JP4528633B2 - Inspection apparatus and method for gravure cylinder - Google Patents

Description

  The present invention relates to a gravure cylinder inspection apparatus and method for inspecting an outer peripheral surface of a gravure cylinder used for gravure printing, and in particular, an inspection for a gravure cylinder capable of inspecting an outer peripheral surface (plate surface) of a gravure cylinder after plate making. The present invention relates to an apparatus and a method.

  In gravure printing, a fine concave portion (cell) corresponding to an image is formed on a gravure cylinder to produce a printing plate, and the cell is filled with ink and transferred to a printing material. A general gravure cylinder uses a cylindrical iron core or aluminum core as a base material, and a plurality of layers such as a base layer and a release layer are formed on the outer peripheral surface of the base material, and then a copper plating layer for image formation (Plate material) is formed. Then, a cell corresponding to the plate making information (original image) is formed on the copper plating layer by a laser exposure device, and then chrome plating or the like for increasing the printing durability of the gravure cylinder is applied to complete the plate making (plate surface production).

  Conventionally, in the above plate making process, defect inspection has been conducted to check whether there are any initial defects such as scratches or dents on the smooth outer peripheral surface (copper plating layer) of the gravure cylinder before plate making (before cell formation). An apparatus for automatically performing this is also known (see, for example, Patent Document 1 and Patent Document 2).

  However, since the above-mentioned conventional apparatus only detects scratches and dents as defects, after making a gravure cylinder (after forming a cell and applying chrome plating, etc.) A distinction cannot be made between a defect and a normal recess (cell).

  Therefore, after making the gravure cylinder, the operator still performs a visual inspection using a magnifying glass or an optical microscope to check whether the plate has been made normally, or makes a proof (test print) to match the original image. Work (so-called calibration work) is required. The visual inspection by the operator is not only very complicated and takes labor and time, but also when the size of the defect is 50 μm or less, the detection is extremely difficult by the operator's visual observation, and the detection accuracy varies. Also, proof printing requires the skill of the operator, depending on the level of proficiency of the operator, printing of minute defects may be insufficient, a large device (proof machine) for proof printing may be required, However, manual operations such as wiping the ink on the printing plate and setting paper are also necessary, and automation and labor saving are difficult.

In addition, the gravure cylinder after plate making is not a defect, but there may be uneven plate making such as spots in the same color area that should be uniform (uniform) or there is a difference in shading. Such plate-making unevenness could hardly be recognized by visual inspection by an operator, and could only be recognized after proof printing.
Japanese Patent Laid-Open No. 05-93694 JP 2002-254590 A

  The present invention has been made in view of the above problems, and can accurately detect defects on the outer peripheral surface of the gravure cylinder after plate making, can detect plate making unevenness, and hassle the time required for proof printing. An object of the present invention is to provide an inspection apparatus and inspection method for a gravure cylinder that can be greatly reduced.

The inspection apparatus for a gravure cylinder of the present invention uses a laser exposure apparatus for plate making, and forms a plate surface image on the outer peripheral surface of the gravure cylinder by forming cells according to the original image bitmap data which is plate making information of the laser exposure apparatus. fabricated by engraving, a testing apparatus for a gravure cylinder for inspecting the outer peripheral surface of the gravure cylinder after the plate-making, and support means for rotatably supporting the gravure cylinder, by scanning the outer peripheral surface of the gravure cylinder defect detection for detecting a scanning means for obtaining a printing plate image as the printing plate image bitmap data, the defective cell in the original image bitmap data and said plate surface image bitmap data by comparing used in plate making and said plate surface image bitmap data the ratio between a plurality of predetermined areas in the unit and, the printing plate image bitmap data of the same color region Comprising a non-uniformity detecting means for detecting the presence or absence of plate-making unevenness by, and a marking means for performing predetermined marking on the outer circumferential surface of the gravure cylinder corresponding to the defective portion in the detected printing plate image bitmap data by the defect detecting means The defect detection means detects a defect of a cell having a predetermined size or more by performing a pattern matching process for each predetermined region corresponding to the plate image bitmap data and the original image bitmap data. In addition, prior to the comparison between the plate image bitmap data and the original image bitmap data , an error generated when the gravure cylinder is made in advance is corrected, and the error correction is performed. the expansion process of each cell of the original image bitmap data or printing plate image bitmap data Characterized in that it is a contraction processing of each cell.

  The scanning means is preferably scannable in the longitudinal direction (X direction) of the gravure cylinder, the circumferential direction (Y direction) of the gravure cylinder, and the direction perpendicular to the gravure cylinder (Z direction).

The gravure cylinder inspection method of the present invention is a gravure cylinder inspection method using the gravure cylinder inspection apparatus, and is a plate image bit map data obtained by scanning the outer peripheral surface of the gravure cylinder after plate making and plate making. The original image bitmap data used in the above is compared, and a cell defect of the plate image bitmap data is detected. Further, after detecting the defect in the cell of said plate face image bitmap data, comparing among a plurality of predetermined areas in said plate plane image bitmap data of the same color area, it is preferable to detect the presence or absence of unevenness .

More preferably, after the outer peripheral surface of the gravure cylinder after plate making is inspected by the gravure cylinder inspection method, the plate surface image bitmap data is given a predetermined color to perform simple proof printing.

  According to the present invention, a gravure cylinder inspection apparatus capable of accurately detecting defects on the outer peripheral surface of a gravure cylinder after plate making, detecting plate making unevenness, and greatly reducing labor required for proof printing, and There is an advantageous effect that an inspection method can be provided.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the illustrated examples are shown by way of example, and it goes without saying that various modifications can be made without departing from the technical idea of the present invention. .

  FIG. 1 is a schematic explanatory view showing an example of a basic apparatus configuration of an inspection apparatus for a gravure cylinder of the present invention. FIG. 2 is a schematic diagram illustrating an example of an original image. FIG. 3 is an enlarged photograph of the main part showing a predetermined area of the original image in an enlarged manner. FIG. 4 is an enlarged photograph of a main part showing a predetermined area of the printing plate image in an enlarged manner. FIG. 4A shows a case where there is a cell defect, and FIG. 4B shows a case where there is no cell defect. 5A and 5B are schematic explanatory views showing the principle of comparison between a predetermined area of the original image and a predetermined area of the plate image. FIG. 5A shows a case where the cell has no defect, and FIG. 5B shows a case where the cell has a defect. . 6A and 6B are schematic explanatory views showing the principle of cell error correction in the original image. FIG. 6A shows a cell before error correction, and FIG. 6B shows a cell after error correction. FIG. 7 is a flowchart showing the overall flow of the inspection method for a gravure cylinder of the present invention. In the figure, reference numeral 2 is an inspection apparatus for a gravure cylinder of the present invention, and reference numeral 4 is a gravure cylinder after plate making. Symbol C is a cell, and symbol P is a pixel.

  First, based on FIG. 1, the basic apparatus structure of the inspection apparatus for gravure cylinders of this invention is demonstrated. The gravure cylinder 4 is formed with a plate surface 6 on which, for example, a letter “A” is made. The inspection apparatus 2 for a gravure cylinder is roughly composed of a support means 10, a scanning means 20, and a defect detection means 30. The support means 10 rotatably supports the gravure cylinder 4, and includes a rotary shaft 12 a inserted through the shaft core of the gravure cylinder 4, a servo motor 12 that rotates the rotary shaft 12 a, and an operation of the servo motor 12. The servo motor 12 is connected to a control device 28 by a signal cable 13, and the rotary encoder 14 is connected to a computer 32 by a signal cable 15. Thereby, the gravure cylinder 4 is supported in a state in which it can be accurately rotated. In the illustrated example, the support means 10 has shown the case where the shaft core of the gravure cylinder 4 is rotatably supported by the rotary shaft 12a. However, the present invention is not limited to such a form. It is good also as a structure which supports an outer peripheral part rotatably so that it may roll with a some roller (refer patent document 2).

  The scanning unit 20 scans the outer peripheral surface of the gravure cylinder 4 and obtains a plate image as bitmap data, and includes an image sensor unit 22 having an image pickup device such as a CCD or CMOS, and a moving mechanism thereof. A sensor head 22a such as a close-up lens is appropriately attached to the image sensor unit 22. The type of image sensor unit 22 is preferably a line sensor (also referred to as a linear sensor) rather than an area sensor. This is because the gravure cylinder 4 is cylindrical, and the area sensor is distorted in the captured image. Further, the image sensor unit 22 is connected to a computer 32 as a defect detection unit 30 described later by the signal cable 11, and transmits a plate image obtained by scanning to the computer 32.

  The moving mechanism of the image sensor unit 22 is for allowing the image sensor unit 22 to move in the longitudinal direction (X direction) and the vertical direction (Z direction) of the gravure cylinder 4. In order to make the image sensor unit 22 movable in the longitudinal direction (X direction) of the gravure cylinder 4, a screw shaft 24a, a servo motor 24 for driving the screw shaft 24a, and a linear scale for measuring the position of the image sensor unit 22 The servo motor 24 is connected to the control device 28 by a signal cable 25. Thereby, the image sensor unit 22 can be accurately moved in the longitudinal direction (X direction) of the gravure cylinder 4. The linear scale 23 may be magnetic or optical. Further, in order to make the image sensor unit 22 movable in the vertical direction (Z direction) of the gravure cylinder 4, a screw shaft 26a and a servo motor 26 for driving the screw shaft 26a are provided. To the control device 28. Thereby, the image sensor unit 22 is movable in the vertical direction (Z direction) of the gravure cylinder 4. The control device 28 is connected to the computer 32 by a signal cable 29 and controls the servo motors 12, 24, 26 based on instructions from the computer 32.

  In this way, the image sensor unit 22 as the scanning unit 20 has the gravure cylinder 4 rotatable by the longitudinal direction (X direction) and the vertical direction (Z direction) of the gravure cylinder 4 and the support unit 10 described above. The gravure cylinder 4 can also be scanned in the circumferential direction (Y direction). Reference numeral 40 denotes a laser pointer as marking means.

  The defect detection means 30 compares the plate image (see FIG. 4) of the printing plate 6 obtained by the scanning means 20 with the original image 8 (see FIGS. 2 and 3) used for plate making, and the defect of the cell in the printing plate image. A computer 32 having an input device such as a keyboard and a mouse, a CPU, a memory, a hard disk, an output device such as a monitor and a printer, and the like. It comprises software programmed to detect a cell defect in the plate image by comparing with a predetermined area of the original image used for the corresponding plate making. Here, the original image 8 is plate making information of the laser exposure apparatus used for plate making and is bitmap data (see FIGS. 2 and 3). As a laser exposure apparatus, one having a resolution of about 3200 dpi (1 pixel = 7.9 μm square) is widely used, but one having a resolution of 12800 dpi or more (1 pixel = 1.9 μm square or less) has been developed. (See Japanese Patent Application No. 2004-241320).

  The defect detection means 30 compares the plate image with the original image and detects cell defects by performing pattern matching processing for each predetermined region corresponding to the plate image and the original image, and detecting a cell defect of a predetermined size or more. Is done. The predetermined area is at least 1 cell and 12 mm square or less, preferably 5 cells or more and 8 mm square or less, and most preferably 20 cells or more and 5 mm square or less. The cell size is not particularly limited, but is generally about 36 μm square (700 lpi) to 508 μm square (50 lpi). 3 and 4 show a 145 μm square (175 lpi) cell.

  The pattern matching processing is not particularly limited by an algorithm or the like, but may be general template matching, for example. In template matching, a predetermined area of an original image is used as a template (reference image), matching is performed so as to overlap the corresponding area of the plate image, and a difference or similarity is calculated from a difference in pixel values ( (See FIG. 5). As well shown in FIG. 5, there is no difference B when there is no cell defect F in the plate image [FIG. 5 (a)], but there is also a difference B when there is a cell defect F [FIG. b)], the difference or similarity is calculated from the difference B. In template matching, the smaller the difference between the two images, the smaller the difference and the greater the similarity. Therefore, if the degree of difference is greater than a predetermined threshold, What is necessary is just to detect the case where it becomes below a threshold value as a defect of the cell more than predetermined size. The predetermined size of the defect may be, for example, about 5 to 40 μm in diameter, preferably about 10 to 30 μm in diameter. This is because even if a fine defect that hardly affects the printing result is detected, the actual profit is small.

  In addition, prior to the comparison between the plate surface image and the original image in the defect detection means 30, it is desirable to correct in advance errors generated when the gravure cylinder 4 is made. In the gravure cylinder 4 after the plate making, cells having the same shape and size as the original image are not necessarily formed by laser exposure or etching at the time of plate making. (See FIGS. 3 and 4). As shown in FIG. 6, if correction of this error is performed on the original image, expansion processing of each cell (processing of adding peripheral pixels of each cell once) may be performed. That is, it is only necessary to add the surrounding pixels by the correction width d to the cell C1 before correction [FIG. 6 (a)] to make the cell C2 after correction [FIG. 6 (b)]. For example, when the cell C1 before correction has a size of 145 μm square, the correction width d is about 3 to 15 μm (2% to 10% of the cell diameter), preferably 5 to 10 μm (3% to 7% of the cell diameter). %). In the case where it is performed on a plate image, the contraction process of each cell (a process of deleting the peripheral pixels of each cell once) may be performed in the same manner.

  Furthermore, if a predetermined marking is performed on the outer peripheral surface of the gravure cylinder corresponding to the defective portion in the plate image detected by the defect detecting means 30, a more preferable aspect is obtained. For example, if the laser pointer 40 is used for marking, it is preferable that the gravure cylinder 4 is not soiled or damaged.

  Furthermore, it is desirable to provide unevenness detecting means 50 for detecting the presence / absence of unevenness of plate making by comparing a plurality of predetermined areas in the same color area of the plate surface image. Similar to the defect detection means 30, the unevenness detection means 50 is realized as software stored in a hard disk or the like of the computer 32. The principle of comparison in the non-uniformity detection means 50 is the same as that in the case of the defect detection means 30, so detailed description thereof will be omitted. However, the difference from the case of the defect detection means 30 is the object of comparison. The comparison is not between the original image and the plate image, but between a plurality of predetermined regions within the same color region of the same plate image, for example, between the plate upper portion 6a and the plate lower portion 6b as shown in FIG. . Although it is not detected as a cell defect even when compared with the original image, there may be unevenness in plate making, such as unevenness in the same color area that should be uniform (uniform) or a difference in light and shade. It is. By comparing between such regions, it is possible to detect the presence or absence of plate making unevenness. Note that the unevenness detection means 50 is not necessarily essential, and may be omitted if there is little possibility of unevenness during plate making.

  Next, an overall flow of the gravure cylinder inspection method of the present invention performed using the gravure cylinder inspection apparatus of the present invention will be described with reference to FIG. First, an original image 8 which is plate making information (bitmap data) used in the laser exposure apparatus is created (see step 100, FIG. 2 and FIG. 3). Based on the original image 8, the plate material is exposed by a laser exposure device and subjected to chrome plating or the like to make a plate (step 110). Thereby, the plate surface 6 is formed on the outer peripheral surface of the gravure cylinder 4. Then, the plate surface 6 on the outer peripheral surface of the gravure cylinder 4 is scanned by using the gravure cylinder inspection device 2 of the present invention to capture a plate surface image (step 120).

  The original image 8 and the plate image of the plate 6 are processed and compared by the defect detection means 30 for each corresponding predetermined area (step 130). Then, the presence / absence of a defect is determined based on a predetermined threshold value, and if there is a cell defect, a warning is displayed on the monitor of the computer 32 or the like, and the corresponding of the gravure cylinder 4 is detected by the laser pointer 40. The location is marked (step 200).

  The worker who has received the report confirms the corresponding part marked with the laser pointer 40 (step 210), and corrects it if possible (step 220). If correction is impossible, the plate material such as a copper plating layer is peeled off (step 230), and laser exposure and plate making are performed again.

  When it is determined by the defect detection means 30 that there is no cell defect (step 140) or when the cell defect is corrected (step 220), the unevenness detection means 50 uses the same color area in the plate image. A plurality of predetermined areas are compared (step 150), and the presence / absence of plate-making unevenness is determined (step 160). If there is unevenness in plate making, a warning is displayed on the monitor of the computer 32 and reported, and the corresponding part of the gravure cylinder 4 is marked with the laser pointer 40 (step 200). The corresponding portion marked with the laser pointer 40 is confirmed (step 210), and if it can be corrected, it is corrected (step 220). If it cannot be corrected, the plate material such as a copper plating layer is peeled off (step 220). 230), laser exposure and plate making are performed again. Note that the determination of the presence or absence of plate making unevenness (step 160) is not necessarily required, and may be omitted if there is little possibility of unevenness during plate making.

  If it is determined by the unevenness detecting means 50 that there is no unevenness in plate making (step 160), the gravure cylinder 4 is finished as a non-defective product.

  Thus, according to the inspection apparatus and method for a gravure cylinder of the present invention, it is possible to accurately detect defects on the outer peripheral surface of the gravure cylinder after plate making, to detect plate making unevenness, and further, It is also possible to reduce proof printing. Further, after the outer peripheral surface of the gravure cylinder 4 after plate making is inspected by the inspection apparatus and method for a gravure cylinder of the present invention, the printing plate image is appropriately colored by using an appropriate software in the computer 32 and simplified. If proof printing is performed, manual proof printing that requires skill can be made almost unnecessary.

It is a schematic explanatory drawing which shows an example of the basic apparatus structure of the inspection apparatus for gravure cylinders of this invention. It is a schematic diagram which shows an example of an original image. It is the principal part enlarged photograph which expands and shows the predetermined area | region of an original image. FIG. 3 is an enlarged photograph of a main part showing a predetermined area of a printing plate image, in which (a) shows a case where there is a cell defect and (b) shows a case where there is no cell defect. 4A and 4B are schematic explanatory views showing the principle of comparison between a predetermined area of an original image and a predetermined area of a plate image, where (a) shows a case where the cell has no defect and (b) shows a case where the cell has a defect. It is a schematic explanatory view showing the principle of error correction of cells in an original image, (a) is a cell before error correction, and (b) is a cell after error correction. It is a flowchart which shows the whole flow of the inspection method for gravure cylinders of this invention.

  2: Inspection apparatus for gravure cylinder, 4: Gravure cylinder, 6: Plate surface, 6b: Plate surface lower part, 6a: Plate surface upper part, 8: Original image, 10: Support means, 11: Signal cable, 12: Servo motor, 12a: Rotation Shaft, 13: signal cable, 14: rotary encoder, 15: signal cable, 20: scanning means, 22: image sensor unit, 22a: sensor head, 23: linear scale, 24: servo motor, 24a: screw shaft, 25: Signal cable, 26: Servo motor, 26a: Screw shaft, 27: Signal cable, 28: Control device, 29: Signal cable, 30: Defect detection means, 32: Computer, 40: Laser pointer, 50: Unevenness detection means, P : Pixel, C: Cell, F: Defect, B: Difference, d: Correction width, C1: Cell before correction, C2: Correction Cell of.

Claims (5)

The laser exposure device used in the plate making and plate-making and fabricating the printing plate image on the outer peripheral surface of the gravure cylinder by forming a cell corresponding to a plate-making information original image bitmap data of the laser exposure apparatus, after the plate-making An inspection apparatus for a gravure cylinder that inspects an outer peripheral surface of a gravure cylinder, wherein a support means for rotatably supporting the gravure cylinder and an outer peripheral surface of the gravure cylinder are scanned to obtain a plate image as plate image bitmap data A scanning means; a defect detecting means for comparing the plate image bitmap data with the original image bitmap data used for plate making to detect a cell defect in the plate image bitmap data ; and the plate image bitmap data Unevenness detection that detects the presence or absence of platemaking unevenness by comparing multiple predetermined areas within the same color area Comprising a stage, and a marking means for performing predetermined marking on the outer circumferential surface of the gravure cylinder corresponding to the defective portion in the detected printing plate image bitmap data by the defect detection means, the defect detecting means, the printing plate image bits A pattern matching process is performed for each predetermined region corresponding to the map data and the original image bitmap data to detect a defect of a cell having a predetermined size or more, and the plate image bitmap data and Prior to the comparison with the original image bitmap data , the error generated when the gravure cylinder is made in advance is corrected, and the error correction is performed for each cell of the original image bitmap data . and characterized by a shrinkage treatment of the cells of expanded processing or printing plate image bitmap data Inspection apparatus for a gravure cylinder that.   2. The inspection apparatus for a gravure cylinder according to claim 1, wherein the scanning means is capable of scanning in the longitudinal direction of the gravure cylinder, the circumferential direction of the gravure cylinder, and the vertical direction of the gravure cylinder. A gravure cylinder inspection method using the gravure cylinder inspection apparatus according to claim 1, wherein the plate surface image bitmap data obtained by scanning the outer peripheral surface of the gravure cylinder after plate making and the original used for plate making are used. An inspection method for a gravure cylinder, comprising comparing image bitmap data and detecting a defect in a cell of the plate image bitmap data . A gravure cylinder inspection method using the gravure cylinder inspection apparatus according to claim 1, wherein the plate surface image bitmap data obtained by scanning the outer peripheral surface of the gravure cylinder after plate making and the original used for plate making are used. comparing the image bitmap data, after detecting a defective cell in said plate plane image bitmap data, comparing among a plurality of predetermined areas in said plate plane image bitmap data of the same color region, detecting the presence or absence of unevenness An inspection method for a gravure cylinder, characterized in that it is made. According to the gravure cylinder inspection method according to claim 3 or 4, after inspecting the outer peripheral surface of the gravure cylinder after plate making, the plate surface image bitmap data is given a predetermined color to perform simple proof printing. An inspection method for a gravure cylinder.