WO2015029788A1 - Système d'impression par jet d'encre et procédé de correction de non décharge et programme associé - Google Patents

Système d'impression par jet d'encre et procédé de correction de non décharge et programme associé Download PDF

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Publication number
WO2015029788A1
WO2015029788A1 PCT/JP2014/071384 JP2014071384W WO2015029788A1 WO 2015029788 A1 WO2015029788 A1 WO 2015029788A1 JP 2014071384 W JP2014071384 W JP 2014071384W WO 2015029788 A1 WO2015029788 A1 WO 2015029788A1
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Prior art keywords
correction
image
nozzle
undischarge
halftone
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PCT/JP2014/071384
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English (en)
Japanese (ja)
Inventor
隆史 涌井
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富士フイルム株式会社
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Publication of WO2015029788A1 publication Critical patent/WO2015029788A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/21—Ink jet for multi-colour printing
    • B41J2/2132—Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding
    • B41J2/2146—Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding for line print heads
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/21—Ink jet for multi-colour printing
    • B41J2/2132—Print quality control characterised by dot disposition, e.g. for reducing white stripes or banding
    • B41J2/2139—Compensation for malfunctioning nozzles creating dot place or dot size errors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/40087—Multi-toning, i.e. converting a continuous-tone signal for reproduction with more than two discrete brightnesses or optical densities, e.g. dots of grey and black inks on white paper
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/401—Compensating positionally unequal response of the pick-up or reproducing head
    • H04N1/4015—Compensating positionally unequal response of the pick-up or reproducing head of the reproducing head
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/405—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
    • H04N1/4055—Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels producing a clustered dots or a size modulated halftone pattern
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J29/00—Details of, or accessories for, typewriters or selective printing mechanisms not otherwise provided for
    • B41J29/38—Drives, motors, controls or automatic cut-off devices for the entire printing mechanism
    • B41J29/393—Devices for controlling or analysing the entire machine ; Controlling or analysing mechanical parameters involving printing of test patterns
    • B41J2029/3935—Devices for controlling or analysing the entire machine ; Controlling or analysing mechanical parameters involving printing of test patterns by means of printed test patterns

Definitions

  • the present invention relates to an inkjet printing system, an undischarge correction method thereof, and a program, and more particularly to an image correction technique for correcting a recording defect due to an undischarge nozzle in an inkjet printing system that performs image recording by a single pass method.
  • the inkjet printing system includes a recording head having a plurality of nozzles, and forms an image on a recording medium such as printing paper by controlling an ink ejection operation from each nozzle based on image data to be printed.
  • the recording head may generate undischargeable nozzles that cannot be discharged due to nozzle clogging or failure of the discharge energy generating element.
  • defective nozzles that cause ejection bends that cause the landing position error to become larger than the allowable value are forcibly discharged so that they are not used for recording, and treated as undischarged nozzles. There is.
  • Non-discharge correction is synonymous with “non-discharge correction” and is referred to as “non-discharge correction” in this specification.
  • Undischarge correction is realized by changing dots that are ejected from other dischargeable nozzles (non-discharge nozzles) close to the discharge failure nozzle.
  • an appropriate condition for correction is that the ink amount is approximately the same before and after the correction. For example, when one nozzle fails to discharge and correction is performed with two nozzles on both sides of the nozzle, the nozzles are supposed to be discharged from the three nozzles, which are the nozzles and the nozzles on both sides. This amount of ink is discharged by two nozzles on both sides.
  • the amount of ink ejected from the correction nozzles on both sides of the non-ejection nozzle is about 1.5 times the ink amount of the normal part (non-correction part)
  • the density difference between the normal part and the correction part will be reduced.
  • the correction part of undischarge correction becomes inconspicuous. Actually, since there is a difference in ejection characteristics for each nozzle, the correction value is given a certain range without strictly increasing the ink amount by a factor of 1.5.
  • the discharge failure correction unit is inside the dot aggregation unit (cluster)
  • the effect of the discharge failure correction differs depending on whether it is a part.
  • the present invention has been made in view of such circumstances, and provides an inkjet printing system, an undischarge correction method, and a program for solving the above-described problems and realizing undischarge correction with an appropriate correction strength. Objective.
  • the ink jet printing system is an ink jet printing system for performing image recording by a single pass method, and cannot be used for image recording among a plurality of nozzles and a recording head.
  • a non-discharge information storage unit that stores position information of non-discharge nozzles
  • a halftone processing unit that quantizes the input image to generate a halftone image indicating a multi-value dot pattern of three or more values
  • an undischarge correction processing unit that performs an image correction process for reducing the visibility of image defects of the recording failure portion by the undischarge nozzle based on the position information of the undischarge nozzle
  • a halftone image expressing gradation by halftone is generated, and discharge failure correction is performed according to the distance in the nozzle arrangement direction from the end in a cluster
  • the non-discharge correction function in the ink jet printing system is realized by a combination of correction processing by the non-discharge correction processing unit and halftone processing by the halftone processing unit, and by a correction process by the non-discharge correction processing unit. possible.
  • the correction strength can be weakened inside the cluster as compared with the end of the cluster.
  • the end of the cluster may be configured to increase the correction strength compared to the inside of the cluster.
  • the ink jet printing system includes a table that defines the correction strength with respect to the distance in the nozzle arrangement direction from the end of the cluster, It can be set as the structure by which the correction intensity
  • the table may be a correction dot conversion table in which the dot size after correction is defined with respect to the dot size before correction.
  • the undischarge correction method according to the sixth aspect is based on discharge from a nozzle other than the undischarge nozzle caused by a recording failure caused by an undischarge nozzle of an inkjet printing system that performs image recording by a single pass method.
  • An undischarge correction method that compensates for dot recording, an undischarge information storage step of storing position information of undischarge nozzles that cannot be used for image recording among a plurality of nozzles in a recording head having a plurality of nozzles;
  • a halftone processing step of generating a halftone image that quantizes the input image and indicates a multi-valued dot pattern of three or more values, and position information of the discharge failure nozzle for the input image or the halftone image
  • a discharge failure correction processing step of performing an image correction process for reducing the visibility of image defects in a recording failure portion by a discharge failure nozzle.
  • a halftone image representing gradation expression is generated by a cluster-type halftone in which two or more dots are agglomeratedly arranged in the nozzle arrangement direction of the network or the recording head, and 2 in the nozzle arrangement direction.
  • the non-discharge correction correction intensity is changed to generate a dot pattern of the non-discharge correction unit adjacent to the defective recording portion. This is an undischarge correction method for performing undischarge correction.
  • a program according to the seventh aspect provides a computer with an undischarge correction function that reduces the visibility of image defects due to recording defects caused by undischarge nozzles of an inkjet printing system that performs image recording by a single pass method.
  • An undischarge information storage function for storing information on the position of undischarge nozzles that cannot be used for image recording among a plurality of nozzles in a print head having a plurality of nozzles, and a program for realizing the program Based on the halftone processing function that quantizes the image to generate a halftone image showing a multi-valued dot pattern of three or more values, and the position information of the discharge failure nozzle for the input image or the halftone image And an undischarge correction processing function that performs image correction processing that reduces the visibility of image defects in defective recording areas due to undischarge nozzles.
  • the halftone processing function generates a halftone image that expresses gradation using an AM (Amplitude Modulation) network or a cluster-type halftone in which two or more dots are aggregated in the nozzle array direction of the recording head.
  • the discharge failure correction is performed by changing the correction strength of the discharge failure correction in accordance with the distance in the nozzle alignment direction from the end of the cluster in which two or more dots are aggregated in the nozzle alignment direction. This is a program for realizing undischarge correction for generating a dot pattern of a portion.
  • an appropriate correction strength can be set according to the positional relationship of the discharge failure correction unit with respect to the cluster shape. Therefore, favorable undischarge correction
  • amendment process by a 1st method The block diagram which showed the flow of the undischarge correction process by a 2nd method Schematic diagram of a discharge failure correction image in discharge failure correction processing according to the first method Schematic diagram of a halftone image that is a halftone processing result of the discharge failure correction image shown in FIG.
  • a diagram showing a configuration example of an inkjet recording apparatus 21A is a perspective plan view showing an example of the structure of the head, and FIG. 21B is a partially enlarged view of the heel portion.
  • Plane perspective view showing another structural example of the head 21 is a cross-sectional view taken along line 23-23 in part (A) of FIG.
  • the non-discharge correction technology changes the dot pattern at the image position corresponding to the nozzles in the vicinity of the non-discharge nozzles in the recording head, so that the non-discharge portions (streaky image defects) caused by the non-discharge nozzles are not discharged.
  • This is a correction technique that compensates for dots recorded by ejection from nozzles other than the nozzles and reduces the visibility of image defects.
  • the first method is a method of obtaining a corrected halftone image by performing correction processing on a multi-tone input image and performing halftone processing on the corrected image data.
  • the second method is a method of obtaining a corrected halftone image by applying correction for correcting the dot arrangement to a halftone image obtained by halftone processing of an input image.
  • FIG. 1 is a block diagram showing a flow of undischarge correction processing according to the first method.
  • the discharge failure correction method 16 according to the first method uses discharge failure information 14 indicating the position of discharge failure nozzles for discharge image correction processing 16 for an input image 12 captured as original image data representing the image content to be printed. I do.
  • the data format of the input image 12 is not particularly limited, here, for the sake of simplicity, it is assumed that the input image 12 is a gradation image having the same color type, number of colors, and resolution as the ink color used in the inkjet printing system. .
  • the image data is 8 bits (256 bits) for each color of CMYK.
  • Image data having (gradation).
  • Undischarge information 14 is information indicating the position of the undischarge nozzle in the recording head of the ink jet printing system (“position information of undischarge nozzle”).
  • position information of undischarge nozzle The position information of undischarge nozzles that cannot be used for image recording can be specified from the output result of the test pattern.
  • the identified undischarge nozzle position information is stored as undischarge information 14 in an undischarge information storage unit such as a memory.
  • the undischarge correction process 16 the image data at the image position in the vicinity of the undischarge nozzle is corrected, and an undischarge corrected image 18 which is corrected multi-tone image data is obtained.
  • a halftone process 20 is performed on the discharge failure correction image 18 thus obtained, and a halftone image 22 which is image data representing a dot pattern is obtained.
  • the halftone process 20 generally quantizes multi-tone image data of M values (M is an integer of 3 or more) and has N values (N is an integer of 2 or more and less than M) that can be recorded by the recording head. It is a process of converting to data.
  • M is an integer of 3 or more
  • N is an integer of 2 or more and less than M
  • It is a process of converting to data.
  • an image signal of 8 bits ⁇ (256 gradations) for each color of CMYK is converted into a signal (dot data) representing a multi-value dot arrangement of three or more values in pixel units.
  • the halftone process 20 is performed with multiple gradations (for example, 4) “Discharge large droplet ink”, “Discharge medium droplet ink”, “Discharge small droplet ink”, “Do not discharge (no droplet)”
  • a dither method, an error diffusion method, or the like is applied to such halftone processing. Large dots are formed on the recording medium by ejecting large drops, medium dots are formed by ejecting medium drops, and small dots are formed by ejecting small drops.
  • the halftone image 22 generated through the halftone process 20 becomes dot data reflecting the gradation correction of the discharge failure correction process 16. That is, in the first method, undischarge correction is performed at the data stage of the continuous tone image before halftone processing, and the signal value (gradation value) corresponding to the image position near the undischarge nozzle is increased. A halftone image 22 corrected by the procedure of performing the halftone process 20 on the discharge failure correction image 18 is obtained.
  • the process of performing the undischarge correction process 16 corresponds to an undischarge correction process process
  • the process of performing the halftone process 20 corresponds to a halftone process process.
  • the undischarge correction function is realized by combining the undischarge correction process 16 and the halftone process 20.
  • FIG. 2 is a block diagram showing the flow of undischarge correction processing by the second method.
  • the undischarge correction method according to the second method converts the input image 12 that is the original image data into a multi-value halftone image 34 by a halftone process 32, and then performs an undischarge operation on the halftone image 34.
  • the discharge failure correction process 36 is performed using the information 14.
  • the undischarge correction process 36 a correction process is performed in which the ink amount of dots corresponding to the adjacent nozzles of the undischarge nozzle is corrected.
  • a discharge failure corrected halftone image 38 which is dot data after discharge failure correction is obtained.
  • the second method performs the halftone process before the undischarge correction, and performs the undischarge correction on the halftone image after the halftone process, thereby performing the undischarge corrected halftone image 38. Have gained.
  • the process of performing the halftone process 32 corresponds to the “halftone process process”, and the process of performing the undischarge correction process 36 corresponds to the “undischarge correction process process”.
  • the discharge failure correction function is realized by the discharge failure correction process 36.
  • FIG. 3 is a schematic diagram of the discharge failure correction image 18
  • FIG. 4 is a schematic view of a halftone image 22 that is a halftone processing result of the discharge failure correction image 18.
  • reference numeral 40 denotes a line-type recording head (line head) in the single-pass inkjet printing system.
  • the recording head 40 includes a plurality of nozzles 42 for ejecting ink droplets.
  • the vertical direction in FIG. 3 is the paper feeding direction, which is called “y direction” or “sub-scanning direction”.
  • a nozzle row 44 in which a plurality of nozzles 42 are arranged in a line along the x direction is depicted.
  • the nozzles are not necessarily arranged in a line.
  • the number of nozzles, nozzle density, and nozzle arrangement in the recording head are not particularly limited, and there may be various forms.
  • a one-dimensional nozzle array in which a large number of nozzles are arranged on a straight line (in a line) at a constant interval may be used.
  • a so-called staggered arrangement may be employed in which each nozzle row is shifted in the nozzle row direction by a half pitch of the nozzle interval (inter-nozzle pitch). Further, in order to achieve higher recording resolution, a configuration in which a large number of nozzles are two-dimensionally arranged on the ink ejection surface (nozzle surface), such as a matrix arrangement in which three or more nozzle rows are arranged, can be employed. .
  • the projected nozzle array in which the nozzles in the two-dimensional nozzle array are projected (orthographically projected) so as to be aligned along the medium width direction (corresponding to the main scanning direction)
  • medium width direction corresponding to the main scanning direction
  • equal intervals means substantially equal intervals as the droplet ejection points that can be recorded by the ink jet printing system.
  • the concept of “equally spaced” also includes cases where the intervals are slightly different in consideration of manufacturing errors and movement of droplets on the medium due to landing interference.
  • nozzle positions can be associated with the order of projection nozzles arranged along the main scanning direction.
  • the term “nozzle position” refers to the position of the nozzle in this substantial nozzle row.
  • the positional relationship in the substantial nozzle row is expressed. Since the nozzle position can be expressed as an x coordinate, the nozzle position can be associated with a position in the x direction (x coordinate).
  • the total number of nozzles constituting the nozzle row 44 is appropriately designed according to the recording resolution and the drawable width.
  • the eighth nozzle from the left among the plurality of nozzles 42 constituting the nozzle row 44 is an undischargeable nozzle 46 that cannot be discharged, and the other nozzles are normal nozzles that can be discharged.
  • the x-direction pixel position corresponding to the position (nozzle number k) of the undischarge nozzle 46 cannot record a dot.
  • the pixel line along the y direction at the corresponding position is a streak generating part in which a white streak (recording defective part) occurs on the print image.
  • the first correction nozzle 47 (nozzle number k-1) and the second correction nozzle 48 (nozzle number k + 1) adjacent to the left and right with the undischarge nozzle 46 interposed therebetween.
  • a pixel position (position indicated by arrows B1 and B2) corresponding to is used as an undischarge correction unit, and correction processing for increasing the gradation value of the pixel corresponding to the undischarge correction unit in the input image (continuous tone image) is performed. .
  • the brightness display (display by shading) of each cell of the pixel grid shown in FIG. 3 reflects the magnitude of the gradation value, and the higher the gradation value, the darker the color is displayed.
  • the gradation value of the pixel position corresponding to the first correction nozzle 47 and the second correction nozzle 48 of the discharge failure correction unit is changed to a value higher than the gradation value of the peripheral part (normal part) which is the non-correction part. ing.
  • FIG. 4 is an example of a halftone process result obtained by performing a halftone process on the corrected image data shown in FIG. 3 (corresponding to the undischarge corrected image 18 in FIG. 1).
  • the higher the gradation the larger the number of dots and the larger the dots appear. Therefore, as shown in FIG. 4, large dots are arranged in the discharge failure correction unit. As a result, the streak due to the undischarge nozzle 46 becomes difficult to see.
  • the undischarge correction process by the first method has been described, but as a result, the dot pattern as shown in FIG. 4 can also be created by the undischarge correction process by the second method.
  • FIGS. 3 and 4 an example is described in which correction is performed with two nozzles, the first correction nozzle 47 and the second correction nozzle 48 adjacent to both sides of the discharge failure nozzle 46, but the range of nozzles used for correction Is not limited to these two nozzles.
  • FIG. 5 is an explanatory diagram showing an example of a recording failure due to an undischarge nozzle in an AM network.
  • the upper left diagram in FIG. 5 represents a dot pattern of a normal image without discharge nozzles (an image without discharge failure).
  • This cluster of dots (dot aggregation portion) is called a cluster.
  • an example of an AM network in which clusters 70 that are clusters of dots of 4 ⁇ 4 pixels are regularly arranged is shown.
  • the upper right diagram in FIG. 5 shows the visual appearance of the print result using the dot pattern in the upper left diagram.
  • the lower left diagram in FIG. 5 shows a dot pattern of an image without undischarge correction (uncorrected image) when the discharge failure nozzle 46 is present in the nozzle row 44 and discharge failure correction is not performed.
  • the lower right diagram in FIG. 5 shows the visual appearance of the print result by the dot pattern in the lower left diagram.
  • the leftmost 4 dots of the cluster indicated by reference numeral 70A cannot be recorded, and the rightmost 4 dots of the cluster indicated by reference 70B cannot be recorded. If the discharge failure correction is not performed for the discharge failure nozzle 46, the amount of ink is insufficient and a white stripe is visually recognized as indicated by broken lines 72A and 72B in the lower right diagram of FIG. .
  • FIG. 6 is an explanatory diagram of an example of occurrence of artifacts due to undischarge correction in the AM network.
  • the left diagram in FIG. 6 is an example of a dot pattern in which discharge failure correction is performed on the discharge failure nozzle 46.
  • this figure shows an example (comparative example) in the case where correction is made with characteristics different from the phase and cycle of the AM network without considering the relationship with the arrangement structure of the clusters in the peripheral portion at the time of discharge failure correction.
  • Reference numerals 75 and 76 denote dots added by the discharge failure correction.
  • the same number of dots as the number of dots that cannot be printed by the discharge nozzle 46 (eight) is added by the correction nozzles 47 and 48 on both sides of the discharge nozzle 46. That is, with respect to the pixel positions corresponding to the right and left correction nozzles 47 and 48 across the discharge failure nozzle 46, four dots 75 and 76 are added to the white background portion before correction (dot off portion between clusters), respectively. It has been made. The added dots 75 and 76 are arranged in a distributed manner so that the dots are distributed almost evenly in the correction portions at the pixel positions corresponding to the correction nozzles 47 and 48, and the ink amount is approximately preserved before and after the correction. As described above, the number of dots and the dot size are determined.
  • the right diagram in FIG. 6 shows the visual appearance of the print result by the dot pattern in the left diagram in FIG.
  • the right side of FIG. 6 shows reduced streak visibility compared to the lower right side of FIG. 5, but compared to the upper right side of FIG. 5, the area where dots are not originally placed (the part that was originally white) Since the additional dots 75 and 76 are placed on the printed matter, when the printed matter is observed close up (for example, when the printed matter is observed at a short distance of about 150 mm to 200 mm), the dot arrangement is visually recognized as a texture, and the correction portion cluster is darkened. appear.
  • the user who observes at a short distance gives a sense of incongruity to the undischarge correction portion.
  • the dot arrangement after the undischarge correction is visually recognized as a texture, which gives a sense of incongruity to the graininess.
  • Such a problem is not limited to the AM network, but also applies to the cluster type halftone in which dots are arranged in an agglomerated manner.
  • the cluster type halftone is not as regularly arranged as the AM network, but has a pattern characteristic similar to that of the AM network in that two or more dots are continuously and aggregated in the nozzle arrangement direction.
  • the AM network and the cluster type halftone originally have very few high-frequency components in the spatial frequency, if a high-frequency component is generated in the non-correction portion as a result of non-discharge correction, it is likely to be visually recognized as an artifact.
  • FIG. 8 shows an example in which correction is performed within a cluster without adding dots to a place that was originally white.
  • the structure of the cluster 70 in the uncorrected halftone image is maintained, and dots are not arranged in the originally white background. 46, the dots 71A and 71B in the clusters 70A and 70B that are defective in recording are corrected to increase the dot size (increase the ink droplet amount).
  • the right diagram in FIG. 8 is obtained by performing a filtering process considering the visual characteristics on the left diagram in FIG.
  • the right figure in FIG. 8 looks very similar to the upper right figure in FIG. 5, and good correction is realized.
  • the dot-off portion is 2 pixels in the non-correction portion, whereas the dot-off portion is 1 pixel in the correction portion. Due to the difference in the repetition period between the dot-on part and the dot-off part, the correction part appears to be connected.
  • the pixel position in the cluster near the edge is corrected to be stronger, and when non-discharge occurs inside the cluster, the correction intensity is weaker than the correction intensity for the edge. It is preferable to correct by the above.
  • the first embodiment an example of undischarge correction in which tone correction is performed on an image before halftone processing will be described. That is, the first embodiment is an aspect of the discharge failure correction method according to the first method described in FIG.
  • the dither method is a method of determining dot on / off by comparing a threshold value given to each pixel by a dither matrix and a gradation value of image data.
  • FIG. 10 is a conceptual diagram of an area division lookup table (LUT).
  • the first column (the leftmost column) in FIG. 10 represents the input gradation, and here, an 8-bit gradation (gradation value 0 to 255) is used.
  • an 8-bit gradation (gradation value 0 to 255) is used.
  • the discharge correction gradation is set above “127”
  • the normal gradation is set below “127”. That is, the range of gradation values 0 to 127 is “normal gradation”, and the range of gradation values 128 to 255 is set to “undischarge correction unit gradation”.
  • Three levels of threshold values are set for each gradation value.
  • FIG. 11 is an explanatory diagram of a region classification method using a dither matrix.
  • a dither matrix 80 of 5 rows ⁇ 5 columns is shown, but this is the actual dither matrix size (number of elements) that is a part of the dither matrix actually used. Can design any size, such as 192x192, 400x500.
  • a value in the range of 0 to 255 is defined for each cell (element) of the dither matrix 80.
  • the magnitude of the value of the element is represented by brightness, and white represents 0, black represents 255, and gray represents a value in between.
  • the position of each cell in the dither matrix 80 is expressed as (u, v) using the row number u and the column number v.
  • the dither matrix 80 has a distribution such that the value gradually increases from the center cell (3, 3) toward the outer periphery. If the value of the element of the dither matrix 80 is x, for example, it can be divided into four types of regions (regions 1 to 4) using three types of threshold values (Th1 ⁇ Th2 ⁇ Th3). That is, the region 1 is a region that satisfies the condition x ⁇ Th1. As shown in the part (B) in FIG. 11, the area 1 has a central (3, 3) and four positions (3, 2), (3,4), (2, 3) at the top, bottom, left and right. , (4, 3).
  • Area 2 is an area that satisfies the condition of Th1 ⁇ x ⁇ Th2. As shown in the part (C) in FIG. 11, the area 2 is in contact with the outside of the area 1 (1,3), (2,2), (2,4), (3,1), (3 , 5), (4, 2), (4, 4), and (5, 3).
  • Area 3 is an area that satisfies the condition of Th2 ⁇ x ⁇ Th3.
  • the region 3 touches the outside of the region 2 (1,2), (1,4), (2,1), (2,5), (4, 1) It is composed of 8 pixels including (4,5), (5,2) and (5,4).
  • Region 4 is a region that satisfies the condition of Th3 ⁇ x.
  • the region 4 includes (1,1), (1,5), (5,1), and (5,5) that are in contact with the outside of the region 3 as shown by the portion (E) in FIG. Consists of pixels.
  • the shape of each region can be changed by changing the threshold values Th1, Th2, and Th3 for each gradation.
  • the overall dot arrangement state (whether the dot is placed or not It is possible to change only the type of dot used (for example, the type of large dot, medium dot, and small dot) without changing the state.
  • FIG. 12 is an explanatory diagram illustrating an example of an operation that can be performed by changing the dot type for each region.
  • a part (A) of FIG. 12 is a pattern when the area 1 and the area 2 described in FIG. 11 are “small dots (small droplets)” and the areas 3 and 4 are “no dots (no drops)”. .
  • the part (B) of FIG. 12 shows a pattern when the area 1 is “large dot (large drop)”, the area 2 is “small dot”, and the areas 3 and 4 are “no dot”.
  • the part (C) in FIG. 12 is a pattern when the areas 1 and 2 are “large dots” and the areas 3 and 4 are “no dots”.
  • FIG. 12 (D) In the description of FIG. 12 (A) to (C), as shown in FIG. 12 (D), “no dot (no droplet)” is white and “large dot (large droplet)” is black. , “Small dots (droplets)” are displayed in gray.
  • various dot patterns can be generated by combining the region dividing method using the dither matrix 80 and the method of changing the dot type for each region.
  • the cluster shape can be manipulated for each gradation. Also, the dot type to be output can be determined for each region.
  • the dots used in the cluster without changing the overall dot arrangement state ie, the cluster shape.
  • the type of can be changed. That is, it is possible to change only the dot type in the cluster without changing the cluster structure (dot on position) by designing the halftone process (reference numeral 20 in FIG. 1).
  • the input gradation includes “normal gradation” used for the normal part (non-correction part) and “undischarge correction gradation” used for the undischarge correction part.
  • a correction gradation value (non-discharge correction value) when performing non-discharge correction for a pixel having a normal gradation value of nLev is previously optimized and determined for each nozzle. This is the discharge correction gradation cLev.
  • discharge failure correction gradation Since the optimum value of the discharge failure correction value differs depending on the nozzle position, a test pattern that simulates the discharge failure nozzle position is output, and the discharge failure correction gradation optimized for each nozzle is determined in advance. deep.
  • a method for obtaining the optimum discharge failure correction value (discharge failure correction gradation) for example, a method described in JP 2012-071474 A can be used.
  • a correspondence relationship that the non-discharge correction gradation cLev is applied at the time of non-discharge correction to the normal gradation nLev is determined in advance.
  • the gradation of the image data is corrected with reference to the correspondence relationship.
  • a dot pattern is defined by halftone processing corresponding to the input gradation of the image data.
  • the total dot generation amount here is approximately equal between nLev and cLev.
  • the difference in the total amount of dot generation is within 5%. If the difference in the total amount of dots generated is within 5%, it is considered that the change (difference) in the cluster shape does not substantially affect the visibility, and this level of difference is acceptable.
  • clusters are formed in sequence from the inside of the cluster in the nozzle array direction toward the cluster edge.
  • the correction intensity can be increased at the cluster end.
  • FIGS. 13 to 17 are diagrams for explaining a method of changing the correction strength of the correction unit by designing the dither matrix.
  • FIG. 13A shows a part of a dither matrix used for cluster type halftone processing.
  • the size of the element value in the dither matrix 82 is displayed in terms of brightness, and the condition of Th1 ⁇ Th2 ⁇ Th3 ⁇ 255 is satisfied.
  • the horizontal direction of the dither matrix 82 is the “nozzle arrangement direction” (nozzle arrangement direction).
  • the cluster gradually grows from the inside of the cluster in the nozzle arrangement direction toward the cluster end as the input gradation value changes from the low gradation to the high gradation (
  • the dots are arranged so that the cluster of dots is expanded.
  • a dither matrix is created in which the element values change stepwise from the inside of the cluster toward the end.
  • Th1, Th2, Th3 and “255” are shown to simplify the explanation.
  • image gradation such as 8 bits or 10 bits. The values are distributed.
  • part of FIG. 13 shows a part forming the left half of the cluster.
  • the elements of the dither matrix constituting one cluster are configured so that the elements of the matrix in the part (A) of FIG. 13 appear symmetrically.
  • the actual dither matrix is configured such that elements as shown in part (B) of FIG. 13 are further arranged periodically.
  • FIG. 14 is an explanatory diagram when no discharge nozzle is present.
  • the region 1 (0 ⁇ x ⁇ Th1) has no dots
  • the region 2 (Th1 ⁇ x ⁇ Th2) has small dots
  • the region 3 The dot generation method of each region is set so that small dots are generated in Th2 ⁇ x ⁇ Th3) and small dots are generated in region 4 (Th3 ⁇ x ⁇ 255).
  • the halftone process is performed by applying the dither matrix 82 of FIG. 13, a dot pattern in which small dots are aggregated to form a cluster as shown by reference numeral 84 in FIG. 14 is obtained.
  • the dot pattern to be generated is made different depending on the position of the undischarge nozzle in the nozzle array 44 of 5 nozzles.
  • FIG. 15 is an explanatory diagram of a method of changing the correction intensity of the correction unit depending on the position of the discharge failure part.
  • the area 1 (0 ⁇ x ⁇ Th1) has no dots and the area 2 (Th1 ⁇ x ⁇ Th2) has The dot generation method of each area is set so that large dots, medium dots in area 3 (Th2 ⁇ x ⁇ Th3), and medium dots in area 4 (Th3 ⁇ x ⁇ 255) are generated.
  • the part (D) in FIG. 15 shows the correspondence between the dot type and the brightness display in the parts (A) to (C) in FIGS.
  • FIG. 15A shows a case where the second nozzle from the left in the nozzle row 44 is a discharge failure nozzle.
  • a position corresponding to the discharge failure nozzle is a streak generation unit.
  • Two nozzles adjacent to both sides serve as correction nozzles.
  • pixels that were originally white (no dots) are left without dots.
  • 15B shows a case where the third nozzle from the left in the nozzle row 44 is an undischarge nozzle.
  • a large dot is placed at “Th1” in (2, 2) and (2, 4), and a medium dot is placed at “Th2” in (2, 3).
  • medium dots are placed in all the fourth pixel columns from the left.
  • (C) part of FIG. 15 is a case where the 4th nozzle from the left in the nozzle row 44 becomes an undischarge nozzle.
  • large dots are placed at “Th1” in (3,1) and (3,5), and medium dots are placed in the remaining correction portions.
  • a correction pattern corresponding to the discharge failure position can be developed. That is, a large dot is generated at the end of the cluster, and a medium dot is generated when going inside the cluster.
  • the correction strength is automatically applied between the end and the inside without determining the position of whether the correction unit is the end or the inside of the cluster. Can be made to change.
  • the correction strength can be changed between the end portion and the inside of the cluster, and the correction strength is automatically increased as the distance from the end portion of the cluster is increased, and the correction strength is decreased inside the cluster.
  • Such an undischarge correction function can be realized.
  • a correction dot conversion table corresponding to the distance from the cluster end in the nozzle arrangement direction is designed in advance, and for each of the correction unit pixels of the given halftone image, the cluster end After calculating the distance from, a process of replacing with a correction dot is performed with reference to the correction dot conversion table according to the type of each dot before correction.
  • the correction dot conversion table is a form of a table that defines the correction strength with respect to the distance in the nozzle arrangement direction from the end of the cluster.
  • 16 (A) represents a halftone image before correction. Similar to FIG. 14, a 5 ⁇ 5 pixel range is shown. It is assumed that the third nozzle from the left in the nozzle row 44 is an undischarge nozzle. In the halftone image 84 before correction, dots are also assigned to pixel positions (undischarge portions) corresponding to undischarge nozzles.
  • the pixel distance from the cluster end is calculated in the lateral direction (nozzle arrangement direction).
  • (B) in FIG. 16 represents the distance from the cluster end in units of pixels (px).
  • the pixel at the end (boundary) of the cluster has a distance “0”, and the distance from the end gradually increases as the distance from the end becomes 1 ⁇ 2 ⁇ 3.
  • the distance is measured from the left to the right, but the distance can also be measured from the right to the left of the cluster. It is only necessary to calculate the distance from both the left and right directions and adopt a short distance.
  • the distance from the cluster end is calculated in units of pixels, but the unit of distance is not limited to this, and any index value may be used as long as it is an index indicating distance.
  • the distance can be expressed using an appropriate function.
  • 16C is an example of the corrected halftone image 85 in which the correction for changing the dot type is performed according to the distance from the cluster end.
  • the size of the dots is displayed in terms of brightness, and the darker the color, the larger the dots.
  • the (D) part of FIG. 16 shows the correspondence between the dot type and the brightness display.
  • FIG. 17 is an example of a correction dot conversion table.
  • the horizontal axis indicates the dot type before correction, and the vertical axis indicates the dot type after correction.
  • the correction dot conversion table actually defines the correspondence between four types of discrete values (dot types) before and after correction, but FIG. 17 shows a continuous straight line for easy understanding. Indicated by.
  • the halftone image of the portion (A) of FIG. 16 is corrected based on the correction dot conversion table of FIG. 17 and the distance information shown in the portion (B) of FIG. ) Part.
  • the correction dot conversion table of FIG. 17 it is preferable to design the table so that the dots are not switched in a white background where no dots are originally placed.
  • the distance from the cluster end of the discharge failure correction unit is obtained for the halftone image, and the dot size is changed with reference to the correction dot conversion table.
  • a correction dot conversion table for “no dot” after correction may be created at a “no dot” location before correction.
  • the difference in the total amount of dots before and after correction is allowed to be about 5%
  • the control of generating dots with a certain probability (with a generation ratio of 5% or less) with respect to “no dot” before correction is also possible. Is possible.
  • FIG. 18 is a block diagram illustrating a configuration of the inkjet printing system according to the first embodiment.
  • the inkjet printing system 110 is a system that performs image recording by a single pass method, and includes an image data input unit 112, a gradation conversion unit 114, an undischarge correction processing unit 118, a halftone processing unit 120, a head driver 122, and a recording head. 124 is provided.
  • the inkjet printing system 110 includes a medium conveyance unit 126 that conveys a recording medium (not shown in FIG. 18), an image reading unit 128 that reads an image recorded on the recording medium by the recording head 124, and an image reading unit.
  • An image analysis unit 130 that analyzes the read image acquired from 128 is provided.
  • the image analysis unit 130 includes a defective nozzle detection unit 132 and an undischarge correction parameter calculation unit 134.
  • the defective nozzle detection unit 132 performs a process of detecting the position of the non-ejection nozzle based on the read image of the defective nozzle detection test chart. Further, the defective nozzle detection unit 132 calculates the landing position error of each nozzle based on the read image of the defective nozzle detection test chart, and forcibly causes discharge failure when the landing position error exceeds an allowable value. Designate an undischarge nozzle. Non-ejection nozzles and non-ejection nozzles detected by the defective nozzle detection unit 132 are treated as non-ejection nozzles.
  • the undischarge nozzle position information (undischarge information) is stored in the undischarge information storage unit 140.
  • the undischarge information storage unit 140 corresponds to an “undischarge information storage unit”, and the step of storing undischarge information in the undischarge information storage unit 140 corresponds to an “undischarge information storage step”.
  • the discharge failure correction parameter calculation unit 134 performs a calculation process for determining an image gradation correction value (discharge failure correction parameter) of the adjacent nozzle with respect to the position of the discharge failure nozzle from the read image of the discharge failure correction parameter acquisition test chart.
  • the discharge failure correction parameter calculation unit 134 generates discharge failure correction LUTs (corresponding to discharge failure correction parameters) that define correction values for discharge failure correction (discharge failure correction gradations) for each nozzle.
  • the discharge failure correction parameter generated by the discharge failure correction parameter calculation unit 134 is stored in the discharge failure correction parameter storage unit 142.
  • the inkjet printing system 110 includes a test chart generation unit 150 that generates data of various test charts including a test chart for detecting defective nozzles, a printing condition management unit 152 that manages printing conditions necessary for executing a print job, A control unit 162 that controls the entire system is provided, and a display unit 164 and an input device 166 are connected to the control unit 162.
  • the display unit 164 and the input device 166 function as a user interface (UI).
  • the input device 166 can employ various means such as a keyboard, a mouse, a touch panel, and a trackball, and may be an appropriate combination thereof.
  • the form by which the display part 164 and the input device 166 are comprised integrally is also possible like the structure which has arrange
  • the operator uses the input device 166 while viewing the contents displayed on the screen of the display unit 164 to input various information such as input of printing conditions, selection of image quality mode, input / editing of attached information, and information search. And the inkjet printing system 110 can be operated. Further, through the display on the display unit 164, the input content and other various information, the system status, and the like can be confirmed.
  • Each unit can be realized by a combination of computer hardware and software used as a control device of the inkjet printing system 110.
  • the image data input unit 112, the gradation conversion unit 114, the undischarge correction processing unit 118, the halftone processing unit 120, and the head driver 122 may be mounted as image processing functions on the ink jet recording apparatus (printer) side. It is possible to mount all or part of these image processing units (112 to 122) on the control device side.
  • the recording head 124 is a line head having a nozzle row in which a plurality of nozzles are arranged over a length corresponding to the entire width of the drawing area in the medium width direction orthogonal to the conveyance direction of the recording medium (maximum width of the image forming area).
  • the medium conveyance direction by the medium conveyance unit 126 is the sub-scanning direction (y direction), and the medium width direction orthogonal to the medium conveyance direction is the main scanning direction (x direction).
  • FIG. 18 only one block is shown as the recording head 124 for the sake of simplicity.
  • a plurality of recording heads respectively corresponding to a plurality of ink colors.
  • CMKY four color inks are used, and a recording head for ejecting each color ink is provided for each color.
  • the number of ink colors and combinations thereof are not limited to this example.
  • a mode in which light color inks such as light cyan (LC) and light magenta (LM) are added, and a mode in which special color inks such as red and green are used are also possible.
  • the inkjet recording head 124 has an ejection energy generating element (for example, a piezoelectric element or a heating element) that generates ejection energy necessary for ink ejection corresponding to each nozzle. It has.
  • the recording head 124 ejects ink droplets on demand according to the drive signal and ejection control signal supplied from the head driver 122.
  • the image data input unit 112 functions as a data acquisition unit for taking in image data (input image 12) representing image contents to be printed (output) by the inkjet printing system 110.
  • the image data input unit 112 can be configured by a data input terminal that takes in image data from an external or other signal processing unit in the apparatus.
  • the image data input unit 112 may employ a wired or wireless communication interface unit, or may employ a media interface unit that reads and writes an external storage medium (removable disk) such as a memory card. Alternatively, an appropriate combination of these aspects may be used.
  • the image data format of the image to be printed can be various.
  • a pre-processing unit (not shown) is used in the preceding stage of the image data input unit 112.
  • the image data is input from the image data input unit 112 after being converted into image data of ink color and resolution used in the inkjet printing system 110 by performing processing such as color conversion and resolution change.
  • RGB image data represented by red (R), green (G), and blue (B) color signals
  • a RIP Raster Image Processor
  • An apparatus or the like performs RGB ⁇ CMYK color conversion processing or resolution conversion processing, converts the RGB image data into CMYK image data suitable for the inkjet printing system 110, and then inputs the converted image data to the image data input unit 112.
  • the gradation conversion unit 114 converts the image data so that the color development characteristics defined by the inkjet printing system 110 are obtained.
  • the gradation conversion unit 114 converts the input CMYK signal (pre-density conversion CMYK signal) into a density-converted CMYK signal in accordance with the gradation conversion LUT specified by the printing condition management unit 152.
  • the input CMYK signal (CMYK signal before density conversion) may be converted into a C signal after density conversion, an M signal after density conversion, a Y signal after density conversion, and a K signal after density conversion.
  • the notation “LUT” in this specification represents a lookup table.
  • the gradation conversion LUT is a table describing the relationship (conversion relationship) of the output signal value to the input signal value.
  • the gradation conversion LUT is defined for each type of recording medium used for printing.
  • a plurality of gradation conversion LUTs are prepared according to the paper type, and an appropriate LUT is referred to according to the paper to be used.
  • Such a gradation conversion LUT is prepared for each ink color.
  • a gradation conversion LUT is provided for each color of CMYK.
  • the input image 12 fetched from the image data input unit 112 is subjected to gradation conversion processing so that a desired gradation is obtained by the gradation conversion unit 114.
  • the gradation converting unit 114 has a density unevenness correction processing function for correcting image data in accordance with the recording characteristics depending on the position (x-direction position) of each nozzle of the recording head 124. That is, the gradation converting unit 114 performs image signal correction for suppressing density unevenness of the print image on the recording medium caused by variations in the ejection characteristics of the nozzles in the recording head 124.
  • a density unevenness correction LUT which is a one-dimensional lookup table for correcting density unevenness describing the conversion relationship between the input signal value and the output signal value, is prepared. Signal values are converted using the LUT.
  • Undischarge correction processing section The discharge failure correction processing unit 118 corrects the image data using the discharge failure information stored in the discharge failure information storage unit 140 and the discharge failure correction parameter stored in the discharge failure correction parameter storage unit 142. Perform correction processing.
  • the halftone processing unit 120 is dot data of N values (N is 3 or more) that can output multi-tone image data by the recording head 124 by a quantization method such as a dither method (so-called digital halftoning processing method). Process to convert to.
  • the N-value image data generated by the halftone processing unit 120 is converted in accordance with the nozzle arrangement and output to the head driver 122.
  • a drive signal (marking signal) is supplied to the recording head 124 via the head driver 122, and the ink ejection operation of the recording head 124 is controlled.
  • the medium transport unit 126 is a means for transporting the recording medium.
  • the recording medium is conveyed at a constant speed in the sub-scanning direction (y direction) orthogonal to the longitudinal direction (x direction) of the recording head 124.
  • the medium conveyance unit 126 can employ various methods such as a drum conveyance method, a belt conveyance method, and a nip conveyance method.
  • the detailed structure of the medium transport unit 126 is not shown, it includes a paper feed roller, a transport motor, a motor drive circuit, and the like.
  • a sensor for example, an encoder for detecting the position of the recording medium.
  • the medium transport unit 126 corresponds to a relative moving unit that moves the recording medium relative to the recording head 124.
  • the image reading unit 128 reads an image recorded on the recording medium by the recording head 124 and converts it into electronic image data (read image data).
  • a CCD line sensor can be used as the image reading unit 128.
  • the image reading unit 128 of this example is an inline sensor installed in the middle of the medium conveyance path, and reads an image recorded by the recording head 124 during conveyance before paper discharge.
  • the image reading unit 128 can read the output results of a density measurement test chart and other test charts described later. Further, the image reading unit 128 can read a print image recorded based on image data to be printed specified in a print job.
  • the test chart generation unit 150 has a function of generating data for a defective nozzle detection test chart for detecting defective nozzles and a non-discharge correction parameter acquisition test chart for calculating non-discharge correction parameters.
  • the test chart generation unit 150 can generate various test chart data such as density measurement test chart data for obtaining density measurement data necessary for calculating density unevenness correction parameters.
  • the test chart generation unit 150 supplies the data of the corresponding test chart to the image data input unit 112 according to the instruction of the control unit 162.
  • the defective nozzle detection test chart for example, a so-called “1 on n off” type test chart can be used.
  • the “1 on n off” type test chart shows the nozzle numbers in order from the end in the main scanning direction with respect to the arrangement of nozzles constituting one nozzle line in the x direction in one line head.
  • the droplet ejection timing is changed for each nozzle number group of AN + B (where N is an integer of 0 or more), and a line group is formed by continuous droplet ejection from each nozzle.
  • the line patterns of adjacent nozzles adjacent to each other do not overlap each other, and independent line patterns (for each nozzle) are formed for each nozzle.
  • the presence / absence of discharge from each nozzle can be ascertained from the output result of the defective nozzle detection test chart.
  • the landing position of each nozzle it is possible to determine that a nozzle having a large landing position error exceeding an allowable value is a discharge bent nozzle.
  • a test chart for detecting defective nozzles is recorded in the margin of the recording medium one by one during printing, and this is read by the image reading unit 128 to detect the occurrence of defective nozzles at an early stage, thereby preventing discharge. Undischarge correction processing by processing is applied.
  • the discharge chart for acquiring discharge failure correction parameters is a density pattern in which discharge failure correction parameters (correction coefficients) are applied to nozzle positions on both sides adjacent to a nozzle that simulates the presence of discharge failure nozzles (intentionally discharge failure). Contains patches.
  • the optimum discharge failure correction parameter can be specified from the drawing result with different discharge failure correction parameter values.
  • An appropriate correction value (correction coefficient) can be determined for each nozzle by creating a patch in which the position of the nozzle that simulates non-ejection is changed.
  • the print condition management unit 152 manages print job information in which image data to be printed is associated with print condition information.
  • the user can input print condition setting information when inputting image data to be printed or after inputting image data.
  • the print condition management unit 152 generates print job information in which print condition setting information is associated with image data to be printed, and stores and manages the information for each print job.
  • For each print job an output image data name, a recording medium type name (paper type), a medium size, and various parameter information used for image processing are stored in association with each other.
  • the print condition management unit 152 sets various parameters and data designated by the print job related to the selection in the corresponding processing unit.
  • the undischarge correction function described in the first and second embodiments can be realized by the inkjet printing system 110 illustrated in FIG.
  • FIG. 19 is a block diagram illustrating a configuration of an inkjet printing system according to the second embodiment. 19, elements that are the same as or similar to those in the configuration shown in FIG. 18 are given the same reference numerals, and descriptions thereof are omitted.
  • the inkjet printing system 170 shown in FIG. 19 includes an undischarge correction processing unit 172 for realizing the undischarge correction function described in FIGS. 13 to 15 and a correction dot conversion in which a correction dot conversion table is stored.
  • the undischarge correction processing unit 172 includes a distance calculation unit 173 that calculates the distance from the cluster end, and a dot replacement unit that performs a dot change process with reference to the correction dot conversion table according to the distance from the cluster end. 174.
  • the halftone processing unit 120 in the ink jet printing system 170 may be of any method as long as it generates a halftone image that expresses gradations using AM network or cluster type halftone.
  • a program for causing a computer to function is a CD-ROM, a magnetic disk, or other computer-readable medium (tangible object).
  • the program can be provided through the information storage medium. Instead of providing the program by storing the program in such an information storage medium, it is also possible to provide the program signal as a download service using a communication network such as the Internet.
  • the computer stores a non-discharge information (non-discharge information storage function), a halftone processing function (halftone processing function), and an image defect in a defective recording area due to a defective nozzle. And a function of performing image correction processing (undischarge correction processing function) that reduces the visibility of the image can be realized, and the undischarge correction described in the above embodiment can be performed.
  • a host control apparatus such as a host computer or a part of a program for realizing print control including an image processing function for performing a halftone process and an undischarge correction process for realizing the undischarge correction function described in the present embodiment It can also be applied as an operation program of a central processing unit (CPU) on the side of a printer (inkjet recording apparatus) as an image output apparatus.
  • CPU central processing unit
  • FIG. 20 is a diagram illustrating a configuration example of the ink jet recording apparatus 300.
  • the ink jet recording apparatus 300 includes a paper feed unit 312, a treatment liquid application unit 314, a drawing unit 316, a drying unit 318, a fixing unit 320, and a paper discharge unit 322.
  • a recording medium 324 that is a sheet is stacked on the paper feed unit 312.
  • the recording media 324 are fed one by one from the paper feed tray 350 of the paper feed unit 312 to the processing liquid application unit 314.
  • a sheet cut paper
  • a configuration in which continuous paper (roll paper) is cut into a necessary size and fed is also possible.
  • the processing liquid application unit 314 is a mechanism that applies the processing liquid to the recording surface of the recording medium 324.
  • the treatment liquid contains a color material aggregating agent that agglomerates the color material (pigment in this example) in the ink applied by the drawing unit 316. When the treatment liquid comes into contact with the ink, the ink becomes a color material. And the solvent are promoted.
  • the processing liquid application unit 314 includes a paper feed cylinder 352, a processing liquid drum 354, and a processing liquid coating device 356.
  • the processing liquid drum 354 includes a claw-shaped holding means (gripper) 355 on the outer peripheral surface thereof, and the recording medium 324 is sandwiched between the claw of the holding means 355 and the peripheral surface of the processing liquid drum 354, thereby The tip can be held.
  • the treatment liquid coating apparatus 356 can apply various methods such as a spray method and an ink jet method in addition to a roller coating method.
  • the recording medium 324 to which the processing liquid is applied is transferred from the processing liquid drum 354 to the drawing drum 370 of the drawing unit 316 via the intermediate transport unit 326.
  • the drawing unit 316 includes a drawing drum 370, a sheet pressing roller 374, and ink jet heads 372M, 372K, 372C, 372Y.
  • the drawing drum 370 includes claw-shaped holding means (grippers) 371 on the outer peripheral surface thereof, like the processing liquid drum 354. Suction holes are provided on the outer peripheral surface of the drawing drum 370, and the recording medium 324 is sucked and held on the outer peripheral surface of the drum by negative pressure suction.
  • a sheet conveyance system including the drawing drum 370 corresponds to the medium conveyance unit 126 (see FIGS. 18 to 19).
  • Each of the inkjet heads 372M, 372K, 372C, and 372Y is a full-line inkjet recording head having a length corresponding to the maximum width of the image forming area on the recording medium 324, and an image forming surface is formed on the ink ejection surface. A nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the region is formed.
  • Each inkjet head 372M, 372K, 372C, 372Y is installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 324 (the rotation direction of the drawing drum 370).
  • the recording medium 324 is transported at a constant speed by the drawing drum 370, and the operation of relatively moving the recording medium 324 and each of the inkjet heads 372M, 372K, 372C, 372Y in this transport direction is performed only once (that is, 1). An image can be recorded in the image forming area of the recording medium 324 in a single sub-scan).
  • the ink jet recording apparatus 300 using four colors of CMYK inks is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and the arrangement order of each color head is not particularly limited.
  • the recording medium 324 on which an image is formed by the drawing unit 316 is transferred from the drawing drum 370 to the drying drum 376 of the drying unit 318 via the intermediate conveyance unit 328.
  • the drying unit 318 is a mechanism for drying moisture contained in the solvent separated by the color material aggregation action, and includes a drying drum 376 and a solvent drying device 378. Similar to the treatment liquid drum 354, the drying drum 376 includes a claw-shaped holding means (gripper) 377 on its outer peripheral surface.
  • the solvent drying device 378 includes a plurality of halogen heaters 380 and a hot air jet nozzle 382.
  • the recording medium 324 that has been dried by the drying unit 318 is transferred from the drying drum 376 to the fixing drum 384 of the fixing unit 320 via the intermediate conveyance unit 330.
  • the fixing unit 320 includes a fixing drum 384, a halogen heater 386, a fixing roller 388, and an in-line sensor 390.
  • the fixing drum 384 includes claw-shaped holding means (grippers) 385 on the outer peripheral surface thereof, like the processing liquid drum 354.
  • the in-line sensor 390 reads an image (including a density measurement test chart, a defective nozzle detection test chart, an undischarge correction parameter acquisition test chart, etc.) formed on the recording medium 324, and the image density, image defect, and the like. And a CCD line sensor or the like is applied.
  • the inline sensor 390 corresponds to the image reading unit 128 described with reference to FIG.
  • the paper discharge unit 322 includes a discharge tray 392, and a transfer drum 394, a conveyance belt 396, and a stretching roller 398 are provided between the discharge tray 392 and the fixing drum 384 of the fixing unit 320 so as to be in contact therewith. Is provided.
  • the recording medium 324 is sent to the transport belt 396 by the transfer drum 394 and discharged to the discharge tray 392. Although the details of the paper transport mechanism by the transport belt 396 are not shown, the recording medium 324 after printing is held at the front end of the paper by a gripper (not shown) gripped between the endless transport belts 396, and the transport belt 396. Is carried above the discharge tray 392.
  • the ink jet recording apparatus 300 of the present example has an ink storage / loading unit that supplies ink to the respective ink jet heads 372M, 372K, 372C, and 372Y, and a treatment liquid applying unit 314. And a head maintenance unit for cleaning each inkjet head 372M, 372K, 372C, 372Y (nozzle surface wiping, purging, nozzle suction, etc.) and a recording medium 324 on the paper transport path.
  • a position detection sensor for detecting the position, a temperature sensor for detecting the temperature of each part of the apparatus, and the like are provided.
  • FIG. 21A is a plan perspective view showing a structural example of the recording head 450
  • FIG. 21B is an enlarged view of a part thereof.
  • 22 is a perspective plan view showing another example of the structure of the recording head 450
  • FIG. 23 is a three-dimensional view of one-channel droplet discharge elements (ink chamber units corresponding to one nozzle 451) serving as a recording element unit.
  • FIG. 22 is a cross-sectional view showing a configuration (a cross-sectional view taken along line 23-23 in FIG. 21).
  • the recording head 450 of this example includes a plurality of ink chamber units (droplets) including nozzles 451 that are ink discharge ports and pressure chambers 452 corresponding to the nozzles 451.
  • (Discharge elements) 453 has a two-dimensionally arranged structure, so that a substantial nozzle interval (projection) that is projected (orthographically projected) along the head longitudinal direction (direction orthogonal to the paper feed direction). Nozzle pitch) is increased.
  • a nozzle row having a length corresponding to the entire width Wm of the drawing area of the recording medium 324 is configured in a direction (arrow M direction; main scanning direction) substantially orthogonal to the feeding direction (arrow S direction; sub-scanning direction) of the recording medium 324.
  • the form to do is not limited to this example.
  • short head modules 460A in which a plurality of nozzles 451 are two-dimensionally arranged are arranged in a staggered manner as shown in the portion (A) in FIG.
  • a mode in which a line head having a nozzle row having a length corresponding to the entire width of the recording medium 324 is formed by connecting, or a mode in which the head modules 460B are connected in a row as shown in FIG. is there.
  • the pressure chamber 452 provided corresponding to each nozzle 451 has a substantially square planar shape (see (A) and (B) in FIG. 21), and one of the corners on the diagonal line. Are provided with an outlet to the nozzle 451, and an inlet (supply port) 454 for supply ink is provided on the other side.
  • the shape of the pressure chamber 452 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon, other polygons, a circle, an ellipse, and the like.
  • the recording head 450 has a structure in which a nozzle plate 451A in which nozzles 451 are formed and a flow path plate 452P in which flow paths such as a pressure chamber 452 and a common flow path 455 are formed are laminated and joined. Become.
  • the flow path plate 452P constitutes a side wall portion of the pressure chamber 452 and a flow path forming a supply port 454 as a throttle portion (most narrowed portion) of an individual supply path that guides ink from the common flow channel 455 to the pressure chamber 452. It is a forming member. Note that, for convenience of explanation, the flow path plate 452P has a structure in which one or a plurality of substrates are stacked, although the illustration is simplified in FIG.
  • the nozzle plate 451A and the flow path plate 452P can be processed into a required shape by a semiconductor manufacturing process using silicon as a material.
  • the common channel 455 communicates with an ink tank (not shown) as an ink supply source, and the ink supplied from the ink tank is supplied to each pressure chamber 452 through the common channel 455.
  • a piezoelectric actuator 458 provided with individual electrodes 457 is joined to a diaphragm 456 constituting a part of the pressure chamber 452 (the top surface in FIG. 23).
  • the diaphragm 456 of this example functions as a common electrode 459 corresponding to the lower electrode of the piezoelectric actuator 458. It is also possible to form the diaphragm with a non-conductive material such as silicon or resin. In this case, a common electrode layer made of a conductive material such as metal is formed on the surface of the diaphragm member.
  • the piezoelectric actuator 458 By applying a driving voltage to the individual electrode 457, the piezoelectric actuator 458 is deformed and the volume of the pressure chamber 452 is changed, and ink is ejected from the nozzle 451 due to the pressure change accompanying this.
  • the ink chamber unit 453 having such a structure is constant along the row direction along the main scanning direction and the oblique column direction having a constant angle ⁇ that is not orthogonal to the main scanning direction.
  • the high-density nozzle head of this example is realized by arranging a large number in a grid pattern with the arrangement pattern.
  • the arrangement form of the nozzles 451 is not limited to the illustrated example, and various nozzle arrangement structures can be applied.
  • the means for generating discharge pressure (discharge energy) for discharging droplets from each nozzle in the recording head is not limited to a piezoelectric actuator (piezoelectric element).
  • various pressure generating elements such as heaters (heating elements) in electrostatic actuators, thermal methods (methods that eject ink using the pressure of film boiling by heating of the heaters), and various other actuators
  • a discharge energy generating element can be applied.
  • Corresponding energy generating elements are provided in the flow path structure according to the ejection method of the head.
  • the “recording medium” includes media called by various terms such as a printing medium, a recording medium, an image forming medium, an image receiving medium, and an ejection medium.
  • the material, shape, etc. of the recording medium are not particularly limited, and a print on which a resin sheet such as continuous paper, cut paper, seal paper, OHP sheet, film, cloth, nonwoven fabric, wiring pattern, or the like is formed.
  • a resin sheet such as continuous paper, cut paper, seal paper, OHP sheet, film, cloth, nonwoven fabric, wiring pattern, or the like is formed.
  • Various sheet bodies can be used regardless of the substrate, rubber sheet, and other materials and shapes.

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Quality & Reliability (AREA)
  • Physics & Mathematics (AREA)
  • Discrete Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Ink Jet (AREA)
  • Particle Formation And Scattering Control In Inkjet Printers (AREA)
  • Color, Gradation (AREA)

Abstract

Cette invention concerne un système d'impression par jet d'encre et son procédé de correction de non décharge de telle sorte que, lors de l'utilisation d'un tramage à modulation d'amplitude ou d'un tramage par cluster pour rendre des tons, une non décharge peut être corrigée avec une puissance de correction appropriée. Un système d'impression par jet d'encre à une seule passe (110) selon un mode de cette invention comprend les éléments suivants : une unité de traitement de tramage (120) qui rend des tons à l'aide soit d'un tramage à modulation d'amplitude, soit d'un tramage par cluster, selon lequel les points sont agencés dans des clusters d'au moins deux points dans la direction d'agencement des buses d'une tête d'impression ; et une unité de traitement de correction de non décharge (118) qui, sur la base des informations de position des buses qui ne se déchargent pas, soumet une image d'entrée ou une image à demi-tons à un procédé de correction d'image qui réduit la visibilité des défauts d'image dans des sections présentant des problèmes d'impression à cause desdites buses qui ne se déchargent pas. Lors de cette correction de non décharge, des formations de points des sections de correction de non décharge situées près des sections présentant des problèmes d'impression sont générées, la puissance de ladite correction de non décharge variant selon la distance, dans la direction d'agencement des buses, par rapport au bord du cluster.
PCT/JP2014/071384 2013-08-30 2014-08-13 Système d'impression par jet d'encre et procédé de correction de non décharge et programme associé WO2015029788A1 (fr)

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JP6062832B2 (ja) * 2013-08-30 2017-01-18 富士フイルム株式会社 インクジェット印刷システム及びその不吐補正方法並びにプログラム
JP6926955B2 (ja) * 2017-11-01 2021-08-25 コニカミノルタ株式会社 画像形成装置、画像処理装置及び画像処理方法
US12090767B2 (en) 2022-09-29 2024-09-17 Ricoh Company, Ltd. Defective nozzle locating mechanism
US12045521B1 (en) 2023-02-21 2024-07-23 Ricoh Company, Ltd. Halftone modification mechanism

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