JP2019136995A - Quality inspection device for cardboard sheet - Google Patents

Abstract

To provide technique capable of keeping track of fluctuations in the coating film thickness of ink during printing and adjusting the coating film thickness by accordingly adjusting an amount of ink transfer and viscosity before printing becomes defective.SOLUTION: A cardboard sheet quality inspection device includes: imaging means 2 for imaging a printing surface of a cardboard sheet; illumination means 3 for illuminating an imaging surface by the imaging means 2; density information acquisition means 41a for acquiring printing density information from RGB levels of image information acquired by the imaging means 2; and determination means 41b for determining whether an amount of ink on the printing surface is proper or not on the basis of the printing density information acquired by the density information acquisition means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cardboard sheet quality inspection apparatus.

  The cardboard sheet is printed by, for example, a flexographic printing machine as described in Patent Document 1. As a method for managing the color of ink, for example, as described in Patent Document 2, it has been proposed to measure a color by using a proofing device similar to a flexographic printing machine and manage the color.

  By the way, in the case of a corrugated cardboard sheet, the ink color is affected by the coating thickness (ink amount). That is, if the coating film thickness is thin, there is a problem in that the influence of the color of the base comes out and the required color does not appear. The coating thickness of the ink varies depending on the amount of ink transferred (primary amount), the properties of the sheet, the viscosity of the ink, and the like, and the amount of ink transferred also varies depending on the viscosity of the ink and various conditions of the printing machine. In addition, the viscosity of the ink also varies from time to time due to water vaporization of the water-based ink. The sheet properties are not constant, and vary greatly as the lot changes.

  Therefore, during printing, the ink coating thickness always fluctuates greatly, and color management is not easy. Actually, during printing, the state of the printed material that is periodically removed is compared with the sample, and the printing device (transfer amount) is adjusted as necessary, and water is added to the ink. Currently.

JP-A-10-157079 Special table 2014-509279 gazette

  Therefore, in view of the above situation, the present invention intends to solve the problem of fluctuations in the coating thickness of the ink during printing, thereby adjusting the transfer amount and viscosity before printing becomes defective. It is in the point of providing the technique which enables adjustment of the coating thickness.

  The present inventor has conceived that the quality of the ink coating film can be estimated by detecting the color of the ink on the printing surface of the corrugated cardboard sheet as a result of examination in view of the present situation. Because it is not possible to use a dedicated spectrometer such as, as a result of further diligent investigation, it is possible to easily determine the quality of the coating thickness by using the density information of the printed ink, if so For example, it is found that density information can be obtained online with a normal imaging camera by diverting an imaging camera of an inspection apparatus conventionally used for printing quality and registration, and the present invention is completed. It came to.

That is, the present invention includes the following inventions.
(1) Imaging means for imaging the printing surface of the cardboard sheet, illumination means for illuminating the imaging surface by the imaging means, and density information acquisition means for acquiring print density information from the RGB level of image information obtained by the imaging means And a cardboard sheet quality inspection apparatus comprising: a determination unit that determines whether the ink amount on the printing surface is good or not based on the print density information acquired by the density information acquisition unit.

  (2) The corrugated cardboard sheet quality inspection apparatus according to (1), wherein the determination unit determines whether the ink amount is good or not by comparing the print density information of a non-defective product stored in advance with a reference density.

  (3) The corrugated cardboard according to (1) or (2), wherein the density information acquisition unit calculates print density information corrected with the color of the sheet background based on the RGB level of the sheet background and the RGB level of the image information. Sheet quality inspection device.

  (4) The imaging unit images a colored region on which ink is placed and a sheet base region on which ink is not placed, and the density information acquisition unit performs RGB of the image information on the colored region obtained by the imaging unit. The corrected print density information is calculated from the level and the RGB level of the image information of the background area, and the determination unit determines the quality of the ink amount based on the corrected print density information of the colored area. (1)-(3) The cardboard sheet quality inspection device according to any one of (1) to (3).

  (5) The cardboard sheet quality inspection device according to (3) or (4), wherein the density information acquisition unit uses the density calculated based on the following (Equation 1) as the corrected print density information.

  (6) Ink color information acquisition means for acquiring ink color information expressed in device-independent color based on the RGB level of the image information obtained by the imaging means is provided (1) to (5) The quality inspection apparatus for cardboard sheets according to any one of the above.

  (7) The determination unit includes a control signal generation unit that calculates a necessary adjustment amount of the ink amount and generates a control signal to be transmitted to the ink amount adjustment mechanism of the printing apparatus based on the adjustment amount. The quality inspection apparatus for corrugated cardboard sheets according to any one of (1) to (6).

  (8) The cardboard sheet quality inspection device according to any one of (1) to (7), wherein the imaging unit also serves as an image acquisition unit for registering the cardboard sheet.

  According to the present invention as described above, the print density information is obtained from the RGB level of the image information obtained by the image pickup means, and the quality of the ink amount (coating film thickness) on the printing surface is determined based on this print density information. The variation of the ink coating thickness can be grasped online during printing, so that the coating thickness can be adjusted by adjusting the transfer amount and viscosity before printing becomes defective. In addition, such an image pickup means can use a normal inexpensive image pickup camera, and can use the image pickup camera of an inspection apparatus conventionally used for printing quality and registration. The rise can also be suppressed.

  In addition, in the case where the determination means determines whether the ink amount is good or bad by comparing the print density information of the non-defective product stored in advance with the reference density and comparing it with the reference density, the quality of the ink amount is determined more accurately by relative comparison Can be judged.

  Further, in the case where the density information acquisition means calculates the print density information corrected with the color of the sheet background based on the RGB level of the sheet background and the RGB level of the image information, the sheet property fluctuations, the illumination means Errors due to illumination fluctuations and other environmental fluctuations can be eliminated by correction, more accurate printing density information can be obtained, and the quality of the ink amount can be more accurately determined. In addition, since the influence of the color of the sheet background can be eliminated, the original color information of the ink can be obtained, thereby making it possible to accurately determine an error in the ink supply.

  More specifically, for example, the imaging unit images a colored region on which ink is placed and a sheet ground region on which ink is not placed, and the density information acquisition unit obtains an image of the colored region obtained by the imaging unit. The corrected print density information is calculated from the RGB level of the information and the RGB level of the image information of the background area, and the determination means determines whether the ink amount is good or not based on the corrected print density information of the colored area. It can be realized by determining.

  More specifically, for example, the density information acquisition unit can realize the density calculated based on the following (Equation 1) as the corrected print density information.

  Further, in the case of providing ink color information acquisition means for acquiring ink color information expressed by device independent color based on the RGB level of image information obtained by the imaging means, the ink information is more detailed. It is possible to obtain the above-mentioned ink, and it is possible to accurately grasp the above-described mistakes in the introduction of ink.

  Further, in the printing apparatus, the determination unit includes a control signal generation unit that calculates a necessary adjustment amount of the ink amount and generates a control signal to be transmitted to the ink amount adjustment mechanism of the printing apparatus based on the adjustment amount. By controlling the ink amount adjusting mechanism, it is possible to perform feedback control so that the ink amount is always appropriate.

  Further, when the image pickup means also serves as an image acquisition means for registering the corrugated cardboard sheet, the efficiency of the apparatus can be improved and the cost increase can be significantly suppressed.

Explanatory drawing which shows the quality inspection apparatus concerning typical embodiment of this invention. The block diagram which similarly shows the processing apparatus of a quality inspection apparatus. The block diagram which similarly shows the memory | storage means of a quality inspection apparatus.

Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in FIG. 1, the cardboard sheet quality inspection apparatus 1 according to the present invention includes an imaging unit 2 that images a printing surface P of the cardboard sheet W, an illumination unit 3 that illuminates the imaging surface F by the imaging unit 2, Based on the density information acquisition unit 41a that acquires the print density information from the RGB level of the image information obtained by the unit 2 and the print density information acquired by the density information acquisition unit, the quality of the ink on the printing surface P is determined. And a determination unit 41b.

  Reference numerals 11A, 11B, and 11C denote printing apparatuses that print different colors of ink, respectively. The number of printing devices is not limited. The printing apparatuses 11A, 11B, and 11C are, for example, flexographic printing machines, and can be applied to various printing apparatuses such as offset printing machines and inkjet printing machines.

  The image pickup means 2 is provided with a plurality of image pickup cameras along the width direction orthogonal to the conveyance direction 10 of the printed material, for example, in the same manner as the image pickup means used in the conventional registration misalignment and print quality inspection apparatus, and covers the entire width of the cardboard sheet W. An area is imaged. A line sensor camera in which a plurality of CCD or CMOS image sensors are arranged in the horizontal direction orthogonal to the transport direction may be used.

  The number and arrangement of the cameras are not particularly limited as long as the cardboard sheet W can be imaged. In addition to the line sensor camera, a single or a plurality of area sensor cameras in which a plurality of CCD and CMOS image sensors are arranged in the vertical and horizontal directions are provided. But you can. The illumination means may be a general illumination used in a normal inspection apparatus.

  The density information acquisition unit 41a and the determination unit 41b are provided in the processing device 41 constituting the computer. Reference numeral 42 denotes a storage means connected to the processing device 41. The processing device 41 is mainly configured by a CPU such as a microprocessor, and is connected to the imaging unit 2, the illuminating unit 3, the storage unit 42, and the adjustment mechanism 12 of the printing devices 11A to 11C through an input / output unit and a bus line. Send and receive various information.

  The storage means 42 includes a storage memory such as RAM and ROM inside and outside the processing device 41, a hard disk, and the like, and stores programs and processing data that define procedures of various processing operations in the processing device 41. FIG. 2 shows the configuration of the processing apparatus 41 of this embodiment, and FIG.

  As shown in FIG. 2, the processing device 41 is functionally a control for controlling the adjustment mechanism of the printing apparatus based on the adjustment amount calculated by the determination unit 41b, in addition to the density information acquisition unit 41a and the determination unit 41b. At least a control signal generation unit 41c that generates a signal and a registration deviation amount calculation processing unit 41d that calculates a registration deviation amount are provided, and these functions are realized by the program.

  The density information acquisition unit 41a includes an image RGB data acquisition processing unit 51 that acquires RGB data of a colored area on which ink is applied from a captured image, and a background RGB data acquisition process that acquires RGB data of a sheet background area on which ink is not applied. And a density calculation processing unit 53 that calculates print density information after correction with the color of the sheet background, based on the RGB data and background RGB data of these landing areas.

  The image RGB data acquisition processing unit 51 detects image RGB data of a colored region painted with each ink from the captured image data acquired from the imaging unit 2, and detects this image RGB data storage unit 42 b of the storage unit 42. To remember. The colored area may be determined as a predetermined area painted with each ink. For example, it may be a register mark of a predetermined color that can be recognized by the shape, or may be an area of each color specified by a color vector from a design. .

  Similarly, the background RGB data acquisition processing unit 52 detects the RGB data of the portion of the background area that is not painted with ink from the captured image data acquired from the imaging unit 2, and stores this data in the background RGB data storage unit of the storage unit 42. Store in 42a.

  The density calculation processing unit 53 calculates the print density information of the picked-up image of the colored region for each ink from each RGB data of these colored regions and the background RGB data stored in the background RGB data storage unit 42a of the storage unit 42. And is stored in the density data storage unit 42c as corrected print density information. The corrected print density information is calculated and stored for each ink. Specifically, the density calculated based on (Equation 1) below is used as the corrected print density information.

  The determination unit 41b includes a comparison value calculation processing unit 54 that compares the calculated print density of the colored region of each ink and the reference density prepared for each ink, and the compared density difference indicates an allowable value. An allowance determination processing unit 55 that determines whether or not the value exceeds the limit, and an adjustment amount calculation processing unit 56 that calculates the adjustment amount of the ink amount adjustment mechanism of the printing apparatus when the allowable value is exceeded.

  The comparison value calculation processing unit 54 obtains the print density information of the non-defective product for each ink stored in the reference density data storage unit 42d in advance for the print density information of the area of the calculated captured image that is painted with each ink. A density comparison value (density difference ΔD) compared with the reference density is calculated as a reference density, and is stored in the density comparison value storage unit 42e for each ink (printing apparatus).

  The tolerance determination processing unit 55 determines whether the ink amount (coating film thickness) is good or not based on whether the density comparison value exceeds a predetermined threshold value, and stores the determination result in the determination result storage unit 42f. The adjustment amount calculation processing unit 56 calculates an adjustment amount for controlling the adjustment mechanism 12 of the printing apparatus based on the density comparison value and the determination result, and stores this in the adjustment amount storage unit 42g. Then, the control signal generation unit 41c generates a control signal to be transmitted to the ink amount adjustment mechanism 12 of the printing apparatuses 11A to 11C based on the adjustment amount, and transmits the control signal to the adjustment mechanism 12 as a control command.

  In the present embodiment, the adjustment mechanism of the printing apparatus is controlled. However, such a control function can be omitted. For example, a display means for displaying the determination result for the operator is provided. It may be anything that you have stopped.

  Moreover, the quality inspection apparatus 1 of this embodiment also serves as an inspection apparatus that detects misregistration. The registration amount calculation processing unit 41d calculates a registration amount by a known method based on the captured image data captured by the imaging unit 2, and stores the result in the registration amount storage unit 42h. For example, it is of course possible to detect a registration mark of each plate and calculate a shift amount, or to register with a pattern. The calculation of these misregistration amounts can use the methods described in Japanese Patent Application Laid-Open No. 2012-240400 and Japanese Patent Application Laid-Open No. 2015-219056 filed by the present applicant.

  Although not shown, the quality inspection apparatus 1 according to the present embodiment also serves as a quality inspection apparatus that detects print defects or stains on symbols other than the amount of ink applied, stains on sheets, and the like. Thus, the quality inspection apparatus of the present invention is capable of simultaneously determining the amount of ink as well as the printing quality such as misregistration and design by using the imaging means 2 for inspection and the illumination means 3 together, While suppressing the increase in cost, it is possible to inspect the amount of ink together with the register and design immediately online, omit the sampling check, enable early start-up of printing, and remarkably improve printing efficiency.

  Further, the processing device 41 further acquires, for each ink, ink color information expressed in device, independent, and color based on the RGB level of the colored region of each ink color in the image information obtained by the imaging means 2. What provided the ink color information acquisition means is preferable. In this case as well, correction is preferably performed using the RGB level of the sheet base region, as in the case of density. As the ink color information, information approximated to the XYZ color system, or information converted into a CIE-Lab color system, which is a reference value color space, using a preset conversion table (profile) is preferable.

  Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and can of course be implemented in various forms without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Quality inspection apparatus 2 Imaging means 3 Illumination means 10 Conveyance direction 11A, 11B, 11C Printing apparatus 12 Adjustment mechanism 41 Processing apparatus 41a Density information acquisition means 41b Determination means 41c Control signal generation means 41d Registration deviation amount calculation processing part 42 Storage means 42a Background RGB data storage unit 42b Image RGB data storage unit 42c Density data storage unit 42d Reference density data storage unit 42e Density comparison value storage unit 42f Determination result storage unit 42g Adjustment amount storage unit 42h Registration deviation amount storage unit 51 Image RGB data acquisition processing Unit 52 background RGB data acquisition processing unit 53 density calculation processing unit 54 comparison value calculation processing unit 55 tolerance determination processing unit 56 adjustment amount calculation processing unit F imaging surface P printing surface W cardboard sheet

Claims (8)

Imaging means for imaging the printing surface of the cardboard sheet;
Illuminating means for illuminating the imaging surface of the imaging means;
Density information acquisition means for acquiring print density information from the RGB level of image information obtained by the imaging means;
A determination unit that determines whether the ink amount on the printing surface is good or not based on the print density information acquired by the density information acquisition unit.
Cardboard sheet quality inspection device.   2. The corrugated cardboard sheet quality inspection apparatus according to claim 1, wherein the determination means determines whether the ink amount is good or not by comparing the print density information of good products stored in advance with a reference density.   3. The corrugated cardboard sheet quality inspection apparatus according to claim 1, wherein the density information acquisition unit calculates print density information corrected with the color of the sheet background based on the RGB level of the sheet background and the RGB level of the image information. . The imaging means images the colored area on which the ink is placed and the sheet base area on which the ink is not placed,
The density information acquisition means calculates the corrected print density information from the RGB level of the image information of the colored area obtained by the imaging means and the RGB level of the image information of the background area,
The determination means determines the quality of the ink amount based on the corrected print density information of the colored area;
The quality inspection apparatus for cardboard sheets according to any one of claims 1 to 3. The cardboard sheet quality inspection device according to claim 3 or 4, wherein the density information acquisition means uses the density calculated based on the following (formula 1) as the corrected print density information.

  The ink color information acquisition means for acquiring ink color information expressed in device-independent color based on the RGB level of image information obtained by the imaging means is provided. The cardboard sheet quality inspection device described in 1. The determination means calculates a necessary adjustment amount of the ink amount,
The cardboard sheet quality inspection apparatus according to claim 1, further comprising a control signal generation unit configured to generate a control signal to be transmitted to an ink amount adjustment mechanism of a printing apparatus based on the adjustment amount.   The cardboard sheet quality inspection apparatus according to any one of claims 1 to 7, wherein the imaging unit also serves as an image acquisition unit for registering the cardboard sheet.

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