting the nozzle row direction, a dot forming operation for forming a dot row along the moving direction and a transport operation (moving operation) for transporting paper in the transport direction that is the nozzle row direction ) May alternately be a printer (serial printer).

  In the above-described embodiment, the ink jet printer has been described. However, the present invention is not limited to this, and the present invention can be applied to a liquid ejecting apparatus that ejects liquid other than ink. For example, a textile printing device for patterning a fabric, a display manufacturing device such as a color filter manufacturing device or an organic EL display, a DNA chip manufacturing device for manufacturing a DNA chip by applying a solution in which DNA is dissolved in a chip, a circuit board manufacturing It may be a device or the like. In addition, the ink ejection method for ejecting ink from the nozzles of the printer 1 may be a piezo method in which an ink chamber is expanded or contracted by driving a piezo element, or bubbles are generated in the nozzle using a heating element. Alternatively, a thermal method in which ink is discharged and ink is ejected by the bubbles may be used.

  In the embodiment described above, the system includes the printer 1, the computer 110, and the scanner 120. However, these may be configured as an integrated apparatus.

<About the scanner>
In the above-described embodiment, the scanner 120 has R, G, and B sensors (for example, a CCD), and reads the reflected light of the light irradiated on the document with each sensor, thereby obtaining R, G, and B color information. Although the sensor-type thing to acquire is used, it is not limited to this. For example, the fluorescent lamps for R, G, and B colors are sequentially blinked, the reflected light is read by a monochrome image sensor, and the R, G, and B color information is acquired, or between the light source and the sensor. An R, G, and B color filter may be provided, and a filter switching type that acquires R, G, and B color information by sequentially switching the color filters may be used.

<About ink>
In the above-described embodiment, UV ink that is cured by UV irradiation is used as the ink. However, the present invention is not limited to this, and ink other than UV ink may be used. However, as the number of types of media to be printed increases, the effect that the BRS correction table does not need to be created for each medium (saving labor and time) becomes more prominent. Therefore, this embodiment is more effective when UV ink is used.

<About the head and nozzle>
In the above-described embodiment, a plurality of heads are provided in a staggered manner. However, the configuration of the head is not limited to this, and for example, one head may be provided over the paper width direction. In this case, the nozzle row may be configured by arranging a plurality of nozzles on a straight line in the paper width direction.

<About correction values>
In the above-described embodiment, the correction value of each raster line is set for each gradation value, but the present invention is not limited to this. For example, each raster line may be associated with a correction value that increases or decreases the density (gradation value) at a predetermined rate. Also in this case, density unevenness can be suppressed as compared with the case where no correction value is provided.

1 printer, 20 head units, 23 heads,
23A 1st head, 23B 2nd head, 23C 3rd head,
30 transport unit, 32A upstream roller, 32B downstream roller,
34 belts, 40 detector groups, 50 controllers,
51 interface, 52 CPU, 53 memory,
54 unit control circuit, 60 irradiation unit 100 printing system, 110 computer,
111 interface, 112 CPU, 113 memory,
120 scanner, 121 reading unit, 122 interface,
123 CPU, 124 memory, 125 scanner controller

Claims (8)

A nozzle row having a plurality of nozzles arranged in a predetermined direction, and ejecting ink from the nozzle row while relatively moving the nozzle row and the medium in a relative movement direction intersecting the predetermined direction, thereby moving the nozzle row in the relative movement direction. A dot forming portion for forming a plurality of dot lines in which the plurality of dots are arranged in the predetermined direction;
A plurality of correction tables created for each dot width, each storing a plurality of correction tables in which density correction values are associated with dot lines;
A detection unit for detecting a dot width of dots formed on the medium by the dot formation unit;
With
Creating a correction table for the certain medium based on the detection result of the detection unit when using a certain medium and the plurality of correction tables stored in the storage unit;
A printing apparatus characterized by that. The printing apparatus according to claim 1,
The dot forming unit forms a pattern of multiple gradations on the medium,
The detection unit detects the dot width for each gradation;
A printing apparatus characterized by that. The printing apparatus according to claim 2,
The printing apparatus, wherein the density correction value corresponding to the dot width is calculated for each gradation. The printing apparatus according to any one of claims 1 to 3,
The dot forming unit forms a single size dot,
The dot width is an average value of dot widths of the single size dots.
A printing apparatus characterized by that. The printing apparatus according to any one of claims 1 to 3,
The dot forming unit forms dots of a plurality of sizes,
The dot width is a weighted average value obtained by weighting the average value of the dot widths of the dots of the plurality of sizes by the occurrence rate of the dots of the plurality of sizes.
A printing apparatus characterized by that. The printing apparatus according to claim 5,
The printing apparatus, wherein the plurality of correction tables are prepared for each dot generation table that defines the generation rate of each dot of the plurality of sizes. The printing apparatus according to any one of claims 1 to 6,
A light source for irradiating the dots formed on the medium with light;
The ink is an ink that is cured by light irradiation.
A printing apparatus characterized by that. A nozzle row having a plurality of nozzles arranged in a predetermined direction, and ejecting ink from the nozzle row while relatively moving the nozzle row and the medium in a relative movement direction intersecting the predetermined direction, thereby moving the nozzle row in the relative movement direction. A printing method of a printing apparatus for forming a plurality of dot lines in which a plurality of dots are arranged in the predetermined direction,
A plurality of correction tables created for each dot width, each storing a plurality of correction tables in which density correction values are associated with dot lines in a storage unit;
Detecting the dot width of dots formed on a medium;
Creating a correction table for the certain medium based on the dot width detected on the certain medium and the plurality of correction tables stored in the storage unit;
Printing on the medium using the created correction table;
A printing method characterized by comprising: