JP6547453B2 - Ink jet recording apparatus and control method of ink jet recording apparatus - Google Patents

Description

  The present invention relates to an inkjet recording apparatus and a control method of the inkjet recording apparatus.

  Conventionally, a recording head is provided, and recording is performed by discharging ink to a recording medium from a plurality of nozzles of the recording head based on image data while relatively moving the recording medium and the recording head There is an inkjet recording apparatus that records an image on a recording medium by performing the operation multiple times. In such an inkjet recording apparatus, when there is a defective nozzle such that the ink is not ejected or the ejection amount and the ejection direction of the ink are not correct, there is a problem that the influence of the defective nozzle appears in the image and the image quality is degraded.

  On the other hand, in each recording operation, ink is prevented from being ejected from the defective nozzle, and the ejection amount of ink from the nearby nozzles located in the vicinity of the defective nozzle is increased to complement non-ejection of the ink by the defective nozzle. There are known techniques for preventing image quality degradation (for example, Patent Document 1).

JP, 2015-24570, A

  However, in the conventional ink jet recording apparatus, depending on the discharge pattern of the ink according to the image data and the state and setting of the ink amount which can be discharged from each nozzle, the ink equal to the ink amount which is not discharged from the defective nozzle in each recording operation. In some cases, the amount can not be increased by discharge from a nearby nozzle. For this reason, there is a problem that the influence of the defective nozzle can not be properly corrected, and the image quality deterioration of the recorded image resulting from the defective discharge of the ink from the nozzle can not be effectively suppressed.

  An object of the present invention is to provide an inkjet recording apparatus and a control method of the inkjet recording apparatus capable of effectively suppressing the image quality deterioration of the recorded image caused by the defective discharge of the ink from the nozzles.

In order to achieve the above object, the invention of an ink jet recording apparatus according to claim 1 is:
Recording means for ejecting ink to the recording medium from each of the plurality of nozzles arranged in the first direction;
Moving means for relatively moving the recording means and the recording medium in a second direction intersecting the first direction;
While the relative movement is performed in the second direction by the movement unit, any one of a plurality of levels of ink is not discharged or discharged from each of the plurality of nozzles to the recording medium based on image data Recording control means for recording the image by performing the recording operation for recording a part of the image related to the image data a plurality of times;
Equipped with
The recording control means
In each of the plurality of printing operations, the ink is not ejected from a defective nozzle preset as a nozzle that does not eject ink normally, and the position is located in the vicinity of the defective nozzle so as to compensate the ink amount that the defective nozzle does not eject. Perform complementary control to perform complementary discharge with the amount of ink to be discharged from the nearby nozzles that normally discharge ink.
When there is a deviation between the amount of ink which is not discharged from the defective nozzle and the amount of change of the amount of ink which is discharged according to the adjustment related to the complementary discharge by the adjacent nozzle in one recording operation. The recording operation performed next to the one recording operation within a predetermined proximity distance from the portion corresponding to the non-ejection of the defective nozzle among the part of the image recorded in the one recording operation In the complementary control, the deviation amount is added to the ink amount which is not discharged from the defective nozzle to determine the change amount in the complementary discharge,
At least one of the plurality of ink amounts excluding non-ejection among the plurality of ink amounts changes the ink amount ejected from the adjacent nozzle from one ink amount to another ink amount among the plurality of ink amounts feasible by, unlike the variation both of any ink amount,
The maximum settable value of the amount of ink which the recording control means discharges from the adjacent nozzles at the time of the complementary discharge is the maximum setting of the amount of ink which the recording control means discharges without performing the complementary control corresponding to the image data. It is characterized by being larger than the possible value .

The invention according to claim 2 is the inkjet recording apparatus according to claim 1,
The recording control means performs the complementary control by determining the change amount in the complementary discharge so as to minimize the deviation amount.

In order to achieve the above object, the invention of the ink jet recording apparatus according to claim 3 is:
Recording means for ejecting ink to the recording medium from each of the plurality of nozzles arranged in the first direction;
Moving means for relatively moving the recording means and the recording medium in a second direction intersecting the first direction;
Correction image data generation means for correcting image data based on information indicating a defective nozzle from which ink is not normally ejected to generate correction image data;
While the relative movement is performed in the second direction by the movement unit, any one of a plurality of levels of ink is not ejected from each of the plurality of nozzles with respect to the recording medium based on the corrected image data or Recording control means for recording the image by performing a plurality of recording operations for discharging a part of the image according to the corrected image data by performing discharge.
Equipped with
The corrected image data generation unit
The pixel value of the pixel corresponding to the defective nozzle is set to a value corresponding to the non-ejection of the ink for the portion corresponding to each of the plurality of printing operations in the image data, and the defective nozzle does not eject The pixel value of the neighboring pixel corresponding to the nearby nozzle is set so as to perform complementary discharge in which the amount of ink ejected from the nearby nozzle located in the vicinity of the defective nozzle and compensating the ink amount properly to compensate for the ink amount is adjusted. Perform complementary correction to set,
In the complementary correction for the portion corresponding to one recording operation of the image data, the ink ejected according to the adjustment related to the complementary ejection by the adjacent nozzle and the amount of ink which is not ejected from the defective nozzle When there is a deviation between the amount of change and the amount of change, a predetermined portion of the image data recorded in the one recording operation is a portion corresponding to non-ejection of the defective nozzle. In the complementary correction with respect to the portion corresponding to the recording operation performed after the one recording operation within the close distance of the ink, the deviation amount is added to the ink amount which is not ejected from the defective nozzle Determining the amount of change in complementary discharge, and setting the pixel value of the neighboring pixel according to the determined amount of change;
At least one of the plurality of ink amounts excluding non-ejection among the plurality of ink amounts changes the ink amount ejected from the adjacent nozzle from one ink amount to another ink amount among the plurality of ink amounts feasible by, unlike the variation both of any ink amount,
The maximum value of the amount of ink ejected from the adjacent nozzles at the time of the complementary discharge corresponding to the pixel value of the adjacent pixel that can be set in the complementary correction can be set in the image data in which the complementary correction is not performed It is characterized in that it is larger than the maximum value of the amount of ink ejected corresponding to the value .

The invention according to a fourth aspect is the inkjet recording apparatus according to the third aspect , wherein
The complementary correction is characterized in that the pixel value of the neighboring pixel is set so as to minimize the displacement amount.

The invention according to claim 5 is the inkjet recording apparatus according to any one of claims 1 to 4 .
The plurality of ink amounts discharged from the plurality of nozzles of the recording unit by the recording control unit include ones in which the magnification of the relatively large ink amount is non-integer with respect to one ink amount. It is characterized by

The invention according to claim 6 is the inkjet recording apparatus according to any one of claims 1 to 5 ,
Reading means for reading an image recorded on the recording medium;
Defective nozzle specifying means for specifying the defective nozzle based on the reading result of the predetermined inspection image by the reading means;
It is characterized by having.

The invention according to claim 7 is the inkjet recording apparatus according to any one of claims 1 to 6 .
The plurality of nozzles may be arranged to be able to eject ink across the recordable width of the image in the first direction on the recording medium.

In order to achieve the above object, the invention of a control method of an ink jet recording apparatus according to claim 8 is:
Recording means for discharging ink to the recording medium from each of the plurality of nozzles arranged in the first direction, and relative movement between the recording means and the recording medium in a second direction intersecting the first direction A control method of an ink jet recording apparatus comprising:
While the relative movement is performed in the second direction by the movement unit, any one of a plurality of levels of ink is not discharged or discharged from each of the plurality of nozzles to the recording medium based on image data A recording control step of recording the image by performing the recording operation of recording a part of the image related to the image data a plurality of times;
In the recording control step,
In each of the plurality of printing operations, the ink is not ejected from a defective nozzle preset as a nozzle that does not eject ink normally, and the position is located in the vicinity of the defective nozzle so as to compensate the ink amount that the defective nozzle does not eject. Perform complementary control to perform complementary discharge with the amount of ink to be discharged from the nearby nozzles that normally discharge ink.
When there is a deviation between the amount of ink which is not discharged from the defective nozzle and the amount of change of the amount of ink which is discharged according to the adjustment related to the complementary discharge by the adjacent nozzle in one recording operation. The recording operation performed next to the one recording operation within a predetermined proximity distance from the portion corresponding to the non-ejection of the defective nozzle among the part of the image recorded in the one recording operation In the complementary control, the deviation amount is added to the ink amount which is not discharged from the defective nozzle to determine the change amount in the complementary discharge,
At least one of the plurality of ink amounts excluding non-ejection among the plurality of ink amounts changes the ink amount ejected from the adjacent nozzle from one ink amount to another ink amount among the plurality of ink amounts feasible by, unlike the variation both of any ink amount,
In the recording control step, the maximum settable value of the amount of ink ejected from the adjacent nozzles at the time of the complementary ejection corresponds to the maximum setting of the amount of ink ejected without performing the complementation control corresponding to the image data in the recording control step. It is characterized by being larger than the possible value .

In order to achieve the above object, the invention of a control method of an ink jet recording apparatus according to claim 9 is:
Recording means for discharging ink to the recording medium from each of the plurality of nozzles arranged in the first direction, and relative movement between the recording means and the recording medium in a second direction intersecting the first direction A control method of an ink jet recording apparatus, comprising: moving means for moving image data; and corrected image data generation means for correcting image data to generate corrected image data;
A corrected image data generation step of correcting the image data to generate the corrected image data based on information indicating a defective nozzle from which the ink is not ejected normally by the corrected image data generation unit;
While the relative movement is performed in the second direction by the movement unit, any one of a plurality of levels of ink is not ejected from each of the plurality of nozzles with respect to the recording medium based on the corrected image data or A recording control step of recording the image by performing a plurality of recording operations of discharging and recording a part of the image according to the corrected image data;
In the corrected image data generation step,
The pixel value of the pixel corresponding to the defective nozzle is set to a value corresponding to the non-ejection of the ink for the portion corresponding to each of the plurality of printing operations in the image data, and the defective nozzle does not eject The pixel value of the neighboring pixel corresponding to the nearby nozzle is set so as to perform complementary discharge in which the amount of ink ejected from the nearby nozzle located in the vicinity of the defective nozzle and compensating the ink amount properly to compensate for the ink amount is adjusted. Perform complementary correction to set,
In the complementary correction for the portion corresponding to one recording operation of the image data, the ink ejected according to the adjustment related to the complementary ejection by the adjacent nozzle and the amount of ink which is not ejected from the defective nozzle When there is a deviation between the amount of change and the amount of change, a predetermined portion of the image data recorded in the one recording operation is a portion corresponding to non-ejection of the defective nozzle. In the complementary correction with respect to the portion corresponding to the recording operation performed after the one recording operation within the close distance of the ink, the deviation amount is added to the ink amount which is not ejected from the defective nozzle Determining the amount of change in complementary discharge, and setting the pixel value of the neighboring pixel according to the determined amount of change;
At least one of the plurality of ink amounts excluding non-ejection among the plurality of ink amounts changes the ink amount ejected from the adjacent nozzle from one ink amount to another ink amount among the plurality of ink amounts feasible by, unlike the variation both of any ink amount,
The maximum value of the amount of ink ejected from the adjacent nozzles at the time of the complementary discharge corresponding to the pixel value of the adjacent pixel that can be set in the complementary correction can be set in the image data in which the complementary correction is not performed It is characterized in that it is larger than the maximum value of the amount of ink ejected corresponding to the value .

  According to the present invention, there is an effect that it is possible to effectively suppress the image quality deterioration of the recorded image caused by the defective discharge of the ink from the nozzle.

FIG. 1 is a view showing a schematic configuration of an ink jet recording apparatus according to an embodiment of the present invention. It is a schematic diagram which shows the structure of a head unit. FIG. 2 is a block diagram showing the main functional configuration of the inkjet recording apparatus. It is a figure which shows an example of the test | inspection image used for specification of a defect nozzle. It is a figure which shows the example of correction | amendment of the image data based on defect nozzle information. It is a figure which shows the example of the complementation of the ink based on the image data after correction | amendment. It is a figure explaining the algorithm of amendment of the image data based on defective nozzle information. It is a flowchart which shows the control procedure of a defect nozzle information acquisition process. It is a flowchart which shows the control procedure of an image recording process. It is a flowchart which shows the control procedure of the image recording process which concerns on a modification.

  Hereinafter, an embodiment according to an image reading apparatus and an inkjet recording apparatus of the present invention will be described based on the drawings.

FIG. 1 is a view showing a schematic configuration of an inkjet recording apparatus 1 according to an embodiment of the present invention.
The inkjet recording apparatus 1 includes a sheet feeding unit 10, an image recording unit 20, a sheet discharging unit 30, and a control unit 40 (FIG. 3). The inkjet recording apparatus 1 conveys the recording medium M stored in the paper feeding unit 10 to the image recording unit 20 under the control of the control unit 40, and the image recording unit 20 records an image on the recording medium M, and the image The recording medium M recorded is conveyed to the paper discharge unit 30. In the present embodiment, as the recording medium M, it is possible to use various media such as paper, cloth or sheet-like resin which can fix the ink ejected on the surface.

The sheet feeding unit 10 includes a sheet feeding tray 11 for storing the recording medium M, a medium feeding unit 12 for conveying the recording medium M from the sheet feeding tray 11 to the image recording unit 20 and supplying the recording medium M, and a delivery drum 13.
The medium supply unit 12 includes a ring-shaped belt 123 supported by two rollers 121 and 122 on the inside. The medium supply unit 12 conveys the recording medium M by rotating the rollers 121 and 122 in a state where the recording medium M is placed on the belt 123.
The delivery drum 13 delivers the recording medium M conveyed by the medium supply unit 12 to the conveyance unit 21 (moving means) of the image recording unit 20. The delivery drum 13 is provided at a position between the medium supply unit 12 and the conveyance unit 21. The delivery drum 13 holds and picks up one end of the recording medium M conveyed by the medium supply unit 12 and delivers it to the conveyance unit 21. A swing arm unit may be provided between the medium supply unit 12 and the delivery drum 13 to deliver the recording medium M from the medium supply unit 12 to the delivery drum 13.

  The image recording unit 20 includes a conveyance unit 21, a heating unit 22, a head unit 23 (recording unit), a fixing unit 24, and a reading unit 25 (reading unit).

  The transport unit 21 includes a ring-shaped transport belt 213 whose inside is supported by two transport rollers 211 and 212 which rotate around a rotation axis extending in the X direction in FIG. 1. The conveyance unit 21 rotates the conveyance rollers 211 and 212 and moves the conveyance belt 213 while the recording medium M delivered from the delivery drum 13 is placed on the conveyance surface of the conveyance belt 213. Are conveyed in the moving direction (conveying direction; Y direction in FIG. 1) (second direction) of the conveying belt 213.

  The heating unit 22 heats the recording medium M placed on the conveyance surface of the conveyance belt 213. The heating unit 22 includes, for example, an infrared heater, and generates heat by energizing the infrared heater based on a control signal supplied from the control unit 40. The heating unit 22 is provided near the conveyance surface of the conveyance belt 213 and positioned upstream of the head unit 23 in the conveyance direction of the recording medium M. The heating unit 22 is controlled by the control unit 40 so that the temperature of the recording medium M placed on the conveyance surface of the conveyance belt 213 and passing near the heating unit 22 becomes a temperature within a predetermined range.

  The head unit 23 discharges the ink to the recording medium M in accordance with the circumferential movement of the transport belt 213 on which the recording medium M is placed, and records an image. The head unit 23 is disposed with a predetermined distance, with the ink discharge surface facing the transport belt 213. In the inkjet recording apparatus 1 of the present embodiment, four head units 23 respectively corresponding to four color inks of yellow (Y), magenta (M), cyan (C) and black (K) are in the conveyance direction of the recording medium M. From the upstream side, they are arranged in the order of Y, M, C, and K in a predetermined interval.

FIG. 2 is a schematic view showing the configuration of the head unit 23. Here, the surface of the head unit 23 facing the transport surface of the transport belt 213 is shown.
In each head unit 23, the nozzles 233 of the plurality of recording elements are arranged in a direction intersecting the conveyance direction of the recording medium M (in the embodiment, a direction orthogonal to the conveyance direction, ie, X direction) (first direction) Four recording heads 232 are provided.
The four recording heads 232 included in the head unit 23 are arranged in a staggered pattern so that the arrangement ranges in the X direction partially overlap each other, and the first, third, and second along the X direction The nozzles 233 of the fourth recording head 232 are located on the same line. Of the portions where adjacent recording heads 232 overlap in the X direction, the arrangement ranges of the nozzles 233 included in each recording head 232 in the X direction overlap in a range R shown in FIG. In the range R, for example, the ink is set to be discharged only from the nozzles 233 of one of the two recording heads 232 having the nozzles 233 in the range R.
The arrangement range of the nozzles 233 included in the head unit 23 in the X direction covers the width in the X direction of the area on which the image is recorded in the recording medium M conveyed by the conveyance unit 21. When recording an image, the position is fixed with respect to the transport unit 21 and used. That is, the inkjet recording apparatus 1 is a single pass type inkjet recording apparatus.
The recording head 232 may have two or more rows of nozzles 233. For example, two rows of the nozzles 233 arranged in the X direction are provided, and the nozzles 233 in the two rows are arranged mutually offset by a half of the arrangement interval of the nozzles 233 in the X direction. Also good.

The head unit 23 further includes a recording head drive unit 231 (FIG. 3) that drives the recording head 232. The recording head drive unit 231 has a drive circuit that supplies a voltage signal of a drive waveform according to image data to each recording head 232, and a drive control circuit that supplies image data to the drive circuit at an appropriate timing. . Here, the image data supplied to the recording head 232 is raster image data obtained by rasterizing vector image data or the like, and the number of gradations is an inkjet recording apparatus by halftone processing as necessary. It is data reduced to a gradation number that can be expressed by 1.
Each of the recording elements included in the recording head 232 includes a pressure chamber for storing ink, a piezoelectric element provided on a wall surface of the pressure chamber, and a nozzle 233. When a voltage signal of a drive waveform for causing the piezoelectric element to deform is applied to the piezoelectric element from the drive circuit of the recording head drive unit 231, the pressure in the pressure chamber changes according to this voltage signal, and the nozzle communicated with the pressure chamber The ink is ejected from 233.

In the present embodiment, image data of four gradations is used, and the amount of ink ejected from the nozzle 233 according to the gradation value (0, 1, 2, 3) (pixel value) of each pixel of the image data is used. The driving waveforms corresponding to the respective gradation values are determined to be 0 pL, 7 pL, 19 pL, and 30 pL, respectively. Therefore, the minimum amount of ink that can be ejected from each nozzle is 7 pL.
As described above, the minimum amount (7 pL) of ink and the amount (19 pL, 30 pL) of the non-integer multiple of the minimum amount are ejected from the nozzle 233 of the head unit 23. That is, the plurality of ink levels discharged from the nozzle 233 include those in which the magnification of the relatively large ink level is non-integer with respect to one ink level. Here, the ink of the non-integer multiple of the minimum amount continuously ejects a plurality of ink droplets of different amounts from the nozzle 233 and integrates the plurality of ink droplets in the air before landing on the recording medium M. It may be generated by

As the ink ejected from the recording head 232, an ink having a property of being phase-changed into gel or sol depending on temperature and being cured by irradiation of energy rays such as ultraviolet rays is used.
Each head unit 23 includes an ink heating unit (not shown). The ink heating unit operates under the control of the control unit 40 and heats the ink stored in the head unit 23 to a sol temperature. The recording head 232 discharges the ink which has been heated to form a sol.

  The fixing unit 24 includes a light emitting unit disposed across the width of the transport belt 213 in the X direction, and irradiates energy beam such as ultraviolet light from the light emitting unit to the recording medium M placed on the transport belt 213 Then, the ink discharged onto the recording medium M is cured and fixed. The light emitting unit of the fixing unit 24 is disposed on the downstream side of the head unit 23 in the transport direction so as to face the transport belt 213.

The reading unit 25 is disposed opposite to the conveyance belt 213 at a position downstream of the recording medium M in the conveyance direction with respect to the fixing position of the ink by the fixing unit 24, and the recording medium M conveyed by the conveyance belt 213 is The recorded image is read in a predetermined reading range, and two-dimensional imaging data of the image is output.
In the present embodiment, the reading unit 25 includes a light source for emitting light to the recording medium M transported by the transport belt 213, and an imaging device for detecting the intensity of reflected light of light incident on the recording medium M in the X direction. And a line sensor arranged in The configuration of the reading unit 25 is not limited to this. For example, an area sensor may be used instead of the line sensor.

The discharge unit 30 includes a delivery drum 31, a delivery unit 32, and a discharge tray 33.
The delivery drum 31 receives the recording medium M transported by the transport unit 21 at the downstream side in the transport direction of the reading unit 25 and delivers the recording medium M to the delivery unit 32. The mechanism for delivering the recording medium M from the transport unit 21 to the delivery unit 32 is not limited to the one using the delivery drum 31, and another known mechanism may be used.
The delivery unit 32 has a ring-shaped belt 323 supported by two conveyance rollers 321 and 322 inside, and the recording medium M delivered from the conveyance unit 21 onto the belt 323 by the delivery drum 31 is conveyed by the belt 323 The sheet is conveyed and sent to the sheet discharge tray 33.
The paper discharge tray 33 is a plate-like member on which the recording medium M transported by the delivery unit 32 is placed.

FIG. 3 is a block diagram showing the main functional configuration of the inkjet recording apparatus 1.
The inkjet recording apparatus 1 includes a control unit having a CPU 41 (central processing unit) (a recording control unit, a correction image data generating unit, a defective nozzle specifying unit), a RAM 42 (random access memory), a ROM 43 (read only memory), and a storage unit 44. 40, a heating unit 22, a recording head drive unit 231 for driving the recording head 232 of the head unit 23, a fixing unit 24, a reading unit 25, a conveyance drive unit 51, an operation display unit 52, and an interface 53. , The bus 54 and the like.

  The CPU 41 reads various control programs and setting data stored in the ROM 43, stores the read control programs and setting data in the RAM 42, executes the program, and performs various arithmetic processing. The CPU 41 thereby controls the overall operation of the inkjet recording apparatus 1. For example, the CPU 41 operates the respective units of the sheet feeding unit 10, the image recording unit 20, and the sheet discharge unit 30 based on the image data stored in the storage unit 44, and causes the recording medium M to record an image.

  The RAM 42 provides a working memory space to the CPU 41 and stores temporary data. The RAM 42 also stores defective nozzle information, which will be described later, and a variable N that indicates the row number of the pixel row that is being corrected in the image data. The RAM 42 may include non-volatile memory.

  The ROM 43 stores various control programs executed by the CPU 41, setting data, and the like. In the program, for example, a defective nozzle information acquisition program for acquiring defective nozzle information used for correction of image data, or a recording medium M using data of the corrected pixel row after correcting the image data for each pixel row And an image recording program for recording an image. Note that instead of the ROM 43, a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

  The storage unit 44 is configured by a DRAM (Dynamic Random Access Memory) or the like. The storage unit 44 stores image data input from the external device 2 through the interface 53 and imaging data by the image reading unit 25 recorded on the recording medium M. Here, for example, the image data input from the external device 2 is subjected to color conversion processing on full color image data of RGB color system, converted to CMYK color system, and halftone processing such as dither processing and error diffusion processing. The data is the data in which the number of gradations of each pixel is reduced to the number of gradations that can be expressed by the ink jet recording apparatus 1, and the data is separated for each of the CMYK colors. The color conversion process and the halftone process may be performed by the control unit 40 of the inkjet recording apparatus 1 or an image processing unit provided separately from the control unit 40.

  The conveyance drive unit 51 supplies a drive signal to a motor for operating the conveyance rollers 211 and 212 of the conveyance unit 21 based on a control signal supplied from the CPU 41 to set the conveyance rollers 211 and 212 at a predetermined speed and timing. Rotate. Further, the conveyance drive unit 51 supplies a drive signal to a motor for operating the medium supply unit 12, the delivery drums 13 and 31, and the delivery unit 32 based on the control signal supplied from the CPU 41 to The paper feed to the conveyance unit 21 and the paper discharge from the conveyance unit 21 are performed.

  The recording head drive unit 231 causes the recording head 232 to discharge ink based on the control signal and image data supplied from the CPU 41. Specifically, when a control signal and image data are supplied from the CPU 41, the drive control circuit of the print head drive unit 231 causes the drive circuit to output a voltage signal of a drive waveform to the piezoelectric element of the print element of the print head 232, A discharge operation in which an amount of ink corresponding to a gradation value of image data is discharged from a nozzle of a recording element, or an ink which is executed when image data corresponds to non-discharge of ink or at intervals of a plurality of image recording operations. The recording head 232 is caused to perform a non-ejection operation that is not ejected.

  The operation display unit 52 includes a display device such as a liquid crystal display or an organic EL display, and an input device such as an operation key or a touch panel disposed on the screen of the display device. The operation display unit 52 causes the display device to display various information, and converts a user's input operation to the input device into an operation signal and outputs the operation signal to the control unit 40.

  The interface 53 is a means for transmitting and receiving data to and from the external device 2, and is constituted of, for example, various serial interfaces, various parallel interfaces, or a combination thereof.

  The external device 2 is, for example, a personal computer, and supplies an image recording command, image data, and the like to the control unit 40 via the interface 53.

Next, the specification of the ejection failure nozzle 233 in the inkjet recording apparatus 1 and the correction of the image data based on the specification result will be described.
In the inkjet recording apparatus 1, when there is a nozzle 233 (referred to as a defective nozzle in this specification) of ejection failure in which the ink is not properly ejected, this defective nozzle is identified, and the correction of suppressing the disturbance of the recorded image due to the defective nozzle Is performed on the image data, and then recording of the image is performed.
The identification of the defective nozzle is performed by recording a predetermined inspection image on the recording medium M and analyzing imaging data obtained by imaging the inspection image by the reading unit 25.

  FIG. 4 is a view showing an example of an inspection image used to identify a defective nozzle. The inspection image is an image recorded on the recording medium M by the head unit 23 and includes a line pattern 60 composed of a plurality of lines 61 extending in the Y direction. Here, each line 61 is recorded by the ink discharged from the single nozzle 233 of the head unit 23. Further, in this line pattern 60, the lines 61 recorded by the adjacent nozzles 233 are shifted in the Y direction and recorded, and the positions of the lines 61 recorded by every seven nozzles 233 in the Y direction are mutually different. It is supposed to match.

Since each of the plurality of lines 61 in the inspection image corresponds to any one of the plurality of nozzles 233, when an abnormality is recognized in a specific line 61 in the imaging data of the inspection image, the specific line 61 (below The nozzle 233 corresponding to (abnormal line) can be specified as a defective nozzle. For example, when the line 61a shown in FIG. 4 is missing in the imaging data of the inspection image, the nozzle 233 corresponding to the line 61a is specified as a defective nozzle that does not eject ink. In addition, when a specific line 61 is not recorded at a predetermined position corresponding to the position of the nozzle 233 in the imaging data of the inspection image, the nozzle 233 corresponding to the specific line 61 has an abnormality in the ink ejection direction. It is identified as a certain defective nozzle.
When a defective nozzle is identified, defective nozzle information indicating the array number of the defective nozzle in the head unit 23 is stored in the RAM 42.

  Subsequently, correction of image data based on the defective nozzle information will be described.

FIG. 5 is a diagram showing an example of correction of image data based on defective nozzle information. FIG. 5 (a) is a diagram showing the gradation value of each pixel included in the range of pixel rows R1 to R14 and pixel columns C1 to C5 in the image data before correction, and FIG. 5 (b) is a diagram showing correction It is a figure which shows the gradation value of each pixel contained in the said range among subsequent image data.
FIG. 6 is a diagram showing an example of ink complementation based on image data after correction. FIG. 6 (a) is a diagram showing the amount of ink to be ejected corresponding to each pixel included in the above range among the image data before correction, by the size of the circular mark, and FIG. 6 (b) is a diagram It is a figure which shows the quantity of the ink discharged corresponding to each pixel of the said range among the image data after correction | amendment by the magnitude | size of a circular mark.
Pixel columns C1 to C5 in FIGS. 5 and 6 respectively correspond to any one of the adjacent five nozzles 233, and the ink corresponding to the pixels included in one pixel column is ejected by the corresponding identical nozzles 233. Ru. In addition, the pixel rows R1 to R14 are formed of pixels corresponding to the five nozzles 233, respectively.

The image data before correction shown in FIG. 5A is image data of three gradations, and the gradation value of each pixel of the image data is any one of “0”, “1”, and “2”. is there. Further, as shown in FIG. 6A, the ink is not ejected in the pixel having the gradation value of “0”, and the ink of 7 pL and 19 pL in the pixels having the gradation value of “1” and “2”, respectively. Is discharged.
Further, the image data after correction shown in FIG. 5B is image data of four gradations, and the gradation value of each pixel of the image data is “0”, “1”, “2”, “ 3). Further, as shown in FIG. 6B, the ink is not ejected in the pixel with the gradation value of “0”, and 7 pL in the pixels with the gradation value of “1”, “2” and “3” respectively. , 19 pL and 30 pL of ink are ejected.
As described above, in the present embodiment, the maximum amount of ink that can be ejected from the nozzle 233 corresponding to the image data after correction is the maximum amount of ink that can be ejected from the nozzle 233 corresponding to the image data before correction. It is larger than the value.

  Here, it is assumed that the nozzle 233 corresponding to the pixel column C3 is specified as the defective nozzle in the defective nozzle information, and the adjacent nozzle (nearby nozzle) adjacent to the defective nozzle is the nozzle 233 which ejects the ink normally. I assume. In this case, as shown in FIG. 5B, in the image data after correction, the gradation value in each pixel included in the pixel column C3 corresponding to the defective nozzle in the image data of FIG. The pixel row corresponding to the adjacent nozzle is performed so that complementary ejection is performed in which the amount of ink ejected from the adjacent nozzle is adjusted so as to compensate the amount of ink which the defective nozzle does not eject while being changed to “0” corresponding to non-ejection of The gradation value of each pixel included in C2 and C4 is set.

The correction (complementary correction) of the gradation value of the image data is performed in the order of the adjacent pixel rows for each pixel row (complement target pixel group) of the image data.
In the complementary correction for each pixel row, the gradation value of the pixel (the pixel of the pixel column C3) corresponding to the defective nozzle in the pixel row to be corrected is set to the value (0) corresponding to the non-ejection of ink. In addition, the amount of ink ejected from the adjacent nozzle is increased from or maintained at the amount corresponding to the image data based on the decrease from the amount corresponding to the image data of the amount of ink ejected from the defective nozzle As described above, the gradation values of the adjacent pixels (pixels in the pixel columns C2 and C4) (nearby pixels) corresponding to the adjacent nozzles are set based on the following algorithm.
That is, in the complementary correction related to the first pixel row in the image data, the complementary error is obtained if there is a complementary error obtained by subtracting the decrease in the amount of ink ejected by the defective nozzle from the increase in the amount of ink ejected from the adjacent nozzle by the complementary correction. Is carried over to the complementary correction relating to the pixel row of the next stage as the carryover complementary error.
In addition, in the complementary correction for the second and subsequent pixel lines in the image data, the absolute value of the cumulative complementary error indicated by the sum of the above-mentioned complementary error and the carried over complementary error carried over by the complementary correction for the previous pixel line. The tone value of the adjacent pixel is set so as to minimize the value, and the accumulated complementation error is carried forward to the complementation correction relating to the pixel row of the next stage as the carryover complementation error.

  FIG. 7 is a diagram for explaining an algorithm of correction of image data based on defective nozzle information. In FIG. 7, a decrease (A) in the amount of ejected ink due to the non-ejection of the defective nozzle and an increase in the amount of ejected ink by the adjacent nozzles by the correction according to each of the pixel rows R1 to R14 shown in FIGS. The minutes (B), (C), the complementation error (B + C-A), and the cumulative complementation error are shown. Specific gradation value correction will be described below using this figure.

First, in the complementary correction related to the pixel row R1 which is the top pixel row, the gradation value of the pixel of the pixel column C3 corresponding to the defective nozzle is changed from "2" to "0". The amount of decrease (A) in the amount of ejected ink corresponding to this change is 19 pL.
Further, the gradation values of the pixels (adjacent pixels) of the pixel arrays C2 and C4 corresponding to the adjacent nozzles are changed such that the absolute value of the complementary error is minimized. That is, the gradation value of the adjacent pixel is set such that the increase in the amount of ink ejected from the adjacent nozzle due to the change of the gradation value is closest to the decrease (A) (19 pL) of the amount of ejected ink. In FIG. 7, the gradation values of the adjacent pixels in the pixel columns C2 and C4 are both changed from “2” to “3”, and the amount of discharged ink corresponding to the adjacent pixels in the pixel columns C2 and C4 is 19 pL to 30 pL, respectively. Is changed to That is, the increase (B) in the amount of discharged ink in the adjacent pixel corresponding to the pixel column C2 and the increase (C) in the amount of discharged ink in the adjacent pixel corresponding to the pixel column C2 are both 11 pL. By performing such complementary correction, the complementation error obtained by subtracting the decrease amount of the discharged ink amount (A) from the sum of the increase amounts (B) and (C) of the discharged ink amount is (11 + 11-19) = 3pL It becomes. In the complementary correction related to the pixel row R1, this value is the minimum value of the complementary error. This complementation error is carried over to the complementation correction according to the pixel row R2 to be performed next as a carryover complementation error.

In the complementary correction for the subsequent pixel row R2, the gradation value of the pixel of the pixel column C3 corresponding to the defective nozzle is changed from "2" to "0", and the reduction amount (A) of the discharged ink amount is 19 pL. .
Further, the change of the gradation value of the adjacent pixel of the pixel column C2, C4 corresponding to the adjacent nozzle is the complementation error concerning the pixel row R2 and the carryover complementation error carried forward by the complementation correction concerning the pixel row R1 of the previous stage. It is performed so that the absolute value of the accumulated complementary error indicated by the sum of. In FIG. 7, the accumulated complementary error that minimizes the absolute value in the pixel row R2 is −5 pL. That is, the gradation value of the adjacent pixel corresponding to the pixel column C2 is changed from "2" to "3", and the increase (B) in the amount of discharged ink is 11pL, and the floor of the adjacent pixel corresponding to the pixel column C4. If the adjustment value remains unchanged at “2” and the increment (C) of the discharged ink amount is 0 pL, and the complementation error relating to the pixel row R2 becomes (11 + 0−19) = − 8 pL, the pixel row The absolute value of the accumulated complementary error (-5 pL) represented by the sum of the complementary error according to R2 and the carried over error (3 pL) from the pixel row R1 is minimized. This accumulated complementation error is carried over to the complementation correction concerning pixel row R3 performed next as a carryover complementation error.
Here, in the case of focusing only on the pixel row R2, the complementation error related to the pixel row R2 becomes 3 pL by changing the gradation values of the adjacent pixels corresponding to the pixel columns C2 and C4 to "3". Therefore, the absolute value of the complementation error becomes smaller. However, by minimizing the absolute value of the accumulated complementation error as described above, it is possible to perform complementation in which the influence of the complementation error relating to the correction performed in the pixel row R1 is suppressed. It is possible to more effectively suppress the image quality deterioration due to

In the complementary correction for the subsequent pixel row R3, the gradation value of the pixel of the pixel column C3 corresponding to the defective nozzle is changed from "2" to "0", and the reduction amount (A) of the ejected ink amount is 19 pL. .
Further, the change of the gradation value of the adjacent pixel corresponding to the pixel column C2, C4 is a sum of the complementation error concerning the pixel row R2 and the carried over complementation error carried over by the complementation correction concerning the pixel row R2 of the previous stage. It is done so that the absolute value of the indicated cumulative complement error is minimized. In FIG. 7, the accumulated complementary error with which the absolute value is minimized in the pixel row R <b> 3 is −2 pL. That is, the gradation values of the adjacent pixels corresponding to the pixel columns C2 and C4 are both changed from "2" to "3", and the increase amounts (B) and (C) of the ink amount are both set to 11 pL. Cumulative complementation represented by the sum of the complementation error relating to the pixel row R3 and the carryover complementation error (−5pL) from the pixel row R2 when the complementation error relating to the pixel row R3 is (11 + 11−19) = 3 pL The absolute value of the error (-2 pL) is minimized. The accumulated complementation error is carried over to the complementation correction relating to the pixel row R4 performed next as the carryover complemented pixel.

  As described above, in the complementary correction for each pixel row, the gradation value of the adjacent pixel is set such that the absolute value of the accumulated complementary error is minimized. The carryover complementation error generated in the complementation correction of the final pixel row is not carried forward to the correction operation for the next image data.

The complementary correction described above can also be expressed in the following manner. That is, as a result of performing the complementary correction on a portion corresponding to one pixel row in the image data, according to the adjustment related to the ink amount which is not discharged from the defective nozzle indicated by the portion and the complementary discharge by the adjacent nozzle. When there is a deviation between the amount of change in the amount of ink ejected and the amount of ink ejected, the amount of deviation is added to the amount of ink that is not ejected from the defective nozzle in the complementary correction for the next pixel row. The pixel value of the adjacent pixel is set such that the absolute value of the sum of the above value and the change amount of the ink amount due to the complementary discharge is minimized.
For example, as a result of the complementation correction relating to the pixel row R2 in FIG. 7, the displacement amount (cumulative complementation error) in the pixel row R2 is −5 pL. Therefore, in the complementary correction for the next pixel row R3, the offset amount (-5 pL) is added to the ink amount (-19 pL) which is not ejected from the defective nozzle, and the added value (-24 pL) and the adjacent nozzles The pixel value of the adjacent pixel is set such that the sum (-2 pL) of the change amount (11 + 11 = 22 pL) of the ink amount due to the complementary discharge from the above becomes minimum.

  In FIGS. 5 to 7, although the case where the defective nozzle is located other than the end of the row of the nozzles 233 in the head unit 23 has been described as an example, the defective nozzle is at the end of the row of the nozzles 233. In the complementary correction in the case of being positioned, the gradation value of the adjacent pixel corresponding to one adjacent nozzle adjacent to the defective nozzle is set.

  Next, a defective nozzle information acquisition process for acquiring defective nozzle information and an image recording process for recording an image based on image data corrected by correcting image data based on the defective nozzle information will be described.

FIG. 8 is a flowchart showing a control procedure of the defective nozzle information acquisition process.
When the defective nozzle information acquisition process is started, the CPU 41 operates the respective units of the sheet feeding unit 10 and the image recording unit 20 based on predetermined inspection image data to the recording medium M conveyed by the conveyance unit 21. The ink is ejected by the head unit 23 to record an inspection image including the line pattern 60 shown in FIG. 4 (step S11). Specifically, the CPU 41 supplies a control signal to the conveyance drive unit 51, places the recording medium M on the conveyance surface of the conveyance belt 213 by the medium supply unit 12 and the delivery drum 13, and circumferentially moves the conveyance belt 213. The recording medium M is transported. Then, the CPU 41 supplies the inspection image data and the control signal to the recording head drive unit 231, and the recording head drive unit 231 causes the recording head 232 to generate a voltage signal of a drive waveform at an appropriate timing according to the movement of the transport belt 213. By outputting the ink, the nozzles of the head unit 23 discharge ink onto the recording medium M conveyed by the conveyance unit 21, and the inspection image is recorded on the recording medium M.

  The CPU 41 causes the reading unit 25 to repeatedly read the inspection image of the recording medium M at appropriate intervals while conveying the recording medium M by the conveyance unit 21, and acquires the imaging data of the inspection image and stores it in the storage unit 44 (step S12). The recording medium M on which the inspection image is captured is conveyed to the paper discharge unit 30 under the control of the CPU 41.

  The CPU 41 determines whether or not there is an abnormal line indicating the presence of a defective nozzle in the line pattern 60 of the inspection image, using the imaging data of the inspection image obtained in step S12 (step S13). For example, the CPU 41 acquires and analyzes the brightness of imaging data at a position of a predetermined analysis line orthogonal to the line 61, and determines whether each line 61 included in the line pattern 60 exists at a predetermined position. When it is determined that all the lines 61 exist in the predetermined position range and there is no missing line or a line shifted from the predetermined position ("No" in step S13), the CPU 41 performs defective nozzle information acquisition processing. Finish.

  If one of the lines 61 does not exist at a predetermined position, and it is determined that there is an abnormal line ("Yes" in step S13), the CPU 41 selects defective nozzle information indicating a defective nozzle corresponding to the abnormal line. It acquires (step S14). Specifically, the CPU 41 specifies the nozzle 233 of the ejection failure corresponding to the missing line 61 or the line 61 shifted from the predetermined position based on the position of the abnormal line in the line pattern 60, and The arrangement position (here, the array number of the nozzle 233) is acquired as defective nozzle information and stored in the RAM 42. When the acquisition of the defective nozzle information for all the abnormal lines is completed, the CPU 41 ends the defective nozzle information acquisition process.

  The above defective nozzle information acquisition processing is executed for each of the head units 23 corresponding to Y, M, C, and K. At that time, an inspection image may be recorded on each of the head units 23 corresponding to Y, M, C, and K on a single recording medium M, or each inspection image is recorded on a separate recording medium M. It is good.

  FIG. 9 is a flowchart showing the control procedure of the image recording process. The image recording process is started when the image data of the image recorded on the recording medium M is supplied from the external device 2 through the interface 53 and stored in the storage unit 44.

  When the image recording process is started, the CPU 41 reads the defective nozzle information stored in the RAM 42 in step S14 (step S21).

  The CPU 41 substitutes 1 into N, which is a variable indicating the row number of the pixel row in the image data of the image recorded by the ink jet recording apparatus 1, and stores it in the RAM 42 (step S22). In the image data according to the present embodiment, it is assumed that the maximum value of N is Nmax.

  The CPU 41 performs complementary correction on the Nth row (Nth pixel row) of the image data based on the defective nozzle information (step S23). Specifically, the CPU 41 acquires the gradation value of the pixel included in the Nth row of the image data, and the gradation value of the pixel corresponding to the defective nozzle indicated by the defective nozzle information in the Nth row is “0”. The tone values of the adjacent nozzles and the corresponding adjacent pixels are set based on the above-described algorithm. The CPU 41 stores the corrected image data of the Nth row in the RAM 42.

The CPU 41 causes the head unit 23 to perform the recording operation of discharging the ink on the recording medium M by the head unit 23 based on the image data of the Nth row corrected in step S23. A portion corresponding to the Nth row is recorded (step S24).
In step S24, the CPU 41 operates the respective units of the sheet feeding unit 10 and the image recording unit 20 to cause the conveyance unit 21 to convey the recording medium M, and the image of the Nth row corrected in step S23 among the image data. Data is read from the RAM 42 and supplied to the recording head drive unit 231 together with a control signal, and the recording head drive unit 231 causes the recording head 232 to output a voltage signal of a drive waveform. Thus, the CPU 41 causes the head unit 23 to eject the ink to the recording medium M at an appropriate timing based on the corrected image data of the Nth row, and corresponds to the Nth row in the image related to the image data. Make the part recorded.

The CPU 41 determines whether the variable N is less than Nmax (step S25). If it is determined that the variable N is less than Nmax ("Yes" in step S25), the CPU 41 substitutes (N + 1) for the variable N and stores it in the RAM 42 (step S26). When the process of step S26 ends, the CPU 41 shifts the process to step S23.
A part of the recording operation according to step S24 and the processes according to steps S25, S26, and S23 started after step S24 may be performed in parallel. That is, while the portion corresponding to the Nth row of the image data is recorded in step S24, the correction of the (N + 1) th row of the image data may be performed.

As described above, in the processing from step S23 to step S24 among the above, the CPU 41 does not eject the ink from the defective nozzle indicated by the defective nozzle information, and from the adjacent nozzle so as to compensate the ink amount which the defective nozzle does not eject. Complementary control is performed to perform complementary discharge in which the amount of ink to be discharged is adjusted. In addition, in the complementary control, the gradation value of the adjacent pixel is set based on the above-described algorithm so that the absolute value of the accumulated complementary error is minimized, and the ejection of the ink corresponding to the set gradation value is performed. To be done.
That is, if there is a deviation between the amount of ink which is not ejected from the defective nozzle and the amount of change of the amount of ink which is ejected according to the adjustment related to the complementary ejection by the adjacent nozzle in one recording operation, In the complementary control related to the recording operation performed next to the one recording operation within a predetermined proximity distance from the portion corresponding to the non-ejection of the defective nozzle among the part of the image recorded in the recording operation of The deviation amount is added to the amount of ink which is not discharged from the nozzles, the amount of change in the complementary discharge is determined, and the complementary discharge is performed. Here, “within a predetermined proximity distance from the portion corresponding to non-ejection of the defective nozzle” means that the visual effect of complementing the non-ejection is obtained for the position corresponding to the non-ejection of the defective nozzle. It says that it is in the range of the position of discharge. For example, in the present embodiment, the distance between a portion corresponding to non-ejection of a defective nozzle in one pixel row and a portion where complementary ejection from an adjacent nozzle is performed in the next pixel row of the one pixel row is predetermined. It is within close distance.

  When it is determined that the variable N is equal to Nmax and the relationship of N <Nmax is not satisfied (“No” in step S25), the CPU 41 causes the paper discharge unit 30 to transport the recording medium M on which the image is captured. End the image recording process.

  As described above, in the inkjet recording apparatus 1 according to the present embodiment, the head unit 23 that ejects ink to the recording medium M from each of the plurality of nozzles 233 arranged in the X direction, and Y crossing the X direction From the plurality of nozzles 233 with respect to the recording medium M based on the image data, while the relative movement in the Y direction is performed by the conveyance unit 21 that relatively moves the head unit 23 and the recording medium M in the Y direction A CPU 41 as recording control means for recording an image by performing a plurality of recording operations for non-discharging or discharging any amount of ink out of four steps and recording a part of an image related to image data a plurality of times; The CPU 41 ejects ink from a defective nozzle which is preset as a nozzle which does not eject ink normally in each of a plurality of printing operations. In addition, the complementary control is performed to adjust the amount of ink to be ejected from the adjacent nozzle adjacent to the defective nozzle and properly discharge the ink so as to compensate the amount of ink that the defective nozzle does not eject. If there is a deviation between the amount of ink which is not ejected from the defective nozzle in operation and the amount of change of the amount of ink which is ejected according to the adjustment related to the complementary ejection by the adjacent nozzle, recording is performed by the one recording operation. In the complementary control related to the printing operation performed next to the one printing operation within a predetermined proximity distance from the portion corresponding to the non-ejection of the defective nozzle among the part of the image, the non-ejection from the defective nozzle The deviation amount is added to the following ink amount to determine a change in complementary discharge (recording control means). As a result, in the complementary control in each recording operation, the amount of ink which is not ejected from the defective nozzle can not be accurately complemented by the amount of change in the amount of ink ejected from the adjacent nozzle, and a deviation amount (cumulative complementation error, carryover complementation error) occurs. Even in this case, the deviation amount is carried over to the complementary control related to the next recording operation, and is complemented by the amount of change in the amount of ink ejected from the adjacent nozzle in the complementary control related to the next recording operation. Therefore, even if the non-ejection of the ink from the defective nozzle can not be accurately compensated in each recording operation, it is possible to effectively suppress the deterioration of the image quality of the recorded image caused by the defective nozzle. Further, since the complementary discharge is performed by the adjacent nozzles located in the vicinity of the defective nozzle, it is possible to minimize the range in which the change of the gradation value due to the complementary control occurs in the image data.

  Further, the CPU 41 determines the amount of change in the complementary discharge so as to minimize the amount of deviation and performs complementary control (recording control means). Thereby, in the complementary control in each recording operation, the influence of the shift amount (forward carryover error) added from the previous stage can be minimized, so that the image quality deterioration of the recorded image due to the defective nozzle can be suppressed more effectively. can do.

  Further, the maximum settable value of the ink amount which the CPU 41 as the recording control means discharges from the nearby nozzles at the time of the complementary discharge is the amount of the ink which the CPU 41 as the recording control means discharges without complementary control. Greater than the maximum settable value. As a result, regardless of the gradation value of the adjacent pixel in the image data, the amount of ink ejected from the adjacent nozzle can be increased in the complementary control. Therefore, it is possible to easily compensate for non-ejection of the ink from the defective nozzle in the complementary control related to each recording operation.

  In addition, for the multiple ink amounts discharged from the plurality of nozzles 233 of the head unit 23 by the CPU 41 as the recording control unit, the ratio of the ink amount that is relatively large to one ink amount is a non-integer included. In such a configuration, there are many cases where the amount of ink that is not ejected from the defective nozzle can not be accurately complemented for each recording operation, but the displacement amount generated in this complementation is used for the complementary control related to the recording operation to be performed next. Since the carry over is carried out and complemented, it is possible to effectively suppress the deterioration of the image quality of the recorded image caused by the defective nozzle.

  Further, the inkjet recording apparatus 1 includes a reading unit 25 that reads an image recorded on the recording medium M, and the CPU 41 identifies defective nozzles based on the reading result of a predetermined inspection image by the reading unit 25 and defective nozzle information Is generated (defective nozzle identification means). As a result, since the defective nozzle can be specified in the inkjet recording apparatus 1, it is possible to more easily and surely suppress the deterioration of the image quality of the recorded image caused by the defective nozzle.

  Further, the plurality of nozzles 233 are arranged to be able to eject ink across the recordable width of the image in the X direction on the recording medium M. Thus, the single-pass type inkjet recording apparatus 1 configured to record an image by ink discharge from the plurality of nozzles 233 in one relative movement between the head unit 23 and the recording medium M is configured. In the single-pass type inkjet recording apparatus 1, ink can not be ejected from different nozzles 233 to a specific position of the recording medium M, and non-ejection of ink by a defective nozzle can not be compensated. The complementation can be performed in the single-pass type inkjet recording apparatus 1 to suppress the deterioration in the image quality of the recorded image caused by the defective nozzle.

(Modification)
Then, the modification of the said embodiment is demonstrated. The present modification differs from the above embodiment in that all pixel rows of image data are corrected in advance to generate corrected image data, and recording of an image is performed based on the generated corrected image data. The other points are the same as those of the above-described embodiment, and therefore, differences will be described below.

FIG. 10 is a flowchart showing the control procedure of the image recording process according to the present modification.
In the image recording process according to the present modification, steps S27 and S28 are executed instead of steps S22 to S26 of the image recording process shown in FIG.

  In the present modification, when the process of step S21 ends, the CPU 41 corrects the image data to generate corrected image data (step S27). That is, the CPU 41 performs complementary correction on all the pixel rows based on the above-described algorithm in the order of arrangement of the pixel rows in the image data, and generates and stores corrected image data consisting of all the corrected pixel rows. It makes part 44 memorize. Note that the corrected image data may be newly generated as data separate from the original image data, or may be corrected image data with respect to the original image data as the corrected image data.

The CPU 41 causes the head unit 23 to eject the ink to the recording medium M based on the corrected image data generated in step S27 to record the entire image (step S28). The operation of each part of the inkjet recording apparatus 1 in step S28 is the same as step S11 except for the image data to be used.
When the recording of the image on the recording medium M is completed, the CPU 41 causes the paper discharge unit 30 to convey the recording medium M, and ends the image recording process.

  The correction image data may be generated by an apparatus outside the inkjet recording apparatus 1. For example, the defective nozzle information acquired by the defective nozzle information acquisition process is transmitted to the external device 2 through the interface 53, and the external device 2 corrects the image data based on the defective nozzle information to generate corrected image data. The image recording process may be performed based on the corrected image data input from the external device 2 to the control unit 40 via the interface 53.

  As described above, in the inkjet recording apparatus 1 according to the present modification, the head unit 23 that ejects ink to the recording medium M from each of the plurality of nozzles 233 arranged in the X direction, and Y crossing the X direction The conveyance unit 21 for relatively moving the head unit 23 and the recording medium M in the direction, and the CPU 41 are provided. The CPU 41 corrects the image data based on the information indicating the defective nozzle from which the ink is not ejected properly. Is generated from the plurality of nozzles 233 based on the corrected image data based on the corrected image data while the relative movement in the Y direction is performed by the transport unit 21. The image is recorded by performing a plurality of recording operations for non-discharging or discharging a quantity of ink and recording a part of the image according to the corrected image data. The CPU 41 as a recording control unit and a correction image data generation unit respectively corresponds the pixel value of the pixel corresponding to the defective nozzle to the non-ejection of the ink for the portion corresponding to each of the plurality of recording operations in the image data. In order to compensate for the amount of ink ejected from a nearby nozzle located adjacent to the defective nozzle and properly discharging the ink so as to compensate for the amount of ink not ejected by the defective nozzle while setting to a value Complementary correction for setting the pixel value of the adjacent pixel corresponding to the adjacent nozzle is performed, and in the complementary correction for the portion corresponding to one recording operation in the image data, the amount of ink which is not ejected from the defective nozzle and the adjacent nozzle If there is a deviation between the amount of change in the amount of ink ejected in accordance with the adjustment relating to the complementary ejection, the image data Complementary correction for the part corresponding to the recording operation performed after the one recording operation within a predetermined proximity distance from the part corresponding to the non-ejection of the defective nozzle among the part of the image recorded in the recording operation Then, the deviation amount is added to the ink amount that is not ejected from the defective nozzle to determine the amount of change in complementary ejection, and the pixel value of the neighboring pixel is set according to the determined amount of change. According to such a configuration, an image in which non-ejection of ink from a defective nozzle is complemented without making timing alignment between the correction of the portion corresponding to each recording operation of the image data and the recording operation by the head unit 23 Can be recorded, so that it is possible to more easily suppress the image quality deterioration of the recorded image caused by the defective nozzle.

  Further, in the complementary correction, the tone values of the neighboring pixels are set so as to minimize the amount of deviation. Thereby, in the complementary control in each pixel row, the influence of the carryover complementation error carried over from the previous stage can be minimized, so that the image quality deterioration of the recorded image due to the defective nozzle can be suppressed more effectively. .

  In addition, the maximum value of the amount of ink ejected from the adjacent nozzles at the time of complementary discharge corresponding to the pixel value of the adjacent pixel that can be set in the complementary correction corresponds to the pixel value that can be set in the image data for which the complementary correction is not performed Is larger than the maximum value of the amount of ink ejected. Thus, regardless of the tone value of the adjacent pixel in the image data, the amount of ink ejected from the adjacent nozzle can be increased by the complementary correction. Therefore, non-ejection of ink from the defective nozzle in each pixel row can be easily compensated.

The present invention is not limited to the above embodiment and modifications, and various modifications are possible.
For example, in the above embodiment, one pixel row constitutes a complementation target pixel group, and the recording operation and the complementation control (complementary correction) are performed for each complementation target pixel group (pixel row). The recording operation and the complementation control (complementary correction) may be performed for each complementation target pixel group including a plurality of adjacent pixel rows.
Further, in the above-described modification, the pixel row of one pixel constitutes the complement target pixel group, and the complement correction is performed for each pixel group (pixel row) of the complement target to generate the corrected image data. However, the complementary correction may be performed for each complementary target pixel group including a plurality of adjacent pixel rows.
In these cases, in the complementation control and the complementation correction, the increase in the amount of discharged ink pertaining to all the adjacent pixels included in the complementation target pixel group is added to all the pixels included in the complementation target pixel group and corresponding to the defective nozzle. A value obtained by subtracting the amount of decrease in the amount of discharged ink may be used as the complementation error relating to the complementation target pixel group.

  Further, although the above embodiment and modification have been described using an example in which the gradation value of the adjacent pixel is set so as to minimize the absolute value of the accumulated complementation error in the complementation correction and the complementation control, the present invention is limited thereto Rather, the tone value of the adjacent pixel in the range where the absolute value of the accumulated complementation error is equal to or less than the absolute value of the value obtained by subtracting the decrease in the amount of ink ejected from the defective nozzle due to nonejection control from the carryover complement error from the previous stage. May be set.

  Further, in the above embodiment and modification, an example in which the adjacent pixel corresponding to the nozzle 233 adjacent to the defective nozzle is corrected in the complementary correction has been described, but the nozzle 233 in the vicinity including the nozzle 233 adjacent to the defective nozzle The tone values of neighboring pixels corresponding to may be corrected. Here, the nozzle 233 in the vicinity of the defective nozzle is at such a position that the visual effect of complementing the non-ejection of the ink from the defective nozzle is obtained in the recording image when the amount of ink ejected by the complementary correction increases. The nozzle 233 is disposed. In this case, when correcting the gradation value of the neighboring pixel corresponding to the neighboring nozzle in the complementary correction, the gradation value of the neighboring pixel corresponding to the nozzle 233 near the defective nozzle may be corrected preferentially.

Moreover, in the said embodiment and modification, although the case where one nozzle 233 was specified as a defect nozzle was mentioned as an example and demonstrated, it is not the meaning limited to this.
For example, when two or more nozzles 233 are specified as defective nozzles, complementary correction may be separately performed for each of the defective nozzles.
In addition, when two adjacent nozzles 233 are specified as defective nozzles, in the complementary correction, the pixel values of adjacent pixels corresponding to the adjacent nozzles respectively adjacent to these two defective nozzles are set to the above-described algorithm. It may be corrected based on the above.

  Moreover, although the said embodiment and modification demonstrated the amount of the ink discharged from the nozzle 233 using the example fixed at 0pL, 7pL, 19pL, 30pL, it is not the meaning limited to this, it is discharged. The present invention may be applied to an inkjet recording apparatus 1 in which the amount of ink used is changed according to the setting related to the ink discharge operation. For example, an inkjet recording in which the voltage signal of the drive waveform supplied from the print head drive unit 231 to the print head 232 is changed according to the environmental temperature, and the amount of ink ejected from the nozzles 233 is changed according to the change. The present invention may be applied to the device 1. In this case, for example, a look-up table indicating the correspondence between the environmental temperature and the amount of discharged ink is stored in the ROM 43, and the above-mentioned is described based on the amount of discharged ink obtained by the CPU 41 referring to the look-up table from the environmental temperature. Correction of image data is performed based on the following algorithm.

  Further, although the above embodiment has been described using an example in which the complementary correction is performed on one pixel row of image data by the operation of the CPU 41 in step S23 of the image recording process shown in FIG. is not. For example, the complementary correction of the pixel row may be performed by supplying a portion related to the pixel row in the image data to a predetermined logic circuit.

  Moreover, although the said embodiment and modification demonstrated the amount of the ink discharged from the nozzle 233 using the example which is four steps including non-discharge (0 pL) of ink, it is not the meaning limited to this, a nozzle The present invention can be applied to an inkjet recording apparatus 1 that ejects an amount of ink of at least two steps from 233.

  Further, in the embodiment and the modification described above, the example in which the ink of the minimum non-integer multiple amount is discharged from the nozzle 233 is described, but the ink of the integer multiple of the minimum amount is discharged from the nozzle 233 The present invention may be applied to the inkjet recording apparatus 1 of FIG. For example, in the complementary control according to one recording operation, the amount of ink ejected from the adjacent nozzle corresponding to the image data is maximum, and the amount of ejected ink can not be increased due to the complementary ejection, and a deviation amount occurs Alternatively, this shift amount may be carried over to the complementary control according to the next recording operation.

  Moreover, although the said embodiment and modification demonstrated using the example which conveys the recording medium M by the conveyance part 21 provided with the conveyance belt 213, it is not the meaning limited to this, for example, conveyance of the conveyance part 21 rotates. The recording medium M may be held and conveyed on the outer peripheral surface of the drum.

  In the above embodiment and the modification, the head unit 23 is fixed, and the recording medium M is conveyed by the conveyance unit 21 to move relative to the head unit 23. However, instead of this, The recording medium M may be fixed, and an image may be recorded by the head unit 23 that moves relative to the recording medium M. Further, the main scanning operation for causing the head unit to eject ink to the recording medium M while moving the head unit and the recording medium M relative to each other in the main scanning direction by the moving means, and the recording medium M in the sub scanning direction by the moving means The present invention may be applied to an ink jet recording apparatus that records an image by repeatedly performing a moving sub-scanning operation.

  Although some embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, but includes the scope of the invention described in the claims and the equivalents thereof. .

DESCRIPTION OF SYMBOLS 1 inkjet recording apparatus 2 external device 10 paper feeding unit 11 paper feeding tray 12 medium supply unit 13 delivery drum 20 image recording unit 21 conveyance unit 211, 212 conveyance roller 213 conveyance belt 22 heating unit 23 head unit 231 head unit 231 recording head drive unit 232 recording Head 233 nozzle 24 fixing unit 25 reading unit 30 discharge unit 31 delivery drum 32 delivery unit 33 discharge tray 40 control unit 41 CPU
42 RAM
43 ROM
44 storage unit 51 transport drive unit 52 operation display unit 53 interface 54 bus 60 line pattern 61, 61a line

Claims (9)

Recording means for ejecting ink to the recording medium from each of the plurality of nozzles arranged in the first direction;
Moving means for relatively moving the recording means and the recording medium in a second direction intersecting the first direction;
While the relative movement is performed in the second direction by the movement unit, any one of a plurality of levels of ink is not discharged or discharged from each of the plurality of nozzles to the recording medium based on image data Recording control means for recording the image by performing the recording operation for recording a part of the image related to the image data a plurality of times;
Equipped with
The recording control means
In each of the plurality of printing operations, the ink is not ejected from a defective nozzle preset as a nozzle that does not eject ink normally, and the position is located in the vicinity of the defective nozzle so as to compensate the ink amount that the defective nozzle does not eject. Perform complementary control to perform complementary discharge with the amount of ink to be discharged from the nearby nozzles that normally discharge ink.
When there is a deviation between the amount of ink which is not discharged from the defective nozzle and the amount of change of the amount of ink which is discharged according to the adjustment related to the complementary discharge by the adjacent nozzle in one recording operation. The recording operation performed next to the one recording operation within a predetermined proximity distance from the portion corresponding to the non-ejection of the defective nozzle among the part of the image recorded in the one recording operation In the complementary control, the deviation amount is added to the ink amount which is not discharged from the defective nozzle to determine the change amount in the complementary discharge,
At least one of the plurality of ink amounts excluding non-ejection among the plurality of ink amounts changes the ink amount ejected from the adjacent nozzle from one ink amount to another ink amount among the plurality of ink amounts feasible by, unlike the variation both of any ink amount,
The maximum settable value of the amount of ink which the recording control means discharges from the adjacent nozzles at the time of the complementary discharge is the maximum setting of the amount of ink which the recording control means discharges without performing the complementary control corresponding to the image data. An ink jet recording apparatus characterized in that the value is larger than the possible value .   The inkjet recording apparatus according to claim 1, wherein the recording control unit performs the complementary control by determining the change amount in the complementary discharge so as to minimize the deviation amount. Recording means for ejecting ink to the recording medium from each of the plurality of nozzles arranged in the first direction;
Moving means for relatively moving the recording means and the recording medium in a second direction intersecting the first direction;
Correction image data generation means for correcting image data based on information indicating a defective nozzle from which ink is not normally ejected to generate correction image data;
While the relative movement is performed in the second direction by the movement unit, any one of a plurality of levels of ink is not ejected from each of the plurality of nozzles with respect to the recording medium based on the corrected image data or Recording control means for recording the image by performing a plurality of recording operations for discharging a part of the image according to the corrected image data by performing discharge.
Equipped with
The corrected image data generation unit
The pixel value of the pixel corresponding to the defective nozzle is set to a value corresponding to the non-ejection of the ink for the portion corresponding to each of the plurality of printing operations in the image data, and the defective nozzle does not eject The pixel value of the neighboring pixel corresponding to the nearby nozzle is set so as to perform complementary discharge in which the amount of ink ejected from the nearby nozzle located in the vicinity of the defective nozzle and compensating the ink amount properly to compensate for the ink amount is adjusted. Perform complementary correction to set,
In the complementary correction for the portion corresponding to one recording operation of the image data, the ink ejected according to the adjustment related to the complementary ejection by the adjacent nozzle and the amount of ink which is not ejected from the defective nozzle When there is a deviation between the amount of change and the amount of change, a predetermined portion of the image data recorded in the one recording operation is a portion corresponding to non-ejection of the defective nozzle. In the complementary correction with respect to the portion corresponding to the recording operation performed after the one recording operation within the close distance of the ink, the deviation amount is added to the ink amount which is not ejected from the defective nozzle Determining the amount of change in complementary discharge, and setting the pixel value of the neighboring pixel according to the determined amount of change;
At least one of the plurality of ink amounts excluding non-ejection among the plurality of ink amounts changes the ink amount ejected from the adjacent nozzle from one ink amount to another ink amount among the plurality of ink amounts feasible by, unlike the variation both of any ink amount,
The maximum value of the amount of ink ejected from the adjacent nozzles at the time of the complementary discharge corresponding to the pixel value of the adjacent pixel that can be set in the complementary correction can be set in the image data in which the complementary correction is not performed An ink jet recording apparatus characterized in that it is larger than the maximum value of the amount of ink ejected corresponding to the value . The inkjet recording apparatus according to claim 3 , wherein in the complementary correction, a pixel value of the neighboring pixel is set so as to minimize the deviation amount. The plurality of ink amounts discharged from the plurality of nozzles of the recording unit by the recording control unit include ones in which the magnification of the relatively large ink amount is non-integer with respect to one ink amount. The ink jet recording apparatus according to any one of claims 1 to 4 , wherein Reading means for reading an image recorded on the recording medium;
Defective nozzle specifying means for specifying the defective nozzle based on the reading result of the predetermined inspection image by the reading means;
The ink jet recording apparatus according to any one of claims 1 to 5 , comprising: 7. The ink jet recording apparatus according to any one of claims 1 to 6 , wherein the plurality of nozzles are arranged to be able to eject ink across the recordable width of the image in the first direction on the recording medium. The inkjet recording device as described. Recording means for discharging ink to the recording medium from each of the plurality of nozzles arranged in the first direction, and relative movement between the recording means and the recording medium in a second direction intersecting the first direction A control method of an ink jet recording apparatus comprising:
While the relative movement is performed in the second direction by the movement unit, any one of a plurality of levels of ink is not discharged or discharged from each of the plurality of nozzles to the recording medium based on image data A recording control step of recording the image by performing the recording operation of recording a part of the image related to the image data a plurality of times;
In the recording control step,
In each of the plurality of printing operations, the ink is not ejected from a defective nozzle preset as a nozzle that does not eject ink normally, and the position is located in the vicinity of the defective nozzle so as to compensate the ink amount that the defective nozzle does not eject. Perform complementary control to perform complementary discharge with the amount of ink to be discharged from the nearby nozzles that normally discharge ink.
When there is a deviation between the amount of ink which is not discharged from the defective nozzle and the amount of change of the amount of ink which is discharged according to the adjustment related to the complementary discharge by the adjacent nozzle in one recording operation. The recording operation performed next to the one recording operation within a predetermined proximity distance from the portion corresponding to the non-ejection of the defective nozzle among the part of the image recorded in the one recording operation In the complementary control, the deviation amount is added to the ink amount which is not discharged from the defective nozzle to determine the change amount in the complementary discharge,
At least one of the plurality of ink amounts excluding non-ejection among the plurality of ink amounts changes the ink amount ejected from the adjacent nozzle from one ink amount to another ink amount among the plurality of ink amounts feasible by, unlike the variation both of any ink amount,
In the recording control step, the maximum settable value of the amount of ink ejected from the adjacent nozzles at the time of the complementary ejection corresponds to the maximum setting of the amount of ink ejected without performing the complementation control corresponding to the image data in the recording control step. A control method of an ink jet recording apparatus characterized in that the value is larger than a possible value . Recording means for discharging ink to the recording medium from each of the plurality of nozzles arranged in the first direction, and relative movement between the recording means and the recording medium in a second direction intersecting the first direction A control method of an ink jet recording apparatus, comprising: moving means for moving image data; and corrected image data generation means for correcting image data to generate corrected image data;
A corrected image data generation step of correcting the image data to generate the corrected image data based on information indicating a defective nozzle from which the ink is not ejected normally by the corrected image data generation unit;
While the relative movement is performed in the second direction by the movement unit, any one of a plurality of levels of ink is not ejected from each of the plurality of nozzles with respect to the recording medium based on the corrected image data or A recording control step of recording the image by performing a plurality of recording operations of discharging and recording a part of the image according to the corrected image data;
In the corrected image data generation step,
The pixel value of the pixel corresponding to the defective nozzle is set to a value corresponding to the non-ejection of the ink for the portion corresponding to each of the plurality of printing operations in the image data, and the defective nozzle does not eject The pixel value of the neighboring pixel corresponding to the nearby nozzle is set so as to perform complementary discharge in which the amount of ink ejected from the nearby nozzle located in the vicinity of the defective nozzle and compensating the ink amount properly to compensate for the ink amount is adjusted. Perform complementary correction to set,
In the complementary correction for the portion corresponding to one recording operation of the image data, the ink ejected according to the adjustment related to the complementary ejection by the adjacent nozzle and the amount of ink which is not ejected from the defective nozzle When there is a deviation between the amount of change and the amount of change, a predetermined portion of the image data recorded in the one recording operation is a portion corresponding to non-ejection of the defective nozzle. In the complementary correction with respect to the portion corresponding to the recording operation performed after the one recording operation within the close distance of the ink, the deviation amount is added to the ink amount which is not ejected from the defective nozzle Determining the amount of change in complementary discharge, and setting the pixel value of the neighboring pixel according to the determined amount of change;
At least one of the plurality of ink amounts excluding non-ejection among the plurality of ink amounts changes the ink amount ejected from the adjacent nozzle from one ink amount to another ink amount among the plurality of ink amounts feasible by, unlike the variation both of any ink amount,
The maximum value of the amount of ink ejected from the adjacent nozzles at the time of the complementary discharge corresponding to the pixel value of the adjacent pixel that can be set in the complementary correction can be set in the image data in which the complementary correction is not performed A control method of an ink jet recording apparatus characterized in that it is larger than the maximum value of the amount of ink ejected corresponding to the value .

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