Inkjet printer

Abstract

To provide an inkjet printer which can reduce erroneous detection of a non-discharging nozzle while suppressing increase in processing time.SOLUTION: A control part scans each stage 24 of a test pattern 21 in image data from the left side to the right side, counts up a count value of a nozzle each time the nozzle pattern 23 or missing of the nozzle pattern 23 is detected after first detection of the nozzle pattern 23, stores a count value corresponding to the detected nozzle pattern 23 and missing of the nozzle pattern 23 and a position in a nozzle arrangement direction, and calculates a nozzle number of the nozzle.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to inkjet printing devices. [Background technology]

[0002] In inkjet printing devices, a technique is known in which a test pattern is printed to detect nozzles that are not ejecting ink (MF: Miss Fire), and the non-ejecting nozzles are detected based on image data obtained by reading the printed test pattern.

[0003] One test pattern is formed by drawing a line segment with each nozzle, drawing a line segment at a position one step lower each time the nozzle number increases by one, and when a predetermined number of steps is reached, returning to the position of the first line segment and drawing a line segment (see Patent Document 1).

[0004] In the process of detecting non-ejecting nozzles using this test pattern, each row of the test pattern in the image data obtained by reading the test pattern is scanned, and when a line segment or missing line segment is detected, the nozzle count value is incremented. If the distance between the detected line segments is greater than a predetermined value, it is determined that there is a missing line segment between the lines, and the missing line segment is detected. A missing line segment is when a line segment is not drawn at a position where a line segment should normally be drawn.

[0005] A missing line segment indicates that the corresponding nozzle is non-ejecting, so in this process, the nozzle number of the non-ejecting nozzle is calculated using the count value of the nozzle corresponding to the missing line segment.

[0006] For example, if a line segment at the upstream end in the scanning direction when scanning each row of the test pattern is missing, the missing line segment cannot be detected, and the count-up starts from a line segment that is not the first line segment. This can result in the nozzle number of a non-ejecting nozzle being calculated incorrectly, i.e., the non-ejecting nozzle being incorrectly detected.

[0007] Furthermore, if there is foreign matter such as dust upstream of the line segment drawn by the nozzle at the upstream end in the scanning direction, the foreign matter may be mistakenly detected as a line segment in the test pattern, causing a count-up to begin. In such cases, the nozzle number of the non-ejecting nozzle may also be calculated incorrectly.

[0008] If the nozzle number of a non-ejecting nozzle is calculated incorrectly, inappropriate image correction may be performed, resulting in a deterioration in print quality.

[0009] In response to this, for example, a method can be considered in which missing line segments are detected based on whether or not there is a line segment at a theoretical position relative to the reference position in the test pattern, and the nozzle number of the non-ejecting nozzle is calculated.

[0010] Another possible method is to regard the position of the line segment at the upstream end of each stage in the scanning direction as a pattern, determine the amount of correction for the count value of each stage by pattern matching, and calculate the nozzle number of the non-ejecting nozzle. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2018-30314 Summary of the Invention [Problem to be solved by the invention]

[0012] However, in the method using the theoretical positions described above, the low reading magnification accuracy of the reading device can lead to erroneous detection of line segments and missing line segments, which can result in the incorrect calculation of the nozzle number of a non-ejecting nozzle.

[0013] Furthermore, the pattern matching method described above requires many patterns, which increases processing time. Also, if there is dust or other foreign matter upstream of the line segment drawn by the nozzle at the upstream end in the scanning direction, matching may be performed using an incorrect pattern, which may result in an incorrect calculation of the nozzle number of the non-ejecting nozzle.

[0014] The present invention has been made in view of the above, and has an object to provide an inkjet printing apparatus that can reduce the false detection of non-ejecting nozzles while suppressing an increase in processing time. [Means for solving the problem]

[0015] In order to achieve the above object, an inkjet printing device of the present invention includes a line-type inkjet head having a plurality of nozzles, and a control unit that causes the inkjet head to print a test pattern on a printing medium, and detects non-ejecting nozzles based on image data generated by reading the printed test pattern, wherein the control unit detects a reference line segment in the image data, scans each row of the test pattern in the image data from one side to the other in the nozzle arrangement direction, and counts up the count value of the nozzle each time it detects a line segment or a missing line segment after detecting the first line segment, stores the count value corresponding to the detected line segment and the missing line segment and its position in the nozzle arrangement direction, and calculates the nozzle number of the nozzle. [Effects of the Invention]

[0016] According to the inkjet printing apparatus of the present invention, it is possible to reduce the false detection of non-ejecting nozzles while suppressing an increase in processing time. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram showing a schematic configuration of an inkjet printing apparatus according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of a transport unit and a printing unit. [Figure 3] FIG. 2 is a plan view of a transport unit and a printing unit. [Figure 4] FIG. 2 is a schematic diagram illustrating the configuration of an inkjet head. [Figure 5] FIG. 10 is a diagram illustrating a test pattern. [Figure 6] 10 is a flowchart illustrating an operation of detecting a non-ejecting nozzle of the inkjet printing device. [Figure 7] 10 is a flowchart of a non-ejection detection process. [Figure 8] 10 is a flowchart of a reference nozzle pattern detection process. [Figure 9] 10 is a flowchart of a nozzle pattern detection process. [Figure 10] 10 is a flowchart of a nozzle pattern detection process. [Figure 11] FIG. 2 is an explanatory diagram of a table memory. [Figure 12] 10A and 10B are diagrams illustrating an example of count values ​​stored by the nozzle pattern detection process. [Figure 13] 10 is a flowchart of a non-ejecting nozzle number calculation process. [Figure 14] 10 is a flowchart of a process for calculating std_dan and x0. [Figure 15] 10 is a flowchart of a process for calculating theory_x[stage]. [Figure 16] FIG. 10 is a diagram showing nozzle patterns and missing nozzle patterns by each nozzle of a nozzle group including a nozzle that has drawn a nozzle pattern with a count value of "0" in the std_dan row. [Figure 17] 10 is a flowchart of a process for calculating save_count [stages]. [Figure 18] 10 is a flowchart of a process for calculating the nozzle number of a non-ejecting nozzle. [Figure 19] FIG. 10 is an explanatory diagram of adjust_count [stages]. [Figure 20] FIG. 10 is a diagram showing nozzle patterns formed by each nozzle of a nozzle group including a nozzle on which a reference nozzle pattern is formed. DETAILED DESCRIPTION OF THE INVENTION

[0018] 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.

[0019] The following embodiments are examples of devices that embody the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not limit the materials, shapes, structures, arrangements, etc. of each component to those described below. The technical idea of ​​the present invention can be modified in various ways within the scope of the claims.

[0020] [First embodiment] Fig. 1 is a block diagram showing a schematic configuration of an inkjet printing apparatus according to a first embodiment of the present invention. Fig. 2 is a schematic configuration diagram of a conveying unit and a printing unit. Fig. 3 is a plan view of the conveying unit and the printing unit. Fig. 4 is a schematic configuration diagram of an inkjet head.

[0021] As shown in FIG. 1, the inkjet printing apparatus 1 according to the first embodiment includes a transport unit 2, a printing unit 3, an image reading unit 4, and a control unit 5.

[0022] The transport unit 2 transports a print medium, namely, paper P. The left-right direction of the inkjet printing device 1 is defined as the left-right direction when facing downstream in the transport direction (corresponding to the relative movement direction) of the paper P by the transport unit 2.

[0023] The printing unit 3 performs printing on the paper P transported by the transport unit 2. The printing unit 3 includes a plurality of line heads 11. In this embodiment, the printing unit 3 includes four line heads 11.

[0024] The line heads 11 perform printing by ejecting ink onto the paper P. The four line heads 11 are arranged in parallel above the transport unit 2 in the transport direction (sub-scanning direction) of the paper P. The four line heads 11 each eject ink of a different color (for example, black, cyan, magenta, or yellow).

[0025] The line head 11 includes a plurality of inkjet heads 16. In this embodiment, the line head 11 includes six inkjet heads 16. In the line head 11, the six inkjet heads 16 are arranged in a staggered pattern along the left-right direction (main scanning direction) perpendicular to the transport direction (sub-scanning direction) of the paper P. In other words, the six inkjet heads 16 are arranged along the left-right direction, and are arranged such that every other inkjet head 16 is shifted in position in the transport direction of the paper P.

[0026] As shown in Figure 4, the inkjet head 16 has a plurality of nozzles 17 that eject ink. Figure 4 is a view of the inkjet head 16 as seen from below.

[0027] The nozzles 17 are arranged in the left-right direction (corresponding to the nozzle arrangement direction). The nozzles 17 are open to a nozzle surface 16a, which is the underside of the inkjet head 16. Each nozzle 17 is assigned a nozzle number indicating the order of the nozzles 17 from the left side (one side in the nozzle arrangement direction). The nozzle numbers are numbered 0 (#0), 1 (#1), 2 (#2), ... starting from the leftmost nozzle 17. The nozzles 17 of the inkjet head 16 are divided into a plurality of nozzle groups 18, each consisting of (M+1) nozzles 17 (corresponding to a predetermined number), which is the same number as the number of rows in a test pattern 21, which will be described later. In the example of the test pattern 21 in FIG. 5, which will be described later, M=3.

[0028] The image reading unit 4 reads a printed image such as a test pattern 21 (to be described later) printed on the paper P, and generates image data.

[0029] The control unit 5 controls the operation of each unit of the inkjet printing apparatus 1. The control unit 5 is configured with a CPU, RAM, ROM, a hard disk, and the like.

[0030] The control unit 5 causes each inkjet head 16 of the printing unit 3 to print a test pattern 21, which will be described later, on paper P, and then performs an operation to detect non-ejecting nozzles 17 based on image data generated by reading the printed test pattern with the image reading unit 4. The operation of detecting non-ejecting nozzles 17 will be described in detail later.

[0031] Next, the test pattern 21 for detecting non-ejecting nozzles 17 will be described.

[0032] As shown in FIG. 5, the test pattern 21 is formed by a plurality of reference nozzle patterns (corresponding to reference line segments) 22 and a plurality of nozzle patterns (corresponding to line segments) 23.

[0033] Here, the test pattern 21 is printed for each inkjet head 16. Figure 5 shows the test pattern 21 printed by the first three inkjet heads 16 from the left, and a portion of the test pattern 21 printed by the fourth inkjet head 16 from the left.

[0034] 5, the leftmost test pattern 21 is printed by the leftmost inkjet head 16, which straddles the left edge of the printable area excluding the margins of the paper P. For this reason, the leftmost inkjet head 16 prints the test pattern 21 not starting with the leftmost nozzle 17, numbered 0, but with each nozzle 17 located to the right of the left edge of the printable area of ​​the paper P. In other words, there is a nozzle 17 at the left end of the leftmost inkjet head 16 that was not used to print the test pattern 21.

[0035] The reference nozzle pattern 22 is made up of straight line segments that run along the sub-scanning direction. The multiple reference nozzle patterns 22 are drawn by any of multiple nozzles 17. That is, the inkjet head 16 draws multiple reference nozzle patterns 22 in one test pattern 21 using different nozzles 17. The reference nozzle pattern 22 is arranged downstream of a column 24 with column number 0, which will be described later, in the transport direction (sub-scanning direction) of the paper P.

[0036] The nozzle pattern 23 is made up of line segments similar to those of the reference nozzle pattern 22. Each nozzle pattern 23 in the test pattern 21 is formed by drawing the nozzle pattern 23 with each nozzle 17 in each of the multiple nozzle groups 18 of the inkjet head 16 shifting its position in the transport direction (sub-scanning direction) of the paper P from a predetermined position on the downstream side (one side) of the test pattern 21 to the upstream side (the other side) as the nozzle number increases.

[0037] In other words, each nozzle 17 draws a nozzle pattern 23 at a position shifted one stage upstream in the transport direction (sub-scanning direction) of the paper P each time the nozzle number increases by one, and when the number of stages reaches (M+1), it returns to the position of the first nozzle pattern 23 (predetermined position) and draws the nozzle pattern 23, thereby forming each nozzle pattern 23 in the test pattern 21.

[0038] As a result, the nozzle patterns 23 in the test pattern 21 are arranged to form (M+1) rows 24, each including a plurality of nozzle patterns 23 and positioned at different positions in the transport direction (sub-scanning direction) of the paper P. In each row 24, the nozzle patterns 23 are arranged at intervals that are (M+1) times the distance of one pitch of the nozzles 17.

[0039] In this embodiment, the column numbers indicating the order of the columns 24 in the transport direction (sub-scanning direction) of the paper P in the test pattern 21 are assigned so that the most downstream column 24 is number 0 (#0), and the numbers increase toward the upstream side, with the most upstream column 24 being number M (#M).

[0040] Next, the operation of detecting a non-ejecting nozzle 17 in the inkjet printing device 1 will be described.

[0041] FIG. 6 is a flowchart for explaining the operation of detecting a non-ejecting nozzle 17.

[0042] In step S1 of FIG. 6, the control unit 5 causes the inkjet heads 16 of each line head 11 to print the test pattern 21 on the paper P while causing the transport unit 2 to transport the paper P.

[0043] Next, in step S2, the control unit 5 causes the image reading unit 4 to read the printed test pattern 21 in response to a user operation to cause the image reading unit 4 to read the test pattern 21 printed on the paper P. The image reading unit 4 reads the printed test pattern 21 and generates image data. In this embodiment, the image data of the test pattern 21 generated by the image reading unit 4 is image data in RGB format.

[0044] Next, in step S3, the control unit 5 executes a non-ejection detection process to detect non-ejecting nozzles 17 based on image data generated by reading the test pattern 21 with the image reading unit 4.

[0045] Next, the non-ejection detection process executed in step S3 of FIG. 6 described above will be described.

[0046] 7 is a flowchart of the non-ejection detection process. The process of the flowchart in FIG.

[0047] 7, the control unit 5 executes a reference nozzle pattern detection process to detect the reference nozzle pattern 22 from the test pattern 21 in the image data. The reference nozzle pattern detection process will be described in detail later.

[0048] Next, in step S12, the control unit 5 executes a nozzle pattern detection process to detect the nozzle pattern 23 from the test pattern 21 in the image data. The nozzle pattern detection process will be described in detail later.

[0049] Next, in step S13, the control unit 5 uses the results of the nozzle pattern detection process to execute a non-ejecting nozzle number calculation process to calculate the nozzle number of the non-ejecting nozzle 17. The non-ejecting nozzle number calculation process will be described in detail later.

[0050] Next, the reference nozzle pattern detection process executed in step S11 of FIG. 7 will be described.

[0051] FIG. 8 is a flowchart of the reference nozzle pattern detection process.

[0052] 8, the control unit 5 sets the variable x, which indicates the position of a pixel in the main scanning direction in the image data, to "0." Here, the position of x=0 is set to the left of the design position where the leftmost nozzle pattern 23 in the test pattern 21 to be processed is to be formed.

[0053] Next, in step S22, the control unit 5 determines whether or not the reference nozzle pattern 22 is present at the position x.

[0054] Specifically, the control unit 5 calculates the average value of any one of R, G, and B values ​​corresponding to the printing color of the test pattern 21 being processed for multiple pixels within a predetermined range in the sub-scanning direction at each of the positions (x-1), x, and (x+1).The control unit 5 then determines that the reference nozzle pattern 22 is located at the x position if the difference between the average value at the x position and the average value at the (x-1) position, and the difference between the average value at the x position and the average value at the (x+1) position are both equal to or greater than a predetermined threshold.

[0055] If it is determined that the reference nozzle pattern 22 is not present at the position x (step S22: NO), then in step S23, the control unit 5 adds "1" to the variable x. After that, the control unit 5 returns to step S22.

[0056] If it is determined that the reference nozzle pattern 22 is at position x (step S22: YES), then in step S24, the control unit 5 stores the position x as std_nzl_x. This completes the series of processes. std_nzl_x is a value that indicates the position of the reference nozzle pattern 22 in the main scanning direction.

[0057] As mentioned above, one test pattern 21 includes multiple reference nozzle patterns 22, and the above-mentioned reference nozzle pattern detection process ends when one reference nozzle pattern 22 is detected. The reason for providing multiple reference nozzle patterns 22 is to reduce the risk of the reference nozzle pattern 22 not being formed due to non-ejection of ink from a nozzle 17.

[0058] Next, the nozzle pattern detection process executed in step S12 of FIG. 7 will be described.

[0059] 9 and 10 are flowcharts of the nozzle pattern detection process.

[0060] In step S31 of FIG. 9, the control unit 5 sets a variable i indicating the row number in the test pattern 21 to "0."

[0061] Next, in step S32, the control unit 5 sets the count value count of the nozzles 17 detected from the test pattern 21 to "0".

[0062] Here, the count value "count" is a value obtained by counting the total number of nozzle patterns 23 and missing nozzle patterns 23 that have been detected since the first nozzle pattern 23 was detected when scanning the row 24 from left to right in the main scanning direction. In other words, the count value "count" is incremented each time a nozzle pattern 23 or missing nozzle pattern 23 is detected since the first nozzle pattern 23 was detected when scanning the row 24 from left to right. In this embodiment, the count value "count" is incremented from "0." The count value "count" corresponds to the detected nozzle patterns 23 and missing nozzle patterns 23, and also corresponds to the nozzles 17 that correspond to them.

[0063] A missing nozzle pattern 23 means that the nozzle pattern 23 is not drawn at a position where the nozzle pattern 23 should be drawn. A missing nozzle pattern 23 indicates that the corresponding nozzle 17 is not ejecting.

[0064] Next, in step S33, the control unit 5 sets "0" to a variable x that indicates the position of a pixel in the main scanning direction in the image data, similar to the variable x in the reference nozzle pattern detection process described above.

[0065] Next, in step S34, the control unit 5 determines whether or not there is a nozzle pattern 23 at the position x in the i-th row 24. The process of determining whether or not there is a nozzle pattern 23 at the position x is the same as the process of determining whether or not there is a reference nozzle pattern 22 at the position x in step S22 of FIG.

[0066] If it is determined that there is no nozzle pattern 23 at the position x (step S34: NO), the control unit 5 adds "1" to the variable x in step S35. After that, the control unit 5 returns to step S34.

[0067] If it is determined that a nozzle pattern 23 is present at position x (step S34: YES), then in step S36, the control unit 5 stores x in the table memory 31 shown in FIG. 11 as the position of the nozzle 17 corresponding to the count value "count" of the i-th row 24. That is, the control unit 5 sets Table(count, i) = x. Here, the table memory 31 uses (count, i) as an address to store the positions in the main scanning direction of the detected nozzle pattern 23 and the nozzle 17 corresponding to the missing nozzle pattern 23, and Table(count, i) is the value of (count, i) in the table memory 31. The example of the table memory 31 shown in FIG. 11 corresponds to the test pattern 21 in the example of FIG. 12, which will be described later.

[0068] Next, in step S37, the control unit 5 determines whether the value obtained by subtracting Table(count-1,i), which indicates the position of the nozzle 17 at (count-1), the count value immediately before the count value count, from Table(count,i) is greater than a specified value.

[0069] Here, the above-mentioned specified value is a value for determining whether or not there is a missing nozzle pattern 23 between the nozzle pattern 23 detected immediately before and the nozzle pattern 23 detected this time. The specified value is set to a predetermined value that is greater than the distance of one pitch of the nozzles 17. If the value obtained by subtracting Table(count-1,i) from Table(count,i) is greater than the specified value, this indicates that there is at least one missing nozzle pattern 23 in a position between them.

[0070] If it is determined that the value obtained by subtracting Table(count-1,i) from Table(count,i) is greater than the specified value (step S37: YES), then in step S38 the control unit 5 stores the position of the non-ejecting nozzle 17 (missing nozzle pattern 23) between Table(count-1,i) and Table(count,i). At this time, the control unit 5 stores the position of the non-ejecting nozzle 17 estimated from x.

[0071] Specifically, the control unit 5 determines the number of non-ejecting nozzles 17 (missing nozzle patterns 23) between Table(count-1,i) and Table(count,i) based on the value obtained by subtracting Table(count-1,i) from Table(count,i).

[0072] Then, for example, if the control unit 5 determines that the number of non-ejecting nozzles 17 between Table(count-1,i) and Table(count,i) is one, the control unit 5 changes the value of Table(count,i) from x to a value obtained by subtracting the distance of one nozzle 17 pitch from x.

[0073] Furthermore, for example, if it is determined that the number of non-ejecting nozzles 17 between Table(count-1,i) and Table(count,i) is two, the control unit 5 changes the value of Table(count,i) from x to a value obtained by subtracting the distance equivalent to two nozzle pitches 17 from x. The control unit 5 also stores the value obtained by subtracting the distance equivalent to one nozzle pitch 17 from x as the value of Table(count+1,i).

[0074] As a result, a missing nozzle pattern 23 is detected, and its position is detected as the position of the non-ejecting nozzle 17 and stored in the table memory 31.

[0075] Here, the value obtained by subtracting the distance of two pitches of the nozzle 17 from the above x, and the value obtained by subtracting the distance of one pitch of the nozzle 17 from x, indicate the position of the non-ejecting nozzle 17 estimated from x.

[0076] Next, in step S39, the control unit 5 stores non-ejection information for the non-ejection nozzles 17 whose positions were stored in step S38.

[0077] Specifically, for example, if the number of non-ejecting nozzles 17 whose positions are stored in step S38 is one, the control unit 5 stores MF_Table(count,i)=True, which indicates that the nozzle 17 corresponding to the position in Table(count,i) is non-ejecting, as the non-ejection information for the position in Table(count,i).Furthermore, for example, if the number of non-ejecting nozzles 17 whose positions are stored in step S38 is two, the control unit 5 stores MF_Table(count,i)=True and MF_Table(count+1,i)=True.

[0078] Next, in step S40, the control unit 5 adds the number of non-ejecting nozzles 17 whose positions were stored in step S38 to the count value count.

[0079] For example, if the number of non-ejecting nozzles 17 whose positions are stored in step S38 is one, the control unit 5 adds "1" to the count value "count." Also, for example, if the number of non-ejecting nozzles 17 whose positions are stored in step S38 is two, the control unit 5 adds "2" to the count value "count."

[0080] Next, in step S41, the control unit 5 sets Table(count, i)=x.

[0081] Next, in step S42, the control unit 5 stores MF_Table(count,i)=False as non-ejection information at the position of Table(count,i), indicating that the nozzle 17 corresponding to the position of Table(count,i) is not non-ejection.

[0082] In step S37, if it is determined that the value obtained by subtracting Table(count-1,i) from Table(count,i) is less than or equal to the specified value (step S37: NO), the control unit 5 proceeds to step S42 and stores MF_Table(count,i)=False.

[0083] Following step S42, in step S43 of FIG. 10, the control unit 5 determines whether the i-th stage 24 is the std_nzl_dan stage.

[0084] Here, the std_nzl_dan column is the column 24 that includes the nozzle pattern 23 drawn by the same nozzle 17 as the nozzle 17 that draws the reference nozzle pattern 22. In other words, the std_nzl_dan column is the column 24 that includes the nozzle pattern 23 at the same position in the main scanning direction as the reference nozzle pattern 22. std_nzl_dan is the value of the column number of the std_nzl_dan column. std_nzl_dan is determined in advance. In the example of FIG. 12, the std_nzl_dan column is column 24 numbered 0.

[0085] If it is determined that the i-th stage 24 is not the std_nzl_dan stage (step S43: NO), the control unit 5 proceeds to step S46, which will be described later.

[0086] If it is determined that the i-th row 24 is the std_nzl_dan row (step S43: YES), in step S44, the control unit 5 determines whether x is greater than the value obtained by subtracting valid_x from std_nzl_x obtained in the above-mentioned reference nozzle pattern detection process and is less than the value obtained by adding valid_x to std_nzl_x.

[0087] Here, valid_x is a preset threshold value for determining whether the detected nozzle pattern 23 is at the same position in the main scanning direction as the reference nozzle pattern 22 detected in the reference nozzle pattern detection process.

[0088] If it is determined that x is greater than (std_nzl_x-valid_x) and less than (std_nzl_x+valid_x) (step S44: YES), then in step S45, the control unit 5 stores the count value "count" as the actual count value. The actual count value is the count value "count" corresponding to the nozzle 17 corresponding to the nozzle pattern 23 at the same position in the main scanning direction as the reference nozzle pattern 22. The control unit 5 then proceeds to step S46.

[0089] In step S44, if it is determined that x is equal to or less than (std_nzl_x-valid_x) or equal to or greater than (std_nzl_x+valid_x) (step S44: NO), the control unit 5 skips step S45 and proceeds to step S46.

[0090] In step S46, the control unit 5 adds "1" to the count value "count."

[0091] Next, in step S47, the control unit 5 determines whether the variable x is "X" which indicates that the variable x is the position of the last pixel in the region where the column 24 is scanned in the main scanning direction.

[0092] If it is determined that x=X is not true (step S47: NO), the control unit 5 adds "1" to the variable x in step S35 of Fig. 9. Thereafter, the control unit 5 returns to step S34.

[0093] If it is determined that x=X (step S47: YES), in step S48, the control unit 5 determines whether the variable i is "M" indicating that the stage 24 is the last stage.

[0094] If it is determined that i=M is ​​not true (step S48: NO), the control unit 5 adds "1" to the variable i in step S49. Thereafter, the control unit 5 returns to step S32 in FIG.

[0095] If the control unit 5 determines that i=M (step S48: YES), the series of processes ends.

[0096] By executing the nozzle pattern detection process as described above, the control unit 5 scans each row 24 of the test pattern 21 in the image data from left to right in the main scanning direction, and stores the count values ​​"count" and positions in the main scanning direction corresponding to the nozzle patterns 23 detected after the first nozzle pattern 23 and missing nozzle patterns 23 in the table memory 31. The control unit 5 also stores the above-mentioned actual count values.

[0097] An example of the count value "count" stored by the nozzle pattern detection process is shown in Fig. 12. The test pattern 21 in the example of Fig. 12, like the left-most test pattern 21 shown in Fig. 5, was printed by the left-most inkjet head 16 that straddles the left edge of the printable area of ​​the paper P. That is, at the left end of the inkjet head 16 that printed the test pattern 21 in the example of Fig. 12, there is a nozzle 17 that was not used in printing the test pattern 21.

[0098] In FIG. 12, the count values ​​"count" corresponding to the respective nozzle patterns 23 and missing nozzle patterns 23 are written adjacent to the positions of the nozzle patterns 23 and missing nozzle patterns 23.

[0099] In the example of FIG. 12, in the first (#1) and second (#2) stages 24, there is a missing nozzle pattern 23 due to a nozzle 17 not ejecting ink.

[0100] In the first row 24, the nozzle pattern 23 that is supposed to be at the left end is missing. This missing nozzle pattern 23 is not detected by the nozzle pattern detection process described above. For this reason, the nozzle pattern 23 to the right of the missing nozzle pattern 23 is detected first, and the count value count for this nozzle pattern 23 is set to "0" and counting up begins.

[0101] In the second row 24, a missing nozzle pattern 23 occurs to the right of the leftmost nozzle pattern 23. This missing nozzle pattern 23 is detected after the first nozzle pattern 23 (the leftmost nozzle pattern 23) is detected in the nozzle pattern detection process described above, and this detection causes the count value "count" to be incremented. In the example of Figure 12, the count value "count" of the nozzle 17 corresponding to this missing nozzle pattern 23 is "2."

[0102] 12, in the image data generated by reading the test pattern 21, there is a foreign substance 36 such as dust to the left of the leftmost nozzle pattern 23 in the third (Mth) row 24. Then, in the nozzle pattern detection process described above, the foreign substance 36 is detected in the third row 24 before the leftmost nozzle pattern 23 is detected, and the count value "count" starts to count up.

[0103] Also, in FIG. 12, next to the reference nozzle pattern 22, the value of the correct count in this example, "5", is written.

[0104] Here, the correct count value is the count value count corresponding to the nozzle pattern 23 in the same position as the reference nozzle pattern 22, when the nozzle 17 on the left side, which has the smallest nozzle number in the inkjet head 16, is used to print the test pattern 21, the nozzle pattern 23 on the left side being drawn in the std_nzl_dan row, which is the row 24 including the nozzle pattern 23 in the same position as the reference nozzle pattern 22, and when the detection of that nozzle pattern 23 starts counting up the count value count. The correct count value is a value that is known in advance.

[0105] As mentioned above, in the example of Figure 12, the std_nzl_dan row is row 0, 24. In the example of Figure 12, the count correct value being "5" means that if the test pattern 21 is printed starting from nozzle 17, number 0, on the left edge of the inkjet head 16, and if nozzle pattern 23 in row 24, number 0, is drawn by nozzle 17, and if counting up of the count value "count" begins upon detection of that nozzle pattern 23, then the count value "count" corresponding to the nozzle pattern 23 in the same position as the reference nozzle pattern 22 will be "5".

[0106] 12 shows, as mentioned above, a test pattern 21 printed by the leftmost inkjet head 16 that straddles the left edge of the printable area of ​​the paper P, and there are nozzles 17 at the left end of the inkjet head 16 that were not used to print the test pattern 21. As a result, the count value "count" corresponding to the nozzle pattern 23 in the same position as the reference nozzle pattern 22 is different from the correct count value of "5."

[0107] 12, the nozzle pattern 23 in the same position as the reference nozzle pattern 22 is the third nozzle pattern 23 from the left in the 0th row 24, and the count value count corresponding to this nozzle pattern 23 is "2." This value is the actual count value mentioned above.

[0108] The actual count value and the correct count value are used when calculating the nozzle number of the non-ejecting nozzle 17 in the non-ejecting nozzle number calculation process executed in step S13 of FIG. 7 described above.

[0109] Next, the above-mentioned non-ejecting nozzle number calculation process will be described.

[0110] FIG. 13 is a flowchart of the non-ejecting nozzle number calculation process.

[0111] 13, the control unit 5 calculates std_dan and x0. Here, std_dan is the row number of the std_dan row, which is the row 24 in which the nozzle pattern 23 whose count value is "0" is located at the rightmost position. x0 is the position in the main scanning direction of the nozzle pattern 23 whose count value is "0" in the std_dan row.

[0112] The process of calculating std_dan and x0 will be described with reference to the flowchart of FIG.

[0113] In step S71 of FIG. 14, the control unit 5 sets the values ​​of both variables max and std_dan to "0."

[0114] Next, in step S72, the control unit 5 sets the variable i indicating the row number in the test pattern 21 to "0".

[0115] Next, in step S73, the control unit 5 determines whether max is smaller than Table(0,i).

[0116] If it is determined that max is smaller than Table(0,i) (step S73: YES), then in step S74, the control unit 5 updates the value of max to the value of Table(0,i). The control unit 5 also updates the value of std_dan to the value of i. The control unit 5 also sets the value of max to x0. After this, the control unit 5 proceeds to step S75.

[0117] In step S73, if it is determined that max is equal to or greater than Table(0,i) (step S73: NO), the control unit 5 proceeds to step S75.

[0118] In step S75, the control unit 5 determines whether the variable i is "M" indicating that the stage 24 is the last stage.

[0119] If it is determined that i=M is ​​not true (step S75: NO), the control unit 5 adds "1" to the variable i in step S76, after which the control unit 5 returns to step S73.

[0120] In step S75, if the control unit 5 determines that i=M (step S75: YES), the series of processes ends.

[0121] 14, the position of the rightmost nozzle pattern 23 among the nozzle patterns 23 whose count value "count" is "0" in each row 24 is calculated as max=x0. In addition, the row number of the std_dan row, which is the row 24 that includes the nozzle pattern 23 located at the x0 position, is calculated.

[0122] 11 and 12, the value "150" corresponding to the count value "0" of the first row 24 in Fig. 11 is calculated as x0. Also, "1" is calculated as the row number of the std_dan row.

[0123] Returning to FIG. 13, in step S62, the control unit 5 calculates theory_x[stage] (theory_x[0] to theory_x[3]).

[0124] theory_x[row] is the theoretical value (theoretical position) based on x0 of the position in the main scanning direction of the nozzle pattern 23 and missing nozzle pattern 23 by each nozzle 17 of the nozzle group 18, including the nozzle 17 that drew the nozzle pattern 23 whose count value count in the std_dan row is "0".

[0125] The process of calculating theory_x[stage] will be described with reference to the flowchart of FIG.

[0126] In step S81 of FIG. 15, the control unit 5 sets a variable i indicating the row number in the test pattern 21 to "0".

[0127] Next, in step S82, the control unit 5 calculates theory_x[i] using the following equation (1).

[0128] theory_x[i]=x0+(i-std_dan)×reading resolution / printing resolution …(1) Here, the “reading resolution” in the formula (1) is the reading resolution of the test pattern 21 by the image reading unit 4. The “printing resolution” is the printing resolution of the test pattern 21 by the inkjet head 16.

[0129] Next, in step S83, the control unit 5 determines whether the variable i is "M" which indicates that the stage 24 is the last stage.

[0130] If it is determined that i=M is ​​not true (step S83: NO), the control unit 5 adds "1" to the variable i in step S84, after which the control unit 5 returns to step S82.

[0131] In step S83, if the control unit 5 determines that i=M (step S83: YES), the series of processes ends.

[0132] 12, the nozzle patterns 23 and missing nozzle patterns 23 in area A surrounded by a two-dot chain line in Fig. 16 are caused by the nozzles 17 of the nozzle group 18 that includes the nozzle 17 that drew the nozzle pattern 23 with a count value of "0" in the first row 24, which is the std_dan row. By processing the flowchart in Fig. 15 as described above, the theoretical positions of the nozzle patterns 23 and missing nozzle patterns 23 in area A are calculated.

[0133] Returning to FIG. 13, in step S63, the control unit 5 calculates save_count [stages] (save_count[0] to save_count[3]).

[0134] save_count[row] is the count value count corresponding to the nozzle pattern 23 and the absence of the nozzle pattern 23 by each nozzle 17 of the nozzle group 18 including the nozzle 17 that drew the nozzle pattern 23 whose count value count in the std_dan row is "0".

[0135] The process of calculating the save_count [stages] will be described with reference to the flowchart of FIG.

[0136] In step S91 of FIG. 17, the control unit 5 sets a variable i indicating the row number in the test pattern 21 to "0".

[0137] Next, in step S92, the control unit 5 sets the count value "count" to "0".

[0138] Next, in step S93, the control unit 5 determines whether Table(count, i) is greater than the value obtained by subtracting valid_x from theory_x[i] and less than the value obtained by adding valid_x to theory_x[i].

[0139] Here, valid_x is the value used in the process of step S44 in the flowchart of Fig. 10. In step S93 of Fig. 17, valid_x is used to determine whether Table(count,i) is within a predetermined range including theory_x[i].

[0140] If it is determined that Table(count, i) is greater than (theory_x[i]-valid_x) and less than (theory_x[i]+valid_x) (step S93: YES), the control unit 5 sets the count value count to save_count[i] in step S94. Thereafter, the control unit 5 proceeds to step S97.

[0141] If it is determined in step S93 that Table(count, i) is less than or equal to (theory_x[i]-valid_x) or greater than or equal to (theory_x[i]+valid_x) (step S93: NO), then in step S95 the control unit 5 determines whether the count value count is the maximum value of the count value count in the i-th row 24.

[0142] If it is determined that the count value "count" is not the maximum value (step S95: NO), the control unit 5 adds "1" to the count value "count" in step S96. Thereafter, the control unit 5 returns to step S93.

[0143] In step S95, if it is determined that the count value "count" is the maximum value (step S95: YES), the control unit 5 proceeds to step S97.

[0144] In step S97, the control unit 5 determines whether the variable i is "M" which indicates that the stage 24 is the last stage.

[0145] If it is determined that i=M is ​​not true (step S97: NO), the control unit 5 adds "1" to the variable i in step S98. Thereafter, the control unit 5 returns to step S92.

[0146] In step S97, if the control unit 5 determines that i=M (step S97: YES), the series of processes ends.

[0147] By the processing of the flowchart in FIG. 17 as described above, the count value count corresponding to the nozzle patterns 23 or missing nozzle patterns 23 within a predetermined range including theory_x[stage] is calculated as save_count[stage].

[0148] In the test pattern 21 of the example of FIG. 12, the count value count corresponding to each of the nozzle patterns 23 and missing nozzle patterns 23 in each row 24 in the area A in FIG. 16 is calculated as save_count[row] for each row 24.

[0149] Returning to Figure 13, in step S64, the control unit 5 calculates the nozzle number of the non-ejecting nozzle 17 corresponding to the missing nozzle pattern 23 detected after the detection of the first nozzle pattern 23 in each row 24, which is the missing nozzle pattern 23 detected in the nozzle pattern detection process described above.

[0150] The process of calculating the nozzle number of the non-ejecting nozzle 17 will be described with reference to the flowchart of FIG.

[0151] The processing in steps S101 and S102 in FIG. 18 is the same as the processing in steps S91 and S92 in FIG. 17 described above.

[0152] In step S103, the control unit 5 determines whether MF_Table(count, i)=True, that is, whether the nozzle 17 corresponding to the position of Table(count, i) is in a non-ejection state.

[0153] If it is determined that MF_Table(count, i)=False (step S103: NO), the control unit 5 proceeds to step S106, which will be described later.

[0154] If it is determined that MF_Table(count, i)=True (step S103: YES), in step S104, the control unit 5 calculates adjust_count[stages] (adjust_count[0] to adjust_count[3], corresponding to the count adjustment value) using the following equation (2).

[0155] adjust_count[i]= save_count[i]-save_count[std_nzl_dan] …(2) Here, adjust_count[stage] is a value used to adjust the count values ​​"count" corresponding to each nozzle 17 in the same nozzle group 18 to the same value. As can be seen from equation (2), adjust_count[stage] for each stage 24 is the value obtained by subtracting save_count[std_nzl_dan], which is the count value "count" for the nozzle 17 that is the target of drawing the nozzle pattern 23 in the std_nzl_dan stage, which is the same stage 24 in the nozzle group 18 as the target of drawing the nozzle pattern 23 by the nozzle 17 that drew the reference nozzle pattern 22, from save_count[stage] for each stage, which is the count value "count" for each nozzle 17 in the nozzle group 18 that includes the nozzle 17 that drew the nozzle pattern 23 whose count value "count" in the std_dan stage is "0".

[0156] In the test pattern 21 of the example in Figure 12, the value of adjust_count[row] for each row 24 is obtained by subtracting the count value "1" that corresponds to the nozzle pattern 23 in region A in row 24 numbered 0, which is the std_nzl_dan row, from the count value "count" that corresponds to each of the nozzle patterns 23 and missing nozzle patterns 23 in each row 24 in region A in Figure 16. The values ​​of adjust_count[row] for each row 24 are shown in Figure 19. In Figure 19, the values ​​of adjust_count[row] for each row 24 are written adjacent to the nozzle patterns 23 and missing nozzle patterns 23 in region A.

[0157] Returning to FIG. 18, in step S105, the control unit 5 calculates the MF nozzle number, which is the nozzle number of the non-ejecting nozzle 17, using the following formula (3).

[0158] MF nozzle number = (count + count reference correction value - adjust_count[i]) × (M + 1) + i ... (3) Here, the count reference correction value is a value for correcting the count value "count" by the amount of deviation between the actual count value and the correct count value, and is the value obtained by subtracting the actual count value from the correct count value. That is, the count reference correction value is expressed by the following equation (4).

[0159] Count standard correction value = Count correct value - Count actual measurement value ... (4) In the example test pattern 21 in Fig. 12, the actual count value is "2" and the correct count value is "5", so the count reference correction value is "3". And, since adjust_count[2] = 1 as shown in Fig. 19, the nozzle number of the non-ejecting nozzle 17 corresponding to the missing nozzle pattern 23 in the second row 24 with a count value of "2" is calculated as "18" from equation (3).

[0160] Also, for example, if the nozzle pattern 23 with a count value of "3" in row 24 of the test pattern 21 in the example of Figure 12 is missing, then adjust_count[3] = 2 as shown in Figure 19, and therefore the nozzle number of the non-ejecting nozzle 17 corresponding to the missing nozzle pattern 23 is calculated as "19" from equation (3).

[0161] In this embodiment, in equation (3), the count value count is corrected by (count reference correction value - adjust_count [stage]) so that the count value count corresponding to the missing nozzle pattern 23 detected after the detection of the first nozzle pattern 23 in each stage 24 becomes the value that would be obtained if the nozzle 17 on the left side, number 0, which has the smallest nozzle number in the inkjet head 16, were used to print the test pattern 21, the leftmost nozzle pattern 23 in each stage 24 was drawn, and the detection of that nozzle pattern 23 started counting up the count value count.

[0162] In other words, (count reference correction value - adjust_count [stage]) is a correction value for each stage 24 that corrects the count value count corresponding to the missing nozzle patterns 23 detected after the detection of the first nozzle pattern 23 in each stage 24 to the value that would be obtained if the nozzle 17 on the left side, number 0, which has the smallest nozzle number in the inkjet head 16, were used to print the test pattern 21, the leftmost nozzle pattern 23 in each stage 24 was drawn, and the detection of that nozzle pattern 23 started counting up the count value count.

[0163] As mentioned above, the count reference correction value is calculated using the correct count value, and adjust_count[stage] is calculated using save_count[stage]. Therefore, the above-mentioned correction value (count reference correction value - adjust_count[stage]) is calculated using the correct count value and save_count[stage].

[0164] By correcting the count value count using this correction value (count reference correction value - adjust_count[i]), the nozzle number of the non-ejecting nozzle 17 can be accurately calculated even if the leftmost nozzle pattern 23 is missing, such as in row 1 24 in the example of Figure 12, or if a foreign object 36 is detected to the left of the leftmost nozzle pattern 23, such as in row 3 24.

[0165] Returning to FIG. 18, in step S106, the control unit 5 determines whether the count value "count" is the maximum value of the count value "count" in the i-th row 24 or not.

[0166] If it is determined that the count value "count" is not the maximum value (step S106: NO), the control unit 5 adds "1" to the count value "count" in step S107. Thereafter, the control unit 5 returns to step S103.

[0167] If it is determined in step S106 that the count value "count" is the maximum value (step S106: YES), then in step S108, the control unit 5 determines whether the variable "i" is "M" indicating that this is the last row 24.

[0168] If it is determined that i=M is ​​not true (step S108: NO), the control unit 5 adds "1" to the variable i in step S109. Thereafter, the control unit 5 returns to step S102.

[0169] In step S108, if the control unit 5 determines that i=M (step S108: YES), the series of processes ends.

[0170] As described above, in the inkjet printing device 1, the control unit 5 calculates the nozzle number (MF nozzle number) of the non-ejecting nozzle 17 corresponding to the missing nozzle pattern 23 detected after the detection of the first nozzle pattern 23 in each row 24 using equation (3) by correcting the count value count corresponding to the nozzle 17 with the corrected value (count reference correction value - adjust_count [row]) calculated using the correct count value and save_count [row].

[0171] As a result, even if the test pattern 21 is missing a nozzle pattern 23 at the left end of a row 24 or a foreign object 36 is detected to the left of the nozzle pattern 23 at the left end of a row 24, the nozzle number of the non-ejecting nozzle 17 corresponding to the missing nozzle pattern 23 detected after the detection of the first nozzle pattern 23 for each row 24 can be accurately calculated.

[0172] Furthermore, the amount of correction for the count value of each stage 24 is determined by pattern matching, which captures the position of the nozzle pattern 23 at the left end of each stage 24 as a pattern, and the increase in processing time is suppressed compared to the method of calculating the nozzle number of the non-ejecting nozzle 17.

[0173] Therefore, the inkjet printing apparatus 1 can reduce the erroneous detection of non-ejecting nozzles 17 while suppressing an increase in processing time.

[0174] Here, a comparative example method for calculating the nozzle number (MF nozzle number) of the non-ejecting nozzle 17 without using adjust_count [stage], which differs from this embodiment, will be described.

[0175] In the method of this comparative example, when the nozzle 17 with the smallest nozzle number among the nozzles 17 used to print the test pattern 21 prints the nozzle pattern 23 in a row 24 whose row number n is "0", the nozzle number (MF nozzle number) of the non-ejecting nozzle 17 corresponding to the missing nozzle pattern 23 detected after the detection of the first nozzle pattern 23 in the i-th row 24 is calculated using the following formula (5):

[0176] MF nozzle number = (count + count reference correction value) × (M + 1) + i ... (5) When n is "1" or greater, the nozzle number (MF nozzle number) of the non-ejecting nozzle 17 corresponding to the missing nozzle pattern 23 detected after the detection of the first nozzle pattern 23 in a stage 24 whose stage number is less than n is also calculated using the above formula (5), where "i" is the stage number of the stage 24.

[0177] When n is "1" or greater, the nozzle number (MF nozzle number) of the non-ejecting nozzle 17 corresponding to the missing nozzle pattern 23 detected after the detection of the first nozzle pattern 23 in a stage 24 with a stage number greater than or equal to n is calculated using the following formula (6), where "i" is the stage number of the stage 24 in question.

[0178] MF nozzle number = (count-1 + count reference correction value) × (M+1) + i ... (6) In the comparative example method described above, if the nozzle pattern 23 at the left end of the row 24 is missing or if a foreign object 36 is detected to the left of the nozzle pattern 23 at the left end of the row 24, the nozzle number of the non-ejecting nozzle 17 in that row 24 will be calculated incorrectly.

[0179] In contrast, in this embodiment, as described above, by calculating the MF nozzle number using equation (3), even if a nozzle pattern 23 at the left end of a row 24 is missing or a foreign object 36 is detected to the left of the nozzle pattern 23 at the left end of a row 24, it is possible to accurately calculate the nozzle number of the non-ejecting nozzle 17 corresponding to the missing nozzle pattern 23 detected after the detection of the first nozzle pattern 23 for each row 24.

[0180] Furthermore, in the inkjet printing device 1, the inkjet head 16 draws multiple reference nozzle patterns 22 in one test pattern 21 using different nozzles 17. This reduces the risk that the reference nozzle patterns 22 will not be formed due to non-ejection of ink from the nozzles 17.

[0181] [Second embodiment] Next, a second embodiment, which is a partial modification of the first embodiment, will be described.

[0182] In the first embodiment, the count value count for each row corresponding to each nozzle 17 of the nozzle group 18 including the nozzle 17 that drew the nozzle pattern 23 with a count value count of "0" in the std_dan row, which is the row 24 on the far right where the nozzle pattern 23 with a count value count of "0" is set to save_count[row] for each row.

[0183] Here, as described above, save_count[stage] in the first embodiment is used to calculate adjust_count[stage], which is used to adjust the count values ​​count corresponding to each nozzle 17 in the same nozzle group 18 to the same value. In other words, save_count[stage] is used to adjust the count values ​​count corresponding to each nozzle 17 in the same nozzle group 18 to the same value.

[0184] In the second embodiment, the count value count for each row corresponding to each nozzle 17 of the nozzle group 18 including the nozzle 17 that drew the reference nozzle pattern 22 is set to save_count[row] for each row so that the count values ​​count corresponding to each nozzle 17 within the same nozzle group 18 are the same value.

[0185] In order to calculate such save_count [stages], in the second embodiment, the control unit 5 calculates theory_x [stages] based on std_nzl_x by replacing x0 with std_nzl_x and std_dan with std_nzl_dan in the processing of the flowchart in Figure 15 described above.

[0186] Then, the control unit 5 calculates save_count [stages] through the process of the flowchart in FIG. 17 described above.

[0187] In the test pattern 21 of the example in FIG. 12, the count value count corresponding to each of the nozzle patterns 23 in each row 24 in the area B in FIG. 20 is calculated as the save_count [row] of each row 24 in the second embodiment.

[0188] In the second embodiment, the control unit 5 omits step S104 in the flowchart of FIG. 18, and performs processing to calculate the MF nozzle number in step S105 using the following equation (7) instead of equation (3).

[0189] MF nozzle number = (count + correct count value - save_count[i]) × (M + 1) + i ... (7) In the second embodiment, in equation (7), the count value count is corrected by (count correct value - save_count [i]) so that the count value count corresponding to the missing nozzle pattern 23 detected after the detection of the first nozzle pattern 23 in each row 24 is corrected to the value that would be obtained if the nozzle 17 on the left side, number 0, which has the smallest nozzle number in the inkjet head 16, were used to print the test pattern 21, the leftmost nozzle pattern 23 in each row 24 was drawn, and the detection of that nozzle pattern 23 started counting up the count value count.

[0190] In other words, (count correct value - save_count [stage]) is a correction value for each stage 24 for correcting the count value count corresponding to the missing nozzle patterns 23 detected after the detection of the first nozzle pattern 23 in each stage 24 to the value that would be obtained if the nozzle 17 on the left side, number 0, which has the smallest nozzle number in the inkjet head 16, were used to print the test pattern 21, the leftmost nozzle pattern 23 in each stage 24 was drawn, and the detection of that nozzle pattern 23 started counting up the count value count.

[0191] By correcting the count value count using this correction value (count correct value - save_count [stage]), in the second embodiment, as in the first embodiment, even if the leftmost nozzle pattern 23 is missing, as in stage 1 24 in the example of Figure 12, or a foreign object 36 is detected to the left of the leftmost nozzle pattern 23, as in stage 3 24, the nozzle number of the non-ejecting nozzle 17 corresponding to the missing nozzle pattern 23 detected after the detection of the first nozzle pattern 23 for each stage 24 can be accurately calculated.

[0192] Here, in the second embodiment, as in the first embodiment, the reference nozzle pattern detection process of step S11 and the nozzle pattern detection process of step S12 in Fig. 7 are performed. However, in the second embodiment, the process of detecting and storing the actual count value in the nozzle pattern detection process (steps S43 to S45) is omitted.

[0193] Furthermore, in the second embodiment, the nozzle group 18 including the nozzle 17 that drew the reference nozzle pattern 22 is located to the right of the nozzle group 18 including the nozzle 17 that drew the nozzle pattern 23 with a count value count of "0" in the rightmost row 24 (std_dan row) in which the nozzle pattern 23 with a count value count of "0" is located. In other words, there is a count value count corresponding to each nozzle 17 of the nozzle group 18 that includes the nozzle 17 that drew the reference nozzle pattern 22.

[0194] If the nozzle group 18 including the nozzle 17 that drew the reference nozzle pattern 22 that is first detected in the reference nozzle pattern detection process is to the left of the nozzle group 18 including the nozzle 17 that drew the nozzle pattern 23 whose count value count in the std_dan row is "0", then it is sufficient to use another reference nozzle pattern 22 that is to the right of the nozzle group 18 including the nozzle 17 that drew the nozzle pattern 23 whose count value count in the std_dan row is "0".

[0195] As explained above, in the second embodiment, the count value "count" for each row corresponding to each nozzle 17 of the nozzle group 18, including the nozzle 17 that drew the reference nozzle pattern 22, is set to "save_count[row]" for each row. The control unit 5 then uses (correct count value - save_count[row]) as a correction value for correcting the count value "count" when calculating the MF nozzle number. In this way, as in the first embodiment, it is possible to reduce erroneous detection of non-ejecting nozzles 17 while suppressing increases in processing time.

[0196] [Other embodiments] As described above, the present invention has been described by the first and second embodiments, but the descriptions and drawings that form part of this disclosure should not be understood to limit the present invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure.

[0197] In the first embodiment described above, the save_count[stage] used to align the count values ​​"count" corresponding to each nozzle 17 within the same nozzle group 18 was the count value "count" for each stage corresponding to each nozzle 17 of the nozzle group 18, including the nozzle 17 that drew the nozzle pattern 23 with a count value "0" in the std_dan stage, which is the stage 24 on the far right where the nozzle pattern 23 with a count value "0" is drawn.

[0198] In addition, in the second embodiment, as save_count[stage], the count value count for each stage corresponding to each nozzle 17 of the nozzle group 18 including the nozzle 17 that drew the reference nozzle pattern 22, which is located to the right of the nozzle group 18 including the nozzle 17 that drew the nozzle pattern 23 whose count value count is "0" in the stage 24 where the nozzle pattern 23 whose count value count is "0" is located at the far right, was used.

[0199] However, without being limited to these, it is possible to use the count value count corresponding to each nozzle 17 of any of the nozzle groups 18 to the right of the nozzle group 18 including the nozzle 17 that drew the nozzle pattern 23 with a count value count of "0" in the row 24 where the nozzle pattern 23 with a count value count of "0" is located at the far right, as the count value count for each row 24 in order to align the count values ​​count corresponding to each nozzle 17 in the same nozzle group 18.

[0200] In the first and second embodiments described above, a line-type inkjet printing device that prints while moving paper has been described, but the present invention is not limited to this and can be applied to any inkjet printing device that prints while moving an inkjet head relative to the print medium. For example, the present invention can also be applied to a serial-type inkjet printing device that prints while moving an inkjet head.

[0201] As such, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention-specifying matters according to the scope of the claims that are appropriate from the above description.

[0202] [Note] The present application discloses the following inventions.

[0203] (Appendix 1) a line-type inkjet head having a plurality of nozzles; a control unit that prints a test pattern on a printing medium using the inkjet head, and detects non-ejecting nozzles based on image data generated by reading the printed test pattern; The control unit Detecting a reference line segment in the image data; For each row of the test pattern in the image data, scanning from one side to the other side in the nozzle arrangement direction, and counting up the count value of the nozzle each time a line segment or a missing line segment is detected after the first line segment is detected, and storing the count value corresponding to the detected line segment or missing line segment and its position in the nozzle arrangement direction; An inkjet printing apparatus that calculates the nozzle number of the nozzle.

[0204] (Appendix 2) the test pattern is formed by drawing the reference line segment along a direction perpendicular to the nozzle arrangement direction from a specific nozzle among the plurality of nozzles, drawing a plurality of line segments on the printing medium from each nozzle along the nozzle arrangement direction while sequentially shifting the line segments in the direction perpendicular to the nozzle arrangement direction, and repeating the same drawing by returning to the initial position in the perpendicular direction every predetermined number of rows; calculating a correction value for each row to correct the count value corresponding to the missing line segment detected after the first detection of the line segment in each row, using a correct count value that is a count value corresponding to the line segment that is at the same position as the reference line segment when it is assumed that the inkjet head is used to print the test pattern starting from the nozzle with the smallest nozzle number, and that the line segment at one end of the nozzle arrangement direction in the row including the line segment at the same position as the reference line segment has been drawn and a count-up of the count value has been started upon detection of the line segment, and a count value corresponding to the line segment or a missing line segment by each nozzle of any one of the nozzle groups on the other side of the nozzle group including the nozzle that corresponds to the line segment that is first detected in the row furthest to the other side in the nozzle arrangement direction; The inkjet printing device described in Appendix 1 is characterized in that the nozzle number of the non-ejecting nozzle corresponding to the missing line segment detected after the detection of the first line segment in each stage is calculated using a value obtained by correcting the count value corresponding to the missing line segment using the correction value of the stage including the missing line segment.

[0205] (Appendix 3) The control unit a count value corresponding to the line segment at the same position as the reference line segment in the nozzle arrangement direction is subtracted from the correct count value to calculate a count reference correction value; calculate, as a count adjustment value for each row, a value obtained by subtracting, from each count value for each row corresponding to the line segment or the missing line segment by each nozzle of the nozzle group including the nozzle corresponding to the first detected line segment in the row whose position in the nozzle arrangement direction of the first detected line segment is furthest to the other, a count value for each row corresponding to the line segment or the missing line segment by a nozzle in the nozzle group that is the target for drawing the line segment in the same row as the row in which the nozzle that drew the reference line segment drew the line segment; 3. The inkjet printing apparatus according to claim 2, wherein the correction value for each stage is calculated by subtracting the count adjustment value for each stage from the count reference correction value.

[0206] (Appendix 4) the nozzle group including the nozzle that drew the reference line segment is located on the other side of the nozzle group including the nozzle corresponding to the line segment that was detected first in the row in which the position of the line segment that was detected first in the nozzle arrangement direction is located on the other side, The control unit The inkjet printing device described in Appendix 2 is characterized in that the correction value for each row is calculated by subtracting from the correct count value each count value for each row corresponding to the line segment or the missing line segment caused by each nozzle of the nozzle group including the nozzle that drew the reference line segment.

[0207] (Appendix 5) 5. The inkjet printing device according to claim 1, wherein the inkjet head draws the plurality of reference line segments using different nozzles. [Explanation of symbols]

[0208] 1. Inkjet printing device 2. Conveyor section 3 Printing Department 4 Image reading unit 5. Control section 11 Line Head 16 Inkjet head 17 nozzles 18 nozzle groups 21 Test Patterns 22 Reference nozzle pattern 23 nozzle patterns 24 steps 31 Table Memory

Claims

1. a line-type inkjet head having a plurality of nozzles; a control unit that prints a test pattern on a printing medium using the inkjet head, and detects non-ejecting nozzles based on image data generated by reading the printed test pattern; The control unit Detecting a reference line segment in the image data; For each row of the test pattern in the image data, scanning from one side to the other side in the nozzle arrangement direction, and counting up the count value of the nozzle each time a line segment or a missing line segment is detected after the first line segment is detected, and storing the count value corresponding to the detected line segment or missing line segment and its position in the nozzle arrangement direction; An inkjet printing apparatus that calculates the nozzle number of the nozzle.

2. the test pattern is formed by drawing the reference line segment along a direction perpendicular to the nozzle arrangement direction from a specific nozzle among the plurality of nozzles, drawing a plurality of line segments on the printing medium from each nozzle along the nozzle arrangement direction while sequentially shifting the line segments in the direction perpendicular to the nozzle arrangement direction, and repeating the same drawing by returning to the initial position in the perpendicular direction every predetermined number of rows; calculating a correction value for each row to correct the count value corresponding to the missing line segment detected after the first detection of the line segment in each row, using a correct count value that is a count value corresponding to the line segment that is at the same position as the reference line segment when it is assumed that the inkjet head is used to print the test pattern starting from the nozzle with the smallest nozzle number, and that the line segment at one end of the nozzle arrangement direction in the row including the line segment at the same position as the reference line segment has been drawn and a count-up of the count value has been started upon detection of the line segment, and a count value corresponding to the line segment or a missing line segment by each nozzle of any one of the nozzle groups on the other side of the nozzle group including the nozzle that corresponds to the line segment that is first detected in the row furthest to the other side in the nozzle arrangement direction; The inkjet printing device according to claim 1, characterized in that the nozzle number of the non-ejecting nozzle corresponding to the missing line segment detected after the detection of the first line segment in each stage is calculated using a value obtained by correcting the count value corresponding to the missing line segment using the correction value of the stage including the missing line segment.

3. The control unit a count value corresponding to the line segment at the same position as the reference line segment in the nozzle arrangement direction is subtracted from the correct count value to calculate a count reference correction value; calculate, as a count adjustment value for each row, a value obtained by subtracting, from each count value for each row corresponding to the line segment or the missing line segment by each nozzle of the nozzle group including the nozzle corresponding to the first detected line segment in the row whose position in the nozzle arrangement direction of the first detected line segment is furthest to the other, a count value for each row corresponding to the line segment or the missing line segment by a nozzle in the nozzle group that is the target for drawing the line segment in the same row as the row in which the nozzle that drew the reference line segment drew the line segment; The inkjet printing apparatus according to claim 2 , wherein the correction value for each stage is calculated by subtracting the count adjustment value for each stage from the count reference correction value.

4. the nozzle group including the nozzle that drew the reference line segment is located on the other side of the nozzle group including the nozzle corresponding to the line segment that was detected first in the row in which the position of the line segment that was detected first in the nozzle arrangement direction is located on the other side, The control unit The inkjet printing device according to claim 2, characterized in that the correction value for each row is calculated by subtracting from the correct count value each of the count values ​​for each row corresponding to the line segment or the missing line segment caused by each nozzle of the nozzle group including the nozzle that drew the reference line segment.

5. 5. The inkjet printing apparatus according to claim 1, wherein the inkjet head draws the plurality of reference line segments using different nozzles.

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