Non-discharge detection apparatus

Abstract

To reduce erroneous detection of nozzle patterns.SOLUTION: A non-discharge detection apparatus comprises a detection unit 22 that detects a nozzle pattern on the basis of a density difference between pixels corresponding to the nozzle pattern and surrounding pixels, and a density of the pixels corresponding to the nozzle pattern, according to image data read from a medium printed based on nozzle pattern data. The detection unit 22 acquires densities of pixels corresponding to the nozzle pattern at a plurality of measurement points, and detects the nozzle pattern when all of the densities at the measurement points are equal to or greater than a predetermined density threshold, and when a density difference between the measurement point and peripheral measurement points separated by a predetermined distance on both sides in a main scanning direction is equal to or greater than a predetermined density difference threshold in any one of the plurality of measurement points.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a non-ejection detection device, and more particularly to a non-ejection detection device that reduces erroneous detection of a nozzle pattern. [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 misfire occurs, where ink is temporarily not ejected due to a nozzle malfunction or the like, white streaks will appear in the printed image.

[0004] Patent document 1 discloses a technology that compares a set threshold value Th with the density (gradation value) detected in the Nth judgment block to determine whether the nozzle corresponding to that judgment block is a non-ejecting nozzle, specifically, whether the gradation value of the Nth judgment block exceeds the gradation value of the threshold value Th. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7143653 Summary of the Invention [Problem to be solved by the invention]

[0006] However, if the presence or absence of a nozzle pattern is determined simply based on density (gradation value) and a threshold value, as in the technology described in Patent Document 1, there is a possibility that if dust with a density exceeding the threshold value is present at the scanning position, this dust will be mistakenly detected as a nozzle pattern (vertical ruled line).

[0007] FIG. 1 is an explanatory diagram illustrating the problems associated with the prior art.

[0008] For example, as shown in FIG. 1(a), if dust J101 is present on the main scanning line R101 between nozzle patterns G101 and G102 on a medium printed based on the read nozzle pattern data, the technology described in Patent Document 1 determines the presence or absence of a nozzle pattern based only on the density (gradation value) and threshold value, and therefore erroneously detects the dust J101 as a pattern (vertical ruled line), as shown in the read data D101.

[0009] Furthermore, when determining vertical lines at multiple locations in the sub-scanning direction, if dust and vertical lines overlap, the density difference between the nozzle pattern and the surrounding area becomes small, and there is a possibility that the nozzles cannot be detected.

[0010] For example, as shown in Figure 1(b), if there is dust J102 with a wide width in the sub-scanning direction in the nozzle pattern G101, the density difference L101, L102 between the nozzle pattern G101 and the surrounding area will be smaller than a predetermined density difference threshold, making it difficult to detect the nozzle pattern G101.

[0011] The present invention has been made in view of the above-mentioned problems, and has an object to provide a non-ejection detection device that reduces erroneous detection of nozzle patterns. [Means for solving the problem]

[0012] In order to achieve the above object, the non-ejection detection device according to the present invention is characterized by: a detection unit that detects the nozzle pattern based on a density difference between a pixel corresponding to the nozzle pattern and a pixel around the pixel, and the density of the pixel corresponding to the nozzle pattern, based on image data read from a medium printed based on nozzle pattern data; The reason is that it is equipped with the following. [Effects of the Invention]

[0013] According to the features of the non-ejection detection device of the present invention, it is possible to reduce erroneous detection of the nozzle pattern. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is an explanatory diagram illustrating a problem in the prior art. [Figure 2] 1 is a block diagram showing a hardware configuration of a non-ejection detection device according to a first embodiment of the present invention. [Figure 3] FIG. 10 is a diagram showing an example of a nozzle pattern image printed based on nozzle pattern data. [Figure 4] 3A and 3B are explanatory diagrams that schematically explain detection of a nozzle pattern in a detection unit that is included in the non-discharge detection device according to the first embodiment of the present invention. [Figure 5] (a) shows an example in which the detection process of the detection unit of the non-ejection detection device according to Example 1 of the present invention determines that the pattern is not a nozzle pattern, and (b) shows an example in which the detection process of the detection unit of the non-ejection detection device according to Example 1 of the present invention determines that the pattern is a nozzle pattern. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.

[0016] 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.

[0017] 2 is a block diagram showing the hardware configuration of the non-discharge detection device 1 according to the first embodiment of the present invention. As shown in the figure, the non-discharge detection device 1 includes an image reading unit 10, a data processing unit 20, an inkjet head control unit 30, and a storage unit 40.

[0018] 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.

[0019] FIG. 3 is a diagram showing an example of a nozzle pattern image printed based on the nozzle pattern data.

[0020] As shown in FIG. 3, the nozzle pattern image has printed thereon a first nozzle pattern H101 corresponding to the first head of the inkjet head, a second nozzle pattern H102 corresponding to the second head, and a third nozzle pattern H103 corresponding to the third head.

[0021] The first to third inkjet heads are arranged in a houndstooth pattern in the sub-scanning direction, and therefore the first to third nozzle patterns H101 to H103 are also printed in a houndstooth pattern.

[0022] The first head has a predetermined number of nozzles in the main scanning direction, and ejects ink from these nozzles in the sub-scanning direction, dividing them into rows 0 to M, starting from the top (left side).Count values ​​are assigned starting from the top (left side), with the first row 0 to M nozzles being counted as "0," and the next row 0 to M nozzles being counted as "1."

[0023] Then, while the paper is transported in the sub-scanning direction, ink is ejected from all the nozzles in each divided row to print, thereby forming the first nozzle pattern H101 shown in FIG.

[0024] Similarly, the second nozzle pattern H102 to the third nozzle pattern H103 are also drawn by ejecting ink from all count nozzles for each divided row while conveying the paper sequentially in the sub-scanning direction.

[0025] Returning to FIG. 2, the data processing unit 20 generates the nozzle pattern described above, and also detects the nozzle pattern based on image data read from a medium printed based on the nozzle pattern data.

[0026] 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 defective nozzles (defective recording elements) where the nozzle holes are clogged or the like.

[0027] The storage unit 40 stores image data for generating nozzle pattern data, and various thresholds such as a density threshold Th1 and a density difference threshold Th2 for detecting nozzle patterns, which will be described later.

[0028] The data processing unit 20 functionally comprises an image input unit 21, a detection unit 22, and a nozzle pattern generation unit 25.

[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 the nozzle pattern based on the read pattern image data acquired by the image input unit 21, based on the density difference between the pixel corresponding to the nozzle pattern and its surrounding pixels, and based on the density of the pixel corresponding to the nozzle pattern.

[0031] The nozzle pattern generating unit 25 generates the nozzle pattern data described above.

[0032] FIG. 4 is an explanatory diagram that schematically explains the detection of the nozzle pattern in the detection unit 22 that is provided in the non-discharge detection device 1 according to the first embodiment of the present invention.

[0033] 4, on a medium printed based on the loaded nozzle pattern data, the pixel densities are obtained at three measurement points S101 to S103 in the sub-scanning direction. Note that, although three measurement points S101 to S103 are set as measurement points in the nozzle pattern G101 here, the number is not limited to this, and two, four or more may also be used. In other words, it is sufficient that at least two or more measurement points are set in the sub-scanning direction.

[0034] The detection unit 22 determines whether the density C101 of measurement point S101, the density C102 of measurement point S102, and the density C103 of measurement point S103 are all equal to or greater than a predetermined density threshold Th1. Specifically, the detection unit 22 determines whether all of the following (Equation 1) to (Equation 3) are satisfied. Here, the density threshold Th1 is set in advance to a value that makes the density determination result true for the nozzle pattern. Note that the densities C101 to C103 may each be the average value of the densities of surrounding pixels in the sub-scanning direction. Concentration C101 > Th1 (Equation 1) Concentration C102 > Th1 (Equation 2) Concentration C103 > Th1 (Equation 3) In the example shown in FIG. 4, measurement points S101 to S103 are set as three locations within nozzle pattern G101, and therefore all of the above (Formula 1) to (Formula 3) are satisfied.

[0035] Furthermore, the detection unit 22 sets peripheral measurement points at a predetermined distance on both sides of each of the measurement points S101 to S103 in the main scanning direction, and determines whether the density difference between the peripheral measurement points and the measurement point is equal to or greater than a predetermined density difference threshold Th2.

[0036] 4, the detection unit 22 sets peripheral measurement points S201 and S301 on either side of the measurement point S101 in the main scanning direction, a predetermined distance apart. Similarly, the detection unit 22 sets peripheral measurement points S202 and S302 on either side of the measurement point S102 in the main scanning direction, a predetermined distance apart. Similarly, the detection unit 22 sets peripheral measurement points S203 and S303 on either side of the measurement point S103 in the main scanning direction, a predetermined distance apart.

[0037] The detection unit 22 determines whether the density difference (absolute value) between any of the measurement points S101 to S103 and the surrounding measurement points S201, S301, S202, S302, S203, S303, which are located a predetermined distance on both sides in the main scanning direction, is greater than or equal to a predetermined density difference threshold Th2.

[0038] Specifically, the detection unit 22 determines whether any of the following (Formula 4) to (Formula 6) is satisfied. Here, the density of peripheral measurement point S201 is density C201, the density of peripheral measurement point S301 is density C301, the density of peripheral measurement point S202 is density C202, the density of peripheral measurement point S302 is density C302, the density of peripheral measurement point S203 is density C203, and the density of peripheral measurement point S303 is density C303. The density difference threshold Th2 is set to a value that makes the density difference determination result true for the combination of the nozzle pattern density and the medium density.

[0039] |C101-C201|>Th2 and |C101-C301|>Th2 (Equation 4) |C102-C202|>Th2 and |C102-C302|>Th2 (Equation 5) |C103-C203|>Th2 and |C103-C303|>Th2 (Equation 6)

[0040] The detection unit 22 then detects a nozzle pattern when all of the densities at the measurement points S101 to S103 are equal to or greater than a predetermined density threshold Th1, and when the density difference (absolute value) between the measurement points S101 to S103 and surrounding measurement points located a predetermined distance away on both sides in the main scanning direction at any of the measurement points S101 to S103 is equal to or greater than a predetermined density difference threshold Th2.

[0041] Figure 5(a) shows an example in which the detection process of the detection unit 22 of the non-ejection detection device 1 of Example 1 of the present invention determines that the pattern is not a nozzle pattern, and Figure 5(b) shows an example in which the detection process of the detection unit 22 of the non-ejection detection device 1 of Example 1 of the present invention determines that the pattern is a nozzle pattern.

[0042] As shown in FIG. 5(a), at measurement points S401 to S403, none of the densities at measurement points S401 to S403 is equal to or greater than the predetermined density threshold Th1, so the detection unit 22 determines that it is not a nozzle pattern.

[0043] Among measurement points S411 to S413, dust J201 is present above measurement point S411, so the density of measurement point S411 is equal to or greater than density threshold Th1, but the densities of measurement points S412 and S413 are less than density threshold Th1. Therefore, because not all of the densities at measurement points S411 to S413 are equal to or greater than predetermined density threshold Th1, detection unit 22 determines that the pattern is not a nozzle pattern.

[0044] Among measurement points S421 to S423, dust J202 is present above measurement points S421 and S422, so the densities at measurement points S421 and S422 are equal to or greater than density threshold Th1, but the density at measurement point S423 is less than density threshold Th1. Therefore, because not all of the densities at measurement points S421 to S423 are equal to or greater than predetermined density threshold Th1, detection unit 22 determines that it is not a nozzle pattern.

[0045] Among measurement points S431 to S433, dust J203 is present above measurement points S431 to S433, so the density of measurement points S431 to S433 is equal to or greater than density threshold Th1. However, because dust J203 is present above measurement points S431 to S433, the density difference between measurement points S431 to S433 and peripheral measurement points located a predetermined distance away on both sides in the main scanning direction at each of measurement points S431 to S433 is less than predetermined density difference threshold Th2. Therefore, detection unit 22 determines that the pattern is not a nozzle pattern.

[0046] As shown in FIG. 5(b), measurement points S501 to S503 are measurement points on nozzle pattern G101, and therefore all of the densities at measurement points S501 to S503 are equal to or greater than a predetermined density threshold Th1, and the density difference between measurement points S501 to S503 and surrounding measurement points located a predetermined distance away on both sides in the main scanning direction at any of measurement points S501 to S503 is equal to or greater than a predetermined density difference threshold Th2, so the detection unit 22 determines that it is a nozzle pattern.

[0047] Because measurement points S511 to S513 are measurement points on nozzle pattern G102, all of the densities at measurement points S511 to S513 are equal to or greater than predetermined density threshold Th1. Because dust J301 is present above measurement point S511, the density difference between measurement point S511 and surrounding measurement points a predetermined distance away on both sides in the main scanning direction is less than predetermined density difference threshold Th2. However, at measurement points S512 to S513, the density difference between measurement points S512 to S513 and surrounding measurement points a predetermined distance away on both sides in the main scanning direction is equal to or greater than predetermined density difference threshold Th2. Therefore, detection unit 22 determines that the pattern is a nozzle pattern.

[0048] Because measurement points S521 to S523 are on nozzle pattern G103, all of the densities at measurement points S521 to S523 are equal to or greater than predetermined density threshold Th1. Because dust J302 is present on measurement point S521, the density difference between measurement points S521 and S522 and peripheral measurement points a predetermined distance away on both sides in the main scanning direction is less than predetermined density difference threshold Th2. However, at measurement point S523, the density difference between measurement point S523 and peripheral measurement points a predetermined distance away on both sides in the main scanning direction is equal to or greater than predetermined density difference threshold Th2. Therefore, detection unit 22 determines that the pattern is a nozzle pattern.

[0049] In this way, the detection unit 22 detects a nozzle pattern if all of the densities at the three measurement points are equal to or greater than the predetermined density threshold Th1, and if the density difference between any of the three measurement points and surrounding measurement points a predetermined distance away on either side in the main scanning direction is equal to or greater than the predetermined density difference threshold Th2. The detection unit 22 then moves a predetermined distance in the main scanning direction to determine three new measurement points, and similarly detects a nozzle pattern if all of the densities at the three measurement points are equal to or greater than the predetermined density threshold Th1, and if the density difference between any of the three measurement points and surrounding measurement points a predetermined distance away on either side in the main scanning direction is equal to or greater than the predetermined density difference threshold Th2. By repeating this process, a nozzle pattern is detected based on the image printed on the entire medium.

[0050] (Addendum) The present application discloses the following inventions.

[0051] (Appendix 1) a detection unit that detects the nozzle pattern based on a density difference between a pixel corresponding to the nozzle pattern and a pixel around the pixel, and the density of the pixel corresponding to the nozzle pattern, based on image data read from a medium printed based on nozzle pattern data; A non-ejection detection device comprising:

[0052] As a result, even if dust with a density exceeding the threshold is present at the scanning position, the dust is not erroneously detected as a nozzle pattern (vertical ruled lines), and even if the dust and the nozzle pattern (vertical ruled lines) overlap, the nozzle pattern can be properly detected. As a result, erroneous detection of the nozzle pattern can be reduced.

[0053] (Appendix 2) The detection unit acquires the density of pixels corresponding to the nozzle pattern at a plurality of measurement points, and detects the nozzle pattern when all of the densities at the measurement points are equal to or greater than a predetermined density threshold, and when the density difference between the measurement point and peripheral measurement points located a predetermined distance away on both sides in the main scanning direction at any of the plurality of measurement points is equal to or greater than a predetermined density difference threshold. 2. The non-ejection detection device according to claim 1.

[0054] As a result, if all of the densities at the measurement points are equal to or greater than a predetermined density threshold, and if the density difference between the measurement point and surrounding measurement points located a predetermined distance away on either side in the main scanning direction at any of the multiple measurement points is equal to or greater than a predetermined density difference threshold, the measurement point is detected as a nozzle pattern. Therefore, even if dust with a density exceeding the threshold is present at the scanning position, the dust will not be mistakenly detected as a nozzle pattern (vertical ruled lines), and the nozzle pattern can be properly detected even if the dust and the nozzle pattern (vertical ruled lines) overlap.

[0055] (Appendix 3) There are at least two measurement points in the sub-scanning direction 3. The non-ejection detection device according to claim 2.

[0056] In this way, the nozzle pattern is detected based on the density at two or more measurement points, so even if dust is present, it can be detected more appropriately. [Explanation of symbols]

[0057] 1. Non-discharge detection device 10 Image reading unit 20 Data Processing Unit 21 Image input unit 22 Detection unit 25 Nozzle pattern generator 30 Inkjet head control unit 40 Storage section

Claims

1. a detection unit that detects the nozzle pattern based on a density difference between a pixel corresponding to the nozzle pattern and a pixel around the pixel, and the density of the pixel corresponding to the nozzle pattern, based on image data read from a medium printed based on nozzle pattern data; A non-ejection detection device comprising:

2. The detection unit acquires the density of pixels corresponding to the nozzle pattern at a plurality of measurement points, and detects the nozzle pattern when all of the densities at the measurement points are equal to or greater than a predetermined density threshold, and when the density difference between the measurement point and peripheral measurement points located a predetermined distance away on both sides in the main scanning direction at any of the plurality of measurement points is equal to or greater than a predetermined density difference threshold.

2. The non-ejection detection device according to claim 1.

3. There are at least two measurement points in the sub-scanning direction.

3. The non-ejection detection device according to claim 2.

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