JP4260001B2 - Inspection method of printed matter - Google Patents

Description

  The present invention relates to a method for inspecting an abnormal portion occurring in a transparent or translucent sheet-like printed material used for a packaging material such as an adhesive tape or food / medicine, which is printed in two colors of single color and white. .

  Various types of adhesive tapes, packaging materials for foods and pharmaceuticals, and the like, which are printed on a transparent or translucent sheet such as the product name, expiration date, and precautions, are known. There are various types of printing depending on the product, and some are printed in a plurality of colors. When inspecting abnormal parts of these sheet-like printed matters (dirt on the surface of printed matter, foreign matter such as dust mixed in the printed matter), it is necessary to inspect the influence of the printed part. In order to remove the print portion, there are a method of inspecting the entire surface by erasing the print portion (erasing the color information of the print portion) and a method of inspecting the print portion by excluding it from the inspection target.

  As a method for erasing and inspecting the print part, when the print part is composed of only a single color print, there is a method of erasing the print part using a light source or an optical filter having the same color (wavelength) as the color of the print part. Are known. In addition, when printing of a plurality of colors (colors of visible light) is present in the printing unit, a method of erasing all the color information of the printing unit using infrared light is known (for example, patent document) 1). In addition, when a portion other than the printing portion of the sheet is a transparent body, a method of erasing the printing portion by arranging a background member having the same color as the printing portion on the back of the sheet-like printing is also known.

On the other hand, as a method of inspecting the printing unit by excluding it from the inspection target, a method of inspecting the printing unit by detecting the printing unit by so-called pattern matching and masking the detected printing unit, or the printing unit periodically in the longitudinal direction. A method of masking the printed portion at the time of the current inspection based on the captured image when the previous printed portion was inspected with respect to the arranged sheet-like test materials is known (for example, see Patent Document 2).
JP 2003-4647 A Japanese Patent No. 2597370

  However, in the case of a sheet-like printed matter on which printing of two colors of single color and white is performed, as described above, single-color illumination of visible light or infrared light is used, or only light of a specific wavelength is transmitted by an optical filter. Even if this method is used, the white print portion cannot be erased (color information cannot be erased). In addition, by arranging the white background member, the white print portion can be erased, but the monochrome print portion cannot be erased (color information cannot be erased).

  On the other hand, when applying a method of inspecting a printing unit by excluding it from the inspection target, the method of detecting the printing unit using pattern matching and masking the detected printing unit increases the processing time required for the mask and increases the efficiency. There is concern that good inspection cannot be performed. Further, the method described in Patent Document 2 is poor in versatility because it is a condition that the printing units are periodically arranged.

  The present invention has been made to solve such a problem of the prior art, and is capable of accurately and efficiently correcting abnormal portions occurring in a transparent or translucent sheet-like printed matter on which printing of two colors of single color and white is performed. It is an object to provide a method that can be well inspected.

In order to solve the above problems, the present invention uses a first illumination unit, an imaging unit, and an image processing unit to detect an abnormal portion that occurs in a transparent or translucent sheet-like printed material on which printing of two colors of single color and white is performed. An arrangement step of arranging a background member of the same color as the monochrome or a white background member on either one of the front and back surfaces of the printed matter, and the monochrome in the arrangement step When arranging the background member of the same color, the single color printed on the sheet-like printed matter by irradiating light of the same color as the single color from the first illumination means to the other surface side of the printed matter When the reflected light from which the white color information is erased is received by the imaging means , or when the white background member is arranged in the arranging step, the other surface of the printed matter is transferred from the first illumination means. White against side Of by irradiating light to erase the white color information printed on a printed material for the reflected light, and reflected light of the same color and the monochrome of the white reflected light color information is erased, by passing an optical filter that transmits only monochromatic color, to erase the color information of the monochromatic printed on the sheet-like printed material, comprising the steps of: receiving light at the imaging unit, an imaging captured by the image pickup means And a step of detecting an abnormal portion by subjecting the image to image processing by the image processing means. The present invention provides a printed matter inspection method (hereinafter referred to as a first inspection method as appropriate).

  According to such an invention, when a background member having the same color as the single color is arranged on either one of the front and back surfaces of the printed matter, the background and the monochrome print are the same color, and the image is picked up by the image pickup means. The single color information is deleted from the captured image. At that time, since the background color of the white printing unit is the same as a single color, the white color information is not erased in the captured image captured by the imaging unit as it is. However, since the light of the same color as the single color is irradiated from the first illumination unit to the other surface side of the printed matter, the white printed portion is also set to the same color as the single color and is captured by the imaging unit. In this case, the white color information is also deleted. On the other hand, when the white background member is disposed on either one of the front and back surfaces of the printed material, white light is irradiated from the first illumination unit to the other surface side of the printed material. By doing so, the white background, the white illumination, and the white printing are the same color, and the white color information is erased in the captured image captured by the imaging unit. At this time, since the monochrome printing unit has a white background color and white illumination, the monochrome color information is not erased in the captured image captured by the imaging unit as it is. However, the reflected light of the same color as the single color out of the reflected light from the white light irradiated on the other surface side of the printed material is received by the imaging means through the optical filter that transmits only the single color light. Therefore, the single color information is also erased in the captured image captured by the imaging means. In order to receive the reflected light of the same color as that of the single color printing portion of the reflected light by the imaging unit, for example, an optical filter that transmits only the single color light may be disposed in front of the imaging unit. As described above, according to the present invention, it is possible to simultaneously erase the color information of the two-color printing portion of single color and white, and it is possible to inspect the abnormal portion with high accuracy without the influence of the printing portion. Furthermore, according to the present invention, since it is not necessary to detect the printing unit using pattern matching or the like, there is an advantage that the inspection efficiency is excellent.

  In the first inspection method, preferably, the background member is transmissive, and the second illumination unit irradiates light on one surface side of the printed matter through the background member. Composed.

  When the abnormal part is located below the printing part (on one side of the printed material) when viewed from the direction of light irradiation by the first illumination means (that is, the other surface side of the printed material), the abnormal part is Therefore, it is difficult for the imaging unit to receive the reflected light from the abnormal part, and it is difficult to detect the abnormal part. In other words, if only the reflected illumination by the first illumination unit is used, it is difficult to detect the abnormal portion on the back surface of the printing unit (for example, the white printing unit). In order to solve this, it is sufficient to employ a configuration in which an illumination unit and an imaging unit that captures reflected light are arranged on each of the front and back surfaces of the printed matter. However, the space and cost required to install these units increase. Have the problem of

  In this regard, according to the invention, the background member is assumed to be transmissive, and light is irradiated to one surface side of the printed matter through the background member by the second illumination unit. The light passes through the printed matter, is emitted from the other surface side of the printed matter, and is received by the imaging means. If the abnormal portion located below the printed portion has light shielding properties, the second By the transparent illumination from the background side by the illuminating means, it is possible to reveal the abnormal part having a light shielding property, and thus it is possible to detect the abnormal part that has been revealed. As described above, according to the present invention, since only the second illumination unit is newly arranged and the first illumination unit and the imaging unit are used together, an increase in necessary space and cost can be suppressed. It is also possible to detect an abnormal part located below the printing part (on one side of the printed matter) with high accuracy.

  According to the present invention, in a transparent or translucent sheet-like printed material on which printing of two colors of single color and white color is performed, the influence of the printing portion can be removed, and an abnormal portion generated in the printed matter can be accurately and efficiently obtained. It is possible to inspect well.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
<First Embodiment>
First, a first inspection method for detecting an abnormal portion by simultaneously erasing the color information of the printing portion of the single color and the white color will be described. FIG. 1 is a schematic configuration diagram showing an embodiment of an inspection apparatus for carrying out the first inspection method according to the present invention. As shown in FIG. 1, an inspection apparatus 10 according to the present embodiment receives an illumination unit 1 for irradiating light to a sheet-like printed matter S to be inspected, and reflected light L from the printed matter S to receive the printed matter S. And an image processing unit 3 for performing image processing on the captured image of the printed matter S imaged by the imaging unit 2. Furthermore, the inspection apparatus 10 according to the present embodiment includes a transport unit 4 for transporting the printed material S, and the light irradiation surface side (front surface side in the present embodiment) and the opposite side (back surface side in the present embodiment) of the printed material S. The background plate 5 or the white background plate 5 ′ having the same color as the single color, the optical filter 6 that transmits only the same color light as the single color printing unit S2, and the optical filter 6 in front of the imaging unit 2 And a filter arrangement device 7 that can be selectively arranged at the optical path position A on the optical path of the reflected light L from the printed matter S and at the retracted position B that retracts from the optical path position A.

  FIG. 2 is a diagram schematically illustrating an example of the printed matter S to be inspected. As shown in FIG. 2, the printed matter S is obtained by forming a monochromatic printing part S2 and a white printing part S3 on a transparent or translucent sheet S1. The printed matter S of the example shown in FIGS. 1 and 2 is a piece obtained by cutting or punching a continuous sheet, but as described later, it should be inspected as a continuous sheet. Is also possible.

  The transport unit 4 according to the present embodiment is formed of belt conveyors 41 and 42 because the printed material S to be inspected is an individual piece, and the printed material S is transported on the belt conveyors 41 and 42. become. More specifically, if the printed matter S is imaged on the belts of the belt conveyors 41 and 42, the contamination of the belt is also imaged at the same time. The belt conveyors 41 and 42 are juxtaposed in the transport direction, and the printed matter S positioned in the gap is imaged. If the interval between the belt conveyors 41 and 42 is long, the printed matter S flutters in the inspection area (imaging area), and a stable image cannot be obtained. It is preferable to make it as narrow as possible in a range where no image is taken.

  When the background plate 5 having the same color as the single color is arranged on the back side of the printed matter S, the background plate 5 is arranged for erasing the color information of the single-color printing portion S2 of the printed matter S. When the background plate 5 ′ is arranged, it is arranged for erasing the color information of the white printing portion S 3 of the printed matter S. Here, when the printed matter S and the background plates 5 and 5 ′ come into contact with each other, there arises a problem that the printed matter S is damaged or the background plates 5 and 5 ′ are stained. Therefore, it is necessary to maintain a certain interval so that the printed matter S and the background plates 5 and 5 ′ do not contact each other. In the present embodiment, as shown in FIG. 1, the background plates 5 and 5 ′ are disposed below the belt surface in the gap between the roll 41 </ b> R of the bell conveyor 41 and the roll 42 </ b> R of the belt conveyor 42. As a result, the background plates 5 and 5 ′ are kept at a constant distance that does not contact the printed material S.

  The illumination part 1 is arrange | positioned above the conveyance part 4, and irradiates light to the printed matter S as mentioned above. The illumination part 1 which concerns on this embodiment is comprised so that the light of the same color as the monochrome printing part S2 of the printed matter S and white light may be irradiated.

  A so-called line sensor camera is used as the imaging unit 2 according to the present embodiment. When inspecting individual products like the printed matter S according to the present embodiment, a two-dimensional camera is often used. However, as described above, if dirt is present in the background conveying unit 4, it may be erroneously detected as an abnormal part. Therefore, in this embodiment, a line sensor camera is used for the imaging unit 2 and the imaging field of view is set to the gap between the belt conveyors 41 and 42 so that the conveyance unit 4 is not imaged. Since the printed matter S is conveyed in one direction (direction indicated by an arrow in FIG. 1) by the conveying unit 4, the area of the printed matter S within the imaging field of the imaging unit 2 changes sequentially, and the entire surface of the printed matter S is changed. It will be imaged. The signal output from the imaging unit 2 is A / D converted and input to the image processing unit 3 as image data.

  The image processing unit 3 detects an abnormal part by performing image processing on the image data captured by the imaging unit 2. FIG. 3 is a block diagram illustrating an example of image processing performed in the image processing unit 3. As shown in FIG. 3, in the image processing unit 3, first, noise removal processing 31 is performed on the captured image data as preprocessing. A specific method of the noise removal process 31 may be appropriately determined according to the properties of the image data. For example, in the case of a rough image, if the smoothing process is performed or if it is known in advance that the abnormal portion is only a dark spot (a pixel whose density value is smaller than that of a pixel corresponding to a normal imaging surface),・ Expand / shrink processing when removing bright points (pixels with density values larger than those corresponding to normal imaging surfaces) by performing expansion processing or when it is known in advance that the abnormal part is only a bright point For example, a process of removing dark spots by applying the above-described method is conceivable. In the contraction / expansion process (opening process), the minimum value of the neighboring pixels is set to the corresponding pixel value in each pixel of the image (similar to the contraction process in the binary image), and then the maximum value of the neighboring pixels is set. Relevant pixel values are set (expansion processing in a binary image). This process erases the bright spot.

  Next, the image processing unit 3 detects an abnormal part based on the image data on which the noise removal process 31 has been performed. More specifically, after the edge of the abnormal part is emphasized by performing the differentiation process 32 so that the abnormal part with a clear edge and fineness is detected, a predetermined threshold is applied to the image after the differentiation process. A binarization process 33 for binarizing the image with values is performed. On the other hand, for abnormal portions that are large and have a gradual change in density, the differential processing 32 cannot detect the abnormal portion or can detect only the edges of the abnormal portion, so the size of the abnormal portion is detected smaller than the actual size. There are many cases. Therefore, the binarization process 34 is performed as it is on the image data after the noise removal process 31 so as to detect such an abnormal part with a large and gradual change in shading. As described above, the abnormal part detected in the binarization process 33 after the differentiation process 32 and the abnormal part detected in the binarization process 34 after the noise removal process 31 are combined (added) 35. The finally detected abnormal part. Of those detected as abnormal portions, if there are noise components or features (area, shape, etc.) that are clearly not considered abnormal portions, it is preferable to exclude them from the abnormal portions.

  As described above, according to the first inspection method carried out by the inspection apparatus 10, when the background plate 5 having the same color as that of the single color printing unit S <b> 2 is disposed on the back side of the printed matter S, the background plate 5 and the monochrome printing unit S2 have the same color, and the color information of the monochrome printing unit S2 in the captured image captured by the imaging unit 2 is deleted. At this time, the optical filter 6 is placed at the retracted position B by the filter placement device 7. Since the white printing unit S1 has the same background color as the single color, white color information is not erased in the captured image captured by the imaging unit 2 as it is. However, the light of the same color as that of the monochromatic printing unit S2 is irradiated from the illumination unit 1 to the surface side of the printed matter S, so that the white printing unit S3 is also made the same color as the monochromatic color and is captured by the imaging unit 2. In this captured image, white color information is also deleted. On the other hand, when the white background plate 5 ′ is disposed on the back surface side of the printed material S, white light is irradiated from the illumination unit 1 to the front surface side of the printed material S. By doing so, the white background plate 5 ′, the white illumination, and the white printing unit S 1 have the same color, and the white color information is erased in the captured image captured by the imaging unit 2. At that time, since the color of the background plate 5 ′ is white and the illumination is white in the monochrome printing unit S 2, the monochrome color information is not erased in the captured image captured by the imaging unit 2 as it is. However, at this time, the optical filter 6 is arranged at the optical path position A by the filter arrangement device 7. Then, the reflected light L of the same color as that of the monochromatic printing unit S2 out of the reflected light L from the white printed matter S irradiated on the surface side of the printed matter S is an optical that allows the imaging unit 2 to transmit only this monochromatic light. Since the light is received through the filter 6, monochromatic color information is also erased in the captured image captured by the imaging unit 2. As described above, according to the present inspection method, the color information of both the monochrome printing unit S2 and the white printing unit S3 can be erased at the same time, and the height of the abnormal portion excluding the influence of the printing units S2 and S3 can be eliminated. Accurate inspection is possible. Furthermore, since it is not necessary to detect the printing units S2 and S3 using pattern matching or the like, there is an advantage that inspection efficiency is excellent.

  Note that when the printed matter S to be inspected is not an individual piece but a continuous one, a configuration of an inspection apparatus as shown in FIG. 4 may be employed. FIG. 4 is a schematic configuration diagram showing an embodiment of an inspection apparatus for performing the first inspection method according to the present invention on a continuous printed matter. As shown in FIG. 4, the inspection apparatus 10 ′ according to the present embodiment also has the same illumination unit 1, imaging unit 2, image processing unit 3, and background plates 5, 5 ′ as the above-described inspection apparatus 10 (see FIG. 1). The only difference is the configuration of the transport section 4 '. In FIG. 4, the optical filter 6 and the filter placement device 7 are not shown. That is, the transport unit 4 ′ according to the present embodiment is composed of rolls 4a and 4b, and the rolls 4a and 4b are always energized with a certain tension or more so that the printed matter S does not flutter. The printed material S is conveyed and supported. The background plates 5 and 5 ′ are arranged at positions lower than the tops of the front and rear rolls 4 a and 4 b so as not to come into contact with the printed matter S. In addition, if the interval between the rolls 4a and 4b is long, the printed product S may be loosened and come into contact with the background plates 5 and 5 '. Therefore, the interval between the two rolls 4a and 4b is such that the printed product S is not loosened. It is said.

  In the configuration of the inspection apparatus shown in FIG. 1 or FIG. 4 described above, only the reflected light L is received by the imaging unit 2. Therefore, the abnormal part hidden under the printing parts S2 and S3 of the printed matter S cannot be detected. More specifically, for example, when the printed matter S has a multilayer structure, the foreign matter existing between the layers becomes an abnormal portion, but the printed portions S2 and S3 are in the intermediate layer, or the uppermost layer and the uppermost layer. In the case of being in both lower layers, an abnormal part may occur below the printing parts S2 and S3 when viewed from the imaging part 2. However, the abnormal part located below the printing parts S2 and S3 when viewed from the imaging part 2 cannot be detected only by the reflected light.

  In order to detect such an abnormal part located below the printing parts S2 and S3, as shown in FIG. 5, the second illumination part 1 ′ is arranged below the background plates 5 and 5 ′, so-called transmission. It is preferable to use illumination together. For example, when the white background plate 5 ′ is arranged, the illumination unit 1 ′ performs transmission illumination with the same color light as that of the monochrome printing unit S <b> 2. According to such a configuration, when the abnormal part has a light shielding property, the light emitted from the illumination unit 1 ′ is shielded by the abnormal part and is not received by the imaging unit 2. Therefore, the abnormal part is detected. It is possible. In addition, as the background plates 5 and 5 ′ in the case of using the transmitted illumination together, the illuminating light from the illuminating unit 1 ′ is blocked by the shielding plate, so that the transmissive plate is transmissive like a translucent diffusion plate. It is necessary to use what has.

Second Embodiment
Next, a description will be given of a second inspection method for erasing the color information of the monochrome printing portion and detecting an abnormal portion in an area other than the white printing portion.

  In the first inspection method described in the first embodiment, the illumination condition is such that all the color information of the printing unit is erased. However, since there are various types of abnormal parts, it is not possible to deal with all abnormal parts only by the first inspection method. For example, when a white abnormal portion exists, when the first inspection method that also erases the color information of the white print portion is adopted, the color information of the white print portion is erased, The color information of the white abnormal part is also erased, and it becomes difficult to detect the abnormal part. In order to solve such a problem, in the second inspection method, in the inspection apparatus for carrying out the first inspection method described with reference to FIG. 1 or FIG. 6 and the filter arrangement device 7 are removed, and the surface of the printed matter S is irradiated from the illuminating unit 1 with the same color light as that of the monochromatic printing unit S2, and the reflected light is received by the imaging unit 2 (or the illuminating unit 1). In the captured image captured by the imaging unit 2, the surface of the printed material S is irradiated with light, and the reflected light having the same color as the monochrome printing unit S 2 is received by the imaging unit 2). The color information of the single color printing unit S2 is erased (therefore, only the white printing unit S3 is revealed in the captured image). Next, in the image processing unit 3, the captured image is binarized with a predetermined threshold value for distinguishing the white printing unit S3 from other regions, and the white printing unit S3 that is manifested in the captured image. To extract. Further, the extracted white printing portion S3 is masked, and an abnormal portion is detected in a region other than the mask region. The specific method for detecting an abnormal part is the same as the first inspection method described above with reference to FIG. For example, when a defect having the same color as the printing color exists, the defect is erased together with printing and cannot be detected. If there is such a defect that cannot be detected, the inspection effect is reduced. Therefore, a defect having the same color as the printing color is detected by using it together with another method. A specific method example will be described. Illumination is limited to transmitted illumination, and the illumination conditions are such that the printed part can be clearly seen.

  As described above, according to the second inspection method, the illumination unit 1 irradiates the surface side of the printed matter S with the same color light as that of the monochromatic printing unit S2, and the reflected light is received by the imaging unit 2. In order to do this (or to irradiate light from the illumination unit 1 to the surface side of the printed matter S and receive reflected light of the same color as that of the single color printing unit S2 in the reflected light by the imaging unit 2) The color information of the monochrome printing unit S2 is deleted from the captured image. Therefore, only the white printing portion S3 is revealed in the captured image. In addition, according to the second inspection method, the image processing unit 3 performs image processing on the captured image, thereby extracting the white printing unit S3 that is manifested in the captured image, and extracting the extracted white printing unit S3. An abnormal part is detected in a region other than. That is, in order to exclude the white print unit S3 from the inspection target, the white print unit S3 is extracted, and the region other than the extracted print unit S3 is inspected. As described above, according to the present inspection method, the color information of the single color printing unit S2 can be erased and the white printing unit S3 can be excluded, and the influence of the printing units S2 and S3 can be eliminated. High-accuracy inspection of abnormal parts is possible.

  In the second inspection method, a threshold value different from the binarization threshold value for detecting an abnormal portion in the region other than the printing unit S3 by the image processing unit 3 for the extracted white printing unit S3. It is preferable that an abnormal part existing in the printing part S3 is detected by binarizing using the. According to such a configuration, when an abnormal part having a density value different from that of the printing unit S3 is present in the white printing unit S3 excluded from the inspection target, the original inspection is performed by adjusting the binarization threshold value. An advantage that an abnormal part that is not a target can also be detected is obtained.

  Next, the extraction method of the printing unit S3 described above will be described in more detail. As a method for easily masking the printing unit S3, a method of enclosing a region corresponding to the printing unit S3 with a predetermined rectangular region and using the rectangular region as a mask can be considered. Occurs. Therefore, in the present embodiment, a mask corresponding to the shape of the printing unit S3 is created. More specifically, first, the printing unit S3 is extracted by binarization. At this time, depending on the binarization threshold value, an abnormal part is also extracted in addition to the printing part S3. Therefore, it is conceivable that not only the printing part S3 but also the abnormal part is masked and the abnormal part is missed. Therefore, it is necessary to determine whether the printing part S3 is an abnormal part or not when extracting the printing part S3. As such a determination method, the printing unit S3 measures the feature amount such as the area, length, and perimeter of the region extracted as a candidate for the printing unit S3 and compares it with the feature amount of the printing unit S3 calculated in advance. A method of determining whether there is an abnormal part or not is possible. According to the method for extracting the printing unit S3 described above, the printing unit S3 is masked on the basis of the captured image itself. Therefore, when the captured image is stretched or the printing unit S3 is displaced. Etc. are also possible. Further, the printing unit S3 does not need to be formed periodically. As another printing discrimination method, the coordinates of the printing unit can be found by pattern matching.

  In the second inspection method, the extracted white printing unit S3 is subjected to image processing by the image processing unit 3 to extract the feature amount of the printing unit S3, and the printing unit S3 itself is extracted based on the extracted feature amount. It is preferable to configure to detect an abnormality. FIG. 6 is an explanatory diagram for explaining an example of a method for detecting an abnormality occurring in the printing unit itself. 6A shows the appearance of the printed portion and the vertical projection profile of the density value when the printing portion is normal, and FIG. 6B shows the vertical appearance of the appearance and the density value of the printed portion when the print portion is abnormal. Each directional projection profile is shown. As shown in FIG. 6, if the width and interval of each character constituting the printing unit (character string) S3 is known in advance, an abnormality such as a missing character can be detected from the width or interval. More specifically, as shown in FIG. 6, the image processing unit 3 calculates the vertical projection profile P of the extracted printing unit S3, and the coordinates of the point at which the value of the profile is greater than a predetermined threshold value. Are calculated sequentially. Next, among the calculated coordinates, the width of the printing unit S3 is calculated from the difference between the maximum coordinate P1 and the minimum coordinate P2, and the calculated width is compared with the normal width to determine whether or not there is an abnormality. Can be determined. As for the spacing between characters, if the difference in the coordinates of the points calculated as described above is larger than the difference in the coordinates of the points in the normal case, the characters are missing between the characters. Can be determined. By the method described above, it is possible to inspect abnormalities occurring in the printing unit itself (such as chipping in the printing unit).

  In addition, it is preferable to use together the 1st test | inspection method demonstrated in 1st Embodiment, and the 2nd test | inspection method demonstrated in 2nd Embodiment. According to such a configuration, the color information of the printing portion of the single color and the white color can be simultaneously erased by the first inspection method, and the abnormal portion can be inspected with high accuracy excluding the influence of the printing portion. In addition, the second inspection method can detect a white abnormal portion that is difficult to detect with the first inspection method with high accuracy, and as a result, has the advantage that various abnormal portions can be detected. Have.

FIG. 1 is a schematic configuration diagram showing an embodiment of an inspection apparatus for carrying out the first inspection method according to the present invention. FIG. 2 is a diagram schematically illustrating an example of the printed matter S to be inspected. FIG. 3 is a block diagram illustrating an example of image processing performed in the image processing unit illustrated in FIG. 1. FIG. 4 is a schematic configuration diagram showing an embodiment of an inspection apparatus for performing the first inspection method according to the present invention on a continuous printed matter. FIG. 5 is a schematic configuration diagram showing another imaging optical system of the inspection apparatus for carrying out the first inspection method according to the present invention. FIG. 6 is an explanatory diagram for explaining an example of a method for detecting an abnormality occurring in the printing unit itself.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Illumination part 2 ... Imaging part 3 ... Image processing part 4 ... Conveyance part 5, 5 '... Background board 6 ... Optical filter 10 ... Inspection apparatus S ... Printed matter

Claims (2)

A method for inspecting an abnormal portion generated in a transparent or translucent sheet-like printed material on which printing of two colors of single color and white is performed using a first illumination unit, an imaging unit, and an image processing unit,
An arrangement step of arranging a background member of the same color as the single color or a white background member on either one of the front and back surfaces of the printed matter;
When arranging the background member of the same color as the single color in the arranging step, by irradiating light of the same color as the single color from the first illumination means to the other surface side of the printed matter, When the imaging unit receives reflected light from which the monochrome and white color information printed on the sheet-like printed material is erased, or when the white background member is arranged in the arranging step, the first illumination is used. By irradiating the other surface side of the printed matter with white light from the means, the white color information printed on the printed matter is erased with respect to the reflected light, and the reflection from which the white color information is erased Of the light, the reflected light of the same color as the single color is passed through an optical filter that transmits only the single color, thereby erasing the single color information printed on the sheet-like printed matter and receiving it by the imaging means. To And-up,
And a step of detecting an abnormal part by performing image processing on the captured image captured by the imaging unit by the image processing unit. The background member has transparency,
The printed matter inspection method according to claim 1, wherein the second illumination unit irradiates light on one surface side of the printed matter through the background member.