JP2009234014A - Table setting method, liquid ejection device and print system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a degradation of image quality when an image is printed by means of a plurality of heads. <P>SOLUTION: This table setting method comprises the printing step of printing a test pattern for detecting an attaching posture of a first head and a second head to a body of a liquid ejection device by allowing the first head and the second head to eject liquid, the detection step of detecting the attaching posture of the first head and the second head in accordance with the printed test pattern, and the setting step of setting a correspondence table indicating correspondence relationship between commanded gradation values and degrees of forming of a plurality of dots having different sizes on the basis of the detected attaching posture. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a table setting method, a liquid ejecting apparatus, and a printing system.

  As a liquid ejecting apparatus, an ink jet printer that prints an image by ejecting liquid (for example, ink) onto various media such as paper, cloth, and film is known. This printer has a head that ejects liquid. When the head ejects liquid, dots constituting an image are formed on the medium.

Here, as dots to be formed, there are a plurality of dots having different sizes in order to correspond to a multi-tone image. The dot size is determined based on a correspondence table indicating a correspondence relationship between the command gradation value and the generation degree of the plurality of dots. For example, when the command tone value is large, a large dot is formed, and when the command tone value is small, a small dot is formed (see Patent Document 1).
JP 2005-206991 A

Incidentally, some printers have a plurality of heads attached from the viewpoint of increasing the printing speed. In such a configuration, the dot formation position for each head may vary due to the mounting accuracy of the head with respect to the printer body. In such a case, for example, deterioration in image quality formed at the boundary between adjacent heads is easily emphasized.
The present invention has been made in view of the above problems, and an object thereof is to suppress deterioration in image quality when an image is printed with a plurality of heads.

In order to solve the above problems, the main present invention is:
A printing step for ejecting liquid to the first head and the second head and printing a test pattern for detecting the mounting state of the first head and the second head with respect to the liquid ejecting apparatus main body, and the printed test pattern Based on the detection step of detecting the mounting state of the first head and the second head;
A setting step for setting a correspondence table indicating a correspondence relationship between the command gradation value and the generation degree of a plurality of dots having different sizes based on the detected attachment state;
It is a table setting method characterized by having.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  At least the following will be made clear by the description of the present specification and the accompanying drawings.

A printing step of ejecting liquid to the first head and the second head and printing a test pattern for detecting the mounting state of the first head and the second head with respect to the liquid ejecting apparatus main body;
A detection step of detecting the mounting state of the first head and the second head based on the printed test pattern;
A setting step for setting a correspondence table indicating a correspondence relationship between the command gradation value and the generation degree of a plurality of dots having different sizes based on the detected attachment state;
A table setting method characterized by comprising:
According to such a table setting method, it is possible to suppress deterioration in image quality when an image is printed with a plurality of heads.

In addition, such a table setting method,
In the setting step,
It is desirable to set by selecting the correspondence table corresponding to the detected attachment state from the plurality of correspondence tables corresponding to each of the plurality of attachment states acquired in advance.
In such a case, since the correspondence table to be selected is acquired in advance, the processing speed of the correspondence table setting process can be increased.

In addition, such a table setting method,
The plurality of dots are a first dot and a second dot larger than the first dot,
In the plurality of correspondence tables, for each correspondence table, the limit value of the maximum generation amount of the first dot with respect to a predetermined area and the magnitude of the command gradation value for starting the generation of the second dot are different. desirable.
In such a case, by changing the limit value of the maximum generation amount of the first dot and the command gradation value for starting the second dot generation, and performing dot formation that can suppress the deterioration of the image quality, it is optimal for the mounting state. First dots and second dots can be generated.

In addition, such a table setting method,
The first head and the second head eject liquids of a plurality of colors,
In the setting step, it is desirable to set the same correspondence table for each of the plurality of colors.
In such a case, if a test pattern for one color is printed, the correspondence table for each color can be set, so there is no need to print a test pattern for a color other than the one color, and the processing speed can be increased.

In addition, such a table setting method,
The test pattern is a first ruled line printed by ejecting liquid onto the first head, and a second ruled line printed at a position away from the first ruled line by ejecting liquid onto the second head. ,
In the detecting step, as the mounting state, a degree of inclination of the first head and the second head with respect to the liquid ejecting apparatus main body is detected based on a printed interval between the first ruled line and the second ruled line. ,
In the setting step,
If the detected degree of inclination is large, a correspondence table is set in which the limit value of the first dot is small and the command gradation value for starting generation of the second dot is small,
When the detected degree of inclination is small, it is desirable to set a correspondence table in which the limit value of the first dot is large and the command gradation value for starting generation of the second dot is large.
In such a case, it is possible to set a correspondence table corresponding to the degree of inclination of the head with respect to the liquid ejecting apparatus main body with a simple test pattern.

A first head and a second head for ejecting liquid;
Printing a test pattern for ejecting liquid to the first head and the second head to detect the mounting state of the first head and the second head with respect to the liquid ejecting apparatus main body;
Based on the printed test pattern, the attachment state of the first head and the second head is detected,
Based on the detected mounting state, a control unit that sets a correspondence table indicating a correspondence relationship between the command gradation value and the generation degree of a plurality of dots having different sizes;
A liquid ejecting apparatus comprising:
According to such a liquid ejecting apparatus, it is possible to suppress deterioration in image quality when an image is printed with a plurality of heads.

A liquid ejecting apparatus having a first head and a second head for ejecting liquid;
Printing a test pattern for ejecting liquid to the first head and the second head to detect the mounting state of the first head and the second head with respect to the liquid ejecting apparatus main body;
Based on the printed test pattern, the attachment state of the first head and the second head is detected,
Based on the detected mounting state, a control unit that sets a correspondence table indicating a correspondence relationship between the command gradation value and the generation degree of a plurality of dots having different sizes;
A printing system comprising:
According to such a printing system, it is possible to suppress deterioration in image quality when printing an image with a plurality of heads.

=== Overview of Printing System ===
FIG. 1 is an explanatory diagram showing an external configuration of a printing system. The printing system 100 includes a printer 1 as an example of a liquid ejecting apparatus, a computer 110, a display device 120, an input device 130, a recording / reproducing device 140, and a scanner 150. The printer 1 is a printing apparatus that prints an image on a medium such as paper, cloth, or film. The computer 110 is communicably connected to the printer 1 and outputs print data corresponding to the image to be printed to the printer 1 in order to cause the printer 1 to print an image.

  A printer driver is installed in the computer 110. The printer driver is a program for causing the display device 120 to display a user interface and converting image data output from the application program into print data. The printer driver is recorded on a recording medium (computer-readable recording medium) such as a flexible disk FD or a CD-ROM. Alternatively, the printer driver can be downloaded to the computer 110 via the Internet. In addition, this program is comprised from the code | cord | chord for implement | achieving various functions.

=== Printer driver ===
FIG. 2 is an explanatory diagram of image processing by the printer driver.
Upon receiving a print command from the user, the printer driver performs resolution conversion processing, color conversion processing, density unevenness correction processing, halftone processing, and rasterization processing. Hereinafter, these processes will be described.

  The resolution conversion process is a process for converting image data (text data, image data, etc.) output from an application program into a resolution for printing on paper. For example, when the resolution for printing an image on paper is specified as 360 × 360 dpi, the image data received from the application program is converted into image data having a resolution of 360 × 360 dpi. Note that the image data after the resolution conversion process is 256-gradation data (RGB data) represented by an RGB color space.

  Here, the image data is a collection of pixel data. A pixel is a unit element constituting an image, and an image is formed by arranging the pixels two-dimensionally. The fact that the image data is 256 gradation data means that one pixel is expressed by 256 gradations, and one pixel data is 8-bit data (2 to the 8th power = 256).

  The color conversion process is a process for converting RGB data into CMYK data represented by a CMYK color space. Through this color conversion process, RGB data for each pixel is converted into CMYK data corresponding to the ink color. The data after the color conversion processing is CMYK data with 256 gradations represented by the CMYK color space.

  In the density unevenness correction processing, the gradation value (input gradation value) of each pixel data (256-level CMYK data) constituting the image data is corrected to a correction value (described later) in order to suppress density unevenness in the printed image. This is a process of correcting based on (BRS correction value).

  The halftone process is a process for converting high gradation number data into gradation number data that can be formed by a printer. For example, data representing 256 gradations is converted into 1-bit data representing 2 gradations or 2-bit data representing 4 gradations by halftone processing. Details of the halftone process will be described later.

  The rasterization process is a process of changing matrix image data in the order of data to be transferred to the printer. The rasterized data is output to the printer as pixel data included in the print data.

=== Configuration of Printer ===
<Inkjet printer configuration>
FIG. 3 is a block diagram of the overall configuration of the printer 1. FIG. 4A is a cross-sectional view of the printer 1. FIG. 4B is a perspective view for explaining the conveyance process and the dot formation process of the printer 1. Hereinafter, the basic configuration of the printer of this embodiment will be described.

  The printer 1 includes a transport unit 20, a head unit 40, a detector group 50, a controller 60, and a drive signal generation unit 70. The printer 1 that has received the print data from the computer 110 as an external device controls each unit (the transport unit 20, the head unit 40, and the drive signal generation unit 70) by the controller 60. The controller 60 controls each unit based on the print data received from the computer 110 and prints an image on paper. The situation in the printer 1 is monitored by a detector group 50, and the detector group 50 outputs a detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the detector group 50.

  The transport unit 20 is for transporting a medium (for example, paper S) in a predetermined direction (hereinafter referred to as a transport direction). The transport unit 20 includes a paper feed roller 21, a transport motor (not shown), an upstream transport roller 23 </ b> A and a downstream transport roller 23 </ b> B, and a belt 24. The paper feed roller 21 is a roller for feeding the paper inserted into the paper insertion slot into the printer. When a transport motor (not shown) rotates, the upstream transport roller 23A and the downstream transport roller 23B rotate, and the belt 24 rotates. The paper S fed by the paper feed roller 21 is conveyed by the belt 24 to a printable area (area facing the head). When the belt 24 transports the paper S, the paper S moves in the transport direction with respect to the head unit 40. The paper S that has passed through the printable area is discharged to the outside by the belt 24. The paper S being conveyed is electrostatically attracted or vacuum attracted to the belt 24.

  The head unit 40 is for ejecting ink, which is an example of a liquid, onto the paper S. The head unit 40 ejects ink onto the paper S being conveyed, thereby forming dots on the paper S and printing an image on the paper S. The head unit 40 of the present embodiment can form dots for the paper width at a time. The configuration of the head unit 40 will be described later.

  The detector group 50 includes a rotary encoder (not shown), a paper detection sensor 53, and the like. The rotary encoder detects the rotation amount of the upstream side conveyance roller 23A and the downstream side conveyance roller 23B. The transport amount of the paper S can be detected based on the detection result of the rotary encoder. The paper detection sensor 53 detects the position of the leading edge of the paper being fed.

  The controller 60 is a control unit for controlling the printer. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 transmits and receives data between the computer 110 which is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM and an EEPROM. The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63.

  The drive signal generation unit 70 is for generating a drive signal COM for driving the head unit 40. The drive signal generation unit 70 includes a plurality of drive signal generation units 71. When the controller 60 sets waveform data in each drive signal generator 71, each drive signal generator 71 generates a drive signal COM having a waveform corresponding to the waveform data. Then, no dot, small dot formation, and medium dot formation according to the drive signal COM are realized.

<Configuration of head unit 40>
FIG. 5A is an explanatory diagram showing an arrangement of a plurality of heads on the lower surface of the head unit 40. FIG. 5B is an explanatory diagram of the positional relationship of each head. The lower surface of the head unit faces the paper S conveyed by the belt 24.

  On the lower surface of the head unit 40, a plurality of heads are arranged in a staggered arrangement. In the following description, the first head 41A, the second head 41B, the third head 41C, the fourth head 41D,... On the upstream side in the transport direction, odd-numbered first head 41A, third head 41C, fifth head 41E,... Are arranged in the paper width direction. Further, even-numbered second head 41B, fourth head 41D, sixth head 41F,... Are arranged in the paper width direction on the downstream side in the transport direction.

  Each of the plurality of heads has a fixing portion 42 that is fixed to the panel 40 a of the head unit 40. The fixing portion 42 is fixed to the panel 40a with screws or the like, so that each head is attached.

  In each head, a black ink nozzle row K, a cyan ink nozzle row C, a magenta ink nozzle row M, and a yellow ink nozzle row Y are formed. Each nozzle row includes a plurality of nozzles (360 nozzles in this embodiment) that are ejection ports for ejecting ink. The plurality of nozzles in each nozzle row are arranged at a constant nozzle pitch along the arrangement direction (paper width direction) in FIG. 5B. Here, the nozzle pitch is 1/360 inch. The nozzles of each head are numbered sequentially from the left in the figure (# 1 to # 360). Each nozzle is provided with a pressure chamber (not shown) containing ink and a driving element (piezo element) for ejecting ink by changing the capacity of the pressure chamber.

  Paper width direction between the leftmost nozzle # 1 of the odd-numbered head (for example, the third head 41C) on the upstream side in the transport direction and the rightmost nozzle # 360 of the even-numbered head (for example, the second head 41B) on the downstream side in the transport direction Is 1/360 inch which is the same as the nozzle pitch. Further, the nozzle # 360 at the right end of the odd-numbered head (for example, the third head 41C) on the upstream side in the transport direction and the nozzle # 1 at the left end of the even-numbered head (for example, the fourth head 41D) on the downstream side in the transport direction. The interval in the paper width direction is 1/360 inch which is the same as the nozzle pitch.

  By arranging the heads in this way, the nozzles can be arranged at intervals of 1/360 inch in the arrangement direction (paper width direction) over the length of the paper to be printed. By arranging the heads in this way, the head unit 40 can form dots (dot rows) arranged at intervals of 1/360 inch in the paper width direction over the length of the paper width. Note that the length between the nozzle # 1 of the head 41A and the nozzle # 360 of the head 41N is smaller than the width of the paper to be printed, and the image is printed within the paper width.

  Of course, the length between the nozzle # 1 of the head 41A and the nozzle # 360 of the head 41N may be greater than the width of the paper to be printed.

=== Halftone processing ===
FIG. 6A is an explanatory diagram of a dot generation rate table. The horizontal axis of the graph is the gradation value (0 to 255), the left side of the vertical axis is the dot generation rate (0 to 100%), and the right side is the level data. In the figure, the generation rate of small dots and the generation rate of medium dots are shown. Here, the dot generation rate is the rate at which dots are formed in pixels in a unit area when the gradation value of the unit area is constant. For example, when the unit area is composed of 16 × 16 pixels, the gradation value of all the pixel data in the unit area is a constant value, and n dots are formed in the unit area, the gradation value The dot generation rate is {n / (16 × 16)} × 100 (%). The level data refers to data representing the dot generation rate in 256 gradations of values 0 to 255.
As described above, the dot generation rate table is a correspondence table that indicates the correspondence between the gradation value and the degree of generation of small dots and medium dots having different sizes.

  FIG. 6B is a diagram showing a state of dot on / off determination by the dither method. The printer driver first determines whether the medium dot level data LVM is greater than a threshold value. A different threshold value is set for each pixel of the dither matrix. For simplification of explanation, a dither matrix of 4 × 4 pixels is used in the figure, but a dither matrix corresponding to a wide range such as 16 × 16 pixels is actually used.

  The image data before halftone processing is a set of 256-tone CMYK pixel data represented by the CMYK color space. Hereinafter, black pixel data (hereinafter referred to as K pixel data) will be described as an example. First, the printer driver sequentially extracts K pixel data from CMYK image data. The printer driver sets the medium dot level data LVM according to the gradation value (data gradation value) of the extracted K pixel data. For example, if the gradation value of certain K pixel data is gr, the medium dot level data LVM of K pixel data is set to 2d.

  Then, it is assumed that the K pixel data is the upper left pixel shown in FIG. 6B and the medium dot level data LVM is “2d = 180”. In this case, the threshold value on the dither matrix corresponding to this pixel is “1”, and the printer driver determines that the medium dot level data is larger than the threshold value. Then, the pixel data of the pixel is converted to “10” (2-bit data), and the process for the pixel data is terminated. A middle dot is formed in the upper left pixel.

  If it is determined that the middle dot level data LVM in the upper left pixel is equal to or less than the threshold value, then the printer driver sets the small dot level data LVS. If the gradation value of certain K pixel data is gr, the small dot level data LVS is set to d. If the printer driver determines that the small dot level data LVS is larger than the threshold value, the printer driver converts the pixel data of the pixel to “01” and ends the processing for the pixel data. A small dot is formed in the pixel.

  On the other hand, when the small dot level data LVS is equal to or smaller than the threshold value, the pixel data of the pixel is converted to “00”, and the process for the pixel data is ended. No dot is formed on that pixel.

  In this way, K pixel data indicating 256 gradations is extracted from the CMYK image data and converted into 2-bit data indicating 3 gradations (medium dots, small dots, no dots). Similarly, pixel data of other colors of 256 gradations are also converted into data of 3 gradations.

  In the above, the halftone process by the dither method has been described, but the present invention is not limited to this. For example, pixel data may be created using the error diffusion method so that the printer 1 can form dots dispersedly.

=== Density unevenness ===
When the printer performs printing, density unevenness occurs in the image. Here, for the sake of simplification of description, the cause of density unevenness occurring in an image printed in a single color will be described. In the case of multicolor printing, the cause of density unevenness described below occurs for each color.

  In the following description, the “unit area” refers to a rectangular area virtually defined on a medium such as paper, and the size and shape are determined according to the printing resolution. For example, when the printing resolution is 360 dpi (array direction) × 360 dpi (transport direction), the unit area is a square shape having a size of approximately 70.56 μm × 70.56 μm (≈ 1/360 inch × 1/360 inch). Become an area. When ink droplets are ejected ideally, the ink droplets land at the center position of the unit area, and then the ink droplet spreads on the medium to form dots in the unit area. One unit area corresponds to one pixel constituting image data. In addition, since a pixel is associated with each unit area, pixel data of each pixel is also associated with each unit area.

  Further, in the following description, “row region” refers to a region constituted by a plurality of unit regions arranged in the paper transport direction. For example, when the printing resolution is 360 dpi × 360 dpi, the row region is a band-like region having a width of 70.56 μm (≈ 1/360 inch) in the arrangement direction. When ink droplets are ideally intermittently ejected from the nozzles onto the paper being conveyed in the conveyance direction, raster lines are formed in this row region. That is, each raster line is formed by ink ejected from only one nozzle. A plurality of pixels arranged in the transport direction are associated with the row area.

  FIG. 7A is an explanatory diagram of a state when dots are ideally formed. In the figure, since dots are ideally formed, each dot is accurately formed in the unit region, and the raster line is accurately formed in the row region. In the drawing, in each row region, an image piece having a density corresponding to the coloring of the region is formed. Here, for simplification of explanation, it is assumed that an image having a constant density is printed so that the dot generation rate is 50%.

  FIG. 7B is an explanatory diagram of density unevenness. Here, it is assumed that the diameter of the nozzle that ejects ink droplets toward the third row region is larger than the diameter of the nozzle that ejects ink droplets toward the other row region. As a result, the amount of ink droplets ejected toward the third row region increases, and the dots formed in the third row region increase. As a result, the image piece (raster line) in the third row region is darker than the image piece (raster line) in the other row region. That is, although an image piece having the same density should be formed in each row area, the image piece is shaded according to the row area. When a print image composed of such raster lines is viewed macroscopically, striped density unevenness along the transport direction is visually recognized. That is, density unevenness occurs according to the characteristics of the nozzle. This density unevenness causes a reduction in image quality of the printed image.

  Therefore, in this embodiment, the gradation value of the pixel data is corrected based on a correction value (BRS correction value described later) set for each row region in order to suppress the density unevenness according to the nozzle characteristics described above. is doing. In other words, the gradation value of the pixel data (CMYK pixel data) of the pixel corresponding to the row region is corrected so that a dark image piece is formed in the row region that is dark and easily visible. Further, the gradation value of the pixel data of the pixel corresponding to the row region is corrected so that a dark image piece is formed in a row region that is easily viewed. For example, the gradation value of the pixel data of the pixel corresponding to the third row region is corrected so that the dot generation rate of the third row region shown in FIG. 7B is lowered. As a result, the dot generation rate of the raster lines in each row area is changed, the density of the image pieces in the row area is corrected, and density unevenness of the entire print image is suppressed.

=== BRS Correction Value Acquisition Process ===
FIG. 8 is a flowchart of the BRS correction value acquisition process. The BRS correction value is a correction value for correcting density unevenness. Each process is realized by a BRS correction program installed in the computer 110.

  First, the computer 110 transmits print data to the printer 1, and the printer 1 prints a test pattern for BRS correction on a test sheet (step S2). The print data is subjected to the halftone process described above.

  FIG. 9A is an explanatory diagram of a test pattern for BRS correction. A test pattern for BRS correction is printed on the test sheet TS1. This test pattern includes four correction patterns for each color, an upper ruled line, a lower ruled line, a left ruled line, and a right ruled line. Each correction pattern is composed of three types of density belt-like patterns. Each strip pattern is formed by ejecting ink from all the nozzles of each head 41. The belt-like pattern is generated from image data having a certain gradation value. In each correction pattern, gradation values 64 (density 25%), 128 (density 50%), and 192 (density 75%) are sequentially arranged from the upper band-shaped pattern, and the patterns are darker in order. . These three types of gradation values (density) are called “command gradation values (command density)” and are represented by symbols Sa (= 64), Sb (= 128), and Sc (= 192).

Next, the inspector sets the test sheet TS1 on which the test pattern is printed on the scanner 150. Then, the computer 110 causes the scanner 150 to read the test pattern and obtains test pattern image data (step S4).
Next, the computer 110 corrects the image data of the test pattern (step S6). As a result, image distortion or the like caused by an error in the reading position of the scanner 150 is corrected.
Next, the computer 110 detects a density measurement value for each row region for each of the four patterns of correction patterns (step S8).

  FIG. 9B is a graph of the measured values of the belt-like pattern having a cyan density of 25%, a density of 50%, and a density of 75%. Although each belt-like pattern is uniformly formed with the command gradation value, shading is generated for each row region. The density difference in the row area is a cause of density unevenness in the printed image.

  Next, the computer 110 calculates a BRS correction value for each row region (step S10). Therefore, a process for making the measurement value of the band-shaped pattern of the gradation value Sb (density 50%) constant will be considered. Here, the average value Cbt of the measurement values of all the row regions of the strip-like pattern having the gradation value Sb is determined as the target value of 50% density. In the row region i where the measured value is lighter than the target value Cbt, it is considered that the gradation value should be corrected to be darker. On the other hand, in the row region j where the measured value is darker than the target value Cbt, it is considered that the gradation value should be corrected to be lighter.

  Therefore, the computer 110 calculates a correction value for each row region. Here, calculation of the correction value for the command gradation value Sb in a certain row region will be described. As will be described below, the correction value for the command gradation value Sb (density 50%) in the row region i in FIG. 9B is calculated based on the measured values of the gradation value Sb and the gradation value Sc (density 75%). Is done. On the other hand, the correction value for the command gradation value Sb of the row region j is calculated based on the measurement values of the gradation value Sb and the gradation value Sa (density 25%).

FIG. 10A is an explanatory diagram of the target command tone value Sbt with respect to the command tone value Sb in the row region i. In this row area i, the measured density value Cb of the belt-like pattern formed with the command gradation value Sb shows a gradation value smaller than the target value Cbt (the density in this row area is lighter than the average density). . If the printer forms a density pattern of the target value Cbt in this row area, the printer driver is commanded based on the target command tone value Sbt calculated by the following equation (linear interpolation based on the straight line BC). I think it would be good.
Sbt = Sb + (Sc−Sb) × {(Cbt−Cb) / (Cc−Cb)}

FIG. 10B is an explanatory diagram of the target command tone value Sbt with respect to the command tone value Sb in the row region j. In this row region j, the measured value Cb of the density of the belt-like pattern formed with the command tone value Sb shows a tone value larger than the target value Cbt (the density of this row region is higher than the average density). . If the density pattern of the target value Cbt is to be formed in this line area by the printer, the printer driver is commanded based on the target command tone value Sbt calculated by the following equation (linear interpolation based on the straight line AB). I think it would be good.
Sbt = Sb− (Sb−Sa) × {(Cbt−Cb) / (Ca−Cb)}
After calculating the target command tone value Sbt in this way, the computer 110 calculates a correction value Hb for the command tone value Sb in this row region by the following equation.
Hb = (Sbt−Sb) / Sb

  The computer 110 calculates a correction value Hb for the gradation value Sb (density 50%) for each row region. Similarly, a correction value Hc for the gradation value Sc (density 75%) is calculated for each row region based on the measurement value Cc and the measurement value Cb of each row region. Similarly, a correction value Ha for the gradation value Sa (density 25%) is calculated for each row region based on the measurement value Ca and the measurement value Cb of each row region. For other colors, three correction values (Ha, Hb, Hc) are calculated for each row region.

  Returning to the flowchart of FIG. The computer 110 transmits the correction data to the printer 1 and stores the BRS correction value in the memory 63 of the printer 1 (step S12).

  FIG. 11 is an explanatory diagram of a cyan correction value table. In the correction value table, three correction values (Ha, Hb, Hc) are associated with each row region. For example, three correction values (Ha_n, Hb_n, Hc_n) are associated with the nth raster line in each row region. The three correction values (Ha_n, Hb_n, Hc_n) correspond to the command gradation values Sa (= 64), Sb (= 128), and Sc (= 192), respectively. These BRS correction values reflect the density unevenness characteristics of individual printers. The same applies to correction value tables for other colors.

  The printer storing the BRS correction value is packed and delivered to the user. When the user prints an image with the printer, the printer corrects the image data of the image to be printed based on the BRS correction value, and performs printing based on the corrected image data. Thereby, the dot generation rate of the raster line in each row region is changed, the density of the image pieces in the row region is corrected, and density unevenness according to the nozzle characteristics of the entire print image is suppressed.

=== Image Quality Evaluation in L * a * b * Color System ===
The above printer can print images of various colors. That is, not only the single colors cyan, magenta, yellow, and black, but also a mixed color (for example, gray) image obtained by mixing these colors can be printed.
As a method for evaluating the image quality of such an image composed of various colors, there is a method for quantitatively evaluating the color by quantifying the color. Here, a system for representing colors numerically is called a color system. As one of the color systems, there is an L * a * b * color system (also called CIELAB). Here, L * (Elster) indicates the lightness among the three attributes of the color, and a * (Aster) and b * (Biester) indicate the hue and saturation.

  By the way, when the image quality was evaluated using the L * a * b * color system before and after applying the BRS correction, the following was found. That is, the brightness of the three attributes is improved by applying the BRS correction. On the other hand, even if BRS correction is applied, the degree of improvement in hue and saturation is small.

  Here, it explains in detail using the measurement result about a * of a * and b *. In this measurement, first, an image quality evaluation pattern for image quality evaluation is printed at a *. Then, the scanner 150 is caused to read the printed image quality evaluation pattern. Furthermore, image quality evaluation is performed based on the read image.

  FIG. 12 is an explanatory diagram of an image quality evaluation pattern. As an image quality evaluation pattern, four patterns (such as a cyan pattern) for each color are printed on paper. Each pattern is composed of a plurality of small patterns (small patterns C1, C2, C3, etc.). These small patterns are formed by ink ejected from different heads. For example, the small patterns C1, M1, Y1, and G1 are formed by ink ejected from the head 41A. Similarly, the small patterns C2, M2, Y2, and G2 are formed by ink ejected from the head 41B. The length of each small pattern in the paper width direction is 1 inch, which is equal to the nozzle width of each head (the length between nozzles # 1 to # 360).

  In this measurement, the image quality evaluation pattern to which BRS correction is not applied and the image quality evaluation pattern to which BRS correction is applied are printed on different papers. Then, the scanner 150 is caused to read two sheets on which the image quality evaluation pattern is printed. Here, the reading resolution of the scanner 150 is 1440 dpi.

  13A to 13D are graphs showing a * of an image quality evaluation pattern to which BRS correction is not applied. 14A to 14D are graphs showing a * of an image quality evaluation pattern to which BRS correction is applied. These graphs are obtained by causing the scanner 150 to read paper on which an image quality evaluation pattern is printed.

  13A and 14A show a single color cyan, FIGS. 13B and 14B show magenta, FIGS. 13C and 14C show yellow, and FIGS. 13D and 14D show mixed colors gray. Yes. For convenience of explanation, FIGS. 13A and 14A show a * of small patterns C1, C2, and C3, and FIGS. 13B and 14B show a * of small patterns M1, M2, and M3. 13C and 14C show a * of small patterns Y1, Y2, and Y3, and FIGS. 13D and 14D show a * of small patterns G1, G2, and G3. Furthermore, the horizontal axis of each graph indicates the position of a pixel (pixel). Pixel positions 1 to 1441 indicate small patterns C1 (M1, Y1, and G1), pixel positions 1442 to 2881 indicate small patterns C2 (M2, Y2, and G2), and pixel positions 2882 to indicate small patterns C3 (M3). , Y3, G3). The vertical axis represents the value of Δa *, which is the difference from the average value of a * values at each pixel position. For this reason, if Δa * is large, it means that the degree of deviation from the average value is large.

  As shown in FIG. 13A to FIG. 13C and FIG. 14A to FIG. 14C for the single colors cyan, magenta, and yellow, the variation range of a * is reduced by applying BRS correction. On the other hand, as shown in FIG. 13D and FIG. 14D, for gray which is a mixed color, even when BRS correction is applied, a state where the fluctuation range of a * is large is maintained. In particular, as shown in FIG. 14D, the variation width of a * is particularly large at the boundary between adjacent heads (for example, the portion around pixel position 1441 corresponding to the boundary between head 41A and head 41B).

  As described above, even if the BRS correction is applied, the image quality of the mixed color image cannot be improved. In particular, the image quality deterioration of the image corresponding to the boundary portion between adjacent heads becomes remarkable.

=== Dot generation rate table setting process ===
In order to suppress the above-described deterioration in the image quality of the mixed-color image, in the present embodiment, a dot generation rate table setting process is performed in which a dot generation rate table is set according to the mounting state of the head.
FIG. 15 is a flowchart of the dot generation rate table setting process. This process is performed before the execution of the BRS correction process. In the following description, each process in the dot generation rate table setting process will be described. Each process is realized by a program installed in the computer 110 as a control unit.

<< Step S102: Print Test Pattern >>
First, the computer 110 ejects ink to each of the heads 41 </ b> A to 41 </ b> N, and prints a test pattern for detecting the mounting state of each head with respect to the main body of the printer 1.

  FIG. 16 is an explanatory diagram of the test pattern. A test pattern is printed on the test sheet TS2. This test pattern is a ruled line printed by ejecting ink (in this embodiment, black ink) onto the heads 41A to 41N.

  For convenience of explanation, FIG. 16 shows only the ruled lines A1 to A5 and the ruled lines B1 to B5 printed by ejecting ink to the head 41A and the head 41B (actually, by other heads, Ruled lines are printed). The ruled lines A1 to A5 are printed by ejecting ink to the head 41A among the heads 41A to 41N. The ruled lines B1 to B5 are printed by ejecting ink onto the head 41B.

  Here, the ruled lines A1 to A5 are printed at predetermined intervals L. Similarly, ruled lines B1 to B5 are also printed at predetermined intervals L. Then, the ruled lines B1 to B5 are printed with being shifted from the ruled lines A1 to A5 by a half (L / 2) of the predetermined interval L. Therefore, the ruled line B1 is located at the center position (control position) between the ruled line A1 and the ruled line A2 in the transport direction.

<< Step S104: Detection of Head Mounting State >>
The computer 110 causes the scanner 150 to read the test sheet TS2 on which ruled lines are printed. Then, the computer 110 detects the head mounting state based on the read ruled line (test pattern).

  Here, the reason why the mounting state of each head can be detected based on the ruled line is as follows. That is, if the mounting accuracy of the head to the panel 40a is good, each ruled line is printed at a control position. On the other hand, if the mounting accuracy of the head is poor, the ruled line is printed at a position shifted from the control position. For this reason, the attachment state of the head can be detected by looking at the printed state of the ruled lines (intervals between the ruled lines A1 to A5 and the ruled lines B1 to B5).

  Specifically, the computer 110 detects the degree of inclination of the head 41A and the head 41B with respect to the panel 40a based on the intervals between the printed ruled lines A1 to A5 and the ruled lines B1 to B5 as the mounting states of the heads 41A and 41B. .

FIG. 17A is a diagram showing ruled lines A1 and A2 and ruled lines B1 and B2 that are ideally printed. Since these ruled lines are ideally printed (in other words, printed at a control position), the ruled line B1 is positioned at the center of the ruled line A1 and the ruled line A2. That is, the ruled line B1 is printed at a position separated from the ruled line A1 by L / 2 in the transport direction (similarly, a position separated from the ruled line A2 by L / 2). Although not shown, the ruled lines B2 to B4 are also located at the center position with respect to the ruled lines A2 to A5. Similarly, the ruled line A2 is located at the center position between the ruled line B1 and the ruled line B2 in the transport direction. Although not shown, the ruled lines A3 to A5 are also located at the center position with respect to the ruled lines B2 to B5.
Thus, when the interval between the ruled line A1 and the ruled line B1 is L / 2, it means that the heads 41A and 42B are attached (the degree of inclination of the head unit 40 with respect to the panel 40a) is good.

FIG. 17B is a diagram showing ruled lines A1 and A2 printed ideally and ruled lines B1 and B2 printed at shifted positions. The ruled lines B1 and B2 are printed out of alignment as a whole, and the interval between the ruled lines B1 and B2 is L. Here, since the ruled lines B1 and B2 are printed out of alignment (in other words, printed at a position displaced from the control position), the interval between the ruled line B1 and the ruled line A1 in the transport direction is L / The value L1 is different from 2. In FIG. 17B, the ruled line B1 is printed closer to the ruled line A2 than the ruled line A1, so the interval L1 between the ruled line B1 and the ruled line A1 is larger than L / 2. On the other hand, the interval L2 between the ruled line B1 and the ruled line A2 is smaller than L / 2. If the interval between the ruled lines is different from L / 2 as described above, it can be estimated that the head is attached with an inclination.
Thus, by measuring the distance between the ruled line A1 (A2,...) And the ruled line B1 (B2,...), The mounting state of the head 41B (the tilted state of the head unit 40 with respect to the panel 40a) can be detected.

Then, the computer 110 calculates the adjustment amount for mounting the head 41B by measuring the interval between the ruled line A1 (A2,...) And the ruled line B1 (B2,...). For example, as shown in FIG. 17A, if the interval between the ruled line A1 and the ruled line B1 is L / 2, the adjustment amount is zero. On the other hand, when the interval between the ruled line A1 and the ruled line B1 is a value different from L / 2 as shown in FIG. 17B, the difference between this value and L / 2 is the adjustment amount.
Similarly, the adjustment amount for attaching the head 41C is calculated based on the interval between the ruled lines B1 to B5 and the ruled line printed by the head 41C.

<< Step S106: Selection of Optimal Dot Generation Rate Table >>
The computer 110 sets a dot generation rate table based on the calculated cooking amount (in other words, the head mounting state). Specifically, the computer 110 selects a dot generation rate table corresponding to the detected head mounting state from a plurality of dot generation rate tables acquired in advance.

  FIG. 18 is a correspondence table between the adjustment amount and the dot generation rate table. This correspondence table is stored in the memory 63. The plurality of dot generation rate tables shown in the correspondence table respectively correspond to head mounting states with different adjustment amounts. That is, when the adjustment amount is different, the dot generation rate table is different.

For example, when the calculated adjustment amount is D1, the computer 110 refers to the correspondence table and selects the dot generation rate table T1. If there is no matching table in the correspondence table, the dot generation rate table with the closest value is selected. As a result, a dot generation rate table suitable for the adjustment amount is selected.
In consideration of the fact that the adjustment amount differs for each head, in the present embodiment, a dot generation rate table corresponding to each head is selected one by one.

  FIG. 19 is a diagram showing a dot generation rate table T1. Here, it is assumed that the table shown in FIG. 6A is a dot generation rate table T3. The difference between the dot generation rate table T1 and the dot generation rate table T3 lies in the small dot limit value and the medium dot generation start gradation value size, as can be seen by comparing FIG. 6A and FIG. That is, the limit value for small dots in the dot generation rate table T1 is 10%, whereas the limit value for small dots in the dot generation rate table T3 is 40%. Further, the gradation value at the start of medium dot generation in the dot generation rate table T1 is smaller than the gradation value at the start of medium dot generation in the dot generation ratio table T3.

  As described above, in the plurality of dot generation rate tables of the correspondence table, the limit value of the maximum generation amount of small dots and the magnitude of the gradation value at the start of generation of medium dots are different for each dot generation rate table. When the adjustment amount is increased, the small dot limit value is decreased, and the medium dot generation start gradation value is decreased.

  In the above, ruled lines are printed with black ink, and the dot generation rate table is selected. The selected dot generation rate table is applied not only to black but also to other colors. That is, the computer 110 sets the same correspondence table for each of the plurality of colors. Accordingly, it is not necessary to print a test pattern for each color, so that the processing speed can be increased.

  When the above-described dot generation rate table setting process ends, the computer 110 executes the BRS correction process described above. That is, the computer 110 causes the printer 1 to print a BRS correction test pattern based on the dot generation rate table T1. As a result, as shown in FIGS. 20A to 20D to be described later, it is possible to suppress deterioration in image quality not only for a single color image but also for a mixed color image.

  In this embodiment, the test pattern printing in step S102 corresponds to the printing step, the head attachment state detection in step S104 corresponds to the detection step, and the optimum dot generation rate table selection in step S106 is performed. This corresponds to the setting step.

=== Effectiveness of Printing System 100 According to the Present Embodiment ===
In the dot generation rate table setting process described above, ink is ejected to the first head (for example, the head 41A) and the second head (for example, the head 41B), and the head 41A and the head 41B are attached to the printer 1 main body. Print a test pattern for detecting (printing step). Further, the mounting state of the head 41A and the head 41B is detected based on the printed test pattern (detection step). Then, based on the detected attachment state, a dot generation rate table (correspondence table) indicating the correspondence between the gradation value (command gradation value) and the generation degree of small dots and medium dots having different sizes. Is set (setting step).

  Accordingly, the correspondence relationship is changed based on the mounting state of the head (for example, when the mounting state of the head is bad, the small dot limit value is reduced, and the gradation value for starting the generation of medium dots is By changing the correspondence relationship so as to be smaller), as shown in the following measurement results, it is possible to suppress deterioration in image quality of an image printed using a plurality of heads.

  Such effectiveness will be described with reference to FIGS. 20A to 20D and FIGS. 14A to 14D described above. 20A to 20D are graphs showing a * of the image quality evaluation pattern printed based on the dot generation rate table (that is, the dot generation rate table T1) set in the dot generation rate table setting process. The graphs of FIGS. 20A to 20D are also obtained by applying the BRS correction and printing the image quality evaluation pattern of FIG. Each of the image quality evaluation patterns shown in FIGS. 14A to 14D described above is printed by applying the dot generation rate table T3 (FIG. 18).

Comparing FIGS. 14A to 14D with FIGS. 20A to 20D, the following can be understood. First, when comparing single colors, the variation width of a * around the pixel position 1441 is smaller in FIGS. 20A to 20C. Furthermore, for gray, which is a mixed color, as can be seen by comparing FIG. 14D and FIG. 20D, the variation range of a * around the pixel position 1441 (the boundary between the head 41A and the head 41B) is further reduced. Thus, the dot generation rate table is set according to the head mounting state (for example, if the head mounting state is bad, the small dot limit value is reduced and the medium dot generation start level is set). By changing the correspondence relationship so that the tone value becomes smaller, it is possible to suppress a decrease in image quality at a *. Although not shown in the drawing, a decrease in image quality can be suppressed even in b * indicating hue and saturation as in a *.
As described above, according to the present embodiment, it is possible to suppress deterioration in image quality when an image is printed with a plurality of heads.

In the setting step, a dot generation rate table corresponding to the detected mounting state is selected from a plurality of dot generation rate tables corresponding to each of the plurality of mounting states acquired in advance. Thus, the dot generation rate table is set (see FIG. 18).
In such a case, since the dot generation rate table to be selected is acquired in advance, the processing speed of the dot generation rate table setting process can be increased.

In the above embodiment, the first head and the second head form a small dot (first dot) and a medium dot (second dot) larger than the small dot as the plurality of dots. . In the plurality of dot generation rate tables, the limit value of the maximum generation amount of small dots for a predetermined area is different from the size of the gradation value at the start of medium dot generation for each dot generation rate table. (See FIG. 6A and FIG. 19).
In such a case, by changing the limit value of small dots and the gradation value at the start of generation of medium dots, dot formation that can suppress deterioration in image quality is performed (when the adjustment amount is large, the dot size is smaller than that of small dots). By increasing the generation ratio of medium dots), it is possible to generate small dots and medium dots suitable for the mounting state.

The first head and the second head eject ink of a plurality of colors. In the setting step, the same dot generation rate table is set for each of the plurality of colors.
In such a case, if a test pattern for one color is printed, the dot generation rate table for each color can be set, so that it is not necessary to print a test pattern for a color other than the one color, and the processing speed can be increased.

In the above embodiment, the test pattern is applied to the first ruled lines (ruled lines A1 to A5) printed by ejecting ink on the first head (head 41A) and the second head (head 41B). A second ruled line (ruled lines B1 to B5) printed at a position away from the first ruled line by ejecting ink (see FIG. 16). In the detection step, the degree of inclination of the head 41A and the head 41B with respect to the main body of the printer 1 is detected based on the intervals between the printed ruled lines A1 to A5 and the ruled lines B1 to B5 (see FIGS. 17A and 17B). In the setting step, when the detected degree of inclination is large, a dot generation rate table in which the limit value of the first dot is small and the gradation value of the second dot generation start is small. Is set, and when the detected degree of inclination is small, a dot generation rate table in which the limit value of the first dot is large and the second dot generation start gradation value is large is set. (FIG. 18).
In such a case, it is possible to generate small dots and medium dots according to the degree of inclination of the head 41A and the head 41B with respect to the printer body with a simple test pattern, and as a result, image quality deterioration can be suppressed (FIGS. 20A to 20D). .

=== Other Embodiments ===
Although the printing system and the like have been described above, 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.

  In the above-described embodiment, the printer has been described. However, the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporizer, organic EL manufacturing apparatus (particularly polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technique as that of the present embodiment may be applied to various liquid ejecting apparatuses to which an ink jet technique such as an apparatus or a DNA chip manufacturing apparatus is applied.

  In the above embodiment, the head forms only small dots and medium dots. However, the present invention is not limited to this. For example, the head may form small dots, medium dots, and large dots. In such a case, the dot generation rate table also corresponds to three dots.

  In the above embodiment, one dot generation rate table is set for each head (step S106). However, the present invention is not limited to this. For example, the dot generation rate table set in the setting process of the dot generation rate table is applied only to the portion corresponding to the boundary between adjacent heads, and the default dot generation rate is applied to other portions of the head. A table may be applied.

  In the above embodiment, the head unit 40 in which the head does not move as shown in FIG. 4A has been described as an example, but a so-called serial printer (a plurality of heads move in a direction intersecting the transport direction). ) Is also applicable.

  In the above-described embodiment, the printer 1 as an example of the liquid ejecting apparatus has only the function of printing an image. However, the present invention is not limited to this. For example, the liquid ejecting apparatus may also have the function of the scanner 150, and the above-described dot generation rate table setting process may be executed by a printer controller (control unit).

  In the printer 1 of the above-described embodiment, ink is ejected by applying a voltage to the drive element (piezo element) to expand and contract the ink chamber, but the invention is not limited thereto. For example, a printer may be used in which bubbles are generated in the nozzles using a heating element and ink is ejected by the bubbles.

It is explanatory drawing which showed the external appearance structure of the printing system. FIG. 6 is an explanatory diagram of image processing by a printer driver. 1 is a block diagram of an overall configuration of a printer 1. FIG. FIG. 4A is a cross-sectional view of the printer 1. FIG. 4B is a perspective view for explaining the conveyance process and the dot formation process of the printer 1. FIG. 5A is an explanatory diagram showing an arrangement of a plurality of heads on the lower surface of the head unit 40. FIG. 5B is an explanatory diagram of the positional relationship of each head. FIG. 6A is an explanatory diagram of a dot generation rate table. FIG. 6B is a diagram showing a state of dot on / off determination by the dither method. FIG. 7A is an explanatory diagram of a state when dots are ideally formed. FIG. 7B is an explanatory diagram of density unevenness. It is a flowchart of the acquisition process of a BRS correction value. It is explanatory drawing of the test pattern for BRS correction | amendment. It is a graph of the measured value of the strip | belt-shaped pattern of density | concentration 25% of cyan, density 50%, and density 75%. FIG. 10A is an explanatory diagram of the target command tone value Sbt with respect to the command tone value Sb in the row region i. FIG. 10B is an explanatory diagram of the target command tone value Sbt with respect to the command tone value Sb in the row region j. It is explanatory drawing of the correction value table of cyan. It is explanatory drawing of an image quality evaluation pattern. 13A to 13D are graphs showing a * of an image quality evaluation pattern to which BRS correction is not applied. 14A to 14D are graphs showing a * of an image quality evaluation pattern to which BRS correction is applied. It is a flowchart of a setting process of a dot generation rate table. It is explanatory drawing about a test pattern. FIG. 17A is a diagram showing ruled lines A1 and A2 and ruled lines B1 and B2 that are ideally printed. FIG. 17B is a diagram showing ruled lines A1 and A2 printed ideally and ruled lines B1 and B2 printed at shifted positions. It is a correspondence table of adjustment amount and dot generation rate table. It is the figure which showed the dot production rate table T1. 20A to 20D are graphs showing a * of the image quality evaluation pattern printed based on the dot generation rate table set in the dot generation rate table setting process.

Explanation of symbols

1 printer, 20 transport unit, 21 paper feed roller,
23A upstream conveyance roller, 23B downstream conveyance roller,
24 belts, 40 head units, 41 heads,
50 detector groups, 53 paper detection sensors, 60 controllers,
61 interface unit, 62 CPU, 63 memory,
64 unit control circuit, 70 drive signal generation unit,
71 drive signal generation unit, 100 printing system, 110 computer,
120 display device, 130 input device, 140 recording / reproducing device,
150 scanner

Claims (7)

A printing step of ejecting liquid to the first head and the second head and printing a test pattern for detecting the mounting state of the first head and the second head with respect to the liquid ejecting apparatus main body;
A detection step of detecting the mounting state of the first head and the second head based on the printed test pattern;
A setting step for setting a correspondence table indicating a correspondence relationship between the command gradation value and the generation degree of a plurality of dots having different sizes based on the detected attachment state;
A table setting method characterized by comprising: The table setting method according to claim 1,
In the setting step,
By selecting the correspondence table corresponding to the detected attachment state from the plurality of correspondence tables corresponding to each of the plurality of attachment states acquired in advance,
A table setting method comprising setting the correspondence table. The table setting method according to claim 2,
The plurality of dots are a first dot and a second dot larger than the first dot,
In the plurality of correspondence tables, for each correspondence table, the limit value of the maximum generation amount of the first dot with respect to a predetermined area is different from the size of the command gradation value at the start of the generation of the second dot. Characteristic table setting method. The table setting method according to claim 3,
The first head and the second head eject liquids of a plurality of colors,
In the setting step, the same correspondence table is set for each of the plurality of colors. The table setting method according to claim 3 or 4, wherein:
The test pattern is a first ruled line printed by ejecting liquid onto the first head, and a second ruled line printed at a position away from the first ruled line by ejecting liquid onto the second head. ,
In the detecting step, as the mounting state, a degree of inclination of the first head and the second head with respect to the liquid ejecting apparatus main body is detected based on a printed interval between the first ruled line and the second ruled line. ,
In the setting step,
If the detected degree of inclination is large, a correspondence table is set in which the limit value of the first dot is small and the command gradation value for starting generation of the second dot is small,
When the detected degree of inclination is small, a correspondence table is set in which the limit value of the first dot is large and the command gradation value for starting generation of the second dot is large. How to set the table. A first head and a second head for ejecting liquid;
Printing a test pattern for ejecting liquid to the first head and the second head to detect the mounting state of the first head and the second head with respect to the liquid ejecting apparatus main body;
Based on the printed test pattern, the attachment state of the first head and the second head is detected,
Based on the detected mounting state, a control unit that sets a correspondence table indicating a correspondence relationship between the command gradation value and the generation degree of a plurality of dots having different sizes;
A liquid ejecting apparatus comprising: A liquid ejecting apparatus having a first head and a second head for ejecting liquid;
Printing a test pattern for ejecting liquid to the first head and the second head to detect the mounting state of the first head and the second head with respect to the liquid ejecting apparatus main body;
Based on the printed test pattern, the attachment state of the first head and the second head is detected,
Based on the detected mounting state, a control unit that sets a correspondence table indicating a correspondence relationship between the command gradation value and the generation degree of a plurality of dots having different sizes;
A printing system comprising: