JP2012154830A - Inspection method and inspection apparatus of printed matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method using normal inspection processing for achieving high-speed processing in each single camera unit by using an image obtained in conveyance as a reference image together with version inspection processing for combining images of a plurality of camera units by using a previously prepared image as a reference image.SOLUTION: The inspection method of a printed matter of which the surface, rear face or both faces are printed and conveyed includes: an illumination step for applying illumination to the surface of the printed matter and/or the rear face of the printed matter; an imaging step for imaging the printed matter synchronously with the conveyance of the printed matte or after a predetermined time interval; and an image processing/defect determination step for determining a defect existing in the printed matter by using image data of the printed matter obtained in the imaging step. The image processing/defect determination step includes a normal inspection step for achieving processing by using the image obtained in conveyance as the reference image and a version inspection processing step for achieving processing by using the previously prepared image as the reference image.

Description

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

Examples of the printing method on the substrate include gravure printing, offset printing, and flexographic printing. Hereinafter, a gravure printing machine will be described as an example.
In general, in a gravure printing machine, a belt-like printed material obtained by printing on an original fabric is conveyed, and an image of the printed material is imaged by an imaging means such as a line sensor camera included in the inspection apparatus, and image data obtained at that time is obtained. Based on the inspection.

In such a printed matter inspection apparatus, a method of using an image obtained by an imaging means as image data for determining pass / fail is known.
When inspecting an image obtained at the time of conveyance as reference data, if the plate making contents of the plate are incomplete or the plate is scratched, the reference data itself is defective.

  Here, as a method for imaging a printed matter with a CCD camera or the like and inspecting the printed matter using image processing, for example, Patent Document 1 is known as a prior art. By the technique described in Patent Document 1, it is possible to inspect using image data that has been produced in advance.

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 pieces of image data are not combined at the time of image input, image processing using a reference image that has been produced in advance is performed. It is difficult to realize. In addition, when it is desired to combine a plurality of image data and to perform high-speed processing of such image data, it is necessary to build a large-scale image processing circuit, and the image in the entire inspection apparatus. It can be considered that the cost load of the processing circuit is increased.

  In order to solve the above-mentioned problems, the present invention provides a normal inspection process that realizes high-speed processing for each single camera unit using the image obtained at the time of conveyance as a reference image, and a plurality of camera units using a pre-manufactured image as a reference image. It is an object of the present invention to provide an inspection method using a plate inspection process for combining images.

In order to achieve the above object, the invention of claim 1
A method for inspecting a printed material that is printed on a front surface, a back surface, or both surfaces thereof,
An illumination stage for illuminating the print surface or / and the print back surface;
An imaging step of capturing the printed matter in synchronization with the conveyance of the printed matter or at a predetermined time interval;
Using image data of the printed matter obtained in the imaging step, and image processing / defect judging step for judging defects present in the printed matter,
The image processing / defect determination step includes a normal inspection step for realizing processing using the image obtained at the time of conveyance as a reference image, and a plate inspection processing step for realizing processing using a pre-made image as a reference image. This is a printed matter inspection method.

In the invention of claim 2,
An inspection device for printed matter on which printing is performed on the front surface, the back surface, or both surfaces thereof,
First illumination means for illuminating the surface of the printed matter;
Second illuminating means for illuminating the back of the printed matter;
Imaging means for imaging the surface of the printed matter at a predetermined time interval or synchronized with the conveyance of the printed matter;
Using image data on the surface of the printed matter obtained in the imaging step, and image processing / defect judging means for judging defects present in the printed matter,
The image processing / defect determination means includes
Normal inspection means for realizing processing using the image obtained at the time of conveyance as a reference image;
Plate inspection processing means for realizing processing using an image produced in advance as a reference image;
It is an inspection apparatus of printed matter characterized by having.

  According to the present invention, normal inspection processing that realizes high-speed processing for each single camera unit using the image obtained at the time of transport as a reference image, and combining processing of images of a plurality of camera units using a pre-manufactured image as a reference image. By using the plate inspection process in combination, it is possible to simultaneously inspect the printed matter of the inspection apparatus having a plurality of camera units and defects due to the plate.

It is a schematic block diagram which shows the inspection apparatus of the printed matter which concerns on this invention. It is a figure which shows the structural example of the imaging part which concerns on this invention, a reflective illumination part, and a drop illumination part. It is an example of the imaging part which has the several camera unit which concerns on this invention. It is the example of an image which acquired the image of the printed matter, and the printed matter by a plurality of image pick-up parts. It is the schematic diagram which showed the transfer path | route of the image output from the imaging part which concerns on this invention. It is the flowchart which showed the whole operation | movement of the synthetic | combination calculating part 43 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. 1 is a schematic configuration diagram illustrating an example of a printed matter inspection apparatus 1 according to the present embodiment. FIG. 1 shows an example in which a printed material printed on one surface of the printed material is inspected. As shown in FIG. 1, a printing machine (not shown) moves the printed material 10 at a predetermined speed, and the inspection device 1 synchronizes with the speed of the printing machine and images the surface of the printed material 10, and the printed material 10. Image data (captured image) obtained by imaging the surface of the printed material 10 by the imaging unit 30 and the reflective illumination unit 20 that irradiates light on the surface of the image, the transmission illumination unit 21 that irradiates light on the back surface of the printed material 10 And an image processing / control unit 40 that extracts and automatically determines a defective portion present in the printed matter 10.

Here, since the printed matter 10 moves at a predetermined speed, the image is picked up by the image pickup unit 30 when passing through the image pickup region of the image pickup unit 30. At this time, a signal for each unit distance is obtained from a unit that accurately measures the amount of movement of the printed material 10 attached to the printing press, and the signal is divided and distributed to the image processing / control unit 40 according to circumstances. Thus, scanning imaging is performed by the imaging unit 30 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, it is more reliable to always perform imaging in synchronization with the conveyance speed of the printing press.

  In addition, as the material of the original fabric of the printed material 10, an original fabric that tends to expand and contract such as a plastic film is often used. When expansion / contraction occurs in the original fabric of the printed matter 10, there is a possibility that the captured image is affected even if the imaging is performed in synchronization with the speed of the printing press. Therefore, in addition to the conveyance speed of the printing press, measurement in consideration of the expansion and contraction of the printed material 10 is necessary. For example, by adopting a measurement method in which a part of the printed material 10 is brought into contact, the influence of expansion and contraction can be reduced.

  FIG. 2 is a diagram illustrating a configuration example of the imaging unit 30, the reflective 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 by being wound into a roll, the conveyance speed is often a constant speed. 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 machine, particularly the conveyance mode such as 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 at an angle Θ shown in FIG. 2 (other than 90 °). 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 light source can be used for the reflective illumination unit 20 as long as it can secure an amount of light with which an image that can be appropriately processed can be obtained. However, when a line sensor camera is used for the imaging unit 30, irradiation is performed in a line shape. Possible lighting systems are suitable. Specifically, a fluorescent lamp, a transmission light, an LED illumination, or the like is selectively used as the reflective illumination unit 20. The reflection illumination unit 20 may be arranged to select one of them depending on the original fabric of the printed matter 10 while arranging irregular reflection, regular reflection, or both, but the type of printing machine (printing method) and the original Any arrangement may be selected depending on the contrary.

  Further, two or more first illumination units 22 may be arranged so that the imaging unit 30 receives an optimal amount of light. In addition, when a fluorescent lamp is employed for the reflective illumination unit 20, a reflective member may be disposed around the reflective illumination unit 20 to increase the amount of light. 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.

  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 light can be used for the transmissive illumination unit 21 as long as an amount of light capable of obtaining an image that can be appropriately processed can be secured. However, when a line sensor camera is used for the imaging unit 30, irradiation is performed in a line shape. Possible lighting systems are suitable. Specifically, a fluorescent lamp, a transmission light, an LED illumination or the like is selectively used as the transmissive illumination unit 21.

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.

  Further, in order to cause the imaging unit 30 to receive an optimal amount of light, two or more second illumination units 23 that emit white light may be arranged. In addition, when a fluorescent lamp is employed for the reflective illumination unit 20, a reflective member may be disposed around the reflective illumination unit 20 to increase the amount of light.

  FIG. 3 is an example of an imaging unit having a plurality of camera units. FIG. 3 shows an example of two camera units, but the number of camera units is not particularly limited. The imaging unit 300 on the left side in FIG. 3 is referred to as camera A, and the imaging unit 301 on the right side in FIG. In general, when an image is acquired by a plurality of camera units, both imaging areas are often overlapped as shown in FIG. This is because when there is no overlapping area, there is a possibility that the size of a defect occurring at the boundary is halved.

  FIG. 4 shows an image of a printed matter (FIG. 4A) and an example of an image (FIG. 4B) obtained by acquiring the printed matter with an imaging unit having a plurality of camera units. FIG. 4 shows an example in which images are acquired by two camera units as shown in FIG. Note that the left end portion of the acquired image by the camera A and the right end portion of the acquired image by the camera B indicate images outside the printed region A and B, respectively.

  FIG. 5 is a schematic diagram illustrating a transfer path of an image output from the imaging unit 30. Images acquired by the respective camera units as shown in FIG. 5 are sent to the image processing control unit 40. The image processing control unit 40 includes an image calculation unit (for camera A) 41, an image calculation unit (for camera B) 42, and a synthesis calculation unit 43. In the case of being configured with two or more camera units, the image calculation unit is configured according to the number. The image captured by each camera unit has a configuration capable of sending the same image to the image processing unit for single processing and the composition processing unit 43 for composition processing.

  In the image processing unit for single processing, the image obtained at the time of conveyance is used as a reference image, and inspection processing is executed. When the image obtained at the time of conveyance is used as the reference image, the difference in the image from the inspection object is very small, so that a high-precision inspection can be performed. The difference in image is the effect of positional deviation between the reference image and the inspection image due to mechanical installation error that occurs when installing the plate cylinder, and the increase gradation value due to the effect of the light emission wavelength of the illumination and the image sensor sensitivity of the camera. And differences in image gradation values due to product variations.

  When these differences are corrected by image processing, there may be a waste of having to provide an additional processing circuit for correction, and anxiety about speeding up due to an increase in processing amount. Further, the correction processing circuit tends to be easily affected by noise and variation due to the correction processing, and thus has an essential problem that the ability to detect an original defect cannot be enhanced. Therefore, in the image processing unit for single processing, an image obtained at the time of conveyance is used as a reference image, and inspection processing is performed, thereby realizing highly accurate inspection. For image processing for single processing, based on the difference processing between the reference image and the inspection image, perform processing such as alignment processing such as pattern matching and normalized correlation, filtering processing such as averaging and maximization, etc. As long as it is possible to make a defect to be detected by the above method obvious, it does not matter which method is adopted.

However, when the image obtained at the time of conveyance is used as a reference image, if the plate making content of the plate is incomplete or the plate is scratched, the image to be used as a reference is already in a defective state, and the defect is not detected in the inspection image. Since this occurs in the same manner, a difference between the reference image and the inspection image cannot be obtained, and a defect cannot be detected.

  Therefore, as shown in FIG. 5, a composition processing unit 43 for composition processing arranged in parallel with the image processing unit for single processing is arranged. In the composition calculation unit 43, an image manufactured in advance is used as a reference image, thereby preventing a defect from entering the image to be used as a reference.

  Pre-produced images are data created during plate making, and when printing the same product, the previous printing and pre-printing camera on the premise that it is known that there is no defect caused by the plate An image captured by the unit can be considered. As long as it is possible to detect defects caused by the plate, any image is not particularly used. If product type information management is possible, the accuracy and reliability can be improved by using a method that uses data that is created at the time of plate making at the first time, and the image that was picked up at the previous printing in the second and subsequent printing. be able to.

  The image captured by the camera unit at the time of the previous printing is the effect of positional displacement due to mechanical installation errors that occur when installing the plate cylinder, and the difference in the increment gradation value due to the effect of the light emission wavelength of the illumination and the image sensor sensitivity of the camera This is useful for improving accuracy and reliability.

(Operation, action, etc.)
FIG. 6 is a flowchart showing the overall operation of the composition calculation unit 43. A known overlapping region is removed from the images input from the camera A and the camera B (step S1).

  The two pieces of image data obtained after the removal are combined so that the boundary portions coincide (step S2). In step 2, processing for reconstructing images obtained by a plurality of camera units as one image is performed.

  Position correction of the synthesized image and the reference image that has been produced in advance is performed (step S3). In Step 3, a correction process is performed to absorb a positional deviation due to a mechanical installation error that occurs when installing the plate cylinder, a positional deviation in the conveyance direction due to a difference in imaging timing, and the like.

  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 mainly by a comparison process with a reference image. At this time, in step 4, the finally obtained image is binarized and multi-valued to extract a defective part.

  Since the composition calculation unit 43 receives image data from an imaging unit having a plurality of camera units and realizes processing, it requires a larger scale process than the image calculation unit for single processing in one camera unit. Conceivable. Processing with a large-scale circuit is expensive in terms of cost, and the printed matter 10 that is printed one after another is always processed, and when high-speed conveyance is performed, the processing time is often limited.

  However, it is possible to reduce the load on the composition calculation unit 43 by specializing the defect to be detected as a defect such as an incomplete plate making content or a scratch on the plate. If the defect to be detected is an incomplete plate-making process or a scratch on the plate, it can be said that the object to be inspected by one printing is sufficient for one plate regardless of whether there is a defect.

  Therefore, it is desirable that the composition calculation unit 43 does not always execute the inspection process continuously, but only needs to execute the process once from the start to the end of printing. With this configuration, there is no need to consider processing time restrictions. In addition, for example, a large-capacity image data can be segmented and processed to reduce the circuit scale. Further, when there is no restriction on the processing time, there is a capacity for executing a process that affects the time many times, so that a more accurate detection process can be realized.

(Effect of this embodiment)
In this embodiment, a normal inspection process that realizes high-speed processing for each single camera unit using the image obtained at the time of conveyance as a reference image, and a version that combines images of a plurality of camera units using a pre-made image as a reference image. The inspection process is used together.

  As described above, according to the printed matter inspection method and inspection apparatus according to the present invention, it is possible to simultaneously inspect the printed matter of the inspection device having a plurality of camera units and the defect caused by the plate, and as a result, the printed matter. In addition to determining 10 inspections with high accuracy, it is possible to determine plate-derived defects with high accuracy.

DESCRIPTION OF SYMBOLS 1 ... Inspection apparatus 10 of printed matter ... Printed matter 20 ... Reflection illumination part 21 ... Transmission illumination part 22 ... First illumination part 23 ... Second illumination part 30 ... Imaging part 31 ... Imaging slit 32 ..Lens 40 for image pickup .... Image processing / control unit 41..Image calculation unit (for camera A)
42..Image calculation unit (for camera B)
43..Compositing operation unit 300..Left side imaging unit (camera A)
301 .. Imaging unit installed on the right side (Camera B)

Claims (2)

A method for inspecting a printed material that is printed on a front surface, a back surface, or both surfaces thereof,
An illumination stage for illuminating the print surface or / and the print back surface;
An imaging step of capturing the printed matter in synchronization with the conveyance of the printed matter or at a predetermined time interval;
Using image data of the printed matter obtained in the imaging step, and image processing / defect judging step for judging defects present in the printed matter,
The image processing / defect determination step includes a normal inspection step for realizing processing using the image obtained at the time of conveyance as a reference image, and a plate inspection processing step for realizing processing using a pre-made image as a reference image. A method for inspecting printed matter. It is an inspection device for printed matter that is printed on the front surface, the back surface, or both surfaces, and conveyed.
First illumination means for illuminating the surface of the printed matter;
Second illuminating means for illuminating the back of the printed matter;
Imaging means for imaging the surface of the printed matter at a predetermined time interval or synchronized with the conveyance of the printed matter;
Using image data on the surface of the printed matter obtained in the imaging step, and image processing / defect judging means for judging defects present in the printed matter,
The image processing / defect determination means includes
Normal inspection means for realizing processing using the image obtained at the time of conveyance as a reference image;
Plate inspection processing means for realizing processing using an image produced in advance as a reference image;
An inspection apparatus for printed matter, comprising: