JP2006007615A - Printing method, printing pattern density reading method, printing apparatus, and printing pattern density reading apparatus - Google Patents

Abstract

It is an object of the present invention to realize a printing method and the like that can correct the density more appropriately.
A first printing step for printing a printing pattern with ink of a predetermined color, a reading step for reading the density of the printing pattern, and a change in density until the density of the printing pattern is stabilized after the reading of the density. A correction value generating step for generating a density correction value for the predetermined color based on the offset value corresponding to the minute and the reading value of the density, while correcting the density of the image for the predetermined color based on the correction value And a second printing step for printing the image on a medium.
[Selection] FIG.

Description

  The present invention relates to a printing method for suppressing uneven density in an image, a printing pattern density reading method, a printing apparatus, and a printing pattern density reading apparatus.

A color ink jet printer (hereinafter referred to as a printer) is known as a printing apparatus that forms an image by ejecting a plurality of colors of ink onto a sheet as a medium. Since such a printer prints an image by discharging ink from a plurality of nozzles as an ink discharge unit, the density is adjusted so that the image printed on the ink discharged from each nozzle has an appropriate density. It is necessary to correct. As this correction method, for example, a predetermined print pattern is printed for each nozzle, the density of the printed pattern is read by a predetermined reading device, and a density correction value is generated based on the read value to correct the density. A method is known (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 3-199052

  By the way, the density of the printed image may converge to a predetermined convergence value after a predetermined time immediately after printing and may be stabilized. For this reason, even if the density correction value is generated based on the density reading value read immediately after printing the print pattern and the density correction is executed using the correction value, the density correction is not performed properly. There is a possibility that a good image cannot be printed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a printing method, a printing pattern density reading method, a printing apparatus, and a printing pattern capable of more appropriately correcting the density. It is to realize a density reading apparatus.

  The main invention is a first printing step for printing a printing pattern with ink of a predetermined color, a reading step for reading the density of the printing pattern, and a change in density until the density of the printing pattern is stabilized after reading the density. A correction value generating step for generating a density correction value for the predetermined color based on the offset value corresponding to the minute and the reading value of the density, while correcting the density of the image for the predetermined color based on the correction value And a second printing step for printing the image on a medium.

  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.

This corresponds to a first printing step for printing a printing pattern with ink of a predetermined color, a reading step for reading the density of the printing pattern, and a change in density until the density of the printing pattern is stabilized after reading the density. A correction value generation step for generating a density correction value for the predetermined color based on the offset value and the read value of the density, and the image on the medium while correcting the image density for the predetermined color based on the correction value. And a second printing step for printing.
According to such a printing method, an offset value corresponding to a change in density from when the density is read to when the density of the print pattern is stabilized is used. Therefore, the density of the print pattern is reduced before the density is stabilized. Even when read, it is possible to generate an appropriate correction value corresponding to the density after stabilization from the read value. As a result, it is possible to perform appropriate density correction when printing an image on a medium.
Further, since it is not necessary to wait for the reading until the density becomes stable, the time required for a series of processing can be shortened.
Here, the fact that the density is stabilized means, for example, that the measured value converges to a predetermined convergence value when the printed pattern is measured with a predetermined density measuring device.

In this printing method, it is preferable that the correction value generation step generates the correction value of the density based on a value obtained by changing the read value by the offset value.
According to such a printing method, since the density correction value is generated based on a value obtained by changing the read value by the offset value, an appropriate correction value corresponding to the density after stabilization can be acquired.

In such a printing method, the changed value is preferably a value obtained by reducing the read value by the offset value.
According to such a printing method, it is possible to perform appropriate density correction when the ink density gradually decreases immediately after printing and converges to a predetermined density. Incidentally, the above-mentioned tendency that the density decreases with time is a tendency corresponding to most inks.

In such a printing method, it is preferable that the correction value is a value obtained by changing only the offset value from the temporary correction value of the density generated based on the read value.
According to such a printing method, the correction value is a value obtained by changing only the offset value from the temporary correction value of the density generated based on the read value. A correction value can be acquired.

In such a printing method, it is preferable that the image is composed of a plurality of different predetermined colors, and the print pattern is printed for each of the predetermined colors, and the offset value is prepared for each of the predetermined colors.
According to such a printing method, multicolor printing using a plurality of predetermined colors can be performed.

In such a printing method, among the plurality of predetermined colors, for the color whose magnitude of change in density from when the density is read until the density of the print pattern is stabilized is smaller than a predetermined threshold, the read value is used. It is desirable to generate a density correction value for the predetermined color based only on the above.
According to such a printing method, for the color whose density change is smaller than the threshold value, the correction value is generated without using the offset value, so that the throughput of the correction value generation step can be improved.

In this printing method, when printing the image by ejecting ink while moving a plurality of ink ejection portions arranged along a predetermined direction for each predetermined color in a moving direction intersecting the predetermined direction. In addition, it is desirable to correct the density of the image for each dot row region in order to suppress density unevenness between the dot row regions in the medium on which the dot row along the moving direction is formed in each ink ejection unit.
According to such a printing method, density unevenness between the dot row regions can be suppressed, and the image quality of the printed image can be improved. The density unevenness between the dot row regions is mainly caused by a change in the interval between the dot rows adjacent in the predetermined direction.

In such a printing method, the print pattern includes a dot row region corresponding to each dot row region of the image, density reading from the print pattern is performed for each dot row region, and the correction value is It is desirable to generate each dot row area.
According to such a printing method, since the correction value is generated for each dot row region, density unevenness between the dot row regions can be reliably suppressed.

In this printing method, the print pattern is printed based on the same density gradation value data over the entire dot row region, and the correction value generating step calculates an average value of the read values over the entire dot row region. It is desirable to calculate the correction value of each dot row region by dividing the deviation between the average value and the read value of each dot row region by the average value.
According to such a printing method, it is possible to effectively suppress density unevenness between the dot row regions.

A first printing step for printing a printing pattern with ink of a predetermined color; a reading step for reading the density of the printing pattern; and a change in density until the density of the printing pattern is stabilized after the reading of the density. A correction value generating step for generating a density correction value for the predetermined color based on the corresponding offset value and the read value of the density, and a medium while correcting the density of the image for the predetermined color based on the correction value. A second printing step for printing the image,
In the correction value generation step, the correction value of the density is generated based on a value obtained by changing the read value by the offset value,
The image is composed of a plurality of different predetermined colors, and the print pattern is printed for each predetermined color, and the offset value is prepared for each predetermined color,
When printing the image by ejecting ink while moving a plurality of ink ejection units arranged along a predetermined direction for each predetermined color in a movement direction intersecting the predetermined direction, each ink ejection unit In order to suppress density unevenness between the dot row regions in the medium in which the dot row along the moving direction is formed, the density of the image is corrected for each dot row region,
The print pattern includes a dot row area corresponding to each dot row area of the image, density reading from the print pattern is performed for each dot row region, and the correction value is set for each dot row region. A printing method characterized by being generated.
According to such a printing method, the effects of the present invention can be most effectively achieved because almost all the effects described above can be achieved.

A reading step for reading the density of a print pattern printed with ink of a predetermined color, and the read value based on an offset value corresponding to a change in density from when the density is read until the density of the print pattern becomes stable And a correction step for correcting the print pattern density reading method.
According to such a print pattern density reading method, an offset value corresponding to a change in density from when the density is read to when the density of the print pattern is stabilized is used. Even if the density of the pattern is read, the corresponding density reading can be obtained from the reading after the density is stabilized.
Further, since it is not necessary to wait for the reading until the density becomes stable, the time required for a series of processing can be shortened.

In such a printed pattern density reading method, it is desirable that the correction step corrects the read value to a value smaller by the offset value.
According to such a print pattern density reading method, the density of the print pattern is read before the density stabilizes with respect to the ink whose density gradually decreases immediately after printing and converges to a predetermined density. However, it is possible to acquire the read value of the corresponding density after the density is stabilized from the read value.

  Further, the printing apparatus includes a printing unit that prints a printing pattern with ink of a predetermined color in accordance with control of the control unit, and a reading unit that reads the density of the printing pattern, and the control unit reads the density. And an offset value corresponding to a change in density until the density of the print pattern becomes stable and a density correction value generated based on the density reading value, and an image is printed on the medium by the printing unit. In this case, it is possible to realize a printing apparatus in which the control unit corrects the density of the image for the predetermined color based on the correction value.

  Further, based on the reading unit that reads the density of the print pattern printed with the ink of the predetermined color, and the offset value corresponding to the change in density from when the density is read until the density of the print pattern is stabilized, It is also possible to realize a print pattern density reading device characterized by having a correction unit for correcting the reading value.

=== Configuration of Printing System 700 ===
Next, an embodiment of the printing system 700 will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram showing an external configuration of the printing system 700, and FIG. 2 is a block diagram showing a configuration of the printing system 700 shown in FIG. The printing system 700 includes an inkjet printer (hereinafter referred to as a printer) 1 as a printing device, a computer 702, a display device 704, an input device 708, a recording / reproducing device 710, and a color scanner (hereinafter referred to as a reading device). 10). The printer 1 is a printing apparatus that prints an image on a medium such as paper, cloth, or film. In the following description, a sheet that is a typical medium will be described as an example.

  The computer 702 includes an internal memory 802 such as a RAM and an external memory such as a hard disk drive unit 804. Various application programs 714, a printer driver 711 (see FIG. 8), and the like are installed in these memories. The computer 702 is communicably connected to the printer 1 and the scanner 10 and outputs print data corresponding to the image to the printer 1 or reads image data from the scanner 10 in order to cause the printer 1 to print an image. Execute the process. The input device 708 is, for example, a keyboard 708A or a mouse 708B, and is used for input of operations of the application program 714, settings of the printer driver 711, and the like. As the recording / reproducing device 710, for example, a flexible disk drive device 710A or a CD-ROM drive device 710B is used.

  The printer driver 711 implements a function for causing the display device 704 to display a screen for setting printing conditions and the like, and a program for realizing a function for converting image data output from the application program 714 into print data. It is. The printer driver 711 is recorded on a recording medium (computer-readable recording medium) such as a flexible disk or a CD-ROM. The printer driver 711 can also be downloaded to the computer 702 via the Internet. And this program is comprised from the code | cord | chord for implement | achieving various functions.

  The “printing apparatus” means the printer 1 in a narrow sense, but means a system of the printer 1 and the computer 702 in a broad sense.

=== Configuration of Scanner 10 ===
FIG. 3 is an explanatory diagram showing a schematic configuration of a scanner 10 as an example of a reading apparatus according to the present invention.

  The scanner 10 includes an original table glass 7 on which an original document 5 to be read including an adjustment correction pattern CP and the like is placed, and a reading surface of the original document 5 placed on the original table glass 7 on the original table glass 7 side. A document table cover 6 for pressing, a reading carriage 16 that faces the document table glass 7 and moves along the document 5 while maintaining a certain distance from the document table 5, and a driving means for moving the reading carriage 16 18, a regulation guide 12 for moving the reading carriage 16 in a stable state, a display unit 36 for displaying information to be transmitted to the operator, an operation unit 34 for operating the scanner 10, and a scanner And a control unit 38 for driving and controlling each of the ten elements.

  The reading carriage 16 is passed through the lens by the light source unit 8 as a light source for irradiating the original 5 with light of three colors through the original table glass 7, the rod lens array 14 for condensing the reflected light from the original 5, and the lens. A contact image sensor unit that is integrated with a linear CCD sensor 15 as an image sensor that receives reflected light as light amount information and outputs the light amount information as a signal, and a guide that engages with the regulation guide 12 A receiving portion 29 is provided. In this embodiment, a CIS (Contact Image Sensor) unit 11 is used as the contact image sensor unit.

  The restriction guide 12 is provided along a direction in which the reading carriage 16 moves (hereinafter referred to as a moving direction) and is formed of a stainless steel cylindrical material. The restriction guide 12 is provided on the reading carriage 16 and passes through two guide receiving portions 29 made of thrust bearings. By increasing the distance in the moving direction of the two guide receiving portions 29 provided on the reading carriage 16, the reading carriage 16 can be moved more stably.

  The driving means 18 includes an annular timing belt 181 fixed to the reading carriage 16, two pulleys 182 and 184 around which the timing belt 181 is bridged, and a pulse motor 183 to which one pulley 182 is attached. ing. The two pulleys 182 and 184 are arranged in the moving direction of the reading carriage 16 at a distance wider than the moving distance, one pulley 182 is fixed to the shaft of the pulse motor 183, and the other pulley 184 is attached to the timing belt 181. Tension is applied. The pulse motor 183 is driven by the motor driver of the control unit 38, and the read image can be enlarged and reduced in the moving direction by the moving speed of the reading carriage 16 changed according to the rotation speed of the pulse motor 183. Become.

  When reading the document, the scanner 10 emits light from the light source unit 8 to irradiate the document 5, and the reflected light is condensed on the linear CCD sensor 15 by the rod lens array 14 while reading the carriage 16. Is moved along the document 5. At this time, the scanner 10 takes in a voltage value as light quantity information indicating the amount of light received by the linear CCD sensor 15 at a predetermined period, thereby obtaining an image corresponding to the distance the reading carriage 16 has moved during one period. Read as data corresponding to the line. At this time, since the amount of light received by the linear CCD sensor 15 differs depending on the density of the original, it is possible to detect the density of the original from the light quantity information.

=== Configuration of Printer 1 ===
4 is a block diagram of the overall configuration of the printer 1 of the present embodiment, FIG. 5 is a schematic diagram of the overall configuration of the printer 1 of the present embodiment, and FIG. 6 is a side sectional view of the overall configuration of the printer 1 of the present embodiment. FIGS. 7A and 7B are explanatory diagrams showing the arrangement of nozzles on the lower surface of the head 41. Hereinafter, the basic configuration of the printer 1 of the present embodiment will be described with reference to these drawings.

  The printer 1 of this embodiment includes a transport unit 20, a print carriage unit 30, a head unit 40, a sensor 50, and a controller 60. The printer 1 that has received the print data from the computer 702 as an external device controls each unit (conveyance unit 20, print carriage unit 30, head unit 40) by the controller 60. The controller 60 controls each unit based on the print data received from the computer 702 and prints an image on the paper P. The situation in the printer 1 is monitored by a sensor 50, and the sensor 50 outputs a detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the sensor 50.

  The transport unit 20 functions as a transport mechanism that transports the paper P, transports the paper P to a printable position, and transports the paper P by a predetermined transport amount in a predetermined direction (hereinafter referred to as a transport direction) during printing. It is for making it happen.

  The transport unit 20 includes a paper feed roller 21, a transport motor 22 (also referred to as a PF motor), a transport roller 23, a platen 24, and a paper discharge roller 25. The paper feed roller 21 is a roller for feeding the paper P inserted into the paper insertion slot into the printer 1. 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 surface of the paper, the paper P can be transported by the length of the circumferential portion and the leading end of the paper P can reach the transporting roller 23. Is possible. The transport motor 22 is a motor for transporting paper in the transport direction, and is constituted by, for example, a DC motor. The transport roller 23 is a roller that transports the paper P fed by the paper feed roller 21 to a printable area, and is driven by the transport motor 22. The platen 24 supports the paper P being printed from the back side of the paper P. The paper discharge roller 25 is a roller for transporting the paper P in the transport direction on the downstream side of the platen 24 in the transport direction. The paper discharge roller 25 rotates in synchronization with the transport roller 23.

  The print carriage unit 30 includes a print carriage 31 and a print carriage motor 32 (hereinafter also referred to as a CR motor). The print carriage motor 32 is a motor for reciprocating the print carriage 31 in a predetermined direction (hereinafter referred to as a print carriage movement direction), and is constituted by a DC motor, for example. The print carriage 31 detachably holds an ink cartridge 90 that stores ink. The print carriage 31 is attached with a head 41 that ejects ink from nozzles serving as ejection units. Therefore, as the print carriage 31 reciprocates, the head 41 and the nozzles also reciprocate in the print carriage movement direction. Therefore, this print carriage movement direction corresponds to the “movement direction” according to the claims.

  The head unit 40 is for ejecting ink onto the paper P. The head unit 40 has a head 41. The head 41 has a plurality of nozzles, and ejects ink intermittently from each nozzle. Then, the ink is intermittently ejected from the nozzles while the head 41 moves in the print carriage movement direction, so that a dot row along the print carriage movement direction is formed on the paper P. Further, an area for forming a dot row along the print carriage movement direction can be virtually determined on a sheet as a pixel row along the print carriage movement direction. It is expressed as “dot line area”. Here, the pixel is a square-shaped grid virtually defined on the paper in order to define a position where dots are formed on the paper by ejecting ink from a nozzle as an ink ejection unit. The arrangement of the nozzles, the configuration of the head 41, the driving circuit for driving the head 41, and the driving method of the head 41 will be described later.

  The sensor 50 includes a linear encoder 51, a rotary encoder 52, a paper detection sensor 53, a paper width sensor 54, and the like. The linear encoder 51 is for detecting the position in the print carriage movement direction, and is attached to the print carriage 31 and formed in the slit plate. A photo interrupter for detecting the slit is provided. The rotary encoder 52 is for detecting the amount of rotation of the transport roller 23, and is a disc-shaped slit plate that rotates as the transport roller 23 rotates, and a photo interrupter that detects a slit formed in the slit plate. Have

  The paper detection sensor 53 is for detecting the leading end position of the paper P to be printed. The paper detection sensor 53 is provided at a position where the front end position of the paper P can be detected while the paper feed roller 21 is transporting the paper P toward the transport roller 23. The paper detection sensor 53 is a mechanical sensor that detects the leading edge of the paper P by a mechanical mechanism. More specifically, the paper detection sensor 53 has a lever that can rotate in the paper transport direction, and this lever is disposed so as to protrude into the transport path of the paper P. As the paper P is transported, the front end of the paper comes into contact with the lever, and the lever is rotated. Therefore, the paper detection sensor 53 detects the position of the leading edge of the paper P and the presence or absence of the paper P by detecting the movement of the lever by a photo interrupter or the like.

  The paper width sensor 54 is attached to the print carriage 31. In the present embodiment, as shown in FIG. 7, the position in the transport direction is attached at substantially the same position as the nozzle on the most upstream side. The paper width sensor 54 is a reflection type optical sensor that receives the reflected light of the light irradiated on the paper P from the light emitting unit at the light receiving unit, and detects the presence or absence of the paper P based on the received light intensity at the light receiving unit. To do. The paper width sensor 54 detects the position of the edge of the paper P while being moved by the print carriage 31 and detects the width of the paper P. The paper width sensor 54 can also detect the leading edge of the paper P depending on the situation.

  The controller 60 is a control unit for controlling the printer 1. The controller 60 includes an interface unit (I / F) 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 702 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 has storage means such as a RAM, an EEPROM, and a ROM. The CPU 62 controls each unit 20, 30, 40 via the unit control circuit 64 in accordance with a program stored in the memory 63. In this embodiment, a correction value table 63a according to the present invention is stored in a partial area of the memory 63, which will be described later.

<Regarding nozzle arrangement and head 41 configuration>
As shown in FIG. 7, on the lower surface of the head 41. A black ink nozzle row N _K, a cyan ink nozzle row N _C, a magenta ink nozzle row N _M, and yellow ink nozzle row N _Y, is formed Yes. That is, the printer 1 has four colors: black (K) ink, cyan (C) ink, and magenta (M) ink as dark-colored ink with high density, and yellow (Y) ink as light-colored ink with low density. Can be ejected. Each nozzle row includes n nozzles (for example, n = 180) for ejecting ink of each color. The plurality of nozzles in each nozzle row are aligned at a predetermined interval (nozzle pitch: k · D) along a predetermined direction orthogonal to the moving direction of the print carriage 31, that is, the conveyance direction of the paper P. Here, D is the minimum dot pitch in the transport direction, that is, the interval at the highest resolution of dots formed on the paper P. 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. In the illustrated example, the nozzles in each nozzle row are assigned a smaller number (# 1 to #n) as the nozzles on the downstream side. That is, the nozzle # 1 is located downstream of the nozzle #n in the transport direction. If such a nozzle array is provided in the head 41, the range in which dots are formed by a single dot forming operation is widened, and the printing time can be shortened. Further, since these nozzle rows are provided for each color of ink, multi-color printing can be performed by appropriately discharging ink from these nozzle rows.

  Each nozzle has an ink flow path communicating with an ink cartridge 90 containing ink, and a pressure chamber (not shown) is provided in the middle of the ink flow path. Each pressure chamber is configured such that its volume contracts and expands by, for example, a piezo element (not shown) as a drive element provided to eject ink droplets from each nozzle.

<About driving the head 41>
FIG. 8 is an explanatory diagram of a drive circuit for the head 41. This drive circuit is provided in the unit control circuit 64 described above. As illustrated, the drive circuit includes an original drive signal generation unit 644A and a drive signal shaping unit 644B. In this embodiment, this drive circuit is provided for each nozzle row, that is, for each nozzle row for each color of black (K), cyan (C), magenta (M), and yellow (Y). The piezo elements are individually driven. In the figure, the number in parentheses at the end of each signal name indicates the number of the nozzle to which the signal is supplied.

  The above-described piezo element is deformed each time the driving pulses W1 and W2 (see FIG. 9) are supplied to cause pressure fluctuations in the ink in the pressure chamber. That is, when a voltage of a predetermined time width is applied between the electrodes provided at both ends of the piezoelectric element, the piezoelectric element is deformed according to the voltage application time, and an elastic film (side wall) that partitions a part of the pressure chamber is formed. Deform. The volume of the pressure chamber changes according to the deformation of the piezo element, and the pressure fluctuation occurs in the ink in the pressure chamber due to the volume change of the pressure chamber. Ink drops are ejected from the corresponding nozzles # 1 to #n due to pressure fluctuations generated in the ink.

The original drive signal generator 644A generates an original drive signal ODRV that is used in common by the nozzles # 1 to #n.
The drive signal shaping unit 644B receives the print signal PRT (i) together with the original drive signal ODRV from the original signal generation unit. The print signal PRT (i) is a signal whose level changes based on the above-described 2-bit print data. The drive signal shaping unit 644B shapes the original drive signal ODRV according to the level of the print signal PRT (i) and outputs it as the drive signal DRV (i) to the piezoelectric elements of the nozzles # 1 to #n. The piezo elements of the nozzles # 1 to #n are driven based on the drive signal DRV from the drive signal shaping unit 644B.

<About head drive signal>
FIG. 9 is a timing chart illustrating each signal. That is, FIG. 3 shows a timing chart of each signal of the original drive signal ODRV, the print signal PRT (i), and the drive signal DRV (i).

  The original drive signal ODRV is a signal used in common for the nozzles # 1 to #n, and is output from the original drive signal generation unit 644A to the drive signal shaping unit 644B. The original drive signal ODRV of the present embodiment is a signal between the first pulse W1 and the second pulse W2 within a time during which the print carriage 31 moves a distance corresponding to one pixel corresponding to the print resolution (hereinafter referred to as one pixel section). It has two pulses. The first pulse W1 is a drive pulse for ejecting a small-sized ink droplet (hereinafter referred to as a small ink droplet) from the nozzle. The second pulse W2 is a drive pulse for discharging a medium size ink droplet (hereinafter referred to as a medium ink droplet) from the nozzle. That is, by supplying the first pulse W1 to the piezo element, a small ink droplet is ejected from the nozzle. When the small ink droplets land on the paper P, small sized dots (small dots) are formed. Similarly, by supplying the second pulse W2 to the piezo element, a medium ink droplet is ejected from the nozzle. When the medium ink droplets land on the paper P, medium-sized dots (medium dots) are formed.

  The print signal PRT (i) is a signal corresponding to each pixel data assigned to each pixel in the print data transferred from a computer or the like. That is, the print signal PRT (i) is a signal corresponding to the pixel data included in the print data. The print signal PRT (i) of this embodiment is a signal having 2-bit information for one pixel. Note that the drive signal shaping unit 644B shapes the original drive signal ODRV according to the signal level of the print signal PRT (i) and outputs the drive signal DRV (i).

  This drive signal DRV is a signal obtained by blocking the original drive signal ODRV in accordance with the level of the print signal PRT. That is, when the print data is “1”, the print signal PRT is at a high level, and the drive signal shaping unit 644B passes the drive pulse corresponding to the original drive signal ODRV as it is to obtain the drive signal DRV (i). On the other hand, when the print data is “0”, the print signal PRT becomes the low level, and the drive signal shaping unit 644B blocks the drive pulse corresponding to the original drive signal ODRV. Then, the drive signal DRV (i) from the drive signal shaping unit 644B is individually supplied to the corresponding piezoelectric element. Further, the piezo element is driven according to the supplied drive signal DRV (i).

  When the print signal PRT (i) corresponds to the 2-bit data “10”, only the first pulse W1 is output in the first half of one pixel section. As a result, medium ink droplets are ejected from the nozzles, and medium dots are formed on the paper P. When the print signal PRT (i) corresponds to the 2-bit data “01”, only the second pulse W2 is output in the second half of one pixel interval. Thereby, a small ink droplet is ejected from the nozzle, and a small dot is formed on the paper P. When the print signal PRT (i) corresponds to the 2-bit data “11”, the first pulse W1 and the second pulse W2 are output in one pixel section. As a result, medium ink droplets and small ink droplets are continuously ejected from the nozzles, and large-sized dots (large dots) are formed on the paper P. That is, the printer 1 can form dots of a plurality of types (here, three types). Further, when the print signal PRT (i) corresponds to the 2-bit data “00”, neither the first pulse W1 nor the second pulse W2 is output in one pixel section. As a result, no ink droplet of any size is ejected from the nozzle, and no dot is formed on the paper P.

  As described above, the drive signal DRV (i) in one pixel section is shaped to have four different waveforms according to four different values of the print signal PRT (i).

=== Printer Driver 711 ===
FIG. 10 is a schematic explanatory diagram of basic processing performed by the printer driver 711. In addition, about the component already demonstrated, the same code | symbol is attached | subjected and description is abbreviate | omitted.

In the computer 702, computer programs such as a video driver 712, an application program 714, and a printer driver 711 are operating under an operating system installed in the computer 702.
The video driver 712 has a function of displaying a predetermined screen on the display device 704 in accordance with a display command from the application program 714 or the printer driver 711.

  The application program 714 has a function of performing image editing, for example, and creates data (image data) related to an image. The user can give an instruction to print an image edited by the application program 714 via the user interface of the application program 714. When the application program 714 receives a print command, the application program 714 outputs image data to the printer driver 711.

  The printer driver 711 receives image data from the application program 714, converts the received image data into printable print data, and outputs the converted print data to the printer 1. The image data has pixel data as data corresponding to each pixel of the image to be printed. Each pixel data is expressed by a gradation value for each color such as RGB or CMYK, and the gradation value is converted according to each processing stage to be described later. In the stage, the print data (data such as dot color and size) corresponding to the dots formed on the paper is converted.

  The print data is data in a format that can be interpreted by the printer 1 and includes the pixel data and various command data. The command data is data for instructing the printer 1 to execute a specific operation, for example, data indicating the carry amount.

  The printer driver 711 performs resolution conversion processing, color conversion processing, halftone processing, rasterization processing, and the like in order to convert image data output from the application program 714 into print data. Hereinafter, various processes performed by the printer driver 711 will be described.

In the resolution conversion process, the resolution when printing the image data (text data, image data, etc.) output from the application program 714 on the paper P (the interval between dots when printing, also called the print resolution). It is processing to convert to. For example, when the print resolution is specified as 720 × 720 dpi, the image data received from the application program 714 is converted into image data having a resolution of 720 × 720 dpi.
In this resolution conversion process, image data is also adjusted in size so as to correspond to the size of a print area to be printed (referred to as an area where ink is actually ejected).

  Note that each pixel data in the image data output from the application program 714 is data indicating gradation values in multiple levels (for example, 256 levels) represented by the RGB color space. Hereinafter, pixel data indicating RGB gradation values is referred to as RGB pixel data, and image data composed of RGB pixel data is referred to as RGB image data.

  The color conversion process is a process of converting each RGB pixel data of the RGB image data into data indicating gradation values of multiple levels (for example, 256 levels) represented by a CMYK color space. Here, the notation CMYK means C is cyan, M is magenta, Y is yellow, and K is black. Hereinafter, pixel data indicating CMYK gradation values is referred to as CMYK pixel data, and image data composed of CMYK pixel data is referred to as CMYK image data. The color conversion processing is performed by the printer driver 711 referring to a table (color conversion lookup table LUT) in which RGB gradation values and CMYK gradation values are associated with each other.

  The halftone process is a process of converting CMYK pixel data having multi-stage gradation values into CMYK pixel data having small-stage gradation values that can be expressed by the printer 1. For example, CMYK pixel data indicating 256 gradation values is converted into 2-bit CMYK pixel data indicating 4 gradation values by halftone processing. This 2-bit CMYK pixel data includes, for example, “no dot formation” (binary value “00”), “small dot formation” (also “01”), “medium dot formation” ( Similarly, “10”) and “large dot formation” (also “11”).

  In such a halftone process, for example, a so-called dither method, γ correction method, error diffusion method, or the like is used to create 2-bit (4-gradation) CMKY pixel data that can be formed by the printer 1 by dispersing dots. To do. In the present embodiment, in the halftone process, density correction described later, that is, correction performed for each dot row region to suppress density unevenness between the dot row regions is also executed.

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

=== About printing operation ===
FIG. 11 is a flowchart of the operation during printing. Each operation described below is executed by the controller 60 controlling each unit in accordance with a program stored in the memory 63. This program has code for executing each operation.

  Print command reception (S001): The controller 60 receives a print command from the computer 702 via the interface unit 61. This print command is included in the header of print data transmitted from the computer 702. Then, the controller 60 analyzes the contents of various commands included in the received print data, and performs the following paper feed operation, transport operation, dot formation operation, and the like using each unit.

  Paper feeding operation (S002): The controller 60 performs a paper feeding operation. The paper feeding operation is a process of moving the paper P to be printed and positioning it at a print start position (so-called cue position). That is, the controller 60 rotates the paper feed roller 21 to send the paper P to be printed to the transport roller 23. Subsequently, the controller 60 rotates the transport roller 23 to position the paper P sent from the paper feed roller 21 at the print start position. When the paper P is positioned at the printing start position, at least some of the nozzles of the head 41 are opposed to the paper P.

  Dot Formation Operation (S003): The controller 60 performs a dot formation operation. The dot forming operation is an operation of forming dots on the paper P by intermittently ejecting ink from the head 41 moving in the print carriage movement direction. At this time, the controller 60 drives the print carriage motor 32 to move the print carriage 31 in the print carriage movement direction. Further, the controller 60 ejects ink from the head 41 based on the print data while the print carriage 31 is moving. When the ink discharged from the head 41 lands on the paper P, dots are formed on the paper P as described above. At this time, if ink is ejected from the nozzles while moving the print carriage 31, a dot row along the moving direction is formed on the paper P.

  Transport Operation (S004): The controller 60 performs a transport operation. The transport operation is a process of moving the paper P relative to the head 41 along the transport direction. The controller 60 drives the transport motor 22 and rotates the transport roller 23 to transport the paper P in the transport direction. By this carrying operation, the head 41 can form dots at positions different from the positions of the dots formed by the dot forming operation described above.

  Paper discharge determination (S005): The controller 60 determines whether or not to discharge the paper P being printed. At this time, if data for printing on the paper P being printed remains, the paper is not discharged. Then, the controller 60 alternately repeats the dot formation operation and the transport operation until there is no more data to be printed, and gradually prints an image composed of dots on the paper P. If there is no more data to print on the paper P being printed, the controller 60 discharges the paper P. That is, the controller 60 rotates the paper discharge roller 25 to discharge the printed paper P to the outside. Note that whether or not to discharge paper may be determined based on a paper discharge command included in the print data.

  Print end determination (S006): The controller 60 determines whether or not to continue printing. When printing on the next sheet P, a new sheet is fed by the sheet feeding operation (S002), printing is continued, and printing is continued. If printing is not performed on the next paper P, the printing operation is terminated.

=== Regarding Cause of Density Unevenness in Image and Method for Suppressing It ===
The density unevenness that occurs in an image printed in multicolor using CMYK ink is basically caused by the density unevenness that occurs in each ink color. For this reason, usually, a method of suppressing density unevenness in an image printed in multiple colors by suppressing density unevenness for each ink color is employed.

  Therefore, here, first, the cause of density unevenness occurring in an image printed in a single color will be described, and then a method for suppressing density unevenness in multicolor printing will be described. Incidentally, the cause of density unevenness described below applies to any of the ink colors of cyan (C), magenta (M), yellow (Y), and black (K). If even one color has this tendency, there is a risk that uneven density appears in an image of multicolor printing.

  FIG. 12 is an explanatory diagram of density unevenness that occurs in the transport direction of the paper P in a single-color printed image. The density unevenness in the conveyance direction illustrated in the figure is seen as stripes parallel to the print carriage movement direction (also referred to as horizontal stripes for convenience). Such horizontal stripe-shaped density unevenness occurs, for example, due to variations in the ink discharge amount for each nozzle, but can also occur due to variations in the processing accuracy of the nozzles. That is, if the flight direction of the ink ejected by the nozzle varies due to variations in the processing accuracy of the nozzle, the dot formation position by the ink that has landed on the paper P may shift in the transport direction with respect to the target formation position. In this case, the formation position of the dot row r constituted by these dots is also shifted from the target formation position in the transport direction.

  Then, the interval between adjacent dot rows r in the transport direction becomes periodically vacant or clogged, and when viewed macroscopically, it appears as horizontal stripe-shaped density unevenness. More specifically, the dots formed by forming more dots or a part of the dots that should be originally formed in the dot row region by relatively widening or narrowing the interval between adjacent dot rows r. The row area looks macroscopically dark, and when a dot that should originally be formed in the dot row area or a part of it is formed in an adjacent dot row area, the dot row area looks macroscopically thin. It is.

  For such a cause of occurrence, density unevenness in multicolor printing can be suppressed by the following method. First, the correction pattern CP as a print pattern is printed for each ink color, and the tendency of the density for each dot row area for each ink color, that is, which dot row region appears darker and which dot row region appears lighter. To grasp the tendency. Then, based on this tendency, a correction value of density is obtained in advance for each dot row region so that the difference in density between them becomes small. Needless to say, these correction values are obtained for each ink color. When the image is actually printed, density correction is performed for each ink color and for each dot row region using the correction value. Incidentally, the actual printing referred to here refers to printing of an image such as a natural image performed by the user, not printing of the correction pattern CP.

  Hereinafter, an image printing method based on this suppression method will be described in detail. For convenience of explanation, numbers (referred to as dot row region numbers) are assigned in order from the downstream to the upstream in the transport direction for each dot row region. For example, the dot row area at the most downstream (uppermost end) of the paper P is the first dot row area.

=== Printing Method of Image According to Reference Example with Density Density Control ===
FIG. 13 is a flowchart illustrating an overall processing procedure of the printing method according to the reference example. First, the printer 1 is assembled on the production line (S110), and then the density correction value is set in the printer 1 by the operator on the inspection line (S120), and then the printer 1 is shipped (S120). S130). Then, a main print of the image is performed by the user who purchased the printer 1, and at the time of the real print, the printer 1 performs the density correction for each dot row region based on the correction value, and the paper P The image is printed on (S140).
Note that the image printing method according to the reference example is realized by the “step of setting a density correction value (S120)” and the “step of printing an image while performing density correction (S140)” in the above steps. Is done. Therefore, the contents of step S120 and step S140 will be described below.

<Step S120: Step of Setting Density Correction Value>
FIG. 14 is a flowchart showing the procedure of step S120 in FIG. FIG. 15 is a block diagram showing the apparatus configuration of the inspection line.
As shown in FIG. 14, this step S120 includes a step of printing the correction pattern CP (S121), a step of reading the density of the correction pattern CP for each dot row region, and recording a read value (S122). And a step (S123) of setting a density correction value for each dot row region based on the recorded value. These steps are executed by the process correction program 716 installed in the computer 702A of the inspection line shown in FIG.

(1) Step S121: Printing Correction Pattern CP First, as shown in FIG. 15, the operator of the inspection line connects the printer 1 for suppressing density unevenness to the computer 702A of the inspection line so as to be communicable. . Next, the process correction program 716 is activated, and the printer is configured to print the correction pattern CP on the paper P based on the print data 802C of the correction pattern CP stored in the memory 802A of the computer 702A. 1 is instructed. The printer 1 prints the correction pattern CP on the paper P based on the print data 802C.

  FIG. 16 shows a correction pattern CP, which is printed for each CMYK ink color. In the illustrated example, the correction patterns CPc, CPm, CPy for each ink color are arranged in the order of cyan (C), magenta (M), yellow (Y), and black (K) along the print carriage movement direction. , CPk are juxtaposed on one sheet of paper P. For each ink color, the correction pattern CP is printed in a strip shape that is long in the transport direction, and the print range in the transport direction covers the entire area of the paper P.

  The print data 802C of each correction pattern CP is generated by performing the above-described halftone processing and rasterizing processing on CMYK image data configured by directly specifying the gradation values of the CMYK ink colors. It is a thing. The gradation value of the pixel data of the CMYK image data is set to the same value over the entire pixel data for each correction pattern CP formed for each ink color. When printing is performed with an ideal head 41 having no variation in processing accuracy, the apparent density of each correction pattern CP is uniform over the entire area.

  Further, the correction pattern CP is printed using the same dot formation operation and transport operation as in the actual printing. Therefore, on the correction pattern CP, the dot row area having the same dot row area number as that at the time of main printing is printed by the same nozzle as at the time of main printing, so that there is a tendency of density unevenness at the time of main printing. This is reproduced on the correction pattern CP. That is, the tendency of which dot row area of which dot row area number is lighter and which is darker can be grasped from this correction pattern CP. This tendency is grasped by the following step S122.

(2) Step S122: Read the density of the correction pattern CP for each dot row region and record the read value. Next, the process correction program 716 gives the operator the density of each correction pattern CP to the scanner of the inspection line. Prompt to read by 10. When the operator places the paper P on which the correction pattern CP is printed on the original platen glass 7 of the scanner 10 and activates the scanner 10, the scanner 10 moves the reading carriage 16 to For each dot row area, the average density of a predetermined number of pixels in the direction along the dot row area is read.

  FIG. 17 shows an example of the reading value of the density of the correction pattern CP for black (K) ink. The horizontal axis in FIG. 17 indicates the dot row area number, and the vertical axis indicates the density reading. Since all the dot row areas constituting the correction pattern CP are printed with the same tone value, the reading values should theoretically be the same regardless of the dot row area. . However, the actual read value varies up and down for each dot row region, and this is density unevenness due to the above-described variation in the processing accuracy of the nozzles. That is, the density of the dot row area with a narrow interval between adjacent dot rows is measured large, while the density of the dot row region with a wide interval is measured small.

  These read values are recorded in the recording table 802B prepared in the memory 802A of the computer 702A while being associated with each dot row area number by the process correction program 716. FIG. 18 shows a conceptual diagram of the recording table 802B. The recording table 802B is prepared for each ink color, and each recording table 802B has a record for recording a read value. Each record is assigned a record number in order, and a read value of the same dot row area number as the record number is recorded. For example, the reading value of the first dot row area is recorded in the first record.

  Incidentally, it is preferable that the read value output from the scanner 10 is a gray scale (data having only color values without color information) indicated by 256 gradation values. This is because if the read value has color information, a process of expressing the read value only with the gradation value of the target ink color must be performed, and the process becomes complicated.

(3) Step S123: A density correction value is set for each dot row area based on the recorded value. Next, the process correction program 716 sets the density based on the read value recorded in each record of the recording table 802B. The correction value is calculated, and the correction value is transmitted to the printer 1 as shown in FIG. Then, the controller 60 of the printer 1 sets the correction value in the correction value table 63 a in its own memory 63.

  FIG. 19 shows a conceptual diagram of the correction value table 63a. Similarly to the recording table 802B, the correction value table 63a is prepared for each ink color, and each correction value table 63a has a record for recording the correction value. Each record is assigned a record number, and the correction value calculated based on the read value is recorded in a record having the same record number as the recording table 802B. For example, the correction value calculated based on the read value of the first record of the recording table 802B is recorded in the first record of the correction value table 63a.

The correction value of the reference example is calculated in the following manner in the form of a correction ratio indicating a correction ratio with respect to the density gradation value. First, an arithmetic average M of all read values is obtained for each ink color, and the obtained arithmetic average M is set as a target value M for the ink color. Then, for each record, a deviation ΔC (= C−M) between the read value C and the target value M is calculated, and a value obtained by dividing the deviation ΔC by the target value M is set as a correction value H of the record. . Incidentally, if the correction value H is expressed by an equation, the following equation 1 is obtained.
Correction value H = ΔC / M
= (C−M) / M (Formula 1)

<Step S140: Step of Full-Printing Image While Correcting Density>
When the correction value is set in the correction value table 63a, the printer 1 is connected to the user's computer 702 and set to the state of the printing system 700 shown in FIG. Then, during the actual printing by the user, it is possible to execute printing while suppressing density unevenness by correcting the density of the image for each dot row region using the correction value table 63a.

  The density correction for each dot row area is performed based on the correction value when the RGB image data supplied from the application program 714 shown in FIG. 10 is converted into print data by the printer driver 711. This is achieved by correcting the pixel data in units corresponding to.

  For example, as described above, RGB image data is converted into CMYK image data by the printer driver 711 through resolution conversion processing and color conversion processing. This CMYK image data is composed of image data represented by 256 gradation values for each ink color of C, M, Y, K, that is, C image data relating to cyan (C), magenta (M ) M image data, yellow (Y) Y image data, and black (K) K image data.

  FIG. 20 is a conceptual diagram showing a pixel data arrangement of these image data, and shows K image data. In addition, each square cell in the figure indicates a pixel, and each pixel has pixel data. In this arrangement, pixel data arranged in a row in the horizontal direction (hereinafter, this row is referred to as a pixel data row) corresponds to the data in the dot row area for the one row. That is, the first pixel data row of these pixel data rows is data relating to the gradation value of the first dot column region, and the second pixel data row is the second dot column. This is data relating to the gradation value of the region, and thereafter, each pixel data row sequentially corresponds to each dot column region.

  Therefore, the pixels constituting each pixel data row are sequentially associated with the respective pixel data rows from the first row to the last row, with the respective correction values from the first record to the last record of the correction value table 63a. If correction is performed by shifting the gradation value of the data by the correction value H, K image data that suppresses density unevenness is generated. Note that image data for suppressing density unevenness is generated in the same manner for other C, M, and Y image data.

  The CMYK image data generated in this way is sent to the printer 1 after being converted into print data through a halftone process and a rasterizing process. After that, the printer 1 prints an image based on the print data, and the image is a good image in which density unevenness is suppressed.

  In the above-described reference example, the density correction based on the correction value is performed on the CMYK image data immediately before the halftone process. However, the present invention is not limited to this, and the density correction is performed in the halftone process. It goes without saying that it is also good.

=== Regarding Problems of “Image Printing Method with Density Density Suppression” According to Reference Example ===
In order to properly perform the density correction described above, it is necessary to accurately obtain the correction value. However, depending on the timing of reading the density of the correction pattern CP, the correction value may not be an appropriate value. Specifically, the density of the printed image is generally the highest immediately after printing, and decreases as the ink diffuses and penetrates the paper P, and converges to a predetermined convergence value and stabilizes (see FIG. 23). Therefore, even if the density correction value is generated based on the read value read from the correction pattern CP immediately after printing, the correction value is based on the density before stabilization, and is based on the read value after stabilization. May be different from the correction value generated. In this case, even if density correction is executed using these correction values as they are, there is a possibility that appropriate density correction cannot be performed and a good image with suppressed density unevenness cannot be printed.

  Therefore, the inspection line process correction program 716 according to the present invention sets the offset value corresponding to the change in density and the read value of the density from when the density is read until the density of the correction pattern CP is stabilized. Based on this, the correction value is generated.

  In this way, even when the density of the correction pattern CP is read immediately after printing, for example, immediately after the density is stabilized, an appropriate correction value corresponding to the density after stabilization is obtained from these read values. Therefore, it is possible to perform appropriate density correction when printing an image. Further, since it is not necessary to wait for the reading until the density is stabilized, there is an effect that the correction value setting operation time can be shortened.

  In the following, the “printing method of an image in which density unevenness is suppressed” using this offset value will be described in detail. The main difference from the above-described reference example is that “the density correction value is set in step S120”. Other steps are the same in the “step to be set” portion. Therefore, the difference in step S120 will be mainly described, and other descriptions will be limited to the extent necessary for understanding the present invention.

=== “Step S120 for Setting Density Correction Value” according to the first embodiment of the present invention ===
FIG. 21 shows a flowchart of step S120 according to the first embodiment. First, in the same manner as in the reference example, the correction pattern CP is printed in step S121, and then in step S122a, the density is read from the correction pattern CP for each dot row region.

  This reading is quickly performed immediately after printing the correction pattern CP from the viewpoint of shortening the working time. However, as described above, immediately after the printing, the density of the correction pattern CP has not yet converged to a predetermined convergence value. Therefore, in step S122a according to the first embodiment, a process of subtracting the offset value α from the read value immediately after printing (referred to as a subtraction process) is added, and the value after the subtraction process is the recording table 802B. To be recorded. Here, the offset value α corresponds to a deviation between the density immediately after printing at the time of reading and the convergence value. Therefore, the value after the subtraction process substantially matches the convergence value.

  This offset value α is set for each ink color in an offset value table (see FIG. 22) provided in advance in the memory 802A. The reason why the ink is set for each ink color is that the amount of change in density differs for each ink color. The offset value α of each ink color can be acquired by checking in advance the density change of the correction pattern CP after printing for each ink color. For example, black (K) will be described as an example. A black (K) correction pattern CPk is printed, and its density is read by the scanner 10 every predetermined time, whereby the density change over time graph (shown in FIG. A concentration change graph). On the density change graph, the deviation between the density at the time of printing and the convergence value is the offset value αk. Incidentally, since the density of the correction pattern CP is read immediately after printing in step 122a, the density at the time of printing is almost read as a read value. Accordingly, since the variation in density change until convergence is extremely small, the convergence value can be estimated with high accuracy based on the read value and the offset value α.

  When step S122a is completed, the process proceeds to step S123, and a correction value is calculated based on the value recorded in the recording table 802B. As described above, the value is calculated based on the offset value α. The value has been corrected. Therefore, in step S123, an appropriate correction value after stabilization of the density can be obtained. Since the subsequent processing including this step S123 is the same as the above-described reference example, the description thereof is omitted.

  Preferably, the offset value α is prepared for each type of paper P. This is because the convergence value differs depending on the type of plain paper or glossy paper.

  Further, for a color in which the density change from the density immediately after printing to the convergence value is smaller than a predetermined threshold value, the density reading value is directly stored in the recording table 802B without performing the offset value α subtraction process in step S122a. It may be recorded. In this case, the throughput of step S120 for setting the density correction value can be improved by the amount that the subtraction process is not performed.

  Incidentally, the step S121, the step S122a, and the step 123 respectively correspond to a “first printing step”, a “reading step”, and a “correction value generation step” according to the claims. Further, step 140 described in detail in the reference example corresponds to a “second printing step” according to the claims.

=== “Step S120 for Setting Density Correction Value” according to Second Embodiment of the Present Invention ===
The offset value α of the first embodiment described above corrects the read value, but the offset value β of the present embodiment is for correcting the correction value calculated based on the read value. It is different in point.

  That is, FIG. 24 shows a flowchart of step S120 according to the second embodiment, but the reading value from the scanner 10 is recorded as it is in the recording table 802B of step S122 as in the above-described reference example. In step S123a, a temporary correction value (referred to as a temporary correction value) is calculated based on the read value. The temporary correction value includes an error corresponding to the density change. Therefore, in order to reduce this error, in step S123a according to the second embodiment, processing for subtracting the offset value β from the provisional correction value (referred to as subtraction processing) is added. The correction value is set in the correction value table 63a.

This offset value β is preset for each ink color in the offset value table of the memory 802A (see FIG. 25). And this offset value (beta) is calculated | required as follows, for example. First, the correction pattern CP is printed. Then, the density of each dot row region is read from the correction pattern CP in two steps, that is, the printing time point and the density convergence time point. Here, the reading value at the time of printing is C1, and the reading value at the time of convergence is C2. Then, when the arithmetic average M1 of the reading values C1 and the arithmetic average M2 of the reading values C2 are calculated for all the dot row regions, respectively, the correction value H1 based on the reading value C1 at the printing time point and the reading at the convergence time point are read. The correction value H2 based on the value C2 is obtained as follows.
H1 = (C1-M1) / M1 (Formula 2)
H2 = (C2-M2) / M2 (Formula 3)
Here, since H1 is a correction value at the time of printing and H2 is a correction value at the time of convergence, the offset value β can be obtained as a deviation between the correction value H1 and the correction value H2, and specifically, Is expressed as in Equation 4.
β = H1-H2 (Formula 4)

=== Other Embodiments ===
The above-described embodiment mainly describes the printing system 700 in which both the printer 1 and the scanner 10 are connected to the computer 702 (702A), and includes a printing method, a density reading method, a printing apparatus, It goes without saying that disclosure of a density reading device and the like is included.
The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

(1) In the first embodiment described above, since the density is read immediately after printing, the variation of the density change from the read value to the convergence value is small, and the offset line α is used as a fixed value and the inspection line computer. It was stored in the memory 802A of 702A. However, if the elapsed time from the printing time point to the reading time point varies greatly every time the correction pattern CP is printed, the offset value α is read from the density change graph every time the correction pattern CP is printed. You may make it ask.
Specifically, the process correction program 716 counts and records the reading time with reference to the printing time of each correction pattern CP. The density change graph is recorded in advance in the memory 802A of the computer 702A. Then, the process correction program 716 reads the density change amount from the density at the time of reading to the convergence value with reference to the density change graph, and sets the density change amount as the offset value α.

(2) In the above-described embodiment, the “step S120 for setting the density correction value” has been described as being performed by the operator on the inspection line. However, the present invention is not limited to this, and the user is allowed to perform this operation. May be. In that case, a recording medium such as a CD-ROM in which the process correction program 716 is recorded is attached to the printer 1 purchased by the user. Then, the user installs the process correction program 716 in his computer 702, and performs the step S 120 himself to set the density correction value in the printer 1. The process correction program 716 may be distributed to the user's computer 702 via the Internet.

(3) In the above-described embodiment, the printer 1 has been described as the printing apparatus. 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.

(4) Since the above-described embodiment is an embodiment of the printer 1, the dye ink or the pigment ink is ejected from the nozzle. However, the ink ejected from the nozzle is not limited to such ink.

(5) 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.

1 is an explanatory diagram showing an external configuration of a printing system 700. FIG. 1 is a block diagram of an overall configuration of a printing system 700. FIG. It is explanatory drawing which shows schematic structure of the scanner 10 as an example of the reading apparatus concerning this invention. 1 is a block diagram of an overall configuration of a printer 1 according to an embodiment. 1 is a schematic diagram of an overall configuration of a printer 1 according to an embodiment. 1 is a side sectional view of an overall configuration of a printer 1 according to an embodiment. FIG. 4 is an explanatory diagram showing the arrangement of nozzles on the lower surface of a head 41. 4 is an explanatory diagram of a drive circuit of a head 41. FIG. It is a timing chart explaining each signal. 3 is a schematic explanatory diagram of basic processing performed by a printer driver 711. FIG. It is a flowchart of the operation | movement at the time of printing. FIG. 6 is a diagram for explaining density unevenness that occurs in the conveyance direction of a sheet P in an image printed in monochrome. It is a flowchart which shows the whole process sequence of the printing method which concerns on a reference example. It is a flowchart which shows the procedure of step S120 in FIG. It is a block diagram which shows the apparatus structure of an inspection line. It is explanatory drawing of correction pattern CP. It is a figure which shows an example of the read value of the density | concentration of correction pattern CP about black (K) ink. It is a conceptual diagram of the recording table 802B. It is a conceptual diagram of the correction value table 63a. It is a conceptual diagram which shows the pixel data arrangement | sequence of K image data. It is a flowchart of step S120 which concerns on 1st Embodiment of this invention. It is a conceptual diagram of the offset value table of 1st Embodiment. It is a density | concentration change graph which shows the time-dependent change of the density | concentration of correction pattern CP. It is a flowchart of step S120 which concerns on 2nd Embodiment of this invention. It is a conceptual diagram of the offset value table of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer (printer), 5 document, 6 document table cover, 7 document table glass, 8 light source part, 10 scanner, 11 CIS unit, 12 regulation guide, 14 rod lens array, 15 CCD sensor, 16 reading carriage, 18 drive Means, 20 transport unit, 21 paper feed roller, 22 transport motor, 23 transport roller, 24 platen, 25 paper discharge roller, 29 guide receiving section, 30 print carriage unit, 31 print carriage, 32 print carriage motor, 34 operation section, 36 display unit, 38 control unit, 40 head unit, 41 head, 50 sensor, 51 linear encoder, 52 rotary encoder, 53 paper detection sensor, 54 paper width sensor, 60 controller, 61 interface unit, 62 C PU, 63 memory, 63a correction value table, 64 unit control circuit, 644A original drive signal generation unit, 644B drive signal shaping unit, 90 ink cartridge, 181 timing belt, 182 pulley, 183 pulse motor, 184 pulley, 700 printing system, 702 (702A) computer, 704 display device, 708 input device, 708A keyboard, 708B mouse, 710 recording / playback device, 710A flexible disk drive device, 710B CD-ROM drive device, 711 printer driver, 712 video driver, 714 application program, 716 Process correction program, 802 (802A) memory, 802B recording table, 802C correction pattern CP print data, 804H Disk drive unit, CP correction pattern, ODRV original drive signal

Claims (14)

A first printing step for printing a print pattern with ink of a predetermined color;
A reading step of reading the density of the print pattern;
A correction value generation step of generating a correction value of a density relating to the predetermined color based on an offset value corresponding to a change in density until the density of the print pattern is stabilized after the reading of the density and the read value of the density. When,
A second printing step of printing the image on a medium while correcting the density of the image for the predetermined color based on the correction value;
A printing method characterized by comprising: The printing method according to claim 1,
In the correction value generation step, the density correction value is generated based on a value obtained by changing the read value by the offset value. The printing method according to claim 2,
The printing method according to claim 1, wherein the changed value is a value obtained by reducing the read value by the offset value. The printing method according to claim 1,
The printing method, wherein the correction value is a value obtained by changing only the offset value from a temporary correction value of the density generated based on the read value. In the printing method in any one of Claims 1 thru | or 4,
The image is composed of a plurality of different predetermined colors,
The print pattern is printed for each predetermined color,
The printing method, wherein the offset value is prepared for each predetermined color. The printing method according to claim 5, wherein
Of the plurality of predetermined colors, for a color whose magnitude of change in density from when the density is read until the density of the print pattern is stabilized is smaller than a predetermined threshold, based on only the read value, A printing method comprising generating a density correction value for the predetermined color. The printing method according to claim 5 or 6,
When printing the image by ejecting ink while moving a plurality of ink ejection units arranged along a predetermined direction for each predetermined color in a moving direction intersecting the predetermined direction,
Printing in which the density of the image is corrected for each dot row region in order to suppress density unevenness between the dot row regions in a medium on which the dot row along the moving direction is formed in each ink discharge unit Method. The printing method according to claim 7,
The print pattern includes a dot row region corresponding to each dot row region of the image,
Reading the density from the print pattern is performed for each dot row region,
The printing method, wherein the correction value is generated for each dot row region. The printing method according to claim 8, wherein
The print pattern is printed based on data of the same density gradation value over the entire dot row region,
In the correction value generating step, an average value of the read values over all dot row regions is calculated, and a deviation between the average value and a read value of each dot row region is divided by the average value to thereby calculate each dot. A printing method comprising calculating a correction value of a row area. This corresponds to a first printing step for printing a printing pattern with ink of a predetermined color, a reading step for reading the density of the printing pattern, and a change in density until the density of the printing pattern is stabilized after reading the density. A correction value generation step for generating a density correction value for the predetermined color based on the offset value and the read value of the density, and the image on the medium while correcting the image density for the predetermined color based on the correction value. A second printing step for printing
In the correction value generation step, the correction value of the density is generated based on a value obtained by changing the read value by the offset value,
The image is composed of a plurality of different predetermined colors, and the print pattern is printed for each predetermined color, and the offset value is prepared for each predetermined color,
When printing the image by ejecting ink while moving a plurality of ink ejection units arranged along a predetermined direction for each predetermined color in a movement direction intersecting the predetermined direction, each ink ejection unit In order to suppress density unevenness between the dot row regions in the medium in which the dot row along the moving direction is formed, the density of the image is corrected for each dot row region,
The print pattern includes a dot row area corresponding to each dot row area of the image, density reading from the print pattern is performed for each dot row region, and the correction value is set for each dot row region. A printing method characterized by being generated. A reading step of reading the density of a print pattern printed with ink of a predetermined color;
A correction step of correcting the read value based on an offset value corresponding to a change in density until the density of the print pattern is stabilized after the density is read;
A method for reading the density of a printed pattern, comprising: The density reading method for a printed pattern according to claim 11,
In the correction step, the read value is corrected to a value smaller by the offset value. A printing unit that prints a print pattern with ink of a predetermined color in accordance with control of the control unit;
A reading unit that reads the density of the printing pattern,
The control unit has an offset value corresponding to a change in density from when the density is read until the density of the print pattern is stabilized, and a density correction value generated based on the density read value,
When printing an image on a medium by the printing unit, the control unit corrects the density of the image for the predetermined color based on the correction value. A reading unit for reading the density of a printing pattern printed with ink of a predetermined color;
A correction unit that corrects the read value based on an offset value corresponding to a change in density from when the density is read until the density of the print pattern is stabilized;
A printed pattern density reading apparatus comprising: