JP2018114625A - Method and inspection device for determining presence or absence of abnormality in nozzle check pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method that enables a nozzle defect to be checked by using one nozzle check pattern image taken with resolution lower than printing resolution of an ink jet printer.SOLUTION: An inspection device 10 comprises a processing part 11 that determines the presence or absence of abnormality in a nozzle check pattern on the basis of mean luminance of a nozzle check pattern image obtained by photographing a nozzle check pattern, which is printed by an ink jet printer, with resolution lower than printing resolution of the ink jet printer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method and an inspection apparatus for determining whether a nozzle check pattern is abnormal.

  Conventionally, an ink jet printer has been used.

  Inkjet printers print characters or figures by ejecting ink droplets from nozzles onto printing paper and printing fine dots on the printing paper.

  A nozzle that ejects ink droplets may cause a nozzle failure in which ink droplets are not ejected normally. When a nozzle failure occurs, a character or a figure printed by an ink jet printer has a dot dropout in which dots are not printed, and desired printing cannot be performed.

  Therefore, ink droplets are ejected from each nozzle and a nozzle check pattern is printed to check the state of the nozzles of the ink jet printer.

  It has also been proposed to inspect the state of the nozzles using a nozzle check pattern image obtained by photographing the printed nozzle check pattern. For the nozzle check pattern image, for example, using a pattern matching method, the reference pattern and the nozzle check pattern image are compared to determine the state of the nozzle.

JP 2006-305798 A

  The nozzle check pattern image is required to have a resolution equal to or higher than the printing resolution of the ink jet printer in order to detect a missing dot where one dot is not printed due to a defect of one nozzle.

  For example, when the resolution of the nozzle check pattern image is half of the printing resolution of the ink jet printer, the size of one pixel of the nozzle check pattern image is two dots printed by two adjacent nozzles of the ink jet printer. Correspond. In this case, even if a defect occurs in one of the two adjacent nozzles of the ink jet printer and dot missing occurs, the effect of dot missing is not sufficiently reflected in one pixel of the nozzle check pattern image. There is a possibility that a nozzle defect cannot be detected.

  Since the printing resolution of the ink jet printer is improved, there is a problem of preparing an expensive camera in order to use a camera having a resolution higher than the printing resolution of the ink jet printer.

  Therefore, there is a case where an image of a nozzle check pattern is taken using a camera with a high resolution. In that case, by reducing the distance between the camera and the printing paper on which the nozzle check pattern is printed, a desired resolution can be obtained as the resolution of the nozzle check pattern image. Since the area is small, in order to photograph the entire nozzle check pattern at once, it is required to divide the nozzle check pattern into a plurality of areas and photograph each divided area using a plurality of cameras. In this case, there arises a problem of preparing a plurality of cameras.

  This specification makes it a subject to provide the method and inspection apparatus which can test | inspect a nozzle defect using one nozzle check pattern image image | photographed with the resolution lower than the printing resolution of an inkjet printer.

  According to the method disclosed in the present specification, an average luminance of a nozzle check pattern image, which is a nozzle check pattern image that is printed by an inkjet printer and is captured at a resolution lower than the print resolution of the inkjet printer. Based on the above, it is determined whether there is an abnormality in the nozzle check pattern.

  In addition, according to the inspection apparatus disclosed in the present specification, a nozzle check pattern image, which is a nozzle check pattern image printed by an inkjet printer, is captured at a resolution lower than the printing resolution of the inkjet printer. On the basis of the average luminance, whether or not the nozzle check pattern is abnormal is determined.

  According to the method disclosed in the present specification described above, a nozzle defect can be inspected using a single nozzle check pattern image photographed at a resolution lower than the printing resolution of the inkjet printer.

  Further, according to the inspection apparatus disclosed in the present specification described above, it is possible to inspect nozzle defects using a single nozzle check pattern image photographed at a resolution lower than the printing resolution of the inkjet printer.

It is a figure showing a 1st embodiment of an inspection device indicated to this specification. It is a figure which shows the nozzle check pattern used by 1st Embodiment of the test | inspection apparatus disclosed to this specification. It is a flowchart explaining operation | movement of the test | inspection apparatus of 1st Embodiment. It is a figure which shows a nozzle check pattern image. It is a figure which shows the nozzle check pattern used by 2nd Embodiment of the test | inspection apparatus disclosed by this specification. It is a flowchart explaining operation | movement of the test | inspection apparatus of 2nd Embodiment. It is a figure which shows a nozzle check pattern image. It is a figure which shows the printing density table | surface which shows the relationship between the dot missing position of a nozzle check pattern image, and the average printing density of a nozzle check pattern image. FIG. 5 is a first diagram illustrating an example of missing dots in a nozzle check pattern image. FIG. 10 is a second diagram illustrating an example of missing dots in a nozzle check pattern image. It is a figure which shows the modification 1 of the nozzle check pattern used by 2nd Embodiment. It is a figure which shows the printing density table | surface which shows the relationship between the dot missing position of the nozzle check pattern image of the modification 1, and the average printing density of a nozzle check pattern image. It is a figure which shows the modification 2 of the nozzle check pattern used by 2nd Embodiment. It is a figure which shows the modification 3 of the nozzle check pattern used by 2nd Embodiment.

  Hereinafter, a preferred first embodiment of an inspection apparatus disclosed in this specification will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and equivalents thereof.

  FIG. 1 is a diagram illustrating a first embodiment of an inspection apparatus disclosed in this specification.

  The inspection apparatus 10 according to the present embodiment determines whether there is an abnormality in the nozzle check pattern based on the average luminance of the nozzle check pattern image obtained by photographing the nozzle check pattern printed by the inkjet printer, and inspects the nozzle defect. The inspection apparatus 10 can be incorporated as an in-line inspection apparatus, for example, in a printing process using an inkjet printer.

  The inspection apparatus 10 includes a processing unit 11, a storage unit 12, a display unit 13, an operation unit 14, an output unit 15, and an image photographing unit 16.

  The processing unit 11 includes one or a plurality of processors and peripheral circuits. The processing unit 11 performs control and various processing of each hardware component of the inspection apparatus 10 according to a predetermined program stored in advance in the storage unit 12, and stores the data generated during the processing temporarily. Part 12 is used.

  The storage unit 12 may include a semiconductor memory such as a random access memory (RAM) or a read only memory (ROM), a magnetic disk, a flash memory, or the like. The storage unit 12 may include a drive that can read a storage medium that stores a predetermined program.

  The display unit 13 can display various types of information under the control of the processing unit 11. For example, a liquid crystal display can be used as the display unit 13.

  The operation unit 14 is operated by an operator of the inspection apparatus 10 and can input various types of information in the process of determining whether there is an abnormality in the nozzle check pattern. As the operation unit 14, for example, a keyboard, a mouse, a touch panel, or the like can be used.

  The output unit 15 outputs a determination result of whether or not the nozzle check pattern is abnormal. For example, a printer can be used as the output unit 15.

  The image photographing unit 16 photographs the nozzle check pattern printed by the ink jet printer. The resolution of the nozzle check pattern image captured by the image capturing unit 16 is lower than the printing resolution of the ink jet printer. The nozzle check pattern image photographed by the image photographing unit 16 is stored in the storage unit 12.

  Note that the inspection apparatus 10 may determine whether there is an abnormality in the nozzle check pattern by inputting an image obtained by capturing the nozzle check pattern instead of capturing the nozzle check pattern using the image capturing unit 16. In this case, the inspection apparatus 10 may not include the image capturing unit 16.

  As the inspection device 10, for example, a computer or a state machine can be used.

  FIG. 2 is a diagram illustrating a nozzle check pattern used in the first embodiment of the inspection apparatus disclosed in this specification.

  The ink jet printer (not shown) has nozzles N1 to N12 arranged in a line. Each of the nozzles N1 to N12 prints by ejecting black ink droplets onto the print medium. The arrangement of the nozzles of the ink jet printer to be inspected by the inspection device 10 and the color of the ink to be printed are not particularly limited.

  One nozzle check pattern has four patterns P1 to P4 when printed normally. The four patterns P1 to P4 are printed side by side so as to extend in the feeding direction of the printing paper that is the printing medium. The pattern P1 is printed by ejecting ink droplets from the nozzle N1. Similarly, the pattern P2 is printed by ejecting ink droplets from the nozzle N4, the pattern P3 is printed by ejecting ink droplets from the nozzle N7, and the pattern P4 is printed by ejecting ink droplets from the nozzle N10. The

  It is preferable not to use adjacent nozzles as the nozzles for printing each pattern from the viewpoint of preventing adjacent printed patterns from being connected to each other due to printing bleeding. In the example shown in FIG. 2, the nozzles that print each pattern are selected with two non-printing nozzles in between.

  In the example shown in FIG. 2, each pattern P <b> 1 to P <b> 4 shows an interval between dots printed by ink droplet ejection in the feeding direction of the printing paper. The dots are shown in an easy-to-understand manner. Actually, there is not always an interval between the dots.

  The first nozzle check pattern has four patterns P1 to P4 printed by the nozzles N1, N4, N7, and N10. The second nozzle check pattern has four patterns P5 to P8 printed by the nozzles N2, N5, N8, and N11. Here, in the second nozzle check pattern, the nozzle N5 is not printed because the nozzle N5 is defective. The third nozzle check pattern has four patterns P9 to P12 printed by the nozzles N3, N6, N9, and N12.

  In the example shown in FIG. 2, the state of each nozzle N1 to N12 can be checked by printing three nozzle check patterns.

  Hereinafter, the operation of the inspection apparatus 10 will be described with reference to the flowchart shown in FIG.

  First, in step S301, the processing unit 11 uses the image photographing unit 16 to photograph the photographing region R1 (see FIG. 2) including the four patterns P1 to P4, and as illustrated in FIG. A nozzle check pattern image H1 is obtained. Similarly, the processing unit 11 uses the image photographing unit 16 to photograph the photographing region R2 (see FIG. 2) including the four patterns P6, P7, and P8, and as illustrated in FIG. A check pattern image H2 is obtained. Further, the processing unit 11 uses the image photographing unit 16 to photograph the photographing region R3 (see FIG. 2) including the four patterns P9 to P12 to obtain a nozzle check pattern image. Each imaging region R1 to R3 has the same shape and the same size.

  Next, in step S303, the processing unit 11 divides the nozzle check pattern image to obtain an average print density of each divided area.

  Specifically, as illustrated in FIG. 4A, the processing unit 11 equally divides the nozzle check pattern image H1 into four divided regions D1 to D4. The four regions D1 to D4 are preferably divided so as to include the same number of patterns. In the example shown in FIG. 4A, each of the divided regions D1 to D4 is divided so as to have one pattern.

  The divided area D1 has a print area on which four dots forming the pattern P1 are printed, and a non-print area corresponding to eight dots. The area of the printing area is 1/3 of the divided area D1, and the area of the non-printing area is 2/3 of the divided area D1. The divided areas D2 to D3 also have the same print area and non-print area.

  In the inspection apparatus 10 according to the present embodiment, when the nozzle check pattern is printed by normal nozzles in each divided area, the print area is determined to be 1/3 of the area of the divided area. .

  Similarly, as illustrated in FIG. 4B, the processing unit 11 equally divides the photographed nozzle check pattern image H2 into four divided regions D5 to D8. Each of the divided regions D5 to D8 is also divided so as to have one pattern. The divided areas D5, D7, and D8 include one pattern, but the divided area D6 does not include a pattern because a pattern is not printed due to a nozzle failure.

  The divided areas D5, D7, and D8 have a print area and a non-print area similarly to the divided area D1. The divided region D6 is a non-printing region because the pattern is not printed due to a nozzle failure. Similarly, for the shooting region R3, the nozzle check pattern image is divided and the average print density of each divided region is obtained.

  And the process part 11 calculates | requires the average brightness | luminance of the pixel in each division area. For example, when the nozzle check pattern image is photographed with a gray scale of 256 gradations, gradation 0 means a black pixel with the lowest luminance, and gradation 255 means a white pixel with the highest luminance. The processing unit 11 calculates the average print density by calculating (255−average luminance) / 255) × 100 after calculating the average gradation of the pixels in each divided region as the average luminance. When the nozzle check pattern image is an RGB image, the average print density can be obtained by the same calculation after the RGB image is converted into a grayscale image.

  The average print density of the divided area D1 is theoretically 33.3% when the brightness of the dots printed with the pattern P1 is gradation 0. Similarly, the average print density of the other divided areas D2 to D4, D5, D7, and D8 is theoretically 33.3%.

  In each divided area, when a nozzle check pattern is printed by a normal nozzle, 1/3 of the area of the divided area is a print area. Therefore, the average print density is 33.3%. This means that the check pattern is normal and the nozzle is not defective.

  On the other hand, since no pattern is printed in the divided area D6, when the luminance of the non-printed area is the gradation 255, the average print density in the divided area D6 is theoretically 100%.

  Next, in step S305 to step S313, the processing unit 11 repeats the process of determining whether there is an abnormality in the nozzle check pattern of each divided region.

  In step S307, the processing unit 11 determines whether or not the absolute value of the difference between the average print density and the reference print density of each divided area is equal to or less than an allowable value. The average print density is a value obtained for each divided region of the nozzle check pattern image in step S303 described above. The reference print density is an average print density that is theoretically obtained when the nozzle check pattern is printed by a normal nozzle. In the inspection apparatus 10 of this embodiment, the reference print density of each divided region is 33.3%. The allowable value can be determined on the basis of printing error of an ink jet printer such as blurring of printing, blurring or misregistration of printing, and a luminance change associated with photographing of a nozzle check pattern image. The allowable value is determined in advance using a nozzle check pattern image obtained by photographing a nozzle check pattern printed using normal nozzles.

  When the absolute value of the difference between the average print density and the reference print density is equal to or smaller than the allowable value (step S307—Yes), the processing unit 11 has no abnormality in the nozzle check pattern of this divided area (ie, Is normal) (step S309). The processing unit 11 stores the divided area and the determination result in the storage unit 12 in association with each other.

  For example, if the absolute value of the difference between the average print density and the reference print density of the divided areas D1 to D4, D5, D7, and D8 where the pattern is normally printed is equal to or less than the allowable value, the divided areas D1 to D4, It is determined that the nozzle check patterns D5, D7, and D8 are normal.

  On the other hand, when the absolute value of the difference between the average print density and the reference print density is larger than the allowable value (step S307-No), the processing unit 11 has an abnormality in the nozzle check pattern of this divided area (that is, It is determined that it is not normal (step S311). The processing unit 11 stores the divided area and the determination result in the storage unit 12 in association with each other.

  For example, if the absolute value of the difference between the average print density and the reference print density in the divided area D6 where no pattern is printed due to a nozzle failure is greater than the allowable value, it is determined that the nozzle check pattern in the divided area D6 has an abnormality. The

  The processing unit 11 repeatedly performs the above-described processing for each divided region.

  Next, in step S <b> 315, the processing unit 11 uses the output unit 15 to output a result of the presence or absence of an abnormality in the nozzle check pattern determined for each divided region. There is a possibility that the nozzle of the ink jet printer corresponding to the pattern of the divided area where the nozzle check pattern is abnormal has a nozzle defect. The operator of the inspection apparatus can inspect the nozzles of the ink jet printer based on the determination result of the inspection apparatus. Note that the inspection apparatus 10 may transmit the determination result using a communication unit (not shown) instead of using the output unit 15.

  According to the inspection apparatus 10 of the present embodiment described above, it is possible to inspect nozzle defects using a single nozzle check pattern image photographed at a resolution lower than the printing resolution of the inkjet printer. Therefore, the nozzles of the ink jet printer can be inspected using a single image capturing unit having a resolution lower than the printing resolution of the ink jet printer.

  Further, by incorporating the inspection apparatus 10 as an in-line inspection apparatus in a printing process using an ink jet printer, it is possible to inspect the nozzle state of the ink jet printer by printing a nozzle check pattern. For example, the nozzle check pattern may be printed in a non-printing area of the printed material.

  Next, a second embodiment of the above-described inspection apparatus will be described below with reference to FIGS. For points that are not particularly described in the second embodiment, the description in detail regarding the first embodiment is applied as appropriate. Moreover, the same code | symbol is attached | subjected to the same component.

  FIG. 5 is a diagram showing a nozzle check pattern used in the second embodiment of the inspection apparatus disclosed in this specification.

  In the inspection apparatus 10 of the present embodiment, by using a nozzle check pattern as shown in FIG. 5, it is determined whether there is an abnormality in the nozzle check pattern based on the average print density of the nozzle check pattern image, and there is a defect. The position of the nozzle can be determined.

  First, the nozzle check pattern shown in FIG. 5 will be described below.

  The ink jet printer (not shown) has nozzles N1 to N12 arranged in a line. Each of the nozzles N1 to N12 prints by ejecting black ink droplets onto the printing paper.

  First, ink droplets are ejected from the nozzle N1, and a pattern Q1 having a first length L1 and printed so as to extend in the feeding direction of the printing paper is printed.

  Next, an ink droplet is ejected from the nozzle N2 adjacent to the nozzle N1, and a pattern Q2 having a second length L2 different from the first length and printed so as to extend in the feeding direction of the printing paper is obtained. Printed.

  Next, an ink droplet is ejected from the nozzle N3 adjacent to the nozzle N2, and has a third length L3 different from the first length and the second length, and extends in the feeding direction of the printing paper. The printed pattern Q3 is printed.

  The patterns Q1 to Q3 are printed using the nozzles N1 to N3, and at the same time, the patterns Q1 to Q3 are printed using the nozzles N4 to N6, the nozzles N7 to 9 and the nozzles N10 to N12, as shown in FIG. A nozzle check pattern is obtained. An interval for two nozzles is arranged between the patterns Q1, an interval for two nozzles is arranged between the patterns Q2, and an interval for two nozzles is arranged between the patterns Q3. Is placed.

  In the example shown in FIG. 5, each pattern Q1 to Q3 has an interval between dots printed by ink droplet ejection in the printing paper feed direction. This is simply shown, and in reality, there is not always an interval between dots.

  Here, the first length L1, the second length L2, and the third length L3 are Ln = L0 × 2 ^ (n−1) (n is a positive integer of 1 to 3, and L0 is Constant). Note that the first length L1, the second length L2, and the third length L3 may be divided into a plurality of straight lines instead of a single straight line as shown in FIG. In this case, the total length of the plurality of straight lines is set to be the first length L1, the second length L2, or the third length L3. A specific example is shown in FIG.

  As for the relationship between the lengths of the patterns, other length relationships may be used as long as the sum of the first length L1 and the second length L2 is not equal to the third length L3. .

  In addition, using M nozzles (M is a positive integer) that are adjacent to each other, the pattern of the first length L1 to the Mth length LM is Ln = L0 × 2 ^ (n−1). ) (N is a positive integer from 1 to M, L0 is a constant) The nozzle check pattern may be formed to have a length relationship.

  In the example shown in FIG. 5, the states of the nozzles N1 to N12 can be checked by printing four sets of patterns Q1 to Q3.

  Hereinafter, the operation of the inspection apparatus 10 of the present embodiment will be described with reference to the flowchart shown in FIG.

  First, in step S601, the processing unit 11 uses the image photographing unit 16 to photograph the photographing region R (see FIG. 5) including the three patterns Q1 to Q3, and as illustrated in FIG. An image H is obtained.

  Next, in step S603, as illustrated in FIG. 7, the processing unit 11 divides the nozzle check pattern image H to obtain an average print density of each divided region.

  Specifically, as illustrated in FIG. 7, the processing unit 11 equally divides the nozzle check pattern image H into four divided regions D1 to D4. Each of the four regions D1 to D4 includes one pattern Q1, a pattern Q2 adjacent to the pattern Q1, and a pattern Q3 adjacent to the pattern Q2.

  The length of each of the divided regions D1 to D4 matches the length of the pattern Q1, the length of the pattern Q2, and the length of the pattern Q3. Here, the length of the divided area is the length of the divided area in the print medium feeding direction.

  Further, the width of each of the divided regions D1 to D4 is equal to the width of the pattern Q1, the width of the pattern Q2, and the width of the pattern Q3. Here, the width of the divided area is the length of the divided area in a direction orthogonal to the feeding direction of the print medium.

  And the process part 11 calculates | requires the average brightness | luminance of the pixel in each division area. For example, when the nozzle check pattern image is photographed with a gray scale of 256 gradations, gradation 0 means a black pixel with the lowest luminance, and gradation 255 means a white pixel with the highest luminance. The processing unit 11 calculates the average print density by calculating (255−average luminance) / 255 × 100 after calculating the average gradation of the pixels in each divided region as the average luminance.

  Next, in step S605 to step S609, the processing unit 11 repeats the process of determining whether there is an abnormality in the nozzle check pattern of each divided region.

  In step S <b> 607, the processing unit 11 refers to the print density table shown in FIG. 8 based on the average print density of each divided area, determines whether there is an abnormality in the nozzle check pattern, and if there is an abnormality in the pattern. Determines the position of the defective nozzle.

  FIG. 8 is a diagram illustrating a print density table showing the relationship between the dot missing position of the nozzle check pattern image and the average print density of the nozzle check pattern image.

  The print density table 800 includes a column 801 indicating the position of missing dots and a column 802 indicating the print density.

  Next, the print density table 800 will be described below with reference to examples of missing dots in the nozzle check pattern image shown in FIGS.

  FIG. 9A shows a nozzle check pattern image when the patterns Q1 to Q3 included in the divided area are normally printed without including any missing dots.

  In FIG. 9A, the area of the printing area forming the patterns Q1 to Q3 is 1/3 of the divided area, and the area of the non-printing area where no dots are printed is 2/3 of the divided area. As shown in FIG. 8, the average print density in the divided area is theoretically 33.3%. In this case, there is no defective nozzle.

  FIG. 9B shows a nozzle check pattern image when the pattern Q1 is not printed due to a nozzle failure. For example, the nozzle N1 has a nozzle defect.

  In FIG. 9B, the area of the non-printing area is increased as compared with the normal case because the pattern Q1 is not printed, and the average print density of the divided area is as shown in FIG. Nozzle failure due to missing, theoretically 28.6%.

  FIG. 9C shows a nozzle check pattern image when the pattern Q2 is not printed due to a nozzle failure. For example, the nozzle N2 has a nozzle defect.

  In FIG. 9C, the area of the non-printing area is increased as compared with the normal case because the pattern Q2 is not printed, and the average printing density of the divided area is as shown in FIG. Nozzle failure due to missing, theoretically 23.8%.

  FIG. 9D shows a nozzle check pattern image when the pattern Q23 is not printed due to a nozzle failure. For example, the nozzle N3 has a nozzle defect.

  In FIG. 9D, the area of the non-printing area is increased as compared with the normal case because the pattern Q3 is not printed, and the average print density of the divided area is as shown in FIG. Nozzle failure due to missing, theoretically 14.3%.

  FIG. 10E shows a nozzle check pattern image when the pattern Q1 and the pattern Q2 are not printed due to nozzle failure. For example, the nozzle N1 and the nozzle N2 have a nozzle defect.

  In FIG. 10E, the area of the non-printing area is increased as compared with the normal case by the amount that the pattern Q1 and the pattern Q2 are not printed, and the average printing density of the divided area is as shown in FIG. Nozzle failure due to left end and center dodging, theoretically 19.0%.

  FIG. 10F shows a nozzle check pattern image when the pattern Q2 and the pattern Q3 are not printed due to a nozzle failure. For example, the nozzle N2 and the nozzle N3 have nozzle defects.

  In FIG. 10 (F), the area of the non-printing area is increased as compared with the case where the patterns Q2 and Q3 are not printed as compared with the normal case, and the average print density of the divided areas is as shown in FIG. In addition, nozzle failure due to the center and right end dodging is theoretically 4.8%.

  FIG. 10G shows a nozzle check pattern image when the patterns Q1 and Q3 are not printed due to nozzle failure. For example, the nozzle N1 and the nozzle N3 have nozzle defects.

  In FIG. 10G, the area of the non-printing area is increased as compared with the case where the pattern Q1 and the pattern Q3 are not printed as compared with the normal case, and the average print density of the divided areas is as shown in FIG. Furthermore, the nozzle failure is caused by the left and right end dodging, which is theoretically 9.5%.

  Based on the average print density of each divided area, the processing unit 11 refers to the print density table 800 shown in FIG. Here, a predetermined error is allowed in the degree of coincidence between the average print density in the divided area and the print density in the print density table 800. This predetermined error is determined based on, for example, the same idea as the allowable value of the first embodiment described above.

  Depending on the state of nozzle failure, one pattern may be partially printed. If the print density table 800 shown in FIG. 8 is used for the average print density of the divided areas including such a pattern, there is a possibility that a matching print density cannot be determined. In order to cope with such a nozzle defect, the print density column 802 has a predetermined range of print density corresponding to each dot missing position column 801 so that each print density range is continuous. A print density table 800 may be created. In this way, the average print density of the divided area is divided into any print density, and the dot missing position can be determined.

  Then, the processing unit 11 determines the dot missing position with reference to the dot missing position of the print density that matches the average print density of the divided area. The processing unit 11 determines that the nozzle check pattern has no abnormality (i.e., is normal) when there is no missing dot position.

  On the other hand, if not, the processing unit 11 determines that the nozzle check pattern is abnormal (that is, not normal). If the processing unit 11 determines that the nozzle check pattern has an abnormality, the processing unit 11 associates the divided areas with the positions of missing dots and stores them in the storage unit 12.

  The processing unit 11 repeatedly performs the above-described processing for each divided region.

  Next, in step S611, the processing unit 11 outputs a result of the presence or absence of an abnormality in the nozzle check pattern determined for each divided region. The processing unit 11 outputs a dot missing position as a nozzle position having a defect for a divided region where the nozzle check pattern is abnormal. The operator of the inspection apparatus can inspect the nozzles of the ink jet printer based on the determination result of the inspection apparatus.

  According to the inspection apparatus of the present embodiment described above, the same effects as those of the first embodiment described above are obtained, and a specific dot missing position is determined for a divided region in which the nozzle check pattern is abnormal. be able to.

  Next, modified examples 1 to 3 of the nozzle check pattern of the above-described second embodiment will be described below with reference to FIGS.

  FIG. 11 is a diagram illustrating a first modification of the nozzle check pattern used in the second embodiment.

  In this modified example, since the pattern Q1 and the pattern Q3 are printed simultaneously, the length of the nozzle check pattern in the feeding direction of the printing paper can be shortened. The length of the nozzle check pattern shown in FIG. 5 in the feeding direction of the printing paper is 21 dots, but the length of the nozzle check pattern shown in FIG. 11 is 18 dots.

  In this modified example, the pattern Q1 printed using the nozzle N1 and the pattern Q1 printed using the nozzle N4 are different in the feed direction of the printing paper to be printed, and the nozzle N2 The pattern Q2 printed using the nozzle N5 and the pattern Q2 printed using the nozzle N5 have different positions in the feeding direction of the printing paper to be printed, and the pattern Q3 printed using the nozzle N3 The pattern Q3 printed using the nozzle N6 is different in position in the feeding direction of the printing paper to be printed, so that the patterns are not adjacent to each other.

  FIG. 12 is a diagram illustrating a print density table showing the relationship between the dot missing position of the nozzle check pattern image of the first modification and the average print density of the nozzle check pattern image.

  When the nozzle check pattern of the first modification is used, a print density table 1200 shown in FIG. 12 is used.

  FIG. 13 is a diagram illustrating a second modification of the nozzle check pattern used in the second embodiment.

  In this modification, the pattern Q3 printed using the nozzle N6 is divided into two straight lines and printed. The pattern Q2 printed using the nozzle N5 is different from the pattern Q2 printed using the nozzle N2 by making the position in the feed direction of the printing paper to be printed different from each other. . Even if each pattern is divided into a plurality of straight lines instead of a single straight line, if the influence on the average luminance of the pixels in the divided area is within an allowable range, the pattern divided into the plurality of straight lines is used. Also good.

  FIG. 14 is a diagram illustrating a modified example 3 of the nozzle check pattern used in the second embodiment.

  In this modified example, since the patterns Q1 to Q3 are printed at the same time, the length of the nozzle check pattern in the feeding direction of the printing paper can be further shortened.

  In addition, it is preferable not to use adjacent nozzles as nozzles for printing each pattern from the viewpoint of preventing adjacent printed patterns from being connected to each other due to printing bleeding. In the example shown in FIG. Thus, depending on the combination of printing paper and ink, there may be a gap between adjacent dots. In such a case, adjacent nozzles may be used as nozzles for printing each pattern.

  In the present invention, the method and the inspection apparatus of the above-described embodiment can be appropriately changed without departing from the gist of the present invention. In addition, the configuration requirements of one embodiment can be applied to other embodiments as appropriate.

  For example, in the above-described embodiment, whether or not the nozzle check pattern is abnormal is determined for each divided region obtained by dividing one nozzle check pattern image, but the theoretical average print density when there is no abnormality in the nozzle is calculated. If it can be obtained, it may be determined whether the nozzle check pattern is abnormal without dividing the nozzle check pattern image.

DESCRIPTION OF SYMBOLS 10 Inspection apparatus 11 Processing part 12 Storage part 13 Display part 14 Operation part 15 Output part 16 Image photographing part 800 Print density table 801 Dot missing position field 802 Print density field N1 to N12 Nozzle R Imaging area H Nozzle check pattern image D1 D4 divided area P1 to P4 pattern Q1 to Q3 pattern 800 Print density table 1200 Print density table

Claims (6)

  Whether the nozzle check pattern image is a nozzle check pattern image printed by an ink jet printer or not, based on the average brightness of the nozzle check pattern image taken at a resolution lower than the print resolution of the ink jet printer. How to judge.   The method according to claim 1, wherein an average luminance of the nozzle check pattern image is compared with a predetermined reference value to determine whether the nozzle check pattern is abnormal. A plurality of nozzle check pattern images obtained by shooting a plurality of nozzle check patterns printed side by side by ejecting ink droplets from a plurality of nozzles arranged in a line in an inkjet printer. Split and
The method according to claim 1, wherein the presence or absence of an abnormality in the nozzle check pattern is determined based on an average luminance of each region.   Ink droplets are ejected from first nozzles of an ink jet printer, the first pattern has a first length and is printed so as to extend in the feeding direction of the print medium, and the second nozzle of the ink jet printer A nozzle check pattern having a second length different from the first length and printed so as to extend in the feeding direction of the print medium was photographed by ejecting ink droplets from The method according to claim 1, wherein the presence or absence of an abnormality in the first pattern or the second pattern is determined based on an average luminance of a nozzle check pattern image.   The first length and the second length Ln are determined as Ln = L0 × 2 ^ (n−1) (n is a positive integer of 1 or 2, and L0 is a constant). The method described.   Whether the nozzle check pattern image is a nozzle check pattern image printed by an ink jet printer or not, based on the average brightness of the nozzle check pattern image taken at a resolution lower than the print resolution of the ink jet printer. Inspection device to judge.

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