Image processing device

Abstract

To perform image correction which makes white streaks inconspicuous, even if the number of non-discharges is large.SOLUTION: An image processing device includes: a division part 26 for dividing a plurality of nozzles of an inkjet into a plurality of regions in a main scanning direction; a storage part 40 for storing a priority table obtained by determining a priority, on the basis of the regions divided by the division part 26 and the color of ink; a detection part 22 for detecting a non-discharge nozzle from image data read out from a medium printed on the basis of nozzle pattern data; and an extraction part 23 for extracting the non-discharge nozzle for a threshold as a collection target, on the basis of the image data and the priority table, when the number of non-discharge nozzles detected by the detection part 22 is equal to or more than a predetermined threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus that performs image correction so that ejection failures are not noticeable even when there are a large number of ejection failures. [Background technology]

[0002] 2. Description of the Related Art Line-type inkjet devices are well known that perform printing by ejecting ink from nozzles in an inkjet head onto a sheet of paper that is being transported based on image data.

[0003] In this inkjet device, if a temporary ink ejection failure occurs due to a nozzle malfunction or the like, white streaks will appear in the printed image.

[0004] Patent Document 1 discloses a technique for automatically detecting the position of a misfire detection pattern in a line-type head inkjet printer, by printing the pattern and reading it with a scanner.

[0005] The misfire detection pattern is a pattern in which one vertical line is formed for each nozzle, and as the nozzle number increases by one, a vertical line is drawn one step down, and when the specified number M steps is reached, printing resumes from step 0. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7143653 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the technology for detecting nozzle positions disclosed in Patent Document 1 scans each row from the left edge to the right, counting up each time a vertical ruled line is detected, and storing the count value, coordinates, and whether or not there is a misfire. Then, misfire information (color number, head number, nozzle number) is stored in non-volatile memory. During printing, the amount of ink in the nozzles on either side of the misfire nozzle is increased based on the stored misfire information, making white stripes less noticeable.

[0008] Therefore, if the number of ejection failures is large, the amount of misfire information data will be correspondingly large.

[0009] However, since the capacity of the nonvolatile memory for storing misfire information is limited, it is difficult to store all the misfire information.

[0010] The present invention has been made in consideration of such problems, and aims to provide an image processing device that can perform image correction in which white streaks are not noticeable by determining a priority order for pixels where white streaks occur, even when there are a large number of non-ejections. [Means for solving the problem]

[0011] In order to achieve the above object, the image processing device according to the present invention is characterized by: a dividing means for dividing a plurality of nozzles of the inkjet into a plurality of regions in a main scanning direction; a storage means for storing a priority order table that defines priorities based on the areas divided by the dividing means and the colors of the inks; a detection means for detecting non-ejecting nozzles from image data read from a medium printed based on the nozzle pattern data; an extraction means for extracting, when the number of non-ejecting nozzles detected by the detection means is equal to or greater than a predetermined threshold, the threshold number of non-ejecting nozzles as targets for correction based on the image data and the priority order table; The reason is that it is equipped with the following. [Effects of the Invention]

[0012] According to the features of the image processing device of the present invention, even when the number of non-ejections is large, image correction can be performed so that white streaks are not noticeable. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a block diagram showing a hardware configuration of an image processing device according to a first embodiment of the present invention. [Figure 2] (a) is a diagram showing an example of image data (read pattern image data) read from a medium printed based on nozzle pattern data, and (b) is a diagram showing an example of an image ejected based on print data without correcting non-ejecting nozzles in the case of (a). [Figure 3] (a) is an explanatory diagram illustrating the division of an area by a division unit provided in an image processing device according to Example 1 of the present invention, and (b) is a diagram showing an example of a priority table generated by a table generation unit provided in an image processing device according to Example 1 of the present invention. [Figure 4] (a) shows an example of read pattern image data read by an image reading unit provided in an image processing device according to Example 1 of the present invention; (b) is a diagram showing pixels corrected in the case of (a) to correspond to non-ejecting nozzles extracted by an extraction unit provided in an image processing device according to Example 1 of the present invention; (c) shows an example of read pattern image data read by an image reading unit; and (d) is a diagram showing pixels corrected in the case of (c) to correspond to non-ejecting nozzles extracted by the extraction unit. [Figure 5] 10 is a flowchart showing the processing contents of a priority order table creation process performed by the image processing device according to the first embodiment of the present invention. [Figure 6] FIG. 10 is a diagram showing an example of allocation information to be read. [Figure 7] 10 is a flowchart showing the processing content of a color number extraction process in step S107 of the priority order table creation processing flow by the image processing device according to the first embodiment of the present invention. [Figure 8] 10 is a flowchart showing the processing content of an area selection process in step S113 of the priority order table creation processing flow by the image processing device according to the first embodiment of the present invention. [Figure 9] 10 is a flowchart showing the processing contents of the area number extraction processing in step S303 of the area selection processing flow by the image processing device according to the first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent parts and components are designated by the same or equivalent reference numerals throughout the drawings. However, it should be noted that the drawings are schematic and may differ from the actual product. Furthermore, the drawings may include parts with different dimensional relationships and ratios.

[0015] Furthermore, the embodiments shown below are merely examples of devices that embody the technical concept of the present invention, and the technical concept of the present invention does not limit the arrangement of each component to that shown below. Various modifications can be made to the technical concept of the present invention within the scope of the claims.

[0016] 1 is a block diagram showing the hardware configuration of an image processing device 1 according to a first embodiment of the present invention. As shown in the figure, the image processing device 1 includes an image reading unit 10, a data processing unit 20, an inkjet head control unit 30, and a storage unit 40.

[0017] The image reading unit 10 obtains image data by irradiating light from a light source onto a medium on which an image is printed and placed on a platen, and reading the light reflected from the exposed surface with a CCD. Here, the image data obtained is image data read from the printed medium based on nozzle pattern data for detecting non-ejection from the nozzles of the inkjet head.

[0018] Figure 2(a) is a diagram showing an example of image data (read pattern image data) read from a medium printed based on nozzle pattern data, and Figure 2(b) is a diagram showing an example of an image ejected based on print data without correcting non-ejecting nozzles in the case of Figure 2(a).

[0019] 2(a), the read pattern image data includes a first nozzle pattern H101 corresponding to an inkjet head that uses K (black) ink, a second nozzle pattern H102 corresponding to an inkjet head that uses C (cyan) ink, a third nozzle pattern H103 corresponding to an inkjet head that uses M (magenta) ink, and a fourth nozzle pattern H104 corresponding to an inkjet head that uses Y (yellow). Note that a nozzle pattern corresponding to an inkjet head that uses Gr (gray) ink may also be provided.

[0020] In the first nozzle pattern H101, there are areas A111 and A112 where white stripes occur at both ends in the main scanning direction due to non-ejecting nozzles.

[0021] Furthermore, there is an area A113 where a white streak occurs near the center in the main scanning direction of the second nozzle pattern H102, and there is an area A114 where a white streak occurs near the center in the main scanning direction of the third nozzle pattern H103.

[0022] As shown in Figure 2(b), when non-ejecting nozzles are ejected based on the print data without being corrected, areas A213 and A214 with noticeable white streaks appear near the center of the image due to the non-ejection of the conspicuous C (cyan) and M (magenta) nozzles.

[0023] Similarly, for K (black), which is relatively noticeable, the non-ejecting nozzles are located at the ends in the main scanning direction, so they are outside the print area and are not affected by white streaks.

[0024] 1, the data processing unit 20 generates the nozzle pattern data and print data for printing described above. The data processing unit 20 also detects the nozzle pattern based on image data read from a medium printed based on the nozzle pattern data, and corrects the nozzles based on the detection results.

[0025] The inkjet head control unit 30 performs printing by ejecting ink from the nozzles of an inkjet head (not shown) onto the transported paper based on the nozzle pattern data output from the data processing unit 20. The nozzles of the inkjet head may include non-ejecting nozzles (defective recording elements) where the nozzle holes are clogged or the like.

[0026] In addition, the inkjet head control unit 30 prints by ejecting ink from the nozzles of an inkjet head (not shown) onto the transported paper based on print data that has been image-corrected by the data processing unit 20 to make white streaks less noticeable.

[0027] The storage unit 40 stores image data for generating nozzle pattern data, print data for printing, and a priority order table, which will be described later.

[0028] The data processing unit 20 functionally comprises an image input unit 21, a detection unit 22, an extraction unit 23, an image generation unit 25, a division unit 26, and a table generation unit 27.

[0029] The image input unit 21 acquires the read pattern image data read by the image reading unit 10.

[0030] The detection unit 22 detects non-ejecting nozzles from image data (read pattern image data) read from a medium printed based on the nozzle pattern data acquired by the image input unit 21. The detection unit 22 then calculates the number of detected non-ejecting nozzles.

[0031] The extraction unit 23 determines whether the number of non-ejecting nozzles detected by the detection unit 22 is equal to or greater than a predetermined threshold value Th1. If the number of non-ejecting nozzles detected by the detection unit 22 is equal to or greater than the predetermined threshold value Th1, the extraction unit 23 extracts non-ejecting nozzles with high priorities by the threshold value Th1 as targets for correction based on the image data and the priority order table. Details will be described later.

[0032] If the priorities are the same, the extraction unit 23 prioritizes and extracts the non-ejecting nozzle that is closer to the center in the main scanning direction as the object of correction.

[0033] The image generation unit 25 generates the nozzle pattern data and print data for printing. The image generation unit 25 also corrects the pixels in the print data read from the storage unit 40 that correspond to the non-ejecting nozzles to be corrected that have been extracted by the extraction unit 23. This makes it possible to perform image correction that makes white streaks less noticeable.

[0034] The dividing unit 26 divides the inkjet nozzles into a plurality of regions in the main scanning direction.

[0035] The table generating unit 27 generates a priority order table in which priorities are set based on the distance to the center of the areas divided by the dividing unit 26 in the main scanning direction and the conspicuousness of the ink color.

[0036] Figure 3(a) is an explanatory diagram illustrating the division of an area by the division unit 26 provided in the image processing device 1 according to Example 1 of the present invention, and Figure 3(b) is a diagram showing an example of a priority table generated by the table generation unit 27 provided in the image processing device 1 according to Example 1 of the present invention.

[0037] 3(a), the dividing unit 26 divides the inkjet nozzles into five regions A to E in the main scanning direction. Region C is the center in the main scanning direction, and regions A and E are end regions in the main scanning direction.

[0038] As shown in Figure 3(b), the priority table sets priorities for combinations of areas A to E divided by the dividing unit 26 and ink colors C (cyan), M (magenta), Y (yellow), K (black), and Gr (gray).

[0039] In principle, the priority order table is set so that the closer to the center in the main scanning direction of the area divided by the dividing unit 26, and the more conspicuous the ink color (the higher the color priority order), the higher the priority order. Here, the conspicuousness of ink colors is assumed to be in the order of C (cyan), M (magenta), K (black), Gr (gray), and Y (yellow).

[0040] Specifically, if the ink color is the same, the closer it is to the center in the main scanning direction, the higher the priority, and if it is the same area, the more noticeable the ink color is (the higher the color priority), the higher the priority is set.

[0041] In the example shown in Figure 3(b), the priority of area C, which is C (cyan) and M (magenta), is "1", the priority of area B is "2", and the priority of area D is "3", so area C, which is closer to the center in the main scanning direction than areas B and D, is set to have a higher priority.

[0042] The priority of area A is "7" and the priority of area E is "8", so areas B and D, which are closer to the center in the main scanning direction than areas A and E, are set to have higher priority.

[0043] In addition, the priority of the C area for C (cyan) and M (magenta) is "1," and the priority of K (black) in the same C area is "4," so the more noticeable the ink color, the higher the priority is set.

[0044] Furthermore, among the areas divided by the dividing unit 26, the priority of a color in the center having a color priority of N, which indicates the conspicuousness of the ink color, is set to be higher than the priority of a color in the edge having a color priority of N-1. Here, the color priorities are set as follows: C (cyan) and M (magenta) are "1", K (black) is "2", Gr (gray) is "3", and Y (yellow) is "4".

[0045] In the example shown in Figure 3(b), the priority of area C, which is the center of K (black) with a color priority of "2", is "4", the priority of area A, which is the edge area of ​​C (cyan) and M (magenta) with a color priority of "1", is "7", and the priority of area E is "8". The priority of the center of K (black) with a color priority of "2" is set to be higher than the priority of the edge areas of C (cyan) and M (magenta) with a color priority of "1".

[0046] FIG. 4 is an explanatory diagram illustrating the effects of the image processing device 1 according to the first embodiment of the present invention.

[0047] Fig. 4(a) shows an example of read pattern image data read by the image reading unit 10, Fig. 4(b) is a diagram showing pixels corrected in accordance with the non-ejecting nozzles extracted by the extraction unit 23 in the case of Fig. 4(a), Fig. 4(c) shows an example of read pattern image data read by the image reading unit 10, and Fig. 4(d) is a diagram showing pixels corrected in accordance with the non-ejecting nozzles extracted by the extraction unit 23 in the case of Fig. 4(c). Here, it is assumed that the threshold value Th1 is "6", that is, six non-ejecting nozzles are extracted as targets for correction.

[0048] As shown in FIG. 4(a), the read pattern image data includes a first nozzle pattern H101, a second nozzle pattern H102, a third nozzle pattern H103, and a fourth nozzle pattern H104 printed thereon.

[0049] In the first nozzle pattern H101, there is an area A101 where three white streaks have occurred on both ends in the main scanning direction due to the occurrence of non-ejecting nozzles, and there is also an area A102 where three white streaks have similarly occurred.

[0050] In addition, there is an area A103 where three white streaks occur near the center in the main scanning direction of the second nozzle pattern H102, and there is an area A104 where three white streaks occur near the center in the main scanning direction of the third nozzle pattern H103.

[0051] Since there are a total of 12 white stripes, the detection unit 22 determines that the number of non-ejecting nozzles is equal to or greater than a predetermined threshold value Th1 (here, 6).

[0052] Therefore, based on the image data and the priority order table, the extraction unit 23 extracts non-ejecting nozzles with a high priority by the threshold value Th1 as correction targets. Here, based on the priority order table, the extraction unit 23 extracts non-ejecting nozzles corresponding to the "3" white streaks in area A103 and non-ejecting nozzles corresponding to the "3" white streaks in area A103 as correction targets.

[0053] As shown in Figure 4(b), when ejection is performed based on the print data after the non-ejecting nozzles have been corrected, C (cyan) and M (magenta) are set to have a higher priority than K (black).As a result of the correction, the white streaks of C (cyan) that exist in area A203 near the center of the image and the white streaks of M (magenta) that exist in area A204 near the center of the image are relatively less noticeable.

[0054] In the read pattern image data shown in Figure 4(c), there is an area A301 where two white streaks occur near the center in the main scanning direction of the second nozzle pattern H102, an area A302 where one white streak occurs near the center in the main scanning direction of the third nozzle pattern H103, and an area A303 where six white streaks occur near the center in the main scanning direction of the fourth nozzle pattern H104.

[0055] Since there are a total of nine white stripes, the detection unit 22 determines that the number of non-ejecting nozzles is equal to or greater than a predetermined threshold value Th1 (here, six).

[0056] Therefore, based on the image data and the priority order table, the extraction unit 23 extracts non-ejecting nozzles with high priority by the threshold value Th1 as targets for correction. Here, based on the priority order table, of the non-ejecting nozzles corresponding to the two white streaks in area A301, the non-ejecting nozzle corresponding to the one white streak in area A302, and the non-ejecting nozzles corresponding to the six white streaks in area A303, three that are close to the center in the main scanning direction are extracted as targets for correction.

[0057] 4(d), when ejection is performed based on the print data after the non-ejecting nozzles have been corrected, the correction results in the C (cyan) white streak present in area A401 near the center of the image and the M (magenta) white streak present in area A402 near the center of the image being relatively less noticeable. Furthermore, since Y (yellow) present in area A403 near the center of the image is an inconspicuous color, it would be possible not to correct the "6" white streaks, but in this case, the "3" white streaks closer to the center are corrected, and the "3" white streaks on the outside are not corrected.

[0058] FIG. 5 is a flowchart showing the processing contents of the priority order table creation processing by the image processing device 1 according to the first embodiment of the present invention.

[0059] As shown in FIG. 5, in step S101, the data processing unit 20 of the image processing device 1 reads the allocation process.

[0060] FIG. 6 is a diagram showing an example of the allocation information to be read.

[0061] As shown in FIG. 6, the allocation information includes information on default color numbers, area numbers, color priority allocation, and area priority allocation.

[0062] In step S103, the data processing unit 20 assigns "1" to Priority_num, which is a variable indicating the priority, and also assigns "1" to the color priority, which is a variable.

[0063] In step S105, the data processing unit 20 determines whether the color priority order exceeds "total number of colors+1."

[0064] If the color priority exceeds "total number of colors + 1" (step S105; YES), the process is terminated, and if the color priority is equal to or less than "total number of colors + 1" (step S105; NO), in step S107, the data processing unit 20 executes color number extraction processing to acquire color indicating the color number. The processing content of the color number extraction processing will be described later.

[0065] In step S109, the data processing unit 20 assigns "1" as an initial value to an area count, which is a counter.

[0066] In step S111, the data processing unit 20 determines whether the area count exceeds the total number of areas.

[0067] If it is determined that the area count exceeds the total number of areas (step S111; YES), the data processing unit 20 increments the color priority order in step S115, and moves the process to step S105.

[0068] On the other hand, if it is determined that the area count is equal to or less than the total number of areas (step S111; NO), the data processing unit 20 executes an area selection process in step S113, and acquires a color indicating a color number and an area indicating an area number, which is a number of a region. The details of the area selection process will be described later.

[0069] In step S117, the data processing unit 20 determines whether color is equal to or greater than 1 and equal to or less than the total number of colors.

[0070] If color is less than 1 or exceeds the total number of colors (step S117; NO), the data processing unit 20 moves the process to step S123.

[0071] On the other hand, if color is equal to or greater than 1 and equal to or less than the total number of colors (step S117; YES), in step S119, the data processing unit 20 assigns Priority_num to the priority corresponding to the color number and area number in the priority table.

[0072] In step S121, the data processing unit 20 increments Priority_num.

[0073] In step S123, the data processing unit 20 increments the area count, and moves the process to step S111.

[0074] FIG. 7 is a flowchart showing the color number extraction process in step S107 of the priority order table creation process flow by the image processing apparatus 1 according to the first embodiment of the present invention.

[0075] As shown in FIG. 7, in step S201, the data processing unit 20 assigns "1" to the color number.

[0076] In step S203, the data processing unit 20 determines whether Color_Priority [color number] is equal to the color priority order.

[0077] If Color_Priority [color number] is equal to the color priority order (step S203; YES), in step S207 the data processing unit 20 sets the color number as a return value in color and returns the process.

[0078] On the other hand, if Color_Priority [color number] is not equal to the color priority order (step S203; NO), the data processing unit 20 increments the color number in step S205.

[0079] FIG. 8 is a flowchart showing the area selection process in step S113 of the priority order table creation process flow by the image processing apparatus 1 according to the first embodiment of the present invention.

[0080] 8, in step S303, the data processing unit 20 executes an area number extraction process to obtain area_num indicating the area number. Details of the area number extraction process will be described later.

[0081] In step S305, the data processing unit 20 determines whether area_num is less than a boundary value. The boundary value is a value used to separate the center and end portions in the main scanning direction. Here, the area in the main scanning direction is divided into five areas, A to E, so the boundary value is set to "4." As a result, the end portions are designated as areas A and E, and the center portion is designated as areas B, C, and D.

[0082] If area_num is less than the boundary value (step S305; YES), in step S309, the data processing unit 20 assigns a value obtained by subtracting "1" from the color priority to color, and assigns area_num to area.

[0083] On the other hand, if area_num is equal to or greater than the boundary value (step S305; NO), in step S307, the data processing unit 20 assigns the color priority to color and assigns area_num to area.

[0084] In step S311, the data processing unit 20 sets color and area as return values ​​and returns the process.

[0085] FIG. 9 is a flowchart showing the area number extraction process in step S303 of the area selection process flow by the image processing apparatus 1 according to the first embodiment of the present invention.

[0086] As shown in FIG. 9, in step S401, the data processing unit 20 assigns "1" to the area number.

[0087] In step S403, the data processing unit 20 determines whether or not Area_Priority [area number] is equal to the area priority level.

[0088] If Area_Priority [area number] is equal to the area priority level (step S403; YES), in step S407 the data processing unit 20 sets the area number as a return value in color and returns the process.

[0089] On the other hand, if Area_Priority [area number] is not equal to the area priority level (step S403; NO), the data processing unit 20 increments the area number in step S405.

[0090] (Addendum) The present application discloses the following inventions.

[0091] (Appendix 1) a dividing means for dividing a plurality of nozzles of the inkjet into a plurality of regions in a main scanning direction; a storage means for storing a priority order table that defines priorities based on the areas divided by the dividing means and the colors of the inks; a detection means for detecting non-ejecting nozzles from image data read from a medium printed based on the nozzle pattern data; an extraction means for extracting, when the number of non-ejecting nozzles detected by the detection means is equal to or greater than a predetermined threshold, the threshold number of non-ejecting nozzles as targets for correction based on the image data and the priority order table; An image processing device comprising:

[0092] As a result, even if the number of non-ejections is large, the non-ejection nozzles with noticeable white streaks up to the threshold number can be preferentially extracted as correction targets, and image correction can be performed so that the white streaks are not noticeable without using a large-capacity non-volatile memory.

[0093] (Appendix 2) The priority table includes: The image is generated based on the distance to the center of the area divided by the dividing means in the main scanning direction and the conspicuousness of the ink color. 2. The image processing device according to claim 1,

[0094] This allows the priority to be higher the closer to the center in the main scanning direction, or the more conspicuous the ink color, so that image correction can be performed more appropriately to make white stripes less noticeable.

[0095] (Appendix 3) The priority table includes: In the area divided by the dividing means, the priority level at the center of a color having a color priority level N, which indicates the conspicuousness of the ink color, is generated so as to be higher than the priority level at the end of a color having a color priority level N-1. 3. The image processing device according to claim 2,

[0096] This allows an appropriate priority to be set for the combination of distance to the center in the main scanning direction and the conspicuousness of the ink color, thereby enabling more appropriate image correction to be performed so that white streaks are less noticeable.

[0097] (Appendix 4) The extraction means If the priorities are the same, the non-ejecting nozzle that is closer to the center in the main scanning direction is preferentially extracted as the correction target. 2. The image processing device according to claim 1,

[0098] This allows the priority to be set appropriately even when the priorities are the same, so that image correction can be performed more appropriately so that white stripes are less noticeable. [Explanation of symbols]

[0099] 1. Image processing device 10 Image reading unit 20 Data Processing Unit 21 Image input unit 22 Detection unit 23 Extraction part 25 Image generation unit 26 Division 27 Table Generation Unit 30 Inkjet head control unit 40 Storage section

Claims

1. a dividing means for dividing a plurality of nozzles of the inkjet into a plurality of regions in a main scanning direction; a storage means for storing a priority order table that defines priorities based on the areas divided by the dividing means and the ink colors; a detection means for detecting non-ejecting nozzles from image data read from a medium printed based on the nozzle pattern data; an extraction means for extracting, when the number of non-ejecting nozzles detected by the detection means is equal to or greater than a predetermined threshold, the threshold number of non-ejecting nozzles as targets for correction based on the image data and the priority order table; An image processing device comprising:

2. The priority table includes: The image is generated based on the distance to the center of the area divided by the dividing means in the main scanning direction and the conspicuousness of the ink color.

2. The image processing device according to claim 1, wherein:

3. The priority table includes: The region divided by the dividing means is generated so that the priority level at the center of a color having a color priority level N, which indicates the conspicuousness of the ink color, is higher than the priority level at the edge of a color having a color priority level N-1.

3. The image processing device according to claim 2.

4. The extraction means If the priorities are the same, the non-ejecting nozzle that is closer to the center in the main scanning direction is preferentially extracted as the correction target.

2. The image processing device according to claim 1, wherein:

Images