JP4715315B2 - Printing apparatus, computer program, printing system, and printing method - Google Patents

Description

  The present invention relates to a printing apparatus, a computer program, a printing system, and a printing method for suppressing image density unevenness.

2. Related Art Inkjet printers (hereinafter referred to as printers) are known as printing apparatuses that form images by ejecting ink onto paper as a medium. In this printer, a dot forming operation for forming dots on a sheet by ejecting ink from a plurality of nozzles moving in the movement direction of the carriage, and a crossing direction in which the sheet intersects the movement direction by a conveyance unit having a conveyance roller ( Hereinafter, the conveying operation of conveying in the conveying direction) 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 intersecting direction, and an image is printed (see, for example, Patent Document 1). In order to suppress the occurrence of density unevenness in such a printer, the density of an image printed based on image data for printing an image of a predetermined density is read for each row area in which raster lines are formed, In some cases, image data of an image to be printed is corrected for each row area based on the read information.
JP-A-6-166247

  However, in the printer as described above, a plurality of raster lines originally formed at equal intervals in the paper conveyance direction may not be formed at equal intervals due to the eccentricity of the conveyance roller. Even if printing is performed based on image data for printing an image with a predetermined density with such a printer, an image with the correct density may not be printed. Further, if image data is corrected for each row area based on information obtained by reading an image having an incorrect density, there is a possibility that appropriate correction is not performed and density unevenness is not corrected.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a printing apparatus, a computer program, a printing system, and a printing method capable of suppressing the influence on correction due to the eccentricity of the conveyance roller. Is to realize.

  The main invention is: (a) a transport unit having a transport roller for transporting a medium for printing an image in the transport direction; and (b) the transport direction based on print data for printing the image. And a nozzle for forming a dot row on the medium transported by the transport unit and (c) a correction pattern in the transport direction. The transport direction, which forms a printed image based on print data for printing the image, and a portion of the transport roller that contacts the medium when the dot row is formed in the most downstream row region When the dot row is formed while performing correction based on the correction pattern in the most downstream row area of the paper, the conveyance roller is in contact with the portion of the conveyance roller that contacts the medium. A controller for controlling the a printing apparatus characterized by having (d).

  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) a transport unit having a transport roller for transporting a medium for printing an image in the transport direction; and (b) a movement that intersects the transport direction based on print data for printing the image. A nozzle for forming a dot row on the medium transported by the transport unit by ejecting ink while moving in the direction, and (c) a correction pattern, which is the most downstream side in the transport direction The most downstream side in the transport direction, which forms an image printed based on print data for printing the image, and a portion of the transport roller that contacts the medium when forming the dot row in the row region When the dot row is formed in the row region while performing correction based on the correction pattern, the conveyance unit is controlled so that the portion of the conveyance roller that contacts the medium coincides with the region. And controller, the printing apparatus characterized by having (d).

  According to such a printing apparatus, an image is formed based on print data for printing an image, and a dot row is formed in the most downstream row region in the transport direction while performing correction based on the correction pattern. At the time of formation, the medium is transported at a position that substantially coincides with the position of the transport roller that contacts the medium when forming a dot row in the most downstream row area in the transport direction, which constitutes the correction pattern. . For this reason, in the medium transport operation when printing an image and the medium transport operation when printing a correction pattern, the dot row formed in the most downstream row region in the transport direction is It is formed after the medium is conveyed at the same site. That is, even if the transport roller is eccentric, the transport amount of the medium transported to form the dot row formed in the most downstream row region in the transport direction has an error due to the eccentricity of the transport roller, This is the same when printing an image and printing a correction pattern. For this reason, by correcting the image data based on the correction pattern, it is possible to perform correction with higher accuracy and to print a good image.

  Here, when a rectangular region virtually defined on a medium such as paper is defined as a “unit region” whose size and shape are determined according to the print resolution, the “row region” refers to the movement direction An area composed of a plurality of unit areas arranged in a row. For example, the “unit area” is a square having a size of about 35.28 μm × 35.28 μm (≈ 1/720 inch × 1/720 inch) when the printing resolution is 720 dpi (moving direction) × 720 dpi (transport direction). It becomes a shape area. When the print resolution is 360 dpi × 720 dpi, the “unit region” is a rectangular region having a size of about 70.56 μm × 35.28 μm (≈ 1/360 inch × 1/720 inch). When ink droplets are ideally ejected, the ink droplets land at the center position of the unit region, and then the ink droplets spread on the medium to form dots in the unit region. For example, when the print resolution is 720 dpi × 720 dpi, the “row region” is a band-like region having a width of about 35.28 μm (≈ 1/720 inch) in the transport direction, and is ideally formed from the nozzle moving in the movement direction. When ink droplets are ejected intermittently, a dot row is formed in this row region.

In this printing apparatus, the printing apparatus has a detection unit for detecting a predetermined reference position on a circumferential surface of the conveyance roller, and the controller is configured to detect the conveyance unit based on the reference position detected by the detection unit. It is desirable to control.
According to such a printing apparatus, the controller controls the conveyance unit based on the reference position on the circumferential surface of the conveyance roller detected by the detection unit, so that the reference position on the circumferential surface of the conveyance roller is accurately determined. It is possible to position in the position. For this reason, it is possible to accurately contact the medium to be transported with a predetermined position on the peripheral surface of the transport roller.

The printing apparatus includes a medium supply unit for supplying the medium to the conveyance unit, and the controller positions the reference position of the conveyance roller at a predetermined rotation start position to configure the correction pattern. When the dot row is formed in the most downstream row region in the transport direction, and correction based on the correction pattern is performed on the most downstream row region in the transport direction that constitutes the image. In forming the dot row, the timing of starting the rotation of the transport roller from the rotation start position is matched with the timing of starting the supply of the medium by the medium supply unit, thereby contacting the medium. It is desirable to match the parts of the transport rollers.
According to such a printing apparatus, the timing at which the conveyance roller starts to rotate from the rotation start position is matched with the timing at which the medium supply unit starts to supply the medium to the conveyance roller positioned at the predetermined rotation start position. The medium supplied from the medium supply unit can be brought into contact with a substantially constant position on the peripheral surface of the transport roller. Therefore, when a dot row is formed in the most downstream row region in the conveyance direction of the correction pattern, and correction is performed on the most downstream row region in the conveyance direction based on the correction pattern. When forming a dot row, it is possible to match the portions on the peripheral surface of the transport roller in contact with the medium by simple control.

In such a printing apparatus, when the medium is discharged, it is preferable that the transport roller is stopped at the rotation start position.
According to such a printing apparatus, it is not necessary to position the transport roller at the rotation start position again when printing on the next medium after discharging one medium. For this reason, it is possible to improve throughput.

In the printing apparatus, it is preferable that the detection unit is a rotary encoder for detecting the rotation of the transport roller.
According to such a printing apparatus, it is possible to easily and more accurately detect the rotation of the transport roller and the position on the circumferential surface.

In such a printing apparatus, the controller corrects the image data based on the result of reading the correction pattern so as to suppress density unevenness between the row regions where the dot rows along the moving direction are formed. Is desirable.
Since the correction based on the result of reading the printed correction pattern is a correction for suppressing density unevenness between the row regions in which the dot rows along the moving direction are formed, in particular each dot constituting the correction pattern It is important that the position in the carrying direction of the row area in which the row is formed coincides with the position in the carrying direction of the row region in which the dot row constituting the image is formed. According to the printing apparatus, the position in the transport direction of the row area in which each dot row constituting the correction pattern is formed and the position in the transport direction of the row area in which the dot row constituting the image is formed are more It is possible to match exactly. Therefore, it is possible to correct the image data more appropriately based on the correction pattern and print a good image.

In this printing apparatus, the image data indicates a gradation value for each unit area formed on the medium, and the correction pattern printed based on the image data indicating a predetermined gradation value is read. It is preferable that correction information is acquired based on a result, and the image data is corrected based on the correction information.
According to such a printing apparatus, since the correction information is acquired based on the result of reading the correction pattern printed based on the image data indicating the predetermined gradation value, the printed correction pattern is read. The result is associated with a predetermined gradation value of the image data. Since the gradation value of the image data is corrected based on the result of reading the correction pattern, the image data can be corrected more appropriately.

In this printing apparatus, it is preferable that the correction pattern is printed for each printing condition when the image is printed, and the rotation start position is set based on the printing condition.
According to such a printing apparatus, since the rotation start position is set for each printing condition, the correction pattern printed for each printing condition is also conveyed by the conveyance roller starting to rotate from the rotation starting position corresponding to the printing condition. Is printed on the printed media. For this reason, a correction pattern corresponding to each printing condition is printed for each printing condition. Therefore, when printing an image under any printing condition, the image data is appropriately corrected and a good image is printed. Is possible.

In such a printing apparatus, the correction pattern includes a plurality of dot rows formed of ink ejected from the nozzles moved in the movement direction based on a gradation value indicating a predetermined density. It is desirable to print side by side along the direction.
According to such a printing apparatus, since a plurality of dot rows are printed side by side along the conveyance direction, it is possible to read density unevenness between the row regions where the dot rows are formed by reading the correction pattern. Since the image data is corrected based on the result of reading the correction pattern, it is possible to appropriately suppress the density unevenness between the column regions in the image to be printed.

(A) a transport unit having a transport roller for transporting a medium for printing an image in the transport direction; and (b) crossing the transport direction based on print data for printing the image. A nozzle for forming a dot row on the medium transported by the transport unit by ejecting ink while being moved in the moving direction, and (c) a correction pattern, which is the most downstream in the transport direction A portion of the transport roller that contacts the medium when forming the dot row in the row region on the side, and an image printed based on print data for printing the image, the most in the transport direction When the dot row is formed in the downstream row region while performing correction based on the correction pattern, the conveyance unit is controlled so that the portion of the conveyance roller that contacts the medium matches. A controller for detecting a predetermined reference position on the peripheral surface of the transport roller, and the controller detects the reference detected by the detection unit. And (e) a medium supply unit for supplying the medium to the conveyance unit, wherein the controller sets the reference position of the conveyance roller to a predetermined rotation start position. And when forming the dot row in the most downstream row region in the transport direction, which constitutes the correction pattern, and in the most downstream row region in the transport direction constituting the image, When forming a dot row while performing correction based on the correction pattern, the rotation of the transport roller relative to the timing at which the medium supply unit starts supplying the medium is performed. By matching the timing at which rotation starts from the start position, the portions of the transport roller that contact the medium are matched, and (f) when the medium is discharged, the transport roller is stopped at the rotation start position. (G) The detection unit is a rotary encoder for detecting the rotation of the transport roller, and (h) the controller is configured to perform density unevenness between the row regions where the dot rows along the moving direction are formed. Image data is corrected based on the result of reading the correction pattern, and (i) the image data indicates a gradation value for each unit area formed on the medium, and is predetermined. Correction information is acquired based on a result of reading the correction pattern printed based on the image data indicating a gradation value, and the image data is corrected based on the correction information. (J) The correction pattern is printed for each printing condition when printing the image, the rotation start position is set based on the printing condition, and (k) the correction pattern is a predetermined value. A plurality of dot rows formed by ink ejected from the nozzles moved in the moving direction on the basis of gradation values indicating the density of the ink; Printing device.
According to such a printing apparatus, the effects of the present invention can be achieved more effectively because the above-described effects can be achieved.

  In addition, the image forming apparatus is moved in a moving direction that intersects the conveying direction based on a conveying unit that includes a conveying roller for conveying a medium for printing an image in the conveying direction, and print data for printing the image. In the printing apparatus having a nozzle for discharging ink while forming a dot row on the medium transported by the transport unit, the most downstream row in the transport direction forms a correction pattern. A portion of the transport roller that contacts the medium when forming the dot row in an area, and an image printed based on print data for printing the image, the most downstream side in the transport direction When the dot row is formed in the row area while performing correction based on the correction pattern, the conveyance unit is controlled so that the portion of the conveyance roller that contacts the medium matches. Computer program for implementing the function of also feasible.

  Also, (A) a computer, and (B) a printing apparatus connected to the computer and having the following (a), (b), and (c), (a) a medium for printing an image is conveyed in the conveyance direction. (B) on the basis of print data for printing the image, ejects ink while moving in a moving direction intersecting the conveying direction, and is conveyed by the conveying unit. A nozzle for forming a dot row on the medium; and (c) the transport contacting the medium when forming the dot row in the most downstream row area in the transport direction, which constitutes a correction pattern. While performing correction based on the correction pattern on the most downstream row area in the transport direction, which constitutes an image printed based on the roller portion and print data for printing the image A printing system comprising a controller (C) for controlling the transport unit so that a part of the transport roller in contact with the medium coincides with the medium when forming a print train is realized. Is possible.

  Further, based on the print data for printing the correction pattern, ink is ejected from nozzles that are moved in a moving direction that intersects the medium conveying direction, and a dot row is formed in the most downstream row region in the carrying direction. And a predetermined portion of a transport roller included in a transport unit for transporting the medium in contact with the medium and transporting the nozzle based on print data for printing an image. And transporting the medium such that the predetermined portion of the transport roller contacts the medium when forming a dot row in the most downstream row region in the transport direction by discharging ink from It is also possible to realize a printing method characterized by having

=== Configuration of Printing System ===
<Printing system>
FIG. 1 is a diagram illustrating the configuration of the printing system 100. The printing system is a system including at least a printing apparatus and a printing control apparatus that controls the operation of the printing apparatus. The printing system 100 according to this embodiment includes a printer 1, a computer 110, a display device 120, an input device 130, a recording / reproducing device 140, and a scanner 150.

  The printer 1 prints an image on a medium such as paper, cloth, film, or OHP paper. The computer 110 is communicably connected to the printer 1. In order to cause the printer 1 to print an image, the computer 110 outputs print data corresponding to the image to the printer 1. Computer programs such as application programs and printer drivers are installed in the computer 110. The computer 110 is installed with a scanner driver for controlling the scanner 150 and receiving image data of a document read by the scanner 150.

<Printer>
FIG. 2 is a block diagram of the overall configuration of the printer 1 as a printing apparatus. FIG. 3A is a schematic diagram of the overall configuration of the printer 1. FIG. 3B is a longitudinal sectional view of the overall configuration 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 carriage unit 30, a head unit 40, a detector group 50, and a controller 60. The printer 1 that has received print data from the computer 110, which is an external device, controls each unit (the conveyance unit 20, the carriage unit 30, and the head unit 40) 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 transports a medium such as paper in a predetermined direction (hereinafter referred to as a transport direction). The transport unit 20 includes a paper feed roller 21 as a medium supply unit, a transport motor 22 (also referred to as a PF motor), a transport roller 23, a platen 24, and a paper discharge roller 25. 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-sectional shape, and the length of the circumferential portion is set longer than the transport distance to the transport roller 23. For this reason, by rotating the paper feed roller once from a state in which the circumferential portion is separated from the paper surface, the paper S can be transported by the length of the circumferential portion and the leading edge of the paper S can reach the transport roller 23. Is possible. The transport roller 23 is a roller for transporting the paper S fed by the paper feed roller 21 to a printable area.

  FIG. 4 is a model diagram for explaining the configuration of the drive unit of the transport unit 20. The paper feed roller 21 and the transport roller 23 are each driven by a single transport motor 22 connected via a gear. For this reason, a clutch 27 is interposed between the paper feed roller 21 and the transport motor 22, and the transport roller 23 can be rotated independently by disengaging the clutch 27. That is, the power of the transport motor 22 is transmitted to the gear G4 provided at one end of the shaft 23a of the transport roller 23 via the three gears G1, G2, G3, and rotates the transport roller 23. Further, the power transmitted to the transport roller 23 is transmitted from the gear G5 provided through the clutch 27 to the other end of the shaft 23a of the transport roller 23 through the three gears G6, G7, and G8. It is transmitted to the gear G9 provided on the shaft 21a, and the paper feed roller 21 is rotated. Here, the ON / OFF timing of the clutch 27 is turned on when the paper feed roller 21 is not in contact with the paper, and turned off after one rotation. That is, the paper feed roller 21 starts to rotate from a certain position and stops once at the original position after one rotation.

  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 1 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 the head in a predetermined movement 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. Further, 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.

  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, when the head 41 is moved in the moving direction, ink droplets (hereinafter referred to as ink droplets) are ejected intermittently, so that a dot row (raster line) along the moving direction is formed on paper as an example of the medium. It is formed.

  FIG. 5 is an explanatory diagram showing the arrangement of nozzles on the lower surface of the head 41. On the lower surface of the head 41, a black ink nozzle group K, a cyan ink nozzle group C, a magenta ink nozzle group M, and a yellow ink nozzle group Y are formed. Each nozzle group includes a plurality of nozzles 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. For example, when the nozzle pitch is 180 dpi (1/180 inch) and the dot pitch in the transport direction is 720 dpi (1/720 inch), k = 4. The nozzles of each nozzle group are assigned a smaller number as the nozzles on the downstream side (# 1 to # 180). Each nozzle is provided with an ink chamber (not shown) and a piezo element (not shown). The ink chamber is expanded and contracted by driving the piezo element, and ink droplets are ejected from the nozzle.

  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 amount of rotation of the transport roller 23, and the code board 52 a of the rotary encoder 52 is provided on the shaft of the transport roller 23. For this reason, one rotation detected by the rotary encoder 52 coincides with one rotation of the transport roller 23. Further, the code board 52a of the rotary encoder 52 has a slit formed over the entire circumference at equal intervals in the circumferential direction, and a small hole formed at one point of the entire circumference in the circumferential direction. have. A detector 52b composed of a light emitting portion and a light receiving portion arranged so as to sandwich the surface of the code board 52a sandwiches the slit and the small hole in the diameter direction of the code board 52a. Two are arranged side by side. That is, one detector 52b detects light passing through the slit to detect the rotation amount of the transport roller 23, and the other detector 52b detects light passing through the small hole to detect the peripheral surface of the transport roller 23. A predetermined position on the upper side, for example, a reference position, or one rotation of the transport roller 23 is detected. That is, the rotary encoder 52 is also a detection unit for detecting the reference position on the peripheral surface of the transport roller 23. The rotary encoder 52 also detects the amount of rotation of the paper feed roller 21 connected to the transport roller 23 via a gear.

  The paper detection sensor 53 is for detecting the position of the leading edge of the paper to be printed. 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 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 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 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.

<Scanner>
FIG. 6A is a longitudinal sectional view of the scanner 150. FIG. 6B is a top view of the scanner 150 with the upper lid 151 removed.

  The scanner 150 includes an upper cover 151, a document table glass 152 on which the document 5 is placed, a reading carriage 153 that moves in the sub-scanning direction while facing the document 5 through the document table glass 152, and a sub-scanning of the reading carriage 153. A guide member 154 for guiding in a direction, a moving mechanism 155 for moving the reading carriage 153, and a scanner controller (not shown) for controlling each part in the scanner 150 are provided. The reading carriage 153 receives an exposure lamp 157 for irradiating the document 5 with light, a line sensor 158 for detecting a line image in the main scanning direction (direction perpendicular to the paper surface in FIG. 6A), and reflected light from the document 5. An optical system 159 for guiding to the line sensor 158 is provided. A broken line inside the reading carriage 153 in the drawing indicates a locus of light.

  When reading the image of the document 5, the operator opens the upper cover 151, places the document 5 on the document table glass 152, and closes the upper cover 151. Then, the scanner controller moves the reading carriage 153 along the sub-scanning direction with the exposure lamp 157 emitting light, and reads the image on the surface of the document 5 by the line sensor 158. The scanner controller transmits the read image data to the scanner driver of the computer 110, whereby the computer 110 acquires the image data of the document 5.

=== Printing method ===
<About printing operation>
FIG. 7 is a flowchart of processing during printing. Each process described below is executed by the controller 60 controlling each unit in accordance with a program stored in the memory 63. This program has a code for executing each process.

  Print command reception (S001): First, the 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 together with information such as print conditions. Then, the 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 controller 60 rotates the paper feed roller 21 and the transport roller 23 to position the paper at the print start position.

  Dot Formation Process (S003): The dot formation process is a process for forming dots on the paper by intermittently ejecting ink from the head 41 that moves along the movement direction. The controller 60 drives the carriage motor 32 to move the carriage 31 in the movement direction. During the movement of the carriage 31, the head 41 is based on data for each unit area (hereinafter referred to as unit area data) included in the print data. Ink is ejected from the ink. 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.

  Transport Process (S004): The transport process is a process of moving the paper relative to the head 41 along the transport direction. The controller 60 rotates the transport roller 23 to transport the paper in the transport direction. By this carrying process, the head 41 can form dots in the next dot forming process at a position different from the position of the dots formed by the previous dot forming process. Details of the paper feed process and the transport process will be described later.

  Paper discharge determination (S005): The controller 60 determines whether paper being printed is being discharged (discharged). If data to be printed remains on the paper being printed, no paper is discharged. The controller 60 alternately repeats the dot formation process and the conveyance process 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 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.

  Print end determination (S007): Next, the 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.

<Raster line formation>
First, normal printing will be described. Normal printing in this embodiment is performed by a printing method called an interlace method (hereinafter referred to as interlaced printing). Here, “interlaced printing” means printing in which a row area where no raster line is recorded is sandwiched between raster lines recorded in one pass. Further, “pass” refers to a dot formation process that is executed while the carriage 31 moves once, and “pass n” refers to an nth dot formation process. The “raster line” is a row of dots arranged in the moving direction, and the “row region” is a region where a raster line can be formed.

  8A and 8B are explanatory diagrams of normal printing. FIG. 8A shows the head position and dot formation in pass n to pass n + 3, and FIG. 8B shows the head position and dot formation in pass n to pass n + 4.

  For convenience of explanation, only one nozzle group of a plurality of nozzle groups is shown, and the number of nozzles in the nozzle group is also reduced. Although the head 41 (or nozzle group) is depicted as moving with respect to the paper, this figure shows the relative position of the head 41 and the paper, Is moved in the transport direction. Also, for convenience of explanation, each nozzle is shown as having only a few dots (circles in the figure), but in reality, ink droplets are ejected intermittently from nozzles that move in the direction of movement. Therefore, a large number of dots are arranged in the moving direction (the row of dots is a raster line). Of course, dots may not be formed depending on the unit area data.

  In the figure, nozzles indicated by black circles are nozzles that can eject ink, and nozzles indicated by white circles are nozzles that cannot eject ink. Further, in the figure, the dot indicated by a black circle is a dot formed in the last pass, and the dot indicated by a white circle is a dot formed in the previous pass.

  In this interlaced printing, each time the paper is transported at a constant transport amount F in the transport direction, each nozzle passes a raster line immediately above the raster line recorded in the immediately preceding pass, that is, the downstream raster line in the transport direction. Record. In order to perform recording with a constant carry amount in this way, (1) the number N (integer) of nozzles that can eject ink is relatively prime to k, and (2) the carry amount F is N · The condition is that it is set to D. Here, N = 7, k = 4, F = 7 · D (D = 1/720 inch).

=== Density Density Correction (Outline) ===
<About density unevenness (banding)>
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.

  FIG. 9A 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, the row region is shown as a region sandwiched between dotted lines, and here is a region having a width of 1/720 inch in the transport direction. 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. 9B is an explanatory diagram of the influence of variations in nozzle processing accuracy. Here, a raster line formed in the second row region is formed closer to the third row region (upstream in the transport direction) due to variations in the flight direction of the ink droplets ejected from the nozzles. Further, the amount of ink droplets ejected toward the fifth row region is small, and the dots formed in the fifth row region are small.
Although an image piece having the same density should be formed in each row region, a density difference occurs in the image piece depending on the position where the raster line is formed due to variations in processing accuracy, etc. . For example, the image piece in the second row region is relatively light and the image piece in the third row region is relatively dark. Further, the image piece in the fifth 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.

  FIG. 9C is an explanatory diagram showing a state when dots are formed by the printing method of the present embodiment. In the present embodiment, the gradation value of the unit area data (CMYK unit area data) of the unit area corresponding to the row area is corrected so that a dark image piece is formed in the dark and easily visible row area. To do. In addition, for a row region that is easily visible, the gradation value of the unit region data of the unit region corresponding to the row region is corrected so that a dark image piece is formed. For example, the dot generation rate of the second row region in the figure is increased, the dot generation rate of the third row region is decreased, and the dot generation rate of the fifth row region is increased. The gradation value of the unit area data of the unit area corresponding to the row area is corrected. 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.

  In FIG. 9B, the reason why the density of the image pieces formed in the third row region is high is not due to the influence of the nozzles that form the raster lines in the third row region, but in the adjacent second row region. This is due to the influence of the nozzles forming the raster line. For this reason, when a nozzle that forms a raster line in the third row region forms a raster line in another row region, an image piece formed in that row region is not always dark. That is, even if the image pieces are formed by the same nozzle, the density may be different if the nozzles that form adjacent image pieces are different. In such a case, the density unevenness cannot be suppressed with the correction value simply associated with the nozzle. Therefore, in the present embodiment, the gradation value of the unit area data is corrected based on the correction value set for each row area.

  For this reason, in this embodiment, in the inspection process of the printer manufacturing factory, the printer prints a correction pattern, reads the correction pattern with a scanner, and determines each column area based on the density of each column area in the correction pattern. Is stored in the memory of the printer. The correction value stored in the printer reflects the density unevenness characteristics of each printer.

  Then, under the user who purchased the printer, the printer driver reads the correction value from the printer, corrects the gradation value of the unit area data based on the correction value, and print data based on the corrected gradation value. And the printer performs printing based on the print data.

<About processing at printer manufacturing plants>
FIG. 10 is a flowchart of the correction value acquisition process performed in the inspection process after manufacturing the printer. First, the inspector connects the printer 1 to be inspected to the computer 110 in the factory (S101). The computer 110 in the factory is also connected to the scanner 150, and in advance a printer driver for causing the printer 1 to print a test pattern, a scanner driver for controlling the scanner 150, and a correction read from the scanner. A correction value acquisition program for performing image processing, analysis, and the like on the pattern image data is installed.
Next, the printer driver of the computer 110 causes the printer 1 to print a test pattern (S102).

  FIG. 11 is an explanatory diagram of a test pattern. FIG. 12 is an explanatory diagram of a correction pattern. In the test pattern, four correction patterns are formed for each color. Each correction pattern is composed of a band-shaped pattern of five types of density, an upper ruled line, a lower ruled line, a left ruled line, and a right ruled line. The belt-like patterns are each generated from image data having a constant gradation value, and the gradation values 76 (density 30%), 102 (density 40%), and 128 (density 50%) are sequentially from the left belt-like pattern. , 153 (density 60%) and 179 (density 70%), and the patterns are darker in order. These five types of gradation values (density) are referred to as “command gradation values (command density)” and are represented by symbols Sa (= 76), Sb (= 102), Sc (= 128), Sd (= 153) and Se (= 179). In normal printing, several thousand raster lines can be formed in the printing area. However, in the printing of the correction pattern, each belt-like pattern has a raster corresponding to the length of at least the circumferential length of the transport roller 23 in the printing area. Lines are formed side by side in the transport direction. The upper ruled line is formed by the first raster line (raster line on the most downstream side in the transport direction) constituting the belt-like pattern. The lower ruled line is formed by the final raster line (raster line on the most upstream side in the transport direction) constituting the belt-like pattern.

  Next, the inspector places the test pattern printed by the printer 1 on the platen glass 152 of the scanner 150, closes the upper cover 151, and sets the test pattern on the scanner 150. Then, the scanner driver of the computer 110 causes the scanner 150 to read the correction pattern (S103). Hereinafter, reading of a cyan correction pattern will be described (the reading of correction patterns for other colors is performed in the same manner).

  FIG. 13 is an explanatory diagram of the reading range of the cyan correction pattern. The range of the alternate long and short dash line surrounding the cyan correction pattern is the reading range when reading the cyan correction pattern. Parameters SX1, SY1, SW1, and SH1 for specifying this range are set in advance in the scanner driver by the correction value acquisition program. If the scanner 150 reads this range, the entire cyan correction pattern can be read even if the test pattern is set to the scanner 150 with a slight shift. By this processing, the image in the reading range in the drawing is read by the computer 110 as read image data having unit read image data for each minimum reading area partitioned by a square having a resolution of 2880 × 2880 dpi.

  Next, the correction value acquisition program of the computer 110 detects the inclination θ of the correction pattern included in the read image data (S104), and performs a rotation process on the read image data according to the inclination θ (S105).

FIG. 14A is an explanatory diagram of read image data at the time of tilt detection. FIG. 14B is an explanatory diagram of detection of the position of the upper ruled line. FIG. 14C is an explanatory diagram of the read image data after the rotation processing.
The correction value acquisition program includes the unit reading image data of the minimum reading area of KX1 from the left and KH minimum reading areas from the top and the minimum reading area of KX2 from the left among the read image data read. Then, the unit read image data of the KH minimum reading areas are taken out from the top. The parameters KX1, KX2, and KH are determined in advance so that the upper ruled line is included in the minimum reading area extracted at this time, and the right ruled line and the left ruled line are not included. Then, in order to detect the position of the upper ruled line, the correction value acquisition program obtains the centroid positions KY1 and KY2 of the gradation values of the extracted KH data, that is, the centroid position in the density distribution. Then, the correction value acquisition program calculates the inclination θ of the correction pattern based on the parameters KX1 and KX2 and the barycentric positions KY1 and KY2 in the density distribution by the following equation, and reads based on the calculated inclination θ. Rotate the image data.
θ = tan-1 {(KY2-KY1) / (KX2-KX1)}

  Next, the correction value acquisition program of the computer 110 trims the read image data, and extracts necessary unit read image data from the read image data (S106).

FIG. 15A is an explanatory diagram of read image data at the time of trimming. FIG. 15B is an explanatory diagram of a trimming position on the upper ruled line.
Similar to the processing in step S104, the correction value acquisition program includes unit read image data of the minimum reading area of KX1 from the left and KH minimum reading areas from the left among the rotated read image data, and The unit reading image data of the minimum reading area of KX2 from the left and the KH minimum reading areas from the top are taken out. Then, in order to detect the position of the upper ruled line, the correction value acquisition program obtains the centroid positions KY1 and KY2 of the gradation values of the extracted KH unit read image data, and calculates the average value of the two centroid positions. To do. Then, the boundary of the minimum reading area that is closest to a position that is ½ the width of the row area from the center of gravity position is determined as the trimming position. In this embodiment, since the resolution of the read image data is 2880 dpi and the width of the row area is 720 dpi, ½ of the width of the row area corresponds to the width of two minimum read areas. Then, the correction value acquisition program cuts out the minimum reading area above the determined trimming position and performs trimming.

FIG. 15C is an explanatory diagram of the trimming position at the lower ruled line.
Almost the same as the upper ruled line side, the correction value acquisition program includes unit read image data of the minimum read area of KX1 from the left and the minimum read area of KH from the left, among the read image data subjected to the rotation processing, The unit reading image data of the minimum reading area of KX2 from the left and the KH minimum reading areas from the bottom is taken out, and the barycentric position of the lower ruled line is calculated. Then, the nearest boundary of the minimum reading area at the position lower by ½ of the width of the row area from the barycentric position is determined as the trimming position. Then, the correction value acquisition program cuts out the minimum reading area below the trimming position and performs trimming. Next, the correction value acquisition program of the computer 110 converts the resolution of the read image data after trimming so that the number of minimum reading areas in the Y direction is the same as the number of raster lines constituting the correction pattern. (S107).

FIG. 16 is an explanatory diagram of resolution conversion.
If the printer 1 ideally forms a correction pattern composed of n raster lines of 720 dpi, and the scanner 150 ideally reads the correction pattern at 2880 dpi (4 times the resolution of the correction pattern), trimming is performed. The number of minimum reading areas in the Y direction of the subsequent read image data should be 4n. However, in actuality, there is an influence of misalignment at the time of printing or reading, and the number of first read areas in the Y direction of the read image data may not be 4n. The number of minimum reading areas in the direction is 4n + α. The correction value acquisition program of the computer 110 performs n / (4n + α) [= [number of raster lines constituting the correction pattern] / [first reading of trimmed read image data in the Y direction] for this read image data. Resolution conversion (reduction processing) is performed at a magnification of [number of areas]]. Here, the bicubic method is used for resolution conversion. As a result, the number of data in the Y direction of the read image data after resolution conversion becomes n. The area indicated by the individual data after the conversion is equivalent to a unit area that is an area where one dot can be formed, and the individual data is set as unit area data. In other words, the read image data of the correction pattern configured by the unit read image data of 2880 dpi is converted into the read image data of the correction pattern configured by the unit area data of 720 dpi. As a result, the number of unit areas arranged in the Y direction is the same as the number of row areas, and the unit area rows and the row areas in the X direction correspond one-to-one. For example, the unit region column in the X direction located at the top corresponds to the first row region, and the unit region row located below corresponds to the second row region. Note that since this resolution conversion is intended to reduce the number of unit area columns in the Y direction to n, resolution conversion (reduction processing) in the X direction may not be performed.

  Next, the correction value acquisition program of the computer 110 measures the density of each of the five types of belt-like patterns in each row region (S108). Hereinafter, the measurement of the density of the left band-shaped pattern formed with the gradation value 76 (density 30%) in the first row area will be described (note that the measurement in the other row areas is performed in the same manner. The density of the belt-like pattern is also measured in the same manner).

FIG. 17A is an explanatory diagram of image data when the left ruled line is detected. FIG. 17B is an explanatory diagram of detection of the position of the left ruled line. FIG. 17C is an explanatory diagram of the measurement range of the density of the band-like pattern having a density of 30% in the first row region.
The correction value acquisition program extracts unit area data of HX unit areas from the top and KX unit areas from the left, from the read image data subjected to resolution conversion. The parameter KX is determined in advance so that the left ruled line is included in the unit area data extracted at this time. Then, the correction value acquisition program obtains the barycentric position of the gradation value of the unit area data of the extracted KX unit areas in order to detect the position of the left ruled line. It is known from the shape of the correction pattern that a strip-shaped pattern having a width of W3 and having a density of 30% exists on the right side by X2 from the position of the center of gravity (position of the left ruled line). Accordingly, the correction value acquisition program extracts the unit area data in the dotted line range excluding the left and right W4 ranges of the belt-like pattern with reference to the center of gravity position, and calculates the average value of the gradation values of the unit area data in this range. The measured value is the density of 30% in the first row region. Note that when measuring the density of a strip-like pattern having a density of 30% in the first row area, unit area data in a range one unit area below the dotted line in the figure is extracted. In this way, the correction value acquisition program measures the density of the five types of belt-like patterns for each row region.

  FIG. 18 is a measurement value table summarizing the measurement results of the densities of the five types of cyan belt-like patterns. As described above, the correction value acquisition program of the computer 110 creates a measurement value table by associating the measurement values of the density of the five types of belt-like patterns for each row region. A measurement value table is also created for other colors. In the following description, the measured values of the band-shaped pattern of the gradation values Sa to Se are set to Ca to Ce for a certain row region, respectively.

  FIG. 19 is a graph of measured values of a band-like pattern having a cyan density of 30%, a density of 40%, and a density of 50%. Although each belt-like pattern is uniformly formed with each command value, shading occurs in each row region. The density difference for each row area is a cause of density unevenness in the printed image.

  In order to eliminate the density unevenness, it is desirable that the measured value of each strip pattern is constant. Therefore, a process for making the measurement value of the belt-like pattern having the gradation value Sb (density 40%) 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 a target value of 40% density. In the row region i where the measurement value is lighter than the target value Cbt, in order for the density measurement value to approach 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, in order for the measured value of density to approach the target Cbt, it is considered that the gradation value should be corrected to be lighter.

  Therefore, the correction value acquisition program of the computer 110 calculates a correction value corresponding to the row region (S109). 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 40%) in the row region i of FIG. 20 is calculated based on the measured values of the gradation value Sb and the gradation value Sc (density 50%). Is done. On the other hand, the correction value for the command gradation value Sb (density 40%) of the row region j is calculated based on the measured values of the gradation value Sb and the gradation value Sa (density 30%).

FIG. 20A 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 region, the measured value Cb of the density of the strip pattern formed with the command tone value Sb shows a tone value smaller than the target value Cbt (in this row region, the average density of the strip pattern having a density of 30%. Paler). If the printer driver causes the printer to form a density pattern of the target value Cbt in this row area, the printer driver is instructed based on the target instruction gradation value Sbt calculated by the following equation (linear interpolation based on the straight line BC). That's fine.
Sbt = Sb + (Sc−Sb) × {(Cbt−Cb) / (Cc−Cb)}

FIG. 20B 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 area, the measured value Cb of the density of the strip pattern formed with the command tone value Sb shows a tone value larger than the target value Cbt (in this row area, the average density of the strip pattern having a density of 30%. Paler). If the printer driver causes the printer to form a density pattern of the target value Cbt in this row area, the printer driver is instructed based on the target command gradation value Sbt calculated by the following equation (linear interpolation based on the straight line AB). That's fine.
Sbt = Sb− (Sb−Sa) × {(Cbt−Cb) / (Ca−Cb)}

After calculating the target command tone value Sbt in this way, the correction value acquisition program calculates a correction value Hb for the command tone value Sb in this row region by the following equation.
Hb = (Sbt−Sb) / Sb

  The correction value acquisition program of the computer 110 calculates a correction value Hb for the gradation value Sb (density 40%) for each row region. Similarly, the correction value acquisition program calculates the correction value Hc for the gradation value Sc (density 50%) for each column region based on the measurement value Cc of each column region and the measurement value Cb or Cd. To do. Similarly, the correction value acquisition program calculates the correction value Hd for the gradation value Sd (density 60%) for each column region based on the measurement value Cd of each column region and the measurement value Cc or Ce. To do. For other colors, three correction values (Hb, Hc, Hd) are calculated for each row region.

Next, the correction value acquisition program of the computer 110 stores the correction value in the memory 63 of the printer 1 (S110).
FIG. 21 is an explanatory diagram of a cyan correction value table. In the correction value table, three correction values (Hb, Hc, Hd) are associated with each row region. For example, three correction values (Hb_n, Hc_n, Hd_n) are associated with the nth raster line in each row region. The three correction values (Hb_n, Hc_n, Hd_n) correspond to the command gradation values Sb (= 102), Sc (= 128), and Sd (= 153), respectively. The same applies to correction value tables for other colors.

  After the correction value is stored in the memory 63 of the printer 1, the correction value acquisition process ends. Thereafter, the connection between the printer 1 and the computer 110 is disconnected, the other inspections for the printer 1 are finished, and the printer 1 is shipped from the factory. The printer 1 also includes a CD-ROM that stores a printer driver.

<About processing under the user>
FIG. 22 is a flowchart of processing performed under the user.
The user who purchased the printer 1 connects the printer 1 to the computer 110 owned by the user (of course, a computer different from the computer at the printer manufacturing factory) (S201, S301). Note that the scanner 150 may not be connected to the user's computer 110.

Next, the user sets the enclosed CD-ROM in the recording / reproducing apparatus 140 and installs the printer driver (S202). The printer driver installed in the computer requests the computer 110 to transmit correction values to the printer 1 (S203). In response to the request, the printer 1 transmits the correction value table stored in the memory 63 to the computer 110 (S302). The printer driver stores the correction value sent from the printer 1 in the memory (S204). Thereby, a correction value table is created on the computer side. After completing the processing so far, the printer driver enters a standby state until a print command is received from the user (NO in S205).
Upon receiving a print command from the user (YES in S205), the printer driver generates print data based on the correction value (S206) and transmits the print data to the printer 1. The printer 1 performs a printing process according to the print data (S303).

FIG. 23 is a flowchart of print data generation processing. These processes are performed by the printer driver.
First, the printer driver performs resolution conversion processing (S211). 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 when printing an image on paper is specified as 720 × 720 dpi, the image data received from the application program is converted into image data having a resolution of 720 × 720 dpi. Note that the image data after the resolution conversion process is 256-gradation data (RGB data) represented by an RGB color space.

  Next, the printer driver performs a color conversion process (S212). The color conversion process is a process for converting RGB data into CMYK data represented by a CMYK color space. This color conversion process is performed by the printer driver referring to a table (color conversion lookup table LUT) in which the gradation values of RGB data and the gradation values of CMYK data are associated with each other. By this color conversion process, RGB data for each unit area is converted into CMYK data corresponding to ink colors. The data after the color conversion processing is CMYK data with 256 gradations represented by the CMYK color space.

  Next, the printer driver performs density correction processing (S213). The density correction process is a process of correcting the gradation value of each unit area data based on the corresponding correction value of the column area to which the unit area data belongs.

  FIG. 24 is an explanatory diagram of density correction processing for the nth row region of cyan. This figure shows how the gradation value S_in of the unit area data of the unit area belonging to the nth row area of cyan is corrected. Note that the corrected gradation value is S_out.

  If the gradation value S_in of the unit area data before correction is the same as the command gradation value Sb, the printer driver corrects the gradation value S_in to the target instruction gradation value Sbt, so An image with the target density Cbt can be formed in the unit area. That is, if the gradation value S_in of the unit area data before correction is the same as the command gradation value Sb, the gradation value S_in (= Sb) is set to Sb using the correction value Hb corresponding to the command gradation value Sb. It is good to correct to x (1 + Hb). Similarly, if the gradation value S of the unit area data before correction is the same as the command gradation value Sc, the gradation value S_in (= Sc) should be corrected to Sc × (1 + Hc).

  On the other hand, when the gradation value S_in before correction is different from the command gradation value, the gradation value S_out to be output is calculated by linear interpolation as shown in the figure. In the linear interpolation in the figure, linear interpolation is performed between the corrected gradation values S_out (Sbt, Sct, Sdt) corresponding to the command gradation values (Sb, Sc, Sd). However, the present invention is not limited to this. For example, the correction value H corresponding to the gradation value S_in is calculated by linearly interpolating between the correction values (Hb, Hc, Hd) corresponding to each command gradation value, and the correction value H is calculated based on the calculated correction value H. The corrected gradation value may be calculated as S_in × (1 + H).

  With the above-described density correction processing, for a column region that is easily visible darkly, the gradation value of the unit region data (CMYK data) of the unit region corresponding to the column region is corrected to be low. On the other hand, for a row area that is easily visible, correction is made so that the gradation value of the unit area data of the unit area corresponding to the row area is high. Note that the printer driver performs the correction process in the same manner for other row regions of other colors.

  Next, the printer driver performs halftone processing (S214). 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. In the halftone process, dithering, γ correction, error diffusion, etc. are used to create unit area data so that the printer can form dots in a dispersed manner. When performing halftone processing, the printer driver refers to the dither table when performing dithering, refers to the gamma table when performing γ correction, and stores diffused errors when performing error diffusion. Refer to the error memory. The data subjected to the halftone process has a resolution (for example, 720 × 720 dpi) equivalent to the RGB data described above.

  In the present embodiment, the printer driver performs halftone processing on the unit area data of the gradation value corrected by the density correction processing. As a result, in a row region that is dark and easily visible, since the gradation value of the unit region data of the row region is corrected to be low, the dot generation rate of the dots constituting the raster line of the row region is low. . On the other hand, the dot generation rate is high in the row region that is easily recognized visually.

  Next, the printer driver performs rasterization processing (S215). 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 unit area data included in the print data.

  If the printer performs a printing process based on the print data generated in this way, as shown in FIG. 9C, the dot generation rate of the raster line in each row area is changed, and the density of the image pieces in the row area is corrected. Thus, density unevenness of the entire printed image is suppressed.

  In the above description, the number of nozzles and the number of row regions (number of raster lines) are reduced to simplify the description. However, the processing performed by the correction value acquisition program, printer driver, and the like is substantially the same.

=== Correspondence between Correction Pattern Raster Line and Image Raster Line ===
As described above, the printer 1 according to the present embodiment obtains correction values corresponding to the respective row regions based on the result of reading the correction pattern printed in advance, and prints the image when printing the image. The image data is corrected based on the correction value of the row area where the raster line of the correction pattern corresponding to each of the raster lines constituting it is formed. Here, the corresponding raster line is a raster line that can be formed on the most upstream side with the raster line that can be formed on the most downstream side in the transport direction as the first raster line in the image data for printing an image and a correction pattern. When the order is assigned, the raster lines are assigned the same order when the image is printed and when the correction pattern is printed. At this time, the raster line does not necessarily have to be actually formed on the paper as long as it can be formed in the image data.

  The correction in the present embodiment corrects the image data so as to suppress density unevenness between the row regions in which the raster lines along the moving direction of the carriage 31 are formed. As described above, the density unevenness between the row regions may occur when any of the raster lines that should be formed at regular intervals in the transport direction is formed at a position shifted in the transport direction. That is, the density unevenness between the row regions is caused not only by the ink ejection characteristics of the nozzles but also by the paper transport characteristics. In particular, when the transport roller for transporting the paper is eccentric, when the paper is transported, the portion of the peripheral surface of the transport roller 23 that is in contact with the paper is different. In some cases, the conveyance amount is different and density unevenness occurs between the row regions.

  Then, when the image data for forming each raster line of the image to be printed is corrected based on the result of reading the printed correction pattern as in the present embodiment, the correction pattern is printed. If the portion of the peripheral surface of the transport roller 23 that comes into contact with the transported paper is different between when the image is corrected and when the image is printed, an appropriate correction may not be performed and a good image may not be printed. For this reason, according to the present invention, the conveyance unit is controlled so that the portions on the circumferential surface of the conveyance roller that come into contact with the conveyed sheet coincide with each other when the correction pattern is printed and when the correction image is printed. The process will be described below.

  Since the method of forming the raster line has been described above as the printing method, here, the sheet to be conveyed is printed when the correction pattern is printed and when the image is printed with correction based on the correction pattern. The paper transport process for matching the portions on the peripheral surface of the transport roller 23 that come into contact with the paper will be mainly described.

  FIG. 25 is a diagram for explaining processing for aligning raster line positions when an image is printed and when a correction pattern is printed.

  After the printer 1 is turned on, the clutch 27 provided on the shaft 23a of the transport roller 23 is disengaged in a standby state where no operation such as printing is performed. By the way, the sheet feeding roller 21 having a D-shaped cross section always rotates once and stops at a fixed position as described above only when the sheet feeding operation is performed by turning ON / OFF the clutch 27, and from the same position. Start spinning. For this reason, even in the standby state, the paper feed roller 21 is stopped at a predetermined position.

  When the printer 1 in the standby state receives a print command signal together with commands indicating print data, printing conditions, and the like from the connected computer 110 (S401), the controller 60 drives the carry motor 22 to move the carry roller 23. Rotate. At this time, the controller 60 monitors the output of the rotary encoder 52, and detects a signal output from the rotary encoder 52 when a small hole provided in the code board 52a is detected (S402). The detected position is one point in the circumferential direction of the code board 52 a and coincides with one point on the circumferential surface of the transport roller 23. The controller 60 recognizes one point on the peripheral surface as a reference position, and positions the peripheral surface of the transport roller 23 so that the reference position of the transport roller 23 is, for example, vertically above the shaft 23a of the transport roller 23. Combine (S404). That is, in the present embodiment, the position where the reference position of the transport roller 23 is positioned vertically above the shaft 23a of the transport roller 23 is the rotation start position.

  While positioning the reference position of the conveyance roller 23 on the vertical axis of the shaft 23a of the conveyance roller 23, the controller 60 analyzes the command indicating the print data and the print condition received together with the print command signal, and prints to be printed. The relative position between the leading edge of the paper and the row area where the raster line can be formed on the most downstream side in the print data to be printed is calculated (S403). At this time, the print data may be image data for printing an image such as a landscape image or character information, or print data for printing various adjustment test patterns including a correction pattern. Also good. In addition, when the command such as the printing condition is analyzed and the command is a command for executing “marginless printing” as the print mode, the row area in which the raster line can be formed on the most downstream side in the print data is the paper area. Since the position is not located above, the position of the row area where the most downstream raster line in the area outside the printing paper can be formed with respect to the leading edge position of the paper is calculated. At this time, the position of the raster line that can be formed on the most downstream side in the transport direction with the ink ejected based on the print data is positioned upstream of the number of pulses from the leading edge of the paper in the output of the rotary encoder 52. In addition, the number of pulses that can be formed downstream of the leading edge of the paper is calculated.

  Next, the controller 60 turns on the clutch 27 to connect the shaft 23a of the transport roller 23 and the gear G5 (S405). Then, by driving the transport motor 22, the paper feed roller 21 positioned at a predetermined position and the transport roller 23 whose reference position is positioned vertically above the shaft 23a of the transport roller 23 start to rotate simultaneously (S406). . That is, the sheet S conveyed by the sheet feeding roller 21 that rotates once from a certain position and the conveying roller 23 that starts to rotate from the reference position at the same timing as the sheet feeding roller 21 are located on the circumferential surface of the conveying roller 23. Always touch at approximately the same position. That is, by matching the timing at which the transport roller 23 positioned at a predetermined rotation start position starts to rotate the transport roller 23 from the rotation start position with the timing at which the paper feed roller 21 starts to supply paper, The paper supplied by the roller 21 can be brought into contact with a substantially constant position on the peripheral surface of the transport roller 23.

  Based on the output of the rotary encoder 52, the controller 60 turns off the clutch 27 at the timing when the paper feed roller 21 makes one rotation, and stops the paper feed roller 21 (S407). Thereafter, the calculated position of the most downstream raster line in the transport direction with respect to the leading edge of the paper, and the position of the nozzle that ejects ink to form a raster line in the row region on the most downstream side with respect to the leading edge of the paper, So that the conveying rollers 23 continue to rotate so as to be equal to each other (S408). At this time, the part on the peripheral surface of the conveying roller where the sheet starts to contact is always substantially constant, and the distance by which the sheet is conveyed after the sheet and the conveying roller come into contact until the conveying roller 23 stops is , Printing method, printing mode and other printing conditions. For this reason, in the print data of the image printed under the same printing conditions, the raster lines arranged in the same order from the top in the transport direction are transported by the same part on the peripheral surface of the transport roller 23.

  When the transport roller 23 is stopped, ink droplets are ejected while moving the carriage 31 to form dots on the paper. Thereafter, an image is printed by repeating a conveyance process for conveying a predetermined amount of paper and a dot formation process for discharging ink from a predetermined nozzle while moving the carriage 31 (S003). The subsequent processing is as described in FIG. At this time, after executing the paper discharge process (S006), the controller 60 rotates the transport roller 23 to the rotation start position, that is, the position where the reference position of the transport roller 23 is located vertically above the shaft 23a. This is stopped to prepare for the next paper feed process (S002). As described above, after the paper discharge process (S006) is completed, the conveyance roller 23 is rotated to the rotation start position and stopped, so that the conveyance roller 23 is not positioned when printing on the next sheet. The paper feed process (S002) can be executed as it is, and the throughput can be improved.

  Then, when the correction pattern used when correcting the image data to suppress the density unevenness between the row areas in which the dot rows along the moving direction of the carriage 31 as described above are suppressed is printed. When the image is printed based on the correction, the correction pattern and the image are printed under the same printing conditions. For this reason, when printing the raster line on the most downstream side in the conveyance direction of the correction pattern, the portion of the conveyance roller 23 that comes into contact with the sheet to convey the sheet and the raster on the most downstream side in the conveyance direction of the corrected image. The portion of the conveyance roller 23 that comes into contact with the sheet for conveying the sheet when printing a line substantially coincides. As a matter of course, the portion of the transport roller 23 that comes into contact with the paper to transport the paper when printing other raster lines also prints the correction pattern and prints the corrected image. So it will be almost the same. For this reason, even when the transport roller 23 is eccentric, the influence of the eccentricity is arranged in the same order from the front end side of the paper when the correction pattern is printed and when the corrected image is printed. The same applies to the raster lines. Therefore, it is more appropriate to print an image on the paper conveyed at the same predetermined portion of the conveyance roller 23 based on the correction pattern printed on the paper conveyed at the predetermined portion of the conveyance roller 23. Correction can be performed, and a good image with reduced density unevenness in the transport direction can be printed. At this time, since the controller 60 controls the transport unit 20 based on the reference position on the peripheral surface of the transport roller 23 detected by the rotary encoder 52, the reference position on the peripheral surface of the transport roller 23 is accurately determined. It is possible to position at the position of, for example, the rotation start position. For this reason, it is possible to accurately contact the sheet to be transported and a predetermined portion on the peripheral surface of the transport roller 23.

  Further, by matching the timing at which the conveyance roller 23 positioned at a predetermined rotation start position begins to be fed by the paper feed roller 21 with the timing at which the conveyance roller 23 starts to rotate from the rotation start position, the paper feed roller 23 The sheet supplied by the roller 21 can be brought into contact with a substantially constant position on the peripheral surface of the transport roller 23. In particular, in the present embodiment, since both the paper feed roller 21 and the transport roller 23 are positioned at a predetermined rotation start position, they are simultaneously started to rotate by the power of the single transport motor 22, so that the correction pattern When forming raster lines in the most downstream row region in the transport direction and forming raster lines in the most downstream row region in the transport direction while performing correction based on the correction pattern. In this case, it is possible to match the portions on the peripheral surface of the transport roller 23 that are in contact with the sheet by simple control.

  Further, as the detection unit for detecting the rotation of the transport roller 23, a rotary encoder provided with a code board 52a on the shaft 23a of the transport roller 23 is used. Therefore, the rotation and peripheral surface of the transport roller 23 can be easily and more accurately performed. It is possible to detect the upper position. Furthermore, since the feed roller 21 is connected to the shaft 23a of the transport roller 23 via gears G5 to G9, the rotation amount of the feed roller 21 can be easily and accurately detected by the rotary encoder. Is possible.

  Further, since the correction value is acquired based on the result of reading the correction pattern printed based on the image data indicating the predetermined gradation value, the result of reading the printed correction pattern and the predetermined value of the image data The gradation value is associated. Since the gradation value of the image data is corrected based on the result of reading the correction pattern, the image data can be corrected more appropriately.

  Further, since the rotation start position of the transport roller 23 is set for each printing condition, the correction pattern printed for each printing condition is also conveyed by the transport roller 23 starting to rotate from the rotation start position corresponding to the printing condition. Printed on. For this reason, a correction pattern corresponding to each printing condition is printed for each printing condition. Therefore, when printing an image under any printing condition, the image data is appropriately corrected and a good image is printed. Is possible.

  According to the printer 1 of the present embodiment, since a plurality of raster lines are printed side by side along the transport direction, it is possible to read density unevenness between row regions where raster lines are formed by reading a correction pattern. It is possible to correct the image data for printing the image based on the result of reading the correction pattern. Therefore, it is possible to appropriately suppress the density unevenness between the row regions in the image to be printed.

  In the present embodiment, the example in which the detection unit for detecting the reference position of the conveyance roller 23 is configured by the rotary encoder 52 has been described, but the detection unit is, for example, a gear provided on the shaft 23 a of the conveyance roller 23. A new gear having the same number of teeth as G4 may be provided and meshed with the gear G4, and electrodes may be provided on the new gear and the gear G4 to detect the reference position of the transport roller 23. Specifically, an electrode is provided at one tooth tip of the gear G4, an electrode is provided over the entire circumference of the new gear, and when the two gears rotate while meshing with each other, the electrode of the gear G4 and the new gear are provided. If a setting is made so that the current flowing when the electrode of the gear G4 is in contact is detected, the position where the electrode of the gear G4 and the electrode of the new gear are in contact can be detected as the reference position.

=== Other Embodiments ===
The above embodiment mainly describes the printing system, but it goes without saying that the disclosure includes the printer 1, the printing apparatus, the printing method, and the like.
Moreover, although the printing system etc. as one embodiment were demonstrated, said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this 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 this embodiment, the printing system and the printing method for correcting the density unevenness generated in the paper conveyance direction have been described. However, the printer 1 is configured by the above correction, such as vibration caused by the movement of the carriage on which the head is mounted. This is also applicable to vertical stripe-shaped density unevenness that occurs in the direction along the transport direction due to the mechanism that performs this.

<About the printer>
In the above-described embodiment, the printer 1 has been described as the printing unit. 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 recording apparatuses to which an ink jet technique is applied such as an apparatus and a DNA chip manufacturing apparatus. These methods and manufacturing methods are also within the scope of application.

<About ink>
In the above-described embodiment, dye ink or pigment ink is ejected from the nozzles of the printer 1 from the nozzles. However, the ink ejected from the nozzle is not limited to such ink.

<About nozzle>
In the above-described embodiment, ink is ejected using a piezoelectric element. However, the method of ejecting ink is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.

<About the carriage moving direction for ejecting ink>
In the above-described embodiment, unidirectional printing in which ink is ejected only when the carriage 31 moves in the forward direction has been described as an example. However, the present invention is not limited to this, and so-called ink ejection is performed when the carriage 31 reciprocates in both directions. Bidirectional printing may be performed.

<Ink colors used for printing>
In the above-described embodiment, multicolor printing in which dots are formed by ejecting four colors of ink of cyan (C), magenta (M), yellow (Y), and black (K) onto the paper S has been described. However, the ink color is not limited to this. For example, in addition to these ink colors, ink such as light cyan (light cyan, LC) and light magenta (light magenta, LM) may be used.
Conversely, monochrome printing may be performed using only one of the four ink colors.

It is a figure for demonstrating the structure of a printing system. 1 is a block diagram of an overall configuration of a printer. FIG. 3A is a schematic diagram of the overall configuration of the printer. FIG. 3B is a longitudinal sectional view of the overall configuration of the printer. It is a model diagram for demonstrating the structure of the drive part of a conveyance unit. It is explanatory drawing which shows the arrangement | sequence of the nozzle in the lower surface of a head. FIG. 6A is a longitudinal sectional view of the scanner. FIG. 6B is a top view of the scanner with the upper lid removed. It is a flowchart of the process at the time of printing. FIG. 8A shows the head position and dot formation in pass n to pass n + 3, and FIG. 8B shows the head position and dot formation in pass n to pass n + 4. 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. It is a flowchart of the correction value acquisition process performed at the inspection process after manufacture of a printer. It is explanatory drawing of a test pattern. It is explanatory drawing of the pattern for a correction | amendment. It is explanatory drawing of the reading range of the pattern for cyan correction. FIG. 14A is an explanatory diagram of read image data at the time of tilt detection. FIG. 14B is an explanatory diagram of detection of the position of the upper ruled line. FIG. 14C is an explanatory diagram of the read image data after the rotation processing. FIG. 15A is an explanatory diagram of read image data at the time of trimming. FIG. 15B is an explanatory diagram of a trimming position on the upper ruled line. FIG. 15C is an explanatory diagram of the trimming position at the lower ruled line. It is explanatory drawing of resolution conversion. FIG. 17A is an explanatory diagram of image data when the left ruled line is detected. FIG. 17B is an explanatory diagram of detection of the position of the left ruled line. FIG. 17C is an explanatory diagram of the measurement range of the density of the band-like pattern having a density of 30% in the first row region. It is the measurement value table which put together the measurement result of the density | concentration of five types of strip | belt-shaped patterns of cyan. It is a graph of the measured value of the strip | belt-shaped pattern of density 30%, density 40%, and density 50% of cyan. FIG. 20A is an explanatory diagram of the target command gradation value Sbt with respect to the command gradation value Sb in the row region i. FIG. 20B 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 a flowchart of the process performed under the user. FIG. 9 is a flowchart of print data generation processing. It is explanatory drawing of the density correction process of the nth row | line area | region of cyan. It is a figure for demonstrating the process which matches the position of a raster line at the time of printing an image, and when printing a correction pattern.

Explanation of symbols

1 printer (inkjet printer), 5 document, 20 transport unit,
21 paper feed roller, 22 transport motor, 23 transport roller, 24 platen,
25 discharge roller, 30 carriage unit, 31 carriage,
32 Carriage motor, 40 head units, 41 heads, 50 detector groups,
51 linear encoder, 52 rotary encoder, 52a code board,
52b detector, 53 paper detection sensor, 54 optical sensor, 60 controller,
61 interface unit, 62 CPU, 63 memory,
64 unit control circuit, 100 printing system, 110 computer,
120 display device, 130 input device, 140 recording / reproducing device,
150 scanner, 151 top cover, 152 platen glass,
153 Reading carriage, 154 guide member, 155 moving mechanism, 157 lamp,
158 Line sensor, 159 optical system

Claims (13)

(A) a transport unit including a transport roller for transporting a medium for printing an image in the transport direction;
(B) Based on print data for printing the image, ink is ejected while moving in a moving direction intersecting the transport direction, and a dot row is formed on the medium transported by the transport unit. A nozzle for,
(C) a portion of the transport roller that contacts the medium when forming the dot row in the most downstream row region in the transport direction, which constitutes the correction pattern;
When forming a dot row while performing correction based on the correction pattern in the most downstream row region in the transport direction, which constitutes a printed image based on print data for printing the image A controller for controlling the transport unit so that a portion of the transport roller in contact with the medium matches.
A printing apparatus having (d). The printing apparatus according to claim 1,
A detection unit for detecting a predetermined reference position on the peripheral surface of the transport roller;
The printing apparatus, wherein the controller controls the transport unit based on the reference position detected by the detection unit. The printing apparatus according to claim 2,
A medium supply unit for supplying the medium to the transport unit;
The controller positions the reference position of the transport roller at a predetermined rotation start position;
When forming the dot row in the most downstream row region in the transport direction, constituting the correction pattern;
In forming the dot row while performing correction based on the correction pattern in the most downstream row region in the transport direction that constitutes the image,
By matching the timing at which the conveyance roller starts to rotate from the rotation start position with the timing at which the medium starts to be supplied by the medium supply unit, the portion of the conveyance roller that contacts the medium is matched. Printing device to do. The printing apparatus according to claim 3.
When the medium is discharged, the conveying roller is stopped at the rotation start position. The printing apparatus according to any one of claims 2 to 4,
The printing apparatus, wherein the detection unit is a rotary encoder for detecting rotation of the transport roller. The printing apparatus according to any one of claims 1 to 5,
The controller corrects image data based on a result of reading the correction pattern so as to suppress density unevenness between row regions in which the dot rows are formed along the moving direction. apparatus. The printing apparatus according to any one of claims 1 to 6,
The image data indicates a gradation value for each unit area formed on the medium,
Obtaining correction information based on the result of reading the correction pattern printed based on the image data indicating a predetermined gradation value;
The printing apparatus, wherein the image data is corrected based on the correction information. The printing apparatus according to any one of claims 3 to 7,
The correction pattern is printed for each printing condition when printing the image,
The printing apparatus, wherein the rotation start position is set based on the printing condition. The printing apparatus according to claim 7 or 8,
The correction pattern is based on a gradation value indicating a predetermined density.
A printing apparatus, wherein a plurality of dot rows formed by ink ejected from the nozzle moved in the moving direction are printed side by side along the transport direction. (A) a transport unit including a transport roller for transporting a medium for printing an image in the transport direction;
(B) Based on print data for printing the image, ink is ejected while moving in a moving direction intersecting the transport direction, and a dot row is formed on the medium transported by the transport unit. A nozzle for,
(C) a portion of the transport roller that contacts the medium when forming the dot row in the most downstream row region in the transport direction, which constitutes the correction pattern;
When forming a dot row while performing correction based on the correction pattern in the most downstream row region in the transport direction, which constitutes a printed image based on print data for printing the image A controller for controlling the transport unit so that the part of the transport roller in contact with the medium coincides,
(D) having a detection unit for detecting a predetermined reference position on the peripheral surface of the transport roller;
The controller controls the transport unit based on the reference position detected by the detection unit,
(E) having a medium supply unit for supplying the medium to the transport unit;
The controller positions the reference position of the transport roller at a predetermined rotation start position;
When forming the dot row in the most downstream row region in the transport direction, constituting the correction pattern;
In forming the dot row while performing correction based on the correction pattern in the most downstream row region in the transport direction that constitutes the image,
By matching the timing at which the conveyance roller starts to rotate from the rotation start position with the timing at which the medium supply unit starts to supply the medium, the portions of the conveyance roller that contact the medium are matched,
(F) When the medium is discharged, the transport roller is stopped at the rotation start position,
(G) The detection unit is a rotary encoder for detecting rotation of the transport roller,
(H) The controller corrects the image data based on the result of reading the correction pattern in order to suppress density unevenness between the row regions where the dot rows along the moving direction are formed,
(I) The image data represents a gradation value for each unit area formed on the medium,
Obtaining correction information based on the result of reading the correction pattern printed based on the image data indicating a predetermined gradation value;
The image data is corrected based on the correction information,
(J) The correction pattern is printed for each printing condition when printing the image,
The rotation start position is set based on the printing conditions,
(K) The correction pattern is based on a gradation value indicating a predetermined density.
A printing apparatus, wherein a plurality of dot rows formed by ink ejected from the nozzle moved in the moving direction are printed side by side along the transport direction. A transport unit including a transport roller for transporting a medium for printing an image in the transport direction;
Nozzles for ejecting ink while moving in a moving direction crossing the transport direction based on print data for printing the image, and forming dot rows on the medium transported by the transport unit And a printing apparatus having
A portion of the transport roller that contacts the medium when forming the dot row in the most downstream row region in the transport direction, which constitutes a correction pattern;
When forming a dot row while performing correction based on the correction pattern in the most downstream row region in the transport direction, which constitutes a printed image based on print data for printing the image A computer program for realizing a function of controlling the transport unit so that a part of the transport roller in contact with the medium matches. (A) a computer, and
(B) a printing apparatus connected to the computer and having the following (a) (b) (c):
(A) a transport unit having a transport roller for transporting a medium for printing an image in the transport direction;
(B) Based on print data for printing the image, the ink is ejected while moving in a moving direction intersecting the transport direction, and a dot row is formed on the medium transported by the transport unit. Nozzle to do,
(C) The portion of the transport roller that contacts the medium when forming the dot row in the most downstream row region in the transport direction, which constitutes the correction pattern, and print data for printing the image Forming a dot row while performing correction based on the correction pattern in the most downstream row region in the transport direction, which constitutes an image printed based on A controller for controlling the conveying section so that the portion of the conveying roller coincides,
A printing system comprising (C). Based on the print data for printing the correction pattern, ink is ejected from the nozzles moved in the moving direction that intersects the medium conveying direction, and a dot row is formed in the most downstream row region in the carrying direction. A step of transporting a predetermined portion of a transport roller included in a transport unit for transporting the medium in contact with the medium;
Based on print data for printing an image, when the ink is ejected from the nozzles to form a dot row in a row region on the most downstream side in the carrying direction, the predetermined portion of the previous carrying roller is Conveying the medium so as to contact the medium;
A printing method characterized by comprising: