JP2014106069A - Printed matter inspection method and printed matter inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method and an inspection device jointly using a normal inspection process for realizing a comparison process with an image obtained at the time of transportation as a reference image and a plate inspection process for performing a division process of the image in the imposition unit in the transportation direction or in the unit capable of the comparison corresponding thereto.SOLUTION: The inspection performed by a normal inspection process part 41 inspects an image of a frame unit repeatedly printed with the image of the frame unit as a reference image A by means of a comparison process with the reference image A. The inspection performed by a plate inspection process unit 42 inspects an image of the pattern contained in the frame unit as a reference image B by means of the comparison process with the other image. Thereby, the inspection of the printed matter is performed jointly using the above two inspections.

Description

  The present invention relates to a printed matter inspection method and inspection device, and more particularly to a printed matter inspection method and inspection device for inspecting defects caused by a plate of a printed matter to be inspected.

  Examples of the printing method on the original fabric include gravure printing, offset printing, and flexographic printing. Hereinafter, a gravure printing machine will be described as an example. Generally, in a gravure printing machine, after printing a predetermined pattern on a strip-shaped original fabric, the printed material is transported at a predetermined speed, and the printed material is imaged by an imaging means such as a line sensor camera included in the inspection apparatus. The printed material is inspected by determining the presence or absence of defects on the printed material using the obtained image data.

  As a method for determining the presence or absence of defects from the image data of printed matter, a process for determining whether there is a difference by comparing another image obtained by capturing the same pattern with a reference image using a pattern having no defect as a reference image The method of performing is common. In the printed matter inspection apparatus as described above, as shown in FIG. 1, an image of one plate cylinder captured at the time of conveyance is obtained using the characteristics of the printed matter 10 in which the same pattern is repeated at a fixed period of one plate cylinder. A method of using the image as a reference image is conceivable. In this case, if a defect due to the plate (such as a character error) or a scratch on the plate (dirt or missing character) occurs, the reference image itself will be defective. Therefore, it is impossible to detect the presence of a defect such as the dirt 11 or the missing character 12 by the comparison process with the reference image.

  Therefore, for example, Patent Document 1 is known as a conventional technique for imaging a printed matter with a CCD camera or the like and inspecting the printed matter using image data. According to the technique described in Patent Document 1, an image having no defect is imaged in advance, and the image data obtained there is used as a reference image to perform a comparison process with an image captured at the time of conveyance. Therefore, it is possible to detect defects caused by the plate.

Japanese Patent No. 3948866

  However, in the technique described in Patent Document 1, in the case of an inspection apparatus having a plurality of camera units, if a plurality of image data obtained from each unit is not synthesized, a comparison process is performed using reference data produced in advance. It is difficult to realize. When it is intended to combine a plurality of image data and to process such image data at a high speed, it is considered that a large-scale processing circuit is required and the cost is increased.

  In addition, when using reference data produced in advance, it is essential to perform an appropriate position correction on the image data obtained at the time of conveyance. In addition, in order to match the data produced in advance with the data obtained at the time of transport, the influence of the expansion / contraction of the printed matter due to the difference in transport conditions and the change in image quality (brightness / contrast, etc.) due to device deterioration, etc. Cannot be ignored, and as a result, the load of reducing the detection accuracy or adding an extra correction process has occurred.

  In order to solve the above-described problems, the present invention provides (1) a normal inspection process that realizes a comparison process using an image obtained during conveyance as a reference image, and (2) an imposition unit of the image in the conveyance direction, or a method equivalent thereto. It is an object of the present invention to provide an inspection method and an inspection apparatus that use a plate inspection process that performs a division process in units that can be compared.

In order to achieve the above object, the invention of claim 1
The printed matter is imaged by illuminating the printed matter while illuminating the printed matter while conveying the printed matter on the front side, the back side, or both sides of which a plurality of imposition unit patterns are printed in frame units. A printed matter inspection method for determining defects existing in a printed matter using the obtained image data,
Normal inspection processing for comparing images included in other frames using the frame-by-frame image obtained at the time of transport as a reference image A, and comparison processing for other images using a pattern image included in the frame unit as a reference image B A printed matter inspection method characterized in that a printed matter is inspected by a plate inspection process.

In the invention of claim 2,
The printed matter is imaged by illuminating the printed matter while illuminating the printed matter while conveying the printed matter on the front side, the back side, or both sides of which a plurality of imposition unit patterns are printed in frame units. A printed matter inspection apparatus for determining defects existing in a printed matter using the obtained image data,
The normal inspection processing unit that compares the reference image A and the image included in the other frame with the image in the frame unit obtained at the time of conveyance, and the other image with the image of the pattern included in the frame unit as the reference image B A printed material inspection apparatus comprising: a plate inspection processing unit for processing.

  According to the present invention, it is possible to inspect the plate for defects at the same time as the printed matter. Further, since the process using the reference data produced in advance as in the technique described in Patent Document 1 is not performed, the load on the synthesis of image data and various correction processes is reduced, and the cost of the inspection process is reduced.・ High accuracy is possible. In addition, since the two processes are used together, the same image data is used for the normal inspection process and the plate inspection process, so that two inspections can be performed in a single apparatus, which is less expensive than using separate apparatuses. Can be realized. In addition, by performing the inspection for defective plates on the production line in the same way as the inspection of printed matter, it is possible to lead to early detection of defective plates, and it is possible to suppress printing defects.

The figure which shows the printed matter with which the same pattern is repeated with the fixed period for one plate cylinder. 1 is a schematic configuration diagram of a printed matter inspection apparatus of the present invention. The figure which shows the structure of the image processing and defect determination part which concerns on this invention. The figure which shows the example of arrangement | positioning of the imaging part which concerns on this invention, a reflective illumination part, and a permeation | transmission illumination part. Schematic for demonstrating the inspection processing unit of the printed matter which concerns on this invention. The figure for demonstrating the inspection method performed by the normal inspection process part, and the inspection method performed by the plate inspection process part. The figure for demonstrating the method of recognizing the number of impositions by detecting the printing mark printed in the vicinity of the imposition unit. The flowchart which shows an example of the whole operation | movement of the plate inspection process part which concerns on this invention. The figure for demonstrating the operation | movement flow of the plate inspection process part which concerns on this invention.

  Hereinafter, embodiments of a printed matter inspection method and apparatus according to the present invention will be described with reference to the drawings.

  FIG. 2 is an example of a schematic configuration diagram of the printed matter inspection apparatus according to the present embodiment. The printed matter inspection apparatus 1 of the present invention shown in FIG. 2 is a reflection illumination unit that is an illumination unit that illuminates the surface of a printed matter 10 on which images of a plurality of imposition units are printed in frame units on the front surface, back surface, or both surfaces thereof. 20, a transmission illumination unit 21, an imaging unit 30 that is a means for imaging the illuminated printed material surface, and an image for determining defects present in the printed material using image data of the printed material surface obtained by the imaging unit 30 And a processing / defect determination unit 40. As shown in FIG. 3, the image processing / defect determination unit 40 includes a normal inspection processing unit 41 that performs comparison processing of images included in other frames using a frame unit image obtained at the time of conveyance as a reference image A, and a frame unit unit. And a plate inspection processing unit 42 that compares the other images with the image of the pattern included in the reference image B as a reference image B. The printed material 10 is conveyed at a predetermined speed by a printing machine (not shown), and is photographed by an imaging unit 30 configured by a camera unit in synchronization with the speed of the printing machine. Using the captured image data (captured image), the image processing / control unit 40 extracts a defective portion present in the printed matter 10 and automatically determines it.

  When configured with a plurality of camera units, it is convenient to arrange a plurality of image processing / control units 40 in parallel according to the number of the camera units, but the present invention is not limited to this.

  In the normal inspection processing unit 41, in order to inspect all the objects with high accuracy, an image obtained at the time of conveyance is used as a reference image, and comparison processing is executed. Further, as described above, the inspection processing is generally performed in units of frames corresponding to one plate cylinder forming the printed matter 10. The inspection process is centered on the difference process between the reference image obtained at the time of transport and the inspection image to be inspected, the alignment process by pattern matching and normalized correlation, the filtering process such as averaging and maximization, As long as it is possible to reveal defects to be detected by performing a process such as a labeling process for extracting defect information from the binary information obtained in step 2, any processing method can be used. Absent.

  Also in the plate inspection processing unit 42, since the defect to be basically captured is not different from the normal inspection processing unit 41, it is desirable to execute the same or similar processing as the normal inspection processing unit 41. By using the same processing configuration as much as possible, the inspection processing program can be used in common. However, with regard to inspection processing in imposition units, it is assumed that there is a difference in the reproducibility of one surface compared to performing inspection processing in frame units. A processing method for preventing erroneous detection, such as mounting a process separately or providing a certain difference in detection sensitivity, is appropriately provided.

  Here, the printed material 10 moves within the imaging field of view at a predetermined speed. At this time, a signal for each unit distance is obtained from a unit (for example, a rotary encoder that measures the amount of movement while being in contact with a roller that conveys the printed matter 10) that measures the amount of movement of the printed matter 10 attached to the printing press. In some cases, the signal is frequency-divided and sent to the image processing / control unit 40 to perform scanning imaging so as not to be affected by the speed fluctuation of the printing press.

  When the conveyance speed of the printing press can be regarded as constant within the resolution range of the imaging unit 30, a method of obtaining an image only by starting imaging with a trigger signal and imaging at a predetermined time interval may be considered. As described above, imaging that is always synchronized with the conveyance speed of the printing press is preferable because it can cope with speed changes.

In addition, as the raw material of the printed material 10, a material such as a plastic film that easily expands and contracts is often used. When the original fabric of the printed material 10 expands or contracts, even if imaging is performed in synchronization with only the conveyance speed of the printing press, the position reproducibility of the captured image may be affected. Therefore, an imaging unit that takes into account the influence of expansion and contraction of the printed matter 10 is required. Therefore, as described above, for example, it is desirable to perform imaging with the influence of expansion and contraction reduced by bringing a part of the unit for measuring the movement amount into contact with the printed matter 10.

  FIG. 4 is a diagram illustrating an arrangement example of the imaging unit 30, the reflection illumination unit 20, and the transmission illumination unit 21. An imaging lens 32 is attached to the imaging unit 30, and the printed material 10 to be imaged is arranged in the vertical direction.

  In the gravure printing machine, since the printed material 10 is manufactured in a roll shape, the conveyance speed is often constant. In this case, since the imaging target always passes under the imaging unit 30, a line sensor camera is used as the imaging unit 30. However, an area sensor camera can also be used as the imaging unit 30 depending on the type of printing press, particularly the conveyance mode (for example, intermittent conveyance).

  Further, although the imaging unit 30 is arranged perpendicularly to the surface of the printed matter 10, in the case of a line sensor camera, an illumination system capable of obtaining an appropriate image can be realized, and the line sensor camera can be arranged in the horizontal direction. As long as it is possible to image the printed matter 10 at the same distance between the pixels, the printed matter 10 may be arranged with the angle Θ shown in FIG. 4 inclined according to the defect to be extracted. The reflective illumination unit 20 is disposed between the printed material 10 and the imaging unit 30 and includes a first illumination unit 22 that irradiates light on the surface of the printed material 10.

  Any illumination method may be used as the illumination method of the reflection illumination unit 20 as long as the amount of light necessary to obtain an image with brightness suitable for the inspection process can be secured. When a camera is used, an illumination system that can irradiate in a line is suitable. Specifically, a fluorescent lamp, a transmission light, an LED illumination, or the like is selectively used as the reflective illumination unit 20. In addition, the reflection illumination unit 20 is provided with irregular reflection, regular reflection, or both depending on the inspection conditions, but the surface state of the printed matter 10 varies depending on the type of printing press (printing method) and the original fabric. Accordingly, an arrangement for causing the imaging unit 30 to receive an optimal amount of light is appropriately selected.

  In FIG. 4, two first illumination units are integrally arranged in the reflective illumination unit 20. However, even when a plurality of the first illumination units are arranged, it may be stored in separate illumination units. The reflective illumination unit 20 is provided with an imaging slit 31. Specifically, as long as the amount of light received by the imaging unit 30 is not affected, the slit 31 may be a space or a transparent member such as glass or transparent acrylic. In addition, two or more first illumination units 22 may be arranged in order to cause the imaging unit 30 to receive an optimal amount of light or to emphasize and detect a specific defect.

  The transmitted illumination unit 21 is disposed so that the printed material 10 is positioned between the imaging unit 30 and the transmitted illumination unit 21. The transmitted illumination unit 21 includes a second illumination unit 23 that irradiates the back surface of the printed material 10 with light. Any kind of the transmitted illumination unit 21 may be used as long as the amount of light necessary to obtain an image having a brightness suitable for the inspection process can be secured. When using, an illumination system that can irradiate in a line shape is suitable. Specifically, a fluorescent lamp, a transmission light, an LED illumination, or the like can be selected and used as the reflective illumination unit 20.

Further, as a method for ensuring the maximum light amount, the transmitted illumination unit 21 may be arranged linearly (on the extension line of the optical axis of the imaging unit 30) with respect to the imaging unit 30, but this may hinder the detection of defects. If the amount of light that does not occur can be secured, the linear arrangement is not necessary. Further, depending on the type of printing press (printing method) and the original fabric, the transmission illumination unit 21 may not be arranged particularly when using an original fabric having low transparency. However, when attaching to a printing press in which the original fabric is uncertain, it is suitable that the transmission illumination unit 21 can be switched between ON and OFF.

  In addition, two or more second illumination units 23 may be arranged so that the imaging unit 30 receives an optimal amount of light.

  FIG. 5 is a schematic diagram for explaining a print processing unit. The printed material 10 is generally manufactured in a form in which several common patterns are arranged over the entire width and the continuity is not interrupted in the conveying direction. As shown in FIG. 5 (a), the pattern for one plate cylinder for forming the printed matter 10 is a frame unit, and as shown in FIG. 5 (b), one of a plurality of the same patterns is included therein. Expressed as imposition unit. That is, in the case of FIG. 5, there are nine impositions of the same pattern in one frame.

  In a normal inspection process in which an image of a frame unit that is generally performed is used as a reference image, the detection performance of variations between impositions of a plate (for example, line width thickening or thinning in imposition units) is detected. There is a feature that can minimize the degree of influence. Therefore, inspection processing is often performed in units of frames. However, when performing inspection processing in units of frames, if a defect with the same periodicity as the plate itself and the plate (this defect is generally called a common defect) occurs, there is a difference between the reference image and the inspection image. Because there is no, the failure cannot be detected.

  Therefore, in the present embodiment, a normal inspection processing unit that realizes comparison processing using an image in frame units as a reference image A, and a version that realizes comparison processing using images of some of the images included in the frame unit as reference images B. The printed material is inspected by the inspection processing unit. FIG. 6 is a diagram for explaining the inspection method performed by the normal inspection processing unit and the inspection method performed by the plate inspection processing unit.

  Fig.6 (a) shows the pattern for 1 frame (frame unit) of printed matter. FIG. 6B is a diagram in which nine imposition units of the printed material are expressed as M1 to M9. First, the inspection performed by the normal inspection processing unit 41 performs an inspection by comparing the frame-by-frame image of M1 to M9 with the reference image A and the frame-by-frame image repeatedly printed with the reference image A. The inspection performed by the plate inspection processing unit 42 is an inspection in which a pattern image included in a frame unit is compared and inspected as a reference image B. Specifically, for example, M1 is set as a reference image B-1, and M2, M3 , M5 and M6 are inspected using M4 as a reference image B-2, and M8 and M9 are similarly inspected using M7 as a reference image B-3. In this case, how to select the reference image B is not particularly limited, and may be appropriately selected according to the size of the pattern in the imposition unit and the processing speed of the inspection apparatus. In this case, the reference images B-1, B-2, and B-3 may be fixed from the start of printing or may be updated for each frame.

  Apart from the method of detecting defects due to plate defects using the actually printed image as the reference image B, reference data other than the actual transport image is used as means for detecting plate defects. It is also possible to take a method (for example, create a reference image from the pattern information of the plate), but when using multiple camera units to improve detection performance, the image data of each camera unit A mechanism for integrating and synthesizing is required, and the extra load increases.

  In addition, when dividing and comparing processing into small areas in the imposition unit including the width direction, when using multiple camera units, the image data of each camera unit is integrated as when using the reference data. -A mechanism for synthesizing is required, and the extra load increases. In addition, there is a disadvantage that the number of operations for the inspection process increases according to the number of impositions.

  However, if the inspection process is limited only by imposition in the transport direction, the disadvantage that the number of operations for the inspection process mentioned above increases when the number of impositions is large cannot be avoided. Therefore, without limiting the inspection process only by imposition in the transport direction, if the number of impositions is large, a constant multiple of the imposition number is used as a division unit so that it is less than the entire frame. It is desirable to adopt a configuration with a low load.

  For example, in FIG. 6, the imposition unit M1 is the reference image B-1, the imposition unit M4 is the reference image B-2, and the imposition unit M7 is the reference image B-3. You may inspect as a unit. That is, an image obtained by combining imposition units M1, M4, and M7 may be used as a reference image, and compared with an image obtained by combining M2, M5, and M8, and may be compared with an image obtained by combining M3, M6, and M9.

  As described above, regarding how to divide the imposition unit with respect to the number of impositions, the method of designing according to the ability of the device to process is considered optimal, and therefore, no particular method is particular about it.

  Methods for recognizing the number of impositions include a method for artificially specifying the number of impositions in advance, a method for detecting periodicity using captured images, an optical sensor that can directly measure the original fabric, etc. (For example, the number of impositions is recognized by detecting the printed mark 43 printed in the vicinity of the imposition unit as shown in FIG. 7), but the recognition method is limited. is not.

  In addition, when dividing an image in imposition units, if the same periodicity can be obtained in each image in the state after the division, inconvenience occurs when performing a specific comparison process. Because there is no, detailed reproduction of imposition is not necessary. That is, as long as the periodicity matches, it is possible to perform the comparison process even in a state where the impositions are cut out.

  Further, in most cases of defect occurrence in plate inspection, defects continuously occur at the same cycle as the plate, and therefore it is assumed that defect information is duplicated even if all the pieces are inspected. Therefore, it is possible to incorporate a mechanism such as limiting the number of inspections for rationalization or eliminating redundant defect information (specifically, inspection is performed on all printed frames). Instead, for example, a plate defect can be inspected even if it is inspected once every 10 frames). As described above, for example, when a configuration that does not require inspection every time is performed, it is possible to gently set time restrictions for inspection and processing as compared with the 100% inspection. If time restrictions are relaxed, it is not necessary to perform high-speed arithmetic processing on a large scale, and it may be possible to realize systemization at low cost.

  FIG. 8 is a flowchart showing an example of the overall operation of the plate inspection processing unit 42 according to the present invention. The overall flow of the plate inspection processing unit 42 will be described with reference to the flowchart of FIG. 8 and a diagram for explaining the operation flow of FIG. The image captured by the imaging unit 30 is input to the image processing / control unit 40 in units of frames (step S1).

  The image data obtained in units of frames is divided vertically with respect to the transport direction according to a predetermined number of divisions (step S2). In this case, for example, (M1, 2, 3), (M4, 5, 6) and (M7, 8, 9) are divided into three (FIG. 9A).

A predetermined comparison process is performed for each of the divided images (step S3). In step 3, one of the divided images is used as a reference image (for example, (M1,2,3) is used as a reference image), and the remaining images ((M4,5,6) and (M7,8,9)). ) Is used as a test image. As a specific processing method, for example, (M1, 2, 3) is changed to (M4, 5, 6) and (
M7, 8, and 9) are also rearranged as a reference image (FIG. 9B), and an image before division is processed as an inspection image in a frame unit ((FIG. 9B is referred to as a reference image). 9 (c) is compared as an inspection image), and all the cases where all the divided images are selected once as a reference and inspection image as a response to a case where a defect enters the selected reference image. However, the method is not limited to the above method as long as the entire frame can be inspected at least once and plate inspection can be realized over the entire area.

  Defective information such as incompleteness of plate making contents and scratches on the plate is detected and quality is determined (step S4). A defect detection process is performed by a comparison process with the reference image. At this time, in step 4, the finally obtained image is binarized and multi-valued to extract a defective part.

  The determination information and the detected defect information are aggregated and transferred in real time (step S5). The transfer destination varies depending on the specifications of the information integration / display unit of the inspection apparatus.

  According to the printed matter inspection method and inspection apparatus according to the present invention, the normal inspection processing that realizes high-speed processing using the image obtained at the time of conveyance as the reference image A, and the imposition unit in the conveyance direction or several surfaces of the captured image A plate inspection process is used in combination with the reference image B as the combination of the attachments.

  Thereby, in the present embodiment, it is possible to simultaneously inspect the inspection of the printed matter of the inspection apparatus and the defect caused by the plate, reduce the load on image data synthesis and various correction processes, and reduce the cost in the inspection process. High accuracy is possible. In addition, by performing the inspection for defective plates on the production line in the same way as the inspection of printed matter, it is possible to lead to early detection of defective plates, and it is possible to suppress printing defects.

DESCRIPTION OF SYMBOLS 1 ... Printed product inspection apparatus 10 ... Printed product 11 ... Dirt 12 ... Character missing 20 ... Reflection illumination part 21 ... Transmission illumination part 22 ... 1st illumination part 23 ... Second illumination unit 30 ... imaging unit 31 ... imaging slit 32 ... imaging lens 39 ... camera acquired image 40 ... image processing / control unit 41 ... normal inspection processing unit 42: Plate inspection processing unit 43: Print marks M1 to M9: Imposition unit

Claims (2)

The printed matter is imaged by illuminating the printed matter while illuminating the printed matter while conveying the printed matter on the front side, the back side, or both sides of which a plurality of imposition unit patterns are printed in frame units. A printed matter inspection method for determining defects existing in a printed matter using the obtained image data,
Normal inspection processing for comparing images included in other frames using the frame-by-frame image obtained at the time of transport as a reference image A, and comparison processing for other images using a pattern image included in the frame unit as a reference image B A printed matter inspection method comprising: inspecting a printed matter by performing plate inspection processing. The printed matter is imaged by illuminating the printed matter while illuminating the printed matter while conveying the printed matter on the front side, the back side, or both sides of which a plurality of imposition unit patterns are printed in frame units. A printed matter inspection apparatus for determining defects existing in a printed matter using the obtained image data,
The normal inspection processing unit that compares the reference image A and the image included in the other frame with the image in the frame unit obtained at the time of conveyance, and the other image with the image of the pattern included in the frame unit as the reference image B A printed matter inspection apparatus comprising: a plate inspection processing unit for processing.

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