JP2006035735A - Printing system, printing method, program and manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing system in which labor for correcting density and waste of time can be suppressed. <P>SOLUTION: This printing system comprises; a moving part for moving an ink ejecting head in a moving direction (A), a carrying part for carrying a medium in a carrying direction (B), a memory for storing a correction value to correct the density of a unit image formed in a unit region adjacent to the carrying direction (C), and a controller for forming the unit image in the unit region with the corrected density based on the correction value corresponding to the unit region, when the gradation value shown by the pixel data corresponding to the unit region on the medium is less than a predetermined gradation value, or for forming the unit image in the unit region without correcting density, when the gradation value shown by the pixel data corresponding to the unit region on the medium is the predetermined gradation value or more (D). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a printing system, a printing method, a program, and a manufacturing method.

  A color inkjet printer (hereinafter referred to as a printer) is known as a printing apparatus that forms an image by ejecting a plurality of colors of ink onto paper as a medium. In this printer, a dot forming operation in which ink is ejected from a head that moves in the carriage movement direction to form dots on the paper, and a crossing direction that intersects the paper movement direction by a conveyance unit (hereinafter also referred to as a conveyance direction). The transfer operation of transferring to the substrate is alternately repeated. As a result, a plurality of raster lines composed of a plurality of dots along the moving direction are formed in the transport direction, and a print image is printed on paper.

In this type of printer, ink droplet ejection characteristics such as the amount of ink droplets and flight direction vary from nozzle to nozzle. This variation in ejection characteristics is undesirable because it causes uneven density in the printed image. Therefore, conventionally, a correction pattern is first printed on paper with each color of ink that can be ejected. Next, the density of the printed correction pattern is read, correction information is acquired based on the read data, and density correction is executed based on the acquired correction information for printing. (For example, see Patent Document 1).
JP-A-6-166247

  In order to perform density correction, a great deal of labor is required, such as a process of printing a correction pattern, a process of reading a correction pattern, and a process of executing density correction based on the read data. On the other hand, if the density correction can be omitted in a region where the effect is small, it is possible to suppress these labor and time waste.

  By the way, density unevenness is likely to occur in a light area of a printed image. For example, when printing an image of a person, density unevenness is likely to occur because the density of the printed image is light in an area representing the skin color of the person. For this reason, it is easy to obtain an effect of density correction in a light density area. On the other hand, density unevenness hardly occurs in a dark area of the printed image, and even if density correction is executed, the effect is small.

  The present invention has been made in view of such problems, and an object of the present invention is to effectively execute density correction.

  The main inventions for achieving the above object are: (A) a moving unit that moves a head for ejecting ink in the moving direction; (B) a conveying unit that conveys the medium in the conveying direction; and (C) the conveying direction in the conveying direction. A memory for storing correction values for correcting the density of unit images formed in adjacent unit areas, and (D) a gradation value indicated by pixel data corresponding to the unit areas on the medium is less than a predetermined gradation value In the case of the above, the unit image is formed in the unit area at the density corrected based on the correction value corresponding to the unit area, and the gradation indicated by the pixel data corresponding to the unit area on the medium And a controller that forms the unit image in the unit area without correcting the density when the value is equal to or greater than the predetermined gradation value.

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

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

(A) a moving unit that moves a head that discharges ink in a moving direction;
(B) a transport unit that transports the medium in the transport direction;
(C) a memory for storing a correction value for correcting the density of a unit image formed in a unit region adjacent in the transport direction;
(D) When the gradation value indicated by the pixel data corresponding to the unit area on the medium is less than a predetermined gradation value, the unit has the density corrected based on the correction value corresponding to the unit area. Forming the unit image in an area;
A controller that forms the unit image in the unit area without correcting the density when the gradation value indicated by the pixel data corresponding to the unit area on the medium is equal to or higher than the predetermined gradation value;
A printing system comprising (E).
According to such a printing system, density unevenness can be efficiently suppressed.

  In this printing system, the head can form dark dots and light dots that absorb light of the same wavelength and have different absorption amounts on the medium, and the gradation value indicated by the pixel data is the predetermined gradation. If it is less than the value, it is desirable that only the light dots are formed on the medium. This eliminates the need to store correction values relating to dark dots, so that density correction can be performed efficiently.

  In this printing system, it is preferable that the head forms the dark dots and the light dots of cyan or magenta. However, the head may form yellow dark dots and light dots.

  In this printing system, it is preferable that the memory stores information regarding the generation rate of the light dots as the correction value. Thereby, the density of the unit image can be corrected by changing the dot generation rate formed in the unit region.

  In this printing system, it is preferable that the memory stores information on the density in the unit area as the correction value. Thereby, density correction can be performed according to the density of the unit area.

  In this printing system, the head forms a correction pattern in which the plurality of unit images are adjacent to each other in the transport direction on the medium, and the memory has a density of the unit area of the correction pattern. The corresponding correction value is preferably stored in association with each unit area. Thereby, density correction according to each dot row region can be performed.

  In this printing system, the head can form dark dots and light dots that absorb light of the same wavelength and have different absorption amounts on the medium, and the correction pattern is formed only of the light dots. It is desirable. Thereby, it is not necessary to create a correction pattern using dark dots, and the labor of the operation can be reduced.

  In this printing system, it is preferable that the controller corrects the density of the unit image by correcting the generation rate of dots formed in the unit area based on the correction value. Thereby, the density of the unit image can be corrected by changing the dot generation rate formed in the unit region.

(A) preparing a printing apparatus that forms a unit image in an adjacent unit region and forms a print image on a medium;
(B) obtaining a correction value associated with the unit area from the printing apparatus;
(C) When the gradation value indicated by the pixel data corresponding to the unit area on the medium is less than a predetermined gradation value, the unit has the density corrected based on the correction value corresponding to the unit area. Forming the unit image in an area;
Forming the unit image in the unit area without correcting the density when the gradation value indicated by the pixel data corresponding to the unit area on the medium is equal to or higher than the predetermined gradation value;
A printing method comprising (D).
According to such a printing method, density unevenness can be effectively suppressed.

A print control apparatus that controls a printing apparatus that forms a unit image in an adjacent unit area and forms a print image on a medium.
Obtaining a correction value associated with the unit area from the printing apparatus;
When the gradation value indicated by the pixel data corresponding to the unit area on the medium is less than a predetermined gradation value, print data is generated from the pixel data according to the correction value corresponding to the unit area,
When the gradation value indicated by the pixel data corresponding to the unit area on the medium is equal to or greater than the predetermined gradation value, the print data is generated from the pixel data without using the correction value,
A program for causing the printing apparatus to transmit the print data.
According to such a program, density unevenness can be effectively suppressed.

(A) preparing a printing apparatus including a head that can absorb light of the same wavelength and can form dark dots and light dots having different absorption amounts on a medium;
(B) the printing apparatus forming a correction pattern including only the light dots on the medium;
(C) detecting the density of each of a plurality of unit images constituting the correction pattern;
(D) storing information relating to the density of the unit image in association with each unit image;
(E) The printing apparatus forms a print image composed of a plurality of unit images on the medium by correcting the density of the unit image composed of the dark dots and the light dots according to the information. Steps,
A printing method comprising (F).
According to such a printing method, density unevenness can be effectively suppressed.

(A) preparing a printing apparatus including a head that can absorb light of the same wavelength and can form dark dots and light dots having different absorption amounts on a medium;
(B) the printing apparatus forming a correction pattern including only the light dots on the medium;
(C) detecting the density of each of a plurality of unit images constituting the correction pattern;
(D) storing information relating to the density of the unit image in the memory of the printing apparatus in association with each unit image;
A manufacturing method of a printing apparatus for storing a correction value characterized by comprising (E).
According to such a printing apparatus manufacturing method, a printing apparatus capable of suppressing density unevenness can be efficiently manufactured.

=== Configuration of Printing System ===
Next, an embodiment of a printing system will be described with reference to the drawings. However, the description of the following embodiments includes embodiments relating to a computer program and a recording medium on which the computer program is recorded.

  FIG. 1 is an explanatory diagram showing an external configuration of a printing system. The printing system 100 includes a printer 1 and a computer 110. 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. Since the computer 110 controls the printer 1 via print data, it is also a print control device.

  The printing system 100 further includes a display device 120, an input device 130, and a recording / reproducing device 140. The display device 120 has a display and displays a user interface such as a printer driver. The input device 130 is, for example, a keyboard 130A or a mouse 130B, and is used for operating an application program, setting a printer driver, or the like along a user interface displayed on the display device 120. As the recording / reproducing device 140, for example, a flexible disk drive device 140A or a CD-ROM drive device 140B is used.

  A printer driver is installed in the computer 110. The printer driver is a program for realizing the function of displaying the user interface on the display device 120 and the function of converting the image data output from the application program into print data. This 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.

=== Configuration of Printer and Computer ===
<About the configuration of the printer and computer>
FIG. 2 is a block diagram of the overall configuration of the computer 110 and the printer 1.

  The computer 110 includes an interface unit 161, a CPU 162, and a computer side memory 163. The interface unit 161 is for transmitting and receiving data between the printer 110 as an external device and the computer 110. The CPU 162 is an arithmetic processing unit for controlling the entire computer 110. The computer-side memory 163 is a storage element that secures an area for storing a program such as a printer driver and a work area. The CPU 162 generates print data from the image data according to the printer driver stored in the computer-side memory 163 and transmits the print data to the printer 1. By installing the printer driver in the computer 110, the CPU 162 and the computer-side memory 163 become a computer-side controller that controls the printer 1 via print data. In the present embodiment, a partial area of the computer-side memory 163 is used as a correction file storage unit 163a for storing a correction file described later.

  The printer 1 includes a transport unit 20, a carriage unit 30, a head unit 40, a detector group 50, and a printer-side controller 60. The printer 1 that has received print data from the computer 110, which is an external device, controls each unit (conveyance unit 20, carriage unit 30, head unit 40) by the printer-side controller 60. The printer-side 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 the detector group 50, and the detector group 50 outputs the detection result to the printer-side controller 60. The printer-side controller 60 controls each unit based on the detection result output from the detector group 50.

  The printer-side controller 60 is a control unit for controlling the printer. The printer-side controller 60 includes an interface unit 61, a CPU 62, a printer-side memory 63, and a unit control circuit 64. The interface unit 61 is for transmitting and receiving 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 printer-side memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and has storage means such as a RAM and an EEPROM. The CPU 62 controls each unit via the unit control circuit 64 according to a program stored in the printer-side memory 63. In the present embodiment, a partial area of the printer-side memory 63 is used as a correction data storage unit 63a for storing correction data described later.

  The computer-side controller (CPU 162 and computer-side memory 163) and the printer-side controller 60 are controllers that control the entire printing system. The printer driver stored in the computer-side memory 163 causes the computer 110 to generate print data and transmit the print data to the printer 1. On the other hand, the program stored in the printer-side memory 63 causes the transport unit 20 to transport the paper, moves the carriage to the carriage unit 30 and causes the head unit 40 to eject ink according to the print data. For this reason, the printer driver and the printer-side program are also programs that cause the printing system to perform printing in cooperation.

  FIG. 3 is a schematic diagram of the overall configuration of the printer 1. FIG. 4 is a cross-sectional view of the overall configuration of the printer 1. Hereinafter, the basic configuration of the printer of this embodiment will be described.

  The transport unit 20 is for feeding a medium (for example, the paper S) to a printable position and transporting the paper by a predetermined transport amount in a predetermined direction (hereinafter referred to as a transport direction) during printing. That is, the transport unit 20 is a transport unit that transports paper. The transport unit 20 includes a paper feed roller 21, a transport motor 22 (also referred to as a PF motor), a transport roller 23, a platen 24, and a paper discharge roller 25. However, in order for the transport unit 20 to function as a transport unit, all of these components are not necessarily required. The paper feed roller 21 is a roller for feeding the paper inserted into the paper insertion slot into the printer. The paper feed roller 21 has a D-shaped cross section, and the length of the circumferential portion is set to be longer than the transport distance to the transport roller 23. 23 can be conveyed. The transport motor 22 is a motor for transporting paper in the transport direction, and is configured by a DC motor, for example. The transport roller 23 is a roller that transports the paper S fed by the paper feed roller 21 to a printable area, and is driven by the transport motor 22. The platen 24 supports the paper S being printed. The paper discharge roller 25 is a roller for discharging the paper S to the outside of the printer, and is provided on the downstream side in the transport direction with respect to the printable area. The paper discharge roller 25 rotates in synchronization with the transport roller 23.

  The carriage unit 30 is for moving (also referred to as “scanning”) the head in a predetermined direction (hereinafter referred to as a moving direction). The carriage unit 30 includes a carriage 31 and a carriage motor 32 (also referred to as a CR motor). The carriage 31 can reciprocate in the moving direction. (Thus, the head moves along the moving direction.) The carriage 31 detachably holds an ink cartridge that stores ink. The carriage motor 32 is a motor for moving the carriage 31 in the movement direction, and is constituted by, for example, a DC motor. The carriage motor 32 serves as a moving unit that moves a head (described later) in the moving direction.

  The head unit 40 is for ejecting ink onto paper. The head unit 40 has a head 41. The head 41 has a plurality of nozzles, and ejects ink intermittently from each nozzle. The head 41 is provided on the carriage 31. Therefore, when the carriage 31 moves in the movement direction, the head 41 also moves in the movement direction. Then, by intermittently ejecting ink while the head 41 is moving in the moving direction, dot lines (raster lines) along the moving direction are formed on the paper.

  The detector group 50 includes a linear encoder 51, a rotary encoder 52, a paper detection sensor 53, an optical sensor 54, and the like. The linear encoder 51 is for detecting the position of the carriage 31 in the moving direction. The rotary encoder 52 is for detecting the rotation amount of the transport roller 23. The paper detection sensor 53 is for detecting the position of the leading edge of the paper to be printed. The paper detection sensor 53 is provided at a position where the position of the leading edge of the paper can be detected while the paper feed roller 21 feeds the paper toward the transport roller 23. The paper detection sensor 53 is a mechanical sensor that detects the leading edge of the paper by a mechanical mechanism. More specifically, the paper detection sensor 53 has a lever that can rotate in the transport direction, and this lever is disposed so as to protrude into the paper transport path. For this reason, since the leading edge of the paper comes into contact with the lever and the lever is rotated, the paper detection sensor 53 detects the position of the leading edge of the paper by detecting the movement of the lever. The optical sensor 54 is attached to the carriage 31. The optical sensor 54 detects the presence or absence of paper by the light receiving unit detecting reflected light of light irradiated on the paper from the light emitting unit. The optical sensor 54 can detect the position of the edge of the paper while being moved by the carriage 31 to detect the width of the paper. The optical sensor 54 also detects the leading end (the end on the downstream side in the transport direction, also referred to as the upper end) and the rear end (the end on the upstream side in the transport direction, also referred to as the lower end) depending on the situation. it can. Since the optical sensor 54 optically detects the edge of the paper, the detection accuracy is higher than that of the mechanical paper detection sensor 53.

<About nozzle>
FIG. 5 is an explanatory diagram showing the arrangement of nozzles on the lower surface of the head 41. Six nozzle groups are formed on the lower surface of the head 41. Each nozzle group includes a plurality of nozzles (180 in this embodiment) that are ejection openings for ejecting ink of each color.

  The plurality of nozzles of each nozzle group are aligned at a constant interval (nozzle pitch: k · D) along the transport direction. Here, D is the minimum dot pitch in the carrying direction (that is, the interval at the highest resolution of dots formed on the paper S). K is an integer of 1 or more.

The nozzles of each nozzle group are assigned a smaller number as the nozzles on the downstream side in the transport direction (# 1 to # 180). It should be noted that the optical sensor 54 described above is located at substantially the same position as the nozzle # 180 on the most upstream side with respect to the position in the paper transport direction.
Each nozzle is provided with an ink chamber (not shown) and a piezoelectric element. By driving the piezo element, the ink chamber expands and contracts, and ink droplets are ejected from the nozzles.

By the way, in an ink jet printer, when a print image is formed on paper, the print image is composed of a large number of dots. In such an ink jet printer, the gradation of the print image is expressed by changing the density of dots on the paper. For example, the density of dots is high in the dark portion of the print image, and the dot density is low in the light portion of the print image.
In the portion where the density of the printed image is light, graininess tends to appear. For example, when printing light cyan using only cyan ink, dots of cyan ink are formed sparsely, resulting in a printed image that looks more like cyan polka dots than light cyan (graininess) ).

  Therefore, the head 41 of this embodiment includes the black ink nozzle group K, the cyan ink nozzle group C, the magenta ink nozzle group M, and the yellow ink nozzle group Y, as well as the light cyan ink nozzle group LC and the light magenta ink nozzle group. LM is formed.

  The light cyan ink nozzle group LC ejects light cyan ink (light ink) having a lighter density than the cyan ink (dark ink) ejected by the cyan ink nozzle group C. Cyan absorbs red light, which is a complementary color, and light cyan dots (light dots) formed with light cyan ink have a smaller amount of red light absorption than dots (dark dots) formed with cyan ink.

  The light magenta ink nozzle group LM ejects light cyan ink (light ink) having a lighter density than the magenta ink (dark ink) ejected by the magenta ink nozzle group M. Magenta has a property of absorbing green light, which is a complementary color, and a dot (light dot) formed with light magenta ink has a smaller amount of green light absorption than a dot (dark dot) formed with magenta ink.

  When printing a light cyan image in this embodiment, light cyan dots are formed on paper using light cyan ink. Compared with the case where only cyan ink is used, if the light cyan dot is used to express a light cyan, the number of dots increases, so that the graininess can be reduced.

  For yellow, light ink is not prepared because the influence of density is small. However, if dark yellow ink (dark ink) is used, deep yellow can be expressed in the printed image. Note that yellow has the property of absorbing blue light, which is a complementary color, but dark yellow dots (dark dots) formed with dark yellow ink are more blue light than dots (light dots) formed with yellow ink. Absorption is high.

=== Printer driver ===
<About processing performed by the printer driver>
FIG. 6 is a schematic explanatory diagram of basic processing performed by the printer driver. The components already described are given the same reference numerals, and the description thereof is omitted.
In the computer 110, computer programs such as a video driver 112, an application program 114, and a printer driver 116 operate under an operating system installed in the computer. The video driver 112 has a function of displaying, for example, a user interface on the display device 120 in accordance with display commands from the application program 114 and the printer driver 116. The application program 114 has a function of performing image editing, for example, and creates data related to an image (image data). The user can give an instruction to print an image edited by the application program 114 via the user interface of the application program 114. When the application program 114 receives a print command, the application program 114 outputs image data to the printer driver 116.

  The printer driver 116 receives image data from the application program 114, converts the image data into print data, and outputs the print data to the printer. Here, the print data is data in a format that can be interpreted by the printer 1, and is data having various command data and pixel data. The command data is data for instructing the printer to execute a specific operation. The pixel data is data relating to the pixels constituting the image. The pixel data in the print data is data relating to dots formed at a position on the paper corresponding to a certain pixel (dot data constituting a print image). On the other hand, the pixel data in the image data is data relating to the color and gradation of the pixels constituting the print image.

  The printer driver 116 performs resolution conversion processing, color conversion processing, halftone processing, rasterization processing, and the like in order to convert the image data output from the application program 114 into print data. Hereinafter, various processes performed by the printer driver 116 will be described.

  The resolution conversion processing is the resolution when printing image data (text data, image data, etc.) output from the application program 114 on the paper S (the interval between dots when printing), and is also referred to as print resolution. ). For example, when the print resolution is specified as 720 × 720 dpi, the image data received from the application program 114 is converted into image data having a resolution of 720 × 720 dpi.

  Note that each pixel data in the image data output from the application program 114 is data indicating multi-level (for example, 256 levels) gradation values represented by the RGB color space. Hereinafter, pixel data indicating RGB gradation values is referred to as RGB pixel data, and image data composed of RGB pixel data is referred to as RGB image data.

  The color conversion process is a process of converting each RGB pixel data of the RGB image data into data indicating gradation values of multiple levels (for example, 256 levels) represented by a CMYK color space. Here, in the notation CMYK, C means cyan, M means magenta, Y means yellow, and K means black. Hereinafter, pixel data indicating CMYK gradation values is referred to as CMYK pixel data, and image data composed of CMYK pixel data is referred to as CMYK image data. The color conversion process is performed by the printer driver 116 referring to a table (color conversion lookup table LUT) in which RGB gradation values and CMYK gradation values are associated with each other.

  The halftone process is a process of converting CMYK pixel data indicating multi-level gradation values into binary pixel data indicating small-level gradation values of colors that can be expressed by the printer 1. For example, CMYK pixel data indicating 256-level gradation values of 4 colors (cyan, magenta, yellow, and black) is converted into 2 colors of 6 colors (cyan, light cyan, magenta, light magenta, yellow, and black) by halftone processing. It is converted into 1-bit binary pixel data indicating the gradation value of the stage. This binary pixel data is data indicating, for example, “no dot formation” (binary value “0”) and “dot formation” (also “1”) for each color. In this embodiment, for simplification of description, pixel data after halftone processing is 1 bit, but may be 2 bits. If the pixel data is 2 bits, it is possible to indicate not only the presence / absence of a dot but also the size of the dot (large dot, medium dot, small dot, etc.). The printer driver 116 converts 256-gradation pixel data into binary pixel data by referring to the dot generation rate table. This dot generation rate table will be described in detail later.

  In such halftone processing, for example, a dither method or the like is used, and binary pixel data that can be formed by the printer 1 in a dispersed manner is created. Further, the method used for the halftone process is not limited to the dither method, and a γ correction method, an error diffusion method, or the like may be used.

  The rasterizing process is a process for changing the CMYK image data subjected to the halftone process in the order of data to be transferred to the printer 1. The rasterized data is output to the printer 1 as the print data.

<About dot generation rate>
7A and 7B are explanatory diagrams of a dot generation rate table used in the above-described halftone process. FIG. 7A is a dot generation rate table for yellow and black. FIG. 7B is a dot generation rate table for cyan and magenta. The horizontal axis indicates the gradation value of pixel data (CMYK pixel data) before halftone processing. The vertical axis represents the dot generation rate. When the dot generation rate is 50% for a certain pixel, the binary pixel data after the halftone process becomes “1” with a probability of 50% (a dot is generated at a position on the paper corresponding to the pixel). Further, when the area of 256 pixels (16 × 16 pixels) has a dot generation rate of 50%, the pixel data after halftone processing indicates that dots are generated at 128 pixels.

  In this embodiment, yellow (and black) expresses gradation with ink of one type of density, and therefore, in the yellow dot generation rate table, the dot generation rate increases as the gradation value increases.

  On the other hand, cyan (and magenta) expresses gradation with two types of ink density, so the cyan dot generation rate table is different from the yellow (and black) dot generation rate table. At a gradation value of 127 or less, the gradation is expressed only by light cyan ink. Therefore, when the gradation value is increased, the dot generation rate of light cyan ink dots (light dots) is increased. With a gradation value of 128 or more, cyan ink dots (dark dots) are generated. When the dark dot generation rate increases, the light dot generation rate decreases.

  In the cyan dot generation rate table, for example, when the gradation value of certain pixel data before halftone processing is 63, the generation rate of light dots for that pixel is 50% and the generation rate of dark dots is 0%. . When the gradation value of certain pixel data before halftone processing is 159, the light dot generation rate for that pixel is 75% and the dark dot generation rate is 25%. That is, when the C (cyan) tone value of certain pixel data before halftone processing is 159, light cyan binary pixel data is “1” with a probability of 75%, and cyan binary pixel data is 25. It becomes “1” with a probability of%.

  Using the dot generation rate table of FIG. 7B, the pixel data of 256 gradations of cyan (or magenta) is converted into binary pixel data of two gradations of cyan and light cyan (or magenta and light magenta) (halftone). It is processed. As a result, 256-color pixel data of 4 colors (CMYK) is converted into half-tone binary pixel data of 6 colors (C, LC, M, LM, Y, K) (halftone processing). .

  According to this dot generation rate table, when the gradation value before halftone processing is 127 or less for pixel data in a certain area, only light dots are formed in the area on the paper corresponding to that area, and the darkness is dark. Dots are not formed.

  In the present embodiment, halftone processing is performed using a dot generation rate table corrected for each dot row region (described later).

=== Printing operation ===
FIG. 8 is a flowchart of processing during printing. Each process described below is executed by the printer-side controller 60 controlling each unit in accordance with a program stored in the printer-side memory 63. This program has a code for executing each process.

  Print command reception (S001): First, the printer-side controller 60 receives a print command from the computer 110 via the interface unit 61. This print command is included in the header of print data transmitted from the computer 110. Then, the printer-side controller 60 analyzes the contents of various commands included in the received print data, and performs the following paper feed processing / conveyance processing / dot formation processing using each unit.

  Paper Feed Process (S002): The paper feed process is a process for supplying paper to be printed into the printer and positioning the paper at a print start position (also referred to as a cue position). The printer-side controller 60 rotates the paper feed roller 21 and sends the paper to be printed to the transport roller 23. Subsequently, the printer-side controller 60 rotates the transport roller 23 to position the paper fed from the paper feed roller 21 at the print start position. When the paper is positioned at the print start position, at least some of the nozzles of the head 41 are opposed to the paper.

  Dot Forming Process (S003): The dot forming process is a process for forming dots on paper by intermittently ejecting ink from a head that moves in the moving direction. The printer-side controller 60 drives the carriage motor 32 to move the carriage 31 in the movement direction. The printer-side controller 60 ejects ink from the head based on the print data while the carriage 31 is moving. When ink droplets ejected from the head 41 land on the paper, dots are formed on the paper. Since ink is intermittently ejected from the moving head 41, a dot row (raster line) composed of a plurality of dots along the moving direction is formed on the paper.

  Conveyance process (S004): The conveyance process is a process of moving the paper relative to the head in the conveyance direction. The printer-side controller 60 drives the carry motor and rotates the carry roller to carry the paper in the carrying direction. By this carrying process, the head 41 can form dots at positions different from the positions of the dots formed by the previous dot formation process.

  Paper discharge determination (S005): The printer-side controller 60 determines whether or not to discharge the paper being printed. If data to be printed remains on the paper being printed, no paper is discharged. Then, the printer-side controller 60 alternately repeats dot formation processing and conveyance processing until there is no more data to be printed, and gradually prints an image composed of dots on paper.

  Paper Discharge Process (S006): When there is no more data to be printed on the paper being printed, the printer-side controller 60 discharges the paper by rotating the paper discharge roller. The determination of whether or not to discharge paper may be based on a paper discharge command included in the print data.

  Determination of printing end (S007): Next, the printer-side controller 60 determines whether or not to continue printing. If printing is to be performed on the next paper, printing is continued and the paper feeding process for the next paper is started. If printing is not performed on the next paper, the printing operation is terminated.

=== Regarding Cause of Density Unevenness in Image ===
The density unevenness that occurs in a multicolor printed image is basically caused by the density unevenness that occurs in each color (cyan, magenta, yellow, black). For this reason, usually, a method of suppressing density unevenness in an image printed in multiple colors by individually suppressing density unevenness of each color is employed. In the following, the cause of density unevenness occurring in a monochrome printed image will be described.

  FIG. 9A is an explanatory diagram of a state when dots are ideally formed. While the carriage moves in the moving direction, ink is ejected from each nozzle, and ink is landed on the paper to form dots. Since each nozzle intermittently ejects ink during movement, a row of dots (raster line) is formed along the movement direction. Each raster line forms an image piece, and the image piece is arranged along the transport direction to form a print image.

  In the figure, since dots are ideally formed, each dot is accurately formed in an imaginary area on paper. Here, an area where a raster line is to be formed is referred to as a “dot row area”. In the figure, a dot row region is shown as a region sandwiched between dotted lines. The dot row region is also a region on paper corresponding to a plurality of pixels arranged in the moving direction.

FIG. 9B is an explanatory diagram of the influence of variations in nozzle processing accuracy. Here, due to the variation in the flight direction of the ink ejected from the nozzle # 2, the raster line formed by the nozzle # 2 is formed so as to be shifted to the raster line formed by the nozzle # 3 (upstream in the transport direction). Yes. Further, the amount of ink ejected from the nozzle # 5 is small, and the dots formed by the nozzle # 5 are small.
Originally, although image pieces having the same density are formed in each dot row area, shading occurs according to the dot row area due to variations in processing accuracy. For example, the image of the second dot row region is relatively light and the image of the third dot row region is relatively dark. Further, the image of the fifth dot row region becomes relatively light.
When the print image composed of such raster lines is viewed macroscopically, stripe-shaped density unevenness along the moving direction of the carriage is visually recognized. This density unevenness causes a reduction in image quality of the printed image.

  In the present embodiment, the dot generation rate is corrected so that a light image piece is formed lightly for a dot row region that is easily visible and dark, and a dark image piece is formed for a dot row region that is light and easily visible. As described above, the dot generation rate is corrected to suppress the density unevenness of the printed image.

  FIG. 9C is an explanatory diagram showing a state when dots are formed by the printing method of the present embodiment. In this embodiment, the dot generation rate in the second dot row region is increased, the dot generation rate in the third dot row region is decreased, and the dot generation rate in the fifth dot row region is increased. Thereby, the density of the image piece formed in each dot row region is corrected, and the density unevenness of the printed image is suppressed.

  By the way, since the dot formation density is originally high in the dark region of the printed image, the macroscopic density is not significantly changed even when the raster lines are formed shifted in the transport direction. That is, density unevenness hardly occurs in a dark area of the printed image. On the other hand, since the dot formation density is low in the light area of the printed image, if the raster line is formed shifted in the transport direction, the change in the dot density increases, which affects the macroscopic density. That is, uneven density tends to occur in a light area of the printed image.

  Therefore, in the present embodiment, density unevenness is effectively suppressed by correcting the density only for a light image.

=== Until the printer of this embodiment is shipped ===
In this embodiment, a printer is manufactured and shipped at a printer manufacturing factory. Then, a user who purchased the printer installs a printer driver in his / her computer and prints an image created by application software using the printer. First, the process until the printer is shipped will be described below.

FIG. 10 is a flowchart until the printer is shipped at the printer manufacturing factory.
First, the printer 1 is manufactured on the manufacturing line (S110). Next, correction data for correcting the density is set in the printer 1 by the operator in charge of inspection (S120). The correction data will be described in detail later.
Next, the printer 1 and the driver CD-ROM are shipped (S130). The driver CD-ROM stores a printer driver that is a program, and is shipped together with the printer 1. The driver CD-ROM stores application software other than the printer driver.

<Step 120: Setting of correction data>
FIG. 11 is a block diagram for explaining a device used for setting correction data. In addition, about the component already demonstrated, the same code | symbol is attached | subjected and description is abbreviate | omitted.
In the figure, a computer 110A is a computer installed on an inspection line in a printer manufacturing factory. In this computer 110A, an application 114A and a printer driver 116A are operating. The application 114A outputs the image data of the correction pattern CP having the designated gradation value to the printer driver 116A. The printer driver converts the image data from the application 114A into print data, and outputs print data for printing the correction pattern CP to the printer 1.

  In the computer 110A, a process correction program 118A is operating. The process correction program can cause the computer 110A to perform correction data generation processing. By this correction data generation processing, the computer 110A reads the correction pattern CP by the scanner device 150, and generates correction data for each dot row area based on the read result (measured value of the density of each dot row area). To do. Then, the computer 110 </ b> A sets the generated correction data (correction data table) in the correction data storage unit 63 a of the printer-side memory 63.

FIG. 12 is a flowchart of the correction data generation process. The correction data setting procedure will be described below with reference to this flowchart.
This setting procedure includes a step of printing the correction pattern CP (S121), a step of reading the correction pattern CP (S122), and a step of setting correction data based on the measured density value for each dot row region (S123). Have Hereinafter, each step will be described in detail.

(1) Regarding printing of correction pattern CP (S121):
First, in step S121, the computer 110A causes the printer to print the correction pattern CP on the paper S, respectively. Here, an operator in charge of inspection connects the printer 1 to a computer 110A installed on the inspection line in a communicable state, and causes the printer 1 to print the correction pattern CP via the user interface of the computer 110A. Note that the printer 1 that prints the correction pattern CP is the printer 1 for which correction data is to be set. That is, the correction data is set for each printer 1.

  FIG. 13 is an explanatory diagram of the printed correction pattern CP. As shown in the drawing, the correction pattern CP of the present embodiment is formed for each of three colors of ink (light cyan ink, light magenta ink, and yellow ink). Note that correction patterns using cyan ink, magenta ink, and black ink are not printed. Here, the light cyan correction pattern CPlc will be described.

  The light cyan correction pattern CPlc has four types of dot generation rate patterns. Each of the four patterns is formed in a strip shape in parallel over the entire area in the transport direction. The four types of dot generation rates here are 20%, 40%, 60%, and 80% (however, the four types of dot generation rates of the yellow correction pattern CPy are 10%, 20%, and 30%. 40%). The dot generation rate of 100% by light cyan corresponds to the cyan gradation value “127” (FIG. 7). Here, a correction pattern CP40% having a dot generation rate of 40% will be described.

  The correction pattern CP40% is printed based on print data generated from image data indicating a belt-like image having a constant density. The correction pattern CP40% is composed of a large number of raster lines arranged in the transport direction. If the printer is ideally manufactured, the correction pattern CP40% is printed at a constant density. However, as described above, due to variations in processing accuracy, density unevenness occurs in the correction pattern CP40%.

  In the present embodiment, only correction patterns for three color inks are printed on the paper S. For this reason, compared with the case where the correction pattern for all six colors of ink is printed, in this embodiment, the area for printing the correction pattern on the paper S can be reduced.

(2) Reading the correction pattern CP (step S122):
Next, the operator in charge of inspection places the paper S on which the correction pattern CP is printed on the scanner device 150, and the computer 110A causes the scanner device 150 to read the correction pattern CP.

  FIG. 14A is a longitudinal sectional view of the scanner device. FIG. 14B is a plan view of the scanner device. The scanner device 150 includes an original table glass 102 on which a paper S on which a correction pattern CP is printed, and a reading carriage 104. The reading carriage 104 moves in a predetermined reading movement direction while facing the paper S placed on the platen glass 102. The reading carriage 104 includes an exposure lamp 106 that irradiates the paper S with light, and a linear sensor 108 that receives reflected light from the paper S over a predetermined range in a direction orthogonal to the reading movement direction. Yes. Then, the correction pattern CP is read from the paper S at a predetermined reading resolution while moving the reading carriage 104 in the reading movement direction. In addition, the broken line in FIG. 14A shows the locus of the light.

  The paper S on which the correction pattern CP is printed is placed on the platen glass 102 as shown in FIG. 14B. Therefore, the linear sensor 108 can simultaneously measure the density of 12 correction patterns (3 colors × 4 types of correction patterns) in a certain dot row region. Then, when the reading carriage 104 moves in the reading movement direction, the density of each dot row region can be measured.

  FIG. 15 shows a part of a measurement result of a pattern with a dot generation rate of 40% of the light cyan ink correction pattern CPlc. The vertical axis represents the measured value, and the horizontal axis represents the dot row area number. Here, the dot row area number is a number assigned to each dot row area virtually defined on the paper from the front side of the paper.

  If the printer is ideally manufactured, since the density of the correction pattern CP40% is constant, the measured value is as shown by the dotted line in the figure. However, since the density of dots in the dot row region varies due to variations in the ink ejection direction, etc., the measured value is as shown by a solid line in the figure.

  In this embodiment, only correction patterns for three color inks are read. For this reason, compared with the case where the correction patterns for all six colors of ink are read, this embodiment can reduce the reading work.

(3) Storage of measurement values for each dot row area (step S123) Next, the computer 110A stores the measurement values in the printer-side memory 63 and stores the correction data table in the printer-side memory 63.
FIG. 16 is a conceptual diagram of a correction data table stored in the printer-side memory 63. This correction data table is prepared for each of light cyan ink, light magenta ink, and yellow ink.

  In each correction data table, measurement values are stored in association with dot row regions and dot generation rates. Each dot row area is numbered, and the number of correction data tables is the same as the number of dot row areas arranged in the transport direction of the printable area of paper. The measured values of the correction patterns CP20%, CP40%, CP60%, and CP80% in the same dot row area are recorded in the same number table.

  The correction data storage unit 63a of the printer-side memory 63 of each printer 1 manufactured at the factory stores a correction data table unique to the printer.

  The printer is shipped with the correction table stored (step S130 described above).

  In this embodiment, only the correction data table for the three colors of ink is stored. For this reason, compared with the case where the correction data table for all six colors of ink is stored, in this embodiment, the amount of data to be stored can be reduced, so that the capacity of the printer-side memory 63 can be reduced.

=== Installation of Printer Driver of this Embodiment ===
FIG. 17 is a flowchart for explaining the flow of processing when installing the printer driver.
The user who purchased the printer connects the printer and the computer 110, and sets the driver CD-ROM bundled with the printer in the CD-ROM drive device 140B of the computer 110. The driver CD-ROM stores programs such as a printer driver and application software.

  When the driver CD-ROM is set in the CD-ROM drive device 140B, the computer 110 installs a printer driver (step S140).

  The printer driver installed in the computer 110 reads the correction data in the correction data table stored in the correction data storage unit 63a of the printer-side memory 63, and reads the read correction data on the computer side. It memorize | stores in the memory 163 (step S150).

  In the present embodiment, only the correction data table for the three colors of ink is stored, so that the correction data is obtained from the printer as compared with the case where the correction data table for all six colors of ink is stored. Reading time for reading is reduced.

  Thereafter, the printer driver creates a correction file based on the acquired correction data (step S160). The creation of the correction file will be described later. The acquisition of the correction data (S150) and the generation of the correction file (step S160) are performed in parallel with the installation process of other application software stored in the driver CD-ROM. When the creation of the correction file and the installation of other application software are completed, the computer 110 ends the operation of the CD-ROM drive device 140B and ends reading of information from the driver CD-ROM.

<Step S160: Creation of Correction File>
FIG. 18 is a graph showing the relationship between the command gradation value and the measured value in a certain dot row region. In the figure, the measured value of the density of the correction pattern CP 40% in a certain dot row region is C (40%), and the measured value of the density of the correction pattern CP 20% in a certain dot row region is C (20%). It shows that there is.

  The correction pattern CP40% described above is printed based on a command gradation value indicating a dot generation rate of 40%. The dot generation rate of 40% corresponds to an image having a gradation value of 102 (256 gradations), but the measured gradation value C (40%) is not necessarily “102” due to variations in processing accuracy. For example, the measured gradation value C (40%) is a value lower than 102 in the dot row region with a low density.

  In other words, when printing an image having a gradation value C (40%), when halftone processing is performed at a dot generation rate corresponding to the gradation value “102”, halftone processing is performed. Even if the accuracy varies, an image having a target gradation value C (40%) is printed.

  Similarly, when printing an image having a gradation value of 90, if halftone processing is performed at a dot generation rate corresponding to the gradation value “S90” in the drawing when halftone processing is performed, variations in processing accuracy may occur. Even if there is, an image having a target gradation value of 90 is printed. The gradation value “S90” can be calculated by linear interpolation based on the measured gradation value C (40%) and the measured gradation value C (20%).

  Thus, when printing with a certain target gradation value, a dot generation rate suitable for the target gradation value can be calculated based on the correction data stored in the correction data storage unit 63a. . In this way, if a suitable dot generation rate is calculated for each tone value of each dot row region, the correction file of this embodiment can be created.

  FIG. 19 is an explanatory diagram of a correction file according to this embodiment. As shown in the drawing, correction files are prepared for light cyan ink, light magenta ink, and yellow ink. The printer driver stores the dot generation rate calculated by linear interpolation in the correction file storage unit 163a of the computer-side memory 163 in association with the dot row region and the gradation value. That is, the printer driver creates a correction file by recording the calculated dot generation rate in the blank in the figure. The correction file includes a dot generation rate table with gradation values 0 to 127 for each dot row region. A different dot generation rate table is obtained for each dot row region.

  The correction file of the present embodiment indicates a dot generation rate for a gradation value of 127 or less, and does not have information indicating a dot generation rate for a gradation value of 128 or more. For this reason, the data amount of the correction file of this embodiment is reduced as compared with the correction file indicating the dot generation rate for all the gradation values in 256 levels. In addition, according to the present embodiment, the printer driver does not calculate the dot generation rate for the gradation value of 128 or more, so that it is possible to reduce the calculation amount of the computer 110 when creating the correction file.

=== Processing at the Time of Printing of this Embodiment ===
<Regarding the dot generation rate of this embodiment>
When the user who installed the printer driver executes printing from the application software, the printer driver acquires image data from the application software, generates print data by resolution conversion processing, color conversion processing, halftone processing, rasterization processing, The print data is transmitted to the printer 1. Hereinafter, the halftone process according to the present embodiment when generating print data will be described.

  FIG. 20A is an explanatory diagram of a yellow dot generation rate table in a certain dot row region. FIG. 20B is an explanatory diagram of a cyan (or magenta) dot generation rate table in a certain dot row region. The dotted line in the figure indicates the dot generation rate in FIGS. 7A and 7B.

  When halftone processing is performed based on the dotted dot generation rate in the figure, density unevenness occurs due to variations in processing accuracy. On the other hand, in this embodiment, as shown by the solid line in the figure, halftone processing is performed using the dot generation rate calculated based on the correction data table.

  When halftone processing is performed on pixel data of a certain dot row area, if the gradation value indicated by the pixel data is 127 or less (less than 128), the printer driver can generate dot generation rate data corresponding to the dot row area, Read from the correction file stored in the correction data storage unit 63a. Then, based on the read dot generation rate data, the printer driver performs halftone processing on the pixel data in the dot row area.

  For example, when the gradation value of the pixel data of a certain dot row region before halftone processing is 63, the dot generation rate of that pixel is usually 25%, but here it is 20% (in other dot row regions) If so, it will be different) Similarly, in this dot row area, when the gradation value of the pixel data before halftone processing is 127 or less, the dot generation rate is lower than the normal dot generation rate.

  The dot row area corresponding to the dot generation rate table in the figure is considered to be a dot row area printed relatively dark due to variations in processing accuracy. In this embodiment, the pixel data corresponding to the dot row area is subjected to halftone processing using the dot generation rate of the correction file, so that the density of dots formed in the dot row area is reduced, The density of the image piece in the dot row area is corrected to the target density.

  In the present embodiment, when the gradation value of the pixel data corresponding to a certain dot row area is 127 or less, dots are formed in the dot row area based on the dot generation rate corresponding to the dot row area. The density of the image piece formed in the dot row area is corrected. As a result, even when printing a light image that easily causes density unevenness, the density of the image pieces constituting the image can be made uniform, and the occurrence of density unevenness can be suppressed.

  On the other hand, when the gradation value of the pixel data corresponding to a certain dot row region is 128 or more, the printer driver performs halftone processing on the pixel data based on the standard dot generation rate table (FIGS. 7A and 7B). . That is, when the gradation value of the pixel data is 128 or more, halftone processing is performed in the same manner regardless of the pixel data of any dot row region. For this reason, when the gradation value of the pixel data is 128 or more, an image piece is formed in the dot row region without correcting the density. As a result, the density of each dot row area differs due to variations in processing accuracy. However, if the gradation value of the pixel data is 128 or more, it is a dark area of the printed image, so that density unevenness is unlikely to occur and density correction is performed. There is no need to do.

<About halftone processing of this embodiment>
FIG. 21 is a flowchart of halftone processing according to this embodiment. The printer driver performs halftone processing on 256-color CMYK image data of four colors after color conversion processing. Here, halftone processing is performed in the order of cyan, magenta, yellow, and black image data. A set of pixel data constituting cyan image data is also referred to as a “cyan plane”.

  First, the printer driver determines whether the target of halftone processing is black plane pixel data (step S201). Since the first processing target is cyan image data, this determination is NO.

  Next, the printer driver determines whether or not the gradation value of the first pixel data on the cyan plane is less than 128 (step S202). If the gradation value of the pixel data is less than 128 (YES in S202), the printer driver performs halftone processing on the pixel data based on the correction file (step S203). That is, the printer driver refers to the correction file (FIG. 19), reads the dot generation rate corresponding to the dot row area to which the pixel data belongs and the gradation value indicated by the pixel data, and generates the read dot generation The pixel data is halftoned according to the rate. On the other hand, if the gradation value of the pixel data is 128 or more (NO in S202), the printer driver performs halftone processing on the pixel data based on the normal dot generation rate table (FIG. 7B) (step S203). . Through step S203 and step S204, the pixel data of 256 gradations of cyan is converted into binary pixel data of cyan and binary pixel data of light cyan.

  Then, the printer driver repeatedly performs the above processing (steps S202 to S204) for all pixel data on the cyan plane (NO in step S205, step S206). When the processing of all pixel data on the cyan plane is completed (YES in step S205), the printer driver sets the process target to the next magenta plane (NO in step S207, step S208).

  Similarly, the printer driver performs halftone processing on all pixels on the magenta plane, halftone processing on all pixels on the yellow plane, and finally sets the black plane as a processing target.

  When the black plane is a processing target, since there is no data relating to the black dot generation rate in the correction file, the printer driver performs a normal dot generation rate table (FIG. 7A) for all pixel data on the black plane. Based on the above, halftone processing is performed (step S209).

  Thereafter, the processing of all the planes is completed (YES in step S207), and the pixel data of 256 gradations are all converted into binary pixel data. Therefore, the printer driver performs the next rasterization processing.

=== Other Embodiments ===
The above-described embodiments are for facilitating the understanding of the present invention, and are 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 head>
In the above-described embodiment, ink is ejected using a piezoelectric element. However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.
In the above-described embodiment, the head is provided on the carriage. However, the head may be provided in an ink cartridge that is detachable from the carriage.

<About moving parts>
In the above-described embodiment, the carriage motor 32 including a DC motor is used as the moving unit that moves the head in the moving direction. However, it is not limited to such a motor. In short, it is sufficient that the moving unit can move the head in the moving direction.

<About the transport unit>
In the above-described embodiment, the transport unit 20 is used as a transport unit that transports a medium such as paper in the transport direction. However, the configuration of the transport unit is not limited to the configuration of the transport unit described above. For example, the transport unit may transport paper by a transport belt instead of the transport roller.

<About unit area>
In the above-described embodiment, as shown in FIG. 9A, a dot row formation region where a raster line is formed is used as a unit region. However, a region between the center of the raster line and the center of the raster line may be used as the unit region. In this case, the image of the unit area between the center of the raster line and the center of the raster line becomes a unit image, and the correction data is created by detecting the density of this unit image.

<About dot size>
In the above-described embodiment, the pixel data is binary in order to simplify the description. However, the present invention is not limited to this, and the pixel data may be 2-bit data so that the pixel data can indicate the size of a dot (large dot, medium dot, small dot, etc.).
In this case, a light gradation image indicated by a low gradation value is mainly formed by small dots. In such a printed image formed with small dots, density unevenness is likely to occur.
Therefore, when the head can form dots having different sizes, a correction pattern including only small dots may be formed. Then, the dot generation rate of small dots may be corrected based on the detection result of the correction pattern. Even in this case, density unevenness of the printed image can be suppressed.

<Regarding the range to be corrected>
According to the above-described embodiment, when the gradation value of the pixel data is 0 to 127, the density correction is performed. However, the range of gradation values to be corrected is not limited to this. For example, the density correction may be performed when the gradation value of the pixel data is 32 to 96. In this way, the density correction is not performed in the entire range below the predetermined gradation value. The density correction may be performed in a specific range less than the value.
In this case, for example, the cyan correction pattern CPlc need only have two types of dot generation rate (40% and 60%) correction patterns, so the correction pattern CP20% and the correction pattern CP80% need not be printed. Also good.

=== Summary ===
(1) The printing system 100 described above includes a carriage motor 32 (an example of a moving unit) that moves a head 41 that ejects ink, and a conveyance unit 20 (an example of a conveyance unit) that conveys paper (an example of a medium) in the conveyance direction. ) And.
In such a printing system, when a print image is formed by alternately repeating the dot formation operation and the conveyance operation, density unevenness may occur. Therefore, in the above-described printing system, correction data (see FIG. 16) is used to correct the density of an image piece (an image piece formed by a raster line, which is an example of a unit image) constituting a print image. And a computer-side memory 163 for storing a correction file (see FIG. 19) created from the correction data.

  The printer driver (specifically, the computer controller (CPU 162 and computer memory 163) of the computer in which the printer driver is installed) generates print data by performing halftone processing based on the dot generation rate indicated by the correction file. To do. When this print data is transmitted to the printer 1, the printer-side controller 60 forms a print image on paper based on the print data. Since the density of the image pieces constituting the print image at this time is corrected based on the correction file, a print image without density unevenness can be obtained.

By the way, if halftone processing is performed on pixel data of all gradation values based on the correction file, the amount of data in the correction file increases. In addition, in order to create such a correction file, enormous operations are required.
On the other hand, density unevenness is likely to occur in a light area of the print image, but is difficult to occur in a dark area of the print image. For this reason, halftone processing is performed only on pixel data with a low gradation value based on the correction file, that is, density correction is performed only on a light area of the print image. It is possible to suppress density unevenness.

  Therefore, when the gradation value of the pixel data is less than 128, the printer driver described above refers to the correction file, performs halftone processing based on the dot generation rate of the dot row area corresponding to the pixel data, When the gradation value of the data is 128 or more, halftone processing is performed based on the normal dot generation rate. When the print data generated in this way is transmitted to the printer, the printer-side controller forms a print image on paper with the density correction of the image pieces in the light area. In other words, in the above-described printing system, the computer-side controller and the printer-side controller 60 perform density correction when the pixel data gradation value is less than 128, and when the pixel data gradation value is 128 or more, the density is corrected. An image piece is formed in each dot row area without correction. Thereby, density unevenness is reduced and the image quality of the printed image is improved.

According to such a printing system, the storage capacity of the printer-side memory 63 that stores correction data can be reduced. If density correction is to be performed on all the gradation values, the printer-side memory requires not only correction data for light cyan ink but also correction data for cyan ink. Need to be larger.
In addition, according to such a printing system, it is possible to reduce the amount of calculation when creating the correction file. If density correction is to be performed on all gradation values, the printer driver needs to calculate not only the dot generation rate of gradation values 0 to 127 but also the dot generation rate of gradation values 128 to 255. There is a huge amount of computation required.

(2) The head 41 described above can form cyan dots (dark dots) and light cyan dots (light dots) that absorb red light and have different amounts of red light absorption. The head described above can form magenta dots (dark dots) and light magenta dots (light dots) that absorb green light and have different amounts of green light absorption. For cyan and magenta, when the gradation value of the pixel data is less than 128, only light dots are formed on the paper (see FIG. 20B).
For this reason, the printer-side memory 63 and the computer-side memory 163 do not need to store correction values for dark dots, and the memory capacity of the memory can be reduced. Further, since only the light ink (light cyan ink and light magenta ink) needs to be used when creating the correction pattern, the labor of the operation can be reduced. Further, when creating correction data, it is only necessary to detect a correction pattern using light ink, so that the labor of the operation can be reduced.

(3) The head 41 described above forms cyan and magenta dark dots and light dots. However, the present invention is not limited to this, and the head 41 may form yellow dark dots and light dots.

(4) The computer-side memory 163 stores the dot generation rate of light dots in each dot row area in the correction file (see FIG. 19). Then, the density of the image piece formed in each dot row region is corrected based on the dot generation rate of the correction file.
However, information to be stored in the computer-side memory 163 is not limited to the dot generation rate. For example, a correction value for correcting the RGB image data after resolution conversion for each dot row region may be stored in the computer-side memory 163. Even in this way, the density of the image piece can be corrected.

(5) The aforementioned printer-side memory 63 stores the measured density value in the dot row area as correction data (see FIG. 16). Then, the density of the image piece formed in each dot row region is corrected by the correction data.

  However, information to be stored in the printer-side memory 63 is not limited to the measurement values of the above-described embodiment. For example, information obtained by calculating a measurement value may be stored.

(6) The above-described head 41 forms a correction pattern CP in which a plurality of image pieces are adjacent to each other in the transport direction (see FIG. 13). The printer-side memory 63 stores a measurement value corresponding to the density of each dot row area of the correction pattern in association with each dot row area (see FIG. 16). The computer-side memory 163 stores a dot generation rate corresponding to the density of each dot row area of the correction pattern in association with each dot row area (see FIG. 19).
Thereby, density correction according to each dot row region can be performed, and density unevenness can be suppressed.

(7) The head 41 described above can form cyan dots (dark dots) and light cyan dots (light dots) that absorb red light and have different amounts of red light absorption. The head described above can form magenta dots (dark dots) and light magenta dots (light dots) that absorb green light and have different amounts of green light absorption.
The correction pattern CPlc is formed only by light cyan dots (light dots), and the correction pattern CPlm is formed only by light magenta dots (light dots). In other words, for example, when creating a correction pattern for correcting the density of a cyan image, it is not necessary to create a correction pattern using cyan ink (dark ink), so that the labor of the operation can be reduced.

(8) The computer-side controller and the printer-side controller 60 described above correct the density of each image piece by correcting the dot generation rate of dots formed in the dot row area based on the correction file.
For example, when attention is paid to a dot row area where a relatively dark image piece is formed, the dot generation rate corresponding to the dot row region in the correction file is smaller than the normal dot generation rate. For this reason, when the computer-side controller performs halftone processing based on the correction file, print data that generates fewer dots than usual is generated. When the printer-side controller 60 performs printing based on such print data, the number of dots constituting the raster line formed in the dot row area is smaller than usual, and the raster line is formed. The image piece is formed lighter than usual, and as a result, density unevenness is suppressed.

(9) If all the elements of the printing system described above are provided, all the described effects can be achieved. However, not all elements of the printing system described above are necessarily required.

(10) In the printing method described above, the user first forms a print image on paper (an example of a medium) by forming an image piece (an example of a unit image) in an adjacent dot row region (an example of a unit region). 1 is connected to the computer 110. Next, the user installs a printer driver in the computer 110, and at this time, the printer driver acquires correction data associated with each dot row area from the printer 1. When the gradation value of the pixel data corresponding to the dot row area on the paper is less than 128, the printer driver is based on the dot generation rate of the correction file created by the correction data corresponding to the dot row area. Then, halftone processing is performed (see step S203 in FIG. 21). When the printer 1 performs printing based on the generated print data, an image piece formed in the dot row area is formed with a corrected density. Further, when the gradation value of the pixel data is 128 or more, the printer driver performs halftone processing based on a normal dot generation rate (step S204 in FIG. 21). When the printer 1 performs printing based on the generated print data, an image piece formed in the dot row area is formed without density correction.

  According to such a printing method, density unevenness can be effectively suppressed. In addition, since the amount of correction data stored in the printer 1 can be small, the time required for the printer driver to acquire correction data is shortened. In addition, the amount of calculation at the time of density correction can be reduced.

(11) The computer 110 (an example of a print control apparatus) in which the above-described printer driver is installed controls the printer 1 that forms an image piece on an adjacent dot row area and forms a print image on paper. Then, the printer driver described above causes the computer 110 to acquire correction data associated with the dot row area from the printer. Then, when the gradation value of the pixel data corresponding to the dot row area on the paper is less than 128, the printer driver causes the computer 110 to generate a dot of the correction file created using the correction data corresponding to the dot row area. Based on the rate, halftone processing is performed (see step S203 in FIG. 21), and print data is generated. The printer driver also causes the computer 110 to perform halftone processing based on the normal dot generation rate when the gradation value of the pixel data corresponding to the dot row area on the paper is 128 or more (step in FIG. 21). In step S204, print data is generated. Then, the printer driver causes the computer 110 to transmit the generated print data to the printer 1.

  Thus, when the printer 1 performs printing based on the print data, a printed image with less density unevenness can be obtained. In addition, since the amount of correction data stored in the printer 1 can be small, the time required for the printer driver to acquire correction data is shortened. In addition, the amount of computation of the computer 110 at the time of density correction can be reduced.

(12) In the printing method described above, an operator in the printer factory first uses cyan dots (an example of dark dots) and light cyan dots (an example of light dots) that absorb red light and have different amounts of red light absorption on paper. A printer 1 that can be formed is prepared, and the printer 1 is caused to form a correction pattern CPlc (see FIG. 13) composed of only light cyan dots on paper. Thereafter, the scanner device 150 reads the correction pattern CPlc and detects the densities of a plurality of image pieces (an example of a unit image, which is composed of raster lines) constituting the correction pattern CPlc. Then, the process correction program 118A of the computer 110A in the factory associates the measured value of density of each image piece (an example of information regarding density) with each dot row area, and stores the correction data storage unit in the printer-side memory 63. 63a (see FIG. 16).
At the time of printing, the printer driver generates print data based on the correction data of the printer 1, and the printer 1 performs printing according to the print data. As a result, the density of each image piece composed of dark dots and light dots is corrected according to the correction data, and a print image composed of a plurality of image pieces is formed on the paper.

  According to such a printing method, a printed image with little density unevenness can be obtained. Further, since it is not necessary to store information regarding dark dots, the amount of information of correction data can be reduced. For this reason, the trouble of creating and reading the correction pattern is reduced.

(13) In the printer manufacturing method described above, an operator in the printer factory first uses cyan dots (an example of dark dots) and light cyan dots (an example of light dots) that absorb red light and have different amounts of red light absorption. Is prepared, and the printer 1 is caused to form a correction pattern CPlc (see FIG. 13) composed of only light cyan dots on paper. Thereafter, the scanner device 150 reads the correction pattern CPlc and detects the densities of a plurality of image pieces (an example of a unit image, which is composed of raster lines) constituting the correction pattern CPlc. Then, the process correction program 118A of the computer 110A in the factory associates the measured value of density of each image piece (an example of information regarding density) with each dot row area, and stores the correction data storage unit in the printer-side memory 63. 63a (see FIG. 16).

  According to such a printer manufacturing method, it is not necessary to store information about dark dots, so that the capacity of the memory 63 of the printer 1 can be reduced. Further, it is possible to reduce the labor of creating and reading a correction pattern when generating correction data to be stored in the memory 63, and the printer can be manufactured efficiently.

It is explanatory drawing which showed the external appearance structure of the printing system. 1 is a block diagram of the overall configuration of a computer 110 and a printer 1. FIG. 1 is a schematic diagram of an overall configuration of a printer 1. FIG. 2 is a cross-sectional view of the overall configuration of the printer 1. FIG. It is explanatory drawing which shows the arrangement | sequence of a nozzle. FIG. 3 is a schematic explanatory diagram of basic processing performed by a printer driver. FIG. 7A is a dot generation rate table for yellow and black. FIG. 7B is a dot generation rate table for cyan and magenta. It is a flowchart of the process at the time of printing. FIG. 9A is an explanatory diagram of a state when dots are ideally formed. FIG. 9B is an explanatory diagram of the influence of variations in nozzle processing accuracy. FIG. 9C is an explanatory diagram showing a state when dots are formed by the printing method of the present embodiment. 6 is a flowchart until a printer is shipped in a printer manufacturing factory. It is a block diagram explaining the apparatus used for the setting of the data for correction | amendment. It is a flowchart of the data generation process for correction | amendment. It is explanatory drawing of the correction pattern CP printed. FIG. 14A is a longitudinal sectional view of the scanner device. FIG. 14B is a plan view of the scanner device. It is a part of measurement result of a pattern with a dot generation rate of 40%. It is a conceptual diagram of the correction data table. FIG. 6 is a flowchart when installing a printer driver. It is a graph which shows the relationship between the command value in a certain dot row area | region, and a measured value. It is explanatory drawing of the file for correction | amendment of this embodiment. FIG. 20A is an explanatory diagram of a yellow dot generation rate table in a certain dot row region. FIG. 20B is an explanatory diagram of a cyan dot generation rate table in a certain dot row region. It is a flowchart of the halftone process of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 20 Carrying unit 21 Paper feed roller 22 Carrying motor 23 Carrying roller 24 Platen 25 Paper discharge roller 30 Carriage unit 31 Carriage 32 Carriage motor 40 Head unit 41 Head 50 Detector group 51 Linear encoder 52 Rotary encoder 53 Paper detection sensor 54 Optical sensor 60 Printer side controller 61 Interface unit 63 Printer side memory 63a Correction data storage unit 64 Unit control circuit 100 Printing system 102 Document table glass 104 Reading carriage 106 Exposure lamp 108 Linear sensor 110 Computer 120 Display device 130 Input device 140 Recording Playback device 150 Scanner device 161 Interface unit 163 Computer side memory 163a Correction file storage unit

Claims (13)

(A) a moving unit that moves a head that discharges ink in a moving direction;
(B) a transport unit that transports the medium in the transport direction;
(C) a memory for storing a correction value for correcting the density of a unit image formed in a unit region adjacent in the transport direction;
(D) When the gradation value indicated by the pixel data corresponding to the unit area on the medium is less than a predetermined gradation value, the unit has the density corrected based on the correction value corresponding to the unit area. Forming the unit image in an area;
A controller that forms the unit image in the unit area without correcting the density when the gradation value indicated by the pixel data corresponding to the unit area on the medium is equal to or higher than the predetermined gradation value;
A printing system comprising (E). The printing system according to claim 1,
The head is capable of forming dark dots and light dots on the medium that absorb light of the same wavelength and have different absorption amounts.
When the gradation value indicated by the pixel data is less than the predetermined gradation value, only the light dot is formed on the medium. The printing system according to claim 2,
The printing system according to claim 1, wherein the head forms the dark dots and the light dots of cyan or magenta. The printing system according to claim 2 or 3,
The printing system according to claim 1, wherein the memory stores information regarding the generation rate of the light dots as the correction value. The printing system according to any one of claims 1 to 3,
The printing system according to claim 1, wherein the memory stores information on the density in the unit area as the correction value. A printing system according to any one of claims 1 to 5,
The head forms a correction pattern in which the plurality of unit images are adjacent to each other in the transport direction on the medium.
The printing system, wherein the memory stores the correction value corresponding to the density of the unit area of the correction pattern in association with each unit area. The printing system according to claim 6, wherein
The head is capable of forming dark dots and light dots on the medium that absorb light of the same wavelength and have different absorption amounts.
The printing system, wherein the correction pattern is formed only by the light dots. A printing system according to any one of claims 1 to 7,
The printing system, wherein the controller corrects the density of the unit image by correcting a generation rate of dots formed in the unit area based on the correction value. (A) a moving unit that moves a head that discharges ink in a moving direction;
(B) a transport unit that transports the medium in the transport direction;
(C) a memory for storing a correction value for correcting the density of a unit image formed in a unit region adjacent in the transport direction;
(D) When the gradation value indicated by the pixel data corresponding to the unit area on the medium is less than a predetermined gradation value, the unit has the density corrected based on the correction value corresponding to the unit area. Forming the unit image in an area;
A controller that forms the unit image in the unit area without correcting the density when the gradation value indicated by the pixel data corresponding to the unit area on the medium is equal to or higher than the predetermined gradation value;
A printing system comprising (E),
(F) The head can form dark dots and light dots that absorb light of the same wavelength and have different absorption amounts on the medium.
(G) When the gradation value indicated by the pixel data is less than the predetermined gradation value, only the light dots are formed on the medium,
(H) The head forms the dark dot and the light dot of cyan or magenta,
(I) The memory stores information regarding the generation rate of the light dots as the correction value,
(J) The head forms a correction pattern in which the plurality of unit images are adjacent in the transport direction on the medium,
The memory stores the correction value corresponding to the density of the unit area of the correction pattern in association with each unit area,
(K) The correction pattern is formed only by the light dots,
(L) The printing system, wherein the controller corrects the density of the unit image by correcting the generation rate of dots formed in the unit area based on the correction value. (A) preparing a printing apparatus that forms a unit image in an adjacent unit region and forms a print image on a medium;
(B) obtaining a correction value associated with the unit area from the printing apparatus;
(C) When the gradation value indicated by the pixel data corresponding to the unit area on the medium is less than a predetermined gradation value, the unit has the density corrected based on the correction value corresponding to the unit area. Forming the unit image in an area;
Forming the unit image in the unit area without correcting the density when the gradation value indicated by the pixel data corresponding to the unit area on the medium is equal to or higher than the predetermined gradation value;
A printing method comprising (D). A print control apparatus that controls a printing apparatus that forms a unit image in an adjacent unit area and forms a print image on a medium.
Obtaining a correction value associated with the unit area from the printing apparatus;
When the gradation value indicated by the pixel data corresponding to the unit area on the medium is less than a predetermined gradation value, print data is generated from the pixel data according to the correction value corresponding to the unit area,
When the gradation value indicated by the pixel data corresponding to the unit area on the medium is equal to or greater than the predetermined gradation value, the print data is generated from the pixel data without using the correction value,
A program for causing the printing apparatus to transmit the print data. (A) preparing a printing apparatus including a head that can absorb light of the same wavelength and can form dark dots and light dots having different absorption amounts on a medium;
(B) the printing apparatus forming a correction pattern including only the light dots on the medium;
(C) detecting the density of each of a plurality of unit images constituting the correction pattern;
(D) storing information relating to the density of the unit image in association with each unit image;
(E) The printing apparatus forms a print image composed of a plurality of unit images on the medium by correcting the density of the unit image composed of the dark dots and the light dots according to the information. Steps,
A printing method comprising (F). (A) preparing a printing apparatus including a head that can absorb light of the same wavelength and can form dark dots and light dots having different absorption amounts on a medium;
(B) the printing apparatus forming a correction pattern including only the light dots on the medium;
(C) detecting the density of each of a plurality of unit images constituting the correction pattern;
(D) storing information relating to the density of the unit image in the memory of the printing apparatus in association with each unit image;
A manufacturing method of a printing apparatus for storing a correction value characterized by comprising (E).

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