JP2019039697A - Laminated sheet defect inspection device and sheet product manufacturing method - Google Patents

Abstract

To provide a technique capable of inspecting a defect generated in a laminated sheet in manufacturing a product in which sheets of two or more layers are stacked.SOLUTION: A defect inspection apparatus 60 for a laminated sheet comprises: an illumination unit 64 for illuminating the laminated sheet from at least one surface side of a front surface side and a rear surface side of the laminated sheet consisting of sheets S1 and S2 of a plurality of layers; a photographing unit 61 for photographing the laminated sheet from at least the other surface side of the front and rear surface sides of the laminated sheet in an illuminated state to obtain an image of the laminated sheet; and an image analyzing unit for analyzing the image of the laminated sheet to inspect the presence or absence of defects in the laminated sheet.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a laminated sheet defect inspection apparatus and a sheet product manufacturing method using the same.

  Conventionally, as a method for inspecting defects (holes, streaks, adhesion of foreign matter, etc.) that occurred in the manufacturing process of sheet products such as toilet paper and tissue paper, while transporting the sheet at high speed using rollers, It is known that a defect generated on a sheet surface is detected by illuminating with a light during the conveyance and photographing the illumination area with a camera.

  With regard to such a defect inspection technique for sheet products, for example, in Patent Document 1, a light and a camera are installed on one side of a sheet to be conveyed, and the reflected light reflected from the sheet surface is captured by the camera. A technique for detecting the above is disclosed.

JP 2017-21003 A

  However, as in the apparatus disclosed in Patent Document 1, a reflection type defect inspection apparatus that captures an image of a sheet surface by applying reflected light from the sheet surface can inspect a sheet layer by layer. When two or more layers are overlapped, only the defect of the sheet facing the camera and the light can be detected, and the defect generated in the sheet located on the opposite side cannot be detected properly. is there. In particular, sanitary paper such as toilet paper often has two or more layers stacked, but when inspecting such sanitary paper for defects, using conventional equipment, It is necessary to inspect the defects layer by layer, and it is difficult to detect defects generated in the laminated sheet after the two-layer sheets are stacked.

  Accordingly, an object of the present invention is to provide a technique capable of inspecting a defect generated in a laminated sheet in manufacturing a product in which two or more layers are stacked.

  The inventor of the present invention has intensively studied the means for solving the problems of the prior art, and as a result, after stacking two layers of sheets, lighting is applied from one side of the laminated sheet, and the lamination is performed from the other side. We obtained the knowledge that defects in the laminated sheet can be detected efficiently by photographing the sheet. The inventor has conceived that the problems of the prior art can be solved based on such knowledge, and has completed the present invention. More specifically, the present invention has the following steps and configurations.

  A first aspect of the present invention relates to a method for manufacturing a sheet product in which two or more sheets are laminated. The present invention is particularly characterized by a defect inspection method included in the manufacturing process of a sheet product. Examples of sheet products are light-transmitting sanitary thin paper such as toilet paper, tissue paper, and kitchen paper. In the production method of the present invention, two or more sheets are first overlapped to obtain a laminated sheet (overlapping step). Next, the laminate sheet is illuminated from at least one of the front and back sides of the laminate sheet, and the laminate sheet is photographed from at least the other side to obtain an image of the laminate sheet (imaging process). Thereafter, the image of the laminated sheet is analyzed to inspect the laminated sheet for defects (image analysis step).

  As shown in the above process, after overlapping two sheets, the illumination light is applied from one side, and the transmitted light is imaged from the other side. Can be detected together. Thereby, sheet products such as tissue paper can be efficiently manufactured.

  In the manufacturing method according to the present invention, in the photographing step, the laminated sheet is illuminated from both the front and back sides of the laminated sheet, and the laminated sheet is applied from at least one side of the front and back sides of the laminated sheet. It is good also as image | photographing and obtaining the image of the said lamination sheet. Here, it is good also as installing an illuminating device in the both surfaces side of a lamination sheet, and carrying out an imaging device only in the single side | surface side of a lamination sheet. In this way, by taking an image of a laminated sheet that is reflected by the reflected light on the surface side of the laminated sheet together with the transmitted light of the laminated sheet, a defect that cannot be detected only by the transmitted light is detected by the imaging device. Therefore, the accuracy of defect detection can be improved. Specifically, according to the transmission method, it is possible to detect a hole generated in the laminated sheet and a foreign matter attached thereto. On the other hand, with the transmission method, it is difficult to detect thin dirt (such as wrinkles) attached to the surface of the laminated sheet. Therefore, in order to detect such thin dirt, the transmission method and the reflection method are used in combination. Thereby, the defect which arose in the lamination sheet can be generally detected.

  In the manufacturing method according to the present invention, in the photographing step, the front side illumination area where the laminated sheet is illuminated by the first illumination device located on the front side of the laminated sheet, and the second illumination located on the back side of the laminated sheet. It is preferable that the laminated sheet is illuminated by the apparatus to form a back side illumination area that is at least partially different from the front illumination area. In this case, it is preferable that an image of an area including at least a part of both the front side illumination area and the back side illumination area is taken by an imaging apparatus located on at least one side of the front side and the back side of the laminated sheet. As described above, it is preferable to adjust the arrangement of the illumination device and the imaging device so that at least a part of the front-side illumination area and at least a part of the back-side illumination area are simultaneously reflected in the imaging range of one imaging device. Thus, the accuracy of defect detection can be improved by using both the transmission method and the reflection method. In addition, for example, by comparing a photographed image when a point of the laminated sheet is located in the front side illumination area with a photographed image when the point is located in the back side illumination area, It is also possible to determine the type of defect (eg, whether it is a hole, a foreign object, or a thin flaw).

  In the manufacturing method according to the present invention, in the photographing process, the laminated sheet is photographed from both the front side and the back side of the laminated sheet to obtain images of the front side and the back side of the laminated sheet. It is preferable to inspect the presence or absence of defects in the laminated sheet by analyzing images on the front and back sides of the sheet. That is, in this embodiment, the lighting device is arranged on both the front surface side and the back surface side of the laminated sheet, and the photographing devices are arranged on both the front surface side and the back surface side of the laminated sheet. By doing in this way, the defect which arose on the surface side and back surface side of the lamination sheet can be test | inspected more correctly.

  In the manufacturing method according to the present invention, the laminated sheet is conveyed at a constant speed in one direction at least during the image analysis process. In this case, it is preferable that the image analysis process detects only an unknown defect portion moving at the same speed in the same direction as the laminated sheet from the image of the laminated sheet. Thereby, it is possible to detect only unknown foreign matter adhering to the laminated sheet or unknown abnormality occurring in the laminated sheet. When manufacturing sanitary thin paper such as tissue paper is considered, paper dust is often scattered around the laminated sheet, so that the paper powder is reflected in the photographed image of the laminated sheet. At this time, in order to avoid an error that detects paper dust as a defect in the image analysis process, the image analysis apparatus (computer) detects only a defective portion that moves at the same speed in the same direction as the laminated sheet. Is preferred. In the image analysis process, it is preferable to detect only an unknown defect portion of the laminated sheet so as not to detect a known defect portion such as a perforation formed on the laminated sheet. For example, by storing features such as the perforation pattern in the image analysis apparatus in advance, it is possible to prevent this apparatus from detecting the perforation as a defect.

  The 2nd side surface of this invention is related with the defect inspection apparatus of a lamination sheet. The defect inspection apparatus includes an overlay unit, an illumination unit, an imaging unit, and an image analysis unit. The overlapping unit overlaps two or more sheets to obtain a laminated sheet. The illumination unit illuminates the laminated sheet from at least one side of the front side and the back side of the laminated sheet. The photographing unit captures an image of the laminated sheet by photographing the laminated sheet from at least the other side of the front surface side and the back surface side of the laminated sheet in a state where the laminated sheet is illuminated by the illumination unit. The image analysis unit analyzes the image of the laminated sheet and inspects whether or not the laminated sheet has a defect.

  According to the present invention, defects produced in a laminated sheet can be inspected when a product in which two or more sheets are stacked is manufactured.

FIG. 1 schematically shows a part of a manufacturing process of a sheet product. FIG. 2 schematically shows a first embodiment of the defect inspection apparatus. FIG. 3 schematically shows a second embodiment of the defect inspection apparatus. FIG. 4 is a block diagram illustrating a functional configuration example of the defect inspection apparatus. FIG. 5 schematically shows the illumination range of the illumination device and the imaging range of the imaging device.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. This invention is not limited to the form demonstrated below, The thing suitably changed in the range obvious to those skilled in the art from the following forms is also included.

  FIG. 1 shows a part of a manufacturing process of a sheet product according to the present invention. The sheet product that can be produced according to the present invention is not particularly limited, but it is preferable to use a light-transmitting thin paper as an object of production in order to efficiently perform a defect inspection by a light transmission method. Examples of tissue paper are household hygiene tissue paper such as tissue paper, toilet paper, and kitchen paper. In the example shown in FIG. 1, embossing and perforation are formed on a laminated sheet after a laminated sheet is formed by overlapping two sheets. In addition, after embossing and perforation, the laminated sheet is inspected for defects.

  More specifically, the sheet member is conveyed from the upstream side of the apparatus on the right side of FIG. 1 toward the downstream side of the apparatus on the left side. A first original roll 11 and a second original roll 12 are located upstream of the apparatus. A long first sheet S <b> 1 is wound around the first original fabric roll 11, and a long second sheet S <b> 2 is wound around the second original fabric roll 12. When the first sheet S1 and the second sheet S2 are fed out from the first original roll 11 and the second original roll 12, respectively, each of the sheets S1 and S2 is driven and rotated by a conveying roller and a driven rotating guide roller. And is superposed on each other in the first superposition unit 20 (superposition roller 21). Here, the multi-layer sheet in which the first sheet S1 and the second sheet S2 are overlapped is referred to as a laminated sheet. The laminated sheet is conveyed to the downstream side of the apparatus.

  The embossing part 30 is located downstream of the first overlapping part 20. In the example shown in FIG. 1, the laminated sheet is separated again into the first sheet S <b> 1 and the second sheet S <b> 2 in the embossing section 30, and embossing is performed for each sheet. The embossing unit 30 includes, for example, embossing rollers 31 and 32 and receiving rollers 33 and 34 at positions facing each other across the conveyance path of each sheet. The first sheet S1 is introduced between the first embossing roller 31 and the first receiving roller 33, and the second sheet S2 is introduced between the second embossing roller 32 and the second receiving roller 34. Is done. Each embossing roller 31, 32 has a plurality of convex portions according to the embossing pattern to be applied to each sheet S1, S2. On the other hand, each of the receiving rollers 33 and 34 is, for example, a metal roller in which a concave pattern complementary to the pattern of the convex portions of the embossing rollers 31 and 32 is formed on the outer peripheral surface, or the outer peripheral surface of the roller is covered with rubber. Rubber rollers can be used. In the embossing part 30, sheets S1 and S2 are introduced between the embossing rollers 31 and 32 and the receiving rollers 33 and 34, and these are sandwiched and pressed so as to correspond to the convex parts of the embossing rollers 31 and 32. The embossed pattern can be embossed on the surface of each sheet S, S2.

  On the downstream side of the embossing section 30, a second overlapping section 40 (overlapping roller 41) is located. In the 2nd superimposition part 40, the 1st sheet | seat S1 and the 2nd sheet | seat S2 which were respectively embossed separately in the embossing part 30 are mutually overlap | superposed. Thereby, a laminated sheet having a two-layer structure in which each layer is embossed is obtained. For example, when manufacturing kitchen paper, an adhesive may be applied between the layers after embossing to bond the two layers.

  On the downstream side of the second overlapping portion 40, a perforation processing portion 50 is located. In the perforation processing unit 50, perforations extending in the width direction (a direction orthogonal to the conveyance direction in a plane) are formed at regular intervals with respect to the laminated sheet. By forming the perforation, the laminated sheet can be easily separated for each predetermined length. The perforation processing unit 50 includes, for example, a fixed blade 51 and a rotary blade 52. On the peripheral surface of the fixed blade 51, a plurality of blades are intermittently provided in a perforated pattern along the axial direction of the roller. By sandwiching the laminated sheet with the rotary blade 52, the blade As a result, perforations are formed in the laminated sheet. Sheet products that require perforation include toilet paper and kitchen paper.

  A log forming unit 70 is located downstream of the perforation processing unit 50. In the log forming unit 70, after the perforation, the laminated sheet is wound up to a predetermined length by a winding roller to form a log. The log of the laminated sheet is then transported to a cutting unit (not shown) and cut into a predetermined width by a log saw or the like to become individual sheet products. In such a process, a roll-shaped sheet product such as a toilet roll or a kitchen roll can be manufactured. However, the present invention can also be applied to sheet products such as tissue paper.

  Further, as shown in FIG. 1, the defect inspection device 60 is provided at a total of two locations between the second overlapping portion 40 and the perforation processing portion 50 and between the perforation processing portion 50 and the log forming portion 70. Are arranged respectively. The defect inspection apparatus 60 inspects the presence or absence of defects in the laminated sheet for the laminated sheet obtained by superimposing the two layers of sheets S1 and S2. For this reason, the defect inspection apparatus 60 should just be provided in the downstream of the overlapping part of the sheet | seats S1 and S2 of two layers at least. However, when embossing or perforation is applied to each sheet as in the example shown in FIG. 1, defects are likely to occur in the sheet in each processing step. Further, it is preferable to provide a defect inspection device 60 at one place immediately after the perforation processing unit 50.

  The defect inspection apparatus 60 basically inspects the presence or absence of a defect in the laminated sheet by photographing the laminated sheet with a camera and analyzing the photographed image. The type of defect to be inspected is not particularly limited. For example, holes or tears, streaks, unevenness, or dirt or foreign matter adhering to the surface of each layer of the laminated sheet may be the subject of inspection. it can.

  FIG. 2 shows a first embodiment of the defect inspection apparatus 60. As shown in FIG. 2, the defect inspection apparatus 60 includes an imaging device 61 (camera) and illumination devices 62 and 64 (lights). The photographing device 61 is a camera for acquiring still image or moving image data. The image data acquired by the imaging device 61 is transmitted to the image analysis device 65 (see FIG. 4), and a predetermined image analysis for defect detection is performed. The camera is, for example, a lens, a mechanical shutter, a shutter driver, a photoelectric conversion element such as a CCD image sensor unit or a CMOS image sensor unit, a digital signal processor (DSP) that reads out the amount of charge from the photoelectric conversion element and generates image data, an IC memory, etc. It is realized with. Note that the camera may shoot a still image, or may shoot a moving image with a predetermined frame rate. Moreover, the illuminating devices 62 and 64 are lights that irradiate illumination light to an area photographed by the photographing device 61 in the laminated sheet. It is preferable that the illuminating devices 62 and 64 irradiate the laminated sheet with white light. Examples of the lighting devices 62 and 64 include fluorescent lamps, LEDs (light emitting diodes), OLEDs (organic light emitting diodes), lamps, arc lamps, and incandescent bulbs.

  As shown in FIG. 2, the laminated sheet is formed by laminating a first sheet S1 and a second sheet S2. Here, for simplification of description, the surface side of the first sheet S1 in the laminated sheet is referred to as “the surface side of the laminated sheet”, and the surface side of the second sheet S2 in the laminated sheet is referred to as “laminate”. It is expressed as “the back side of the sheet”.

  In the example shown in FIG. 2, the photographing device 61 and the first lighting device 62 are arranged on the front surface side of the laminated sheet, and the second lighting device 64 is arranged on the back surface side of the laminated sheet. The photographing device 61 photographs the surface of the first sheet S1, and the first illumination device 62 applies illumination light to the photographing range from the same direction as the photographing device 61. For this reason, the light irradiated from the first lighting device 62 and reflected by the surface of the first sheet S1 enters the photographing device 61. On the other hand, the second illumination device 64 is disposed at a position facing the imaging device 61 with the laminated sheet interposed therebetween. The second lighting device 64 applies illumination light to the photographing range of the photographing device 61 from the back side of the laminated sheet. For this reason, the light irradiated from the second illumination device 64 and transmitted through the laminated sheet enters the imaging device 61. Further, the image data of the laminated sheet imaged by the photographing device 61 is analyzed by an image analysis device 65 described later and used for checking whether or not the laminated sheet has a defect.

  As described above, after the first and second sheets S1 and S2 are overlaid, the illumination light is applied from the back surface side, and the transmitted light is imaged from the front surface side, thereby generating each sheet constituting the laminated sheet. Defects can be detected together. That is, by detecting the transmitted light of the laminated sheet with the photographing device 61, if a defect such as a hole or a foreign substance adheres to any of the sheets S1 and S2 constituting the laminated sheet, the photographed image is displayed. In some cases, there will be a difference between light and dark, or a black shadow will be reflected. When such an abnormality is included in the photographed image, it can be determined by the image analysis device 65 that the laminated sheet has a defect. Further, as in the embodiment shown in FIG. 2, the imaging device detects the defect that could not be detected only by the transmitted light by imaging the reflected light on the surface side of the laminated sheet together with the transmitted light of the laminated sheet. can do. Specifically, depending on the transmission method, it is possible to detect holes generated in the laminated sheet and foreign matters attached to the hole, but it is difficult to detect thin dirt (such as wrinkles) attached to the surface of the laminated sheet. It is. On the other hand, according to the reflection method, it is possible to detect thin stains attached to the surface of the laminated sheet. Therefore, by using both the transmission method and the reflection method, defects generated in the laminated sheet can be generally detected.

  FIG. 3 shows an embodiment of a defect inspection apparatus 60 different from FIG. In the example illustrated in FIG. 3, the first photographing device 61 and the first lighting device 62 are disposed on the front surface side of the laminated sheet, and the second photographing device 63 and the second lighting device 64 are disposed on the rear surface side of the laminated sheet. Is arranged. Similar to the embodiment of FIG. 2, the first photographing device 61 photographs the surface of the first sheet S <b> 1, and the first illumination device 62 photographs the same from the same direction as the first photographing device 61. The area is illuminated. The second lighting device 64 is disposed at a position facing the first imaging device 61 across the laminated sheet, and emits illumination light from the back surface side of the laminated sheet to the imaging range of the first imaging device 61. I guess. Further, in the embodiment of FIG. 3, the second imaging device 63 images the surface of the second sheet S <b> 2, and the first illumination device 62 captures the image from the same direction as the second imaging device 63. The area is illuminated. For this reason, the light irradiated from the second illumination device 64 and reflected by the surface of the second sheet S <b> 2 enters the second imaging device 63. The first lighting device 62 is disposed at a position facing the second imaging device 63 with the laminated sheet interposed therebetween. The first lighting device 62 applies illumination light to the imaging range of the second imaging device 63 from the surface side of the laminated sheet. For this reason, the light irradiated from the first illumination device 62 and transmitted through the laminated sheet enters the second imaging device 63. Image data of the laminated sheet captured by the first and second imaging devices 61 and 63 is analyzed by an image analysis device 65 described later and used for checking whether or not a defect has occurred in the laminated sheet.

  A feature of the embodiment of FIG. 3 is that the first lighting device 62 provides the first photographing device 61 with the reflected light on the surface side of the laminated sheet, and at the same time, the second photographing device 63 is laminated. The second illuminating device 64 provides the reflected light on the back side of the laminated sheet to the second photographing device 63 and at the same time to the first photographing device 61. They are arranged so as to provide the transmitted light of the laminated sheets. In this way, the two lighting devices 62 and 64 function as reflected light illumination and transmitted light illumination, respectively. Furthermore, according to the embodiment of FIG. 3, the two imaging devices 61 and 63 perform defect inspection by both the reflection method and the transmission method from the front surface side of the laminated sheet, and also from the back surface side of the laminated sheet. And defect inspection by both transmission methods. As described above, in this embodiment, highly efficient defect inspection can be performed in a compact space by the efficient arrangement of the photographing devices 61 and 63 and the lighting devices 62 and 64.

  FIG. 4 shows an example of the functional configuration of the image analysis device 65 connected to each of the imaging devices. A general computer may be used for the image analysis device 65. The image analysis device 65 includes an interface for the photographing device, and receives image data acquired by the photographing device. The image analysis device 65 includes a control calculation unit 65a, a storage unit 65b, an operation unit 65c, and a display unit 65d. The control calculation unit 65a controls each of the elements 65b to 65d, and performs image analysis processing of the image data acquired from the imaging apparatus in accordance with a defect inspection computer program stored in the storage unit 65b. The control calculation unit 65a can be realized by a processor such as a CPU or a GPU. The storage unit 65b can be realized by a nonvolatile memory such as an HDD or SDD, or a volatile memory such as a RAM or DRAM. The operation unit 65c is configured by an input device such as a mouse, a keyboard, a touch panel, and a microphone, and receives operation information from a person. The display unit 65d is a display device such as a liquid crystal display or an organic EL display, and may display image data acquired from the photographing device. The display unit 65d0 may be integrated with the operation unit 65c to form a touch panel display.

  The control calculation unit 65a of the image analysis device 65 basically measures the density for each pixel or pixel group of the image data of the laminated sheet, and when there is a darker or brighter part than the normal density range, It is determined that there is a defect in the laminated sheet of image data. For example, when a foreign substance adheres to the laminated sheet, the density of the foreign substance portion appears dark. For example, a foreign object attached to the back layer with respect to the photographing device (camera) is photographed by the photographing device through the front layer, but the foreign matter appears dimly in the photographed image. Further, when a hole is opened in one layer of the laminated sheet, the density of the hole portion appears bright in the image data acquired by the transmission method. In other words, the hole formed in one layer of the laminated sheet shows that the transmitted light appears brighter by reducing the layer of the hole by one layer regardless of whether the front side layer has a hole or the back side layer has a hole. It becomes. In this way, the control calculation unit 65a determines that the part where the density of the image data is abnormal is a defective part of the laminated sheet.

  FIG. 5A shows the relationship between the imaging range of the laminated sheet by the first imaging device 61 included in the embodiment shown in FIG. 3 and the illumination areas by the first illumination device 62 and the second illumination device 64. Is schematically shown. As shown in FIG. 5, an illumination area (front-side illumination area) by the first illumination device 62 located on the front side of the laminated sheet and an illumination area (back-side illumination) by the second illumination device 64 located on the back side of the laminated sheet. Area) is partially overlapped, but the other part is not overlapped. For this reason, the illumination range of each illuminating device 62 and 64 includes a front side illumination area, a back side illumination area, and an overlapping area thereof. In this case, the arrangement and the angle of view of the first imaging device 61 are adjusted so that a part of the front side illumination area and a part of the back side illumination area fall within the imaging range with the overlapping area as the center. Since the front side illumination area is an area illuminated by the first illumination device 62 arranged in the same direction as the first imaging device 61, the reflected light from the surface of the laminated sheet is incident on the first imaging device 61. To do. On the other hand, the back side illumination area is an area illuminated by the second illumination device 64 disposed at a position facing the first imaging device 61 across the laminated sheet. Is transmitted through the laminated sheet.

  Here, the 1st imaging device 61 has caught the front side illumination area except a superimposition area | region, and the back side illumination area except a superimposition area | region simultaneously in the imaging | photography range. Here, the first imaging device 61 has a first timing in which a certain point P is in the front side illumination area (excluding the superimposition area) and a first timing in which the same point P is in the back side illumination area (excluding the superposition area). At the timing of 2, it is preferable to perform shooting at least twice in a time zone in which the same point is included in the shooting range. That is, since the laminated sheet is conveyed in the same direction at the same speed, a certain point P in the laminated sheet moves from the front side illumination area to the back side illumination area as time elapses. At this time, the first photographing device 61 has the first timing when the point P is in the front side illumination area (excluding the superimposition area) and the second timing when the same point P is in the back side illumination area (excluding the superposition area). The image of the laminated sheet is taken at at least two timings. The two frames acquired in this way are transmitted to the image analysis device 65 and used for image analysis. The image analysis apparatus 65 can use the comparison result of frames obtained by photographing the same point twice or more for defect inspection processing. Note that the photographing apparatus may photograph at least the still image at the two timings described above, or may photograph a moving image having a frame rate including the two timings.

  FIG. 5B shows an abnormal part photographed in the front side illumination area (excluding the superimposition area) and a back side illumination area (superimposition area is shown) when an abnormal part is included in the image captured by the first photographing device 61. The state of the change of the abnormal part image | photographed by (except) is typically shown. Here, for the first imaging device 61, the front side illumination area is an area for imaging by the reflection method, and the back side illumination area is an area for imaging by the transmission method. The image captured by the reflection method is easy to detect thin wrinkles attached to the imaging surface, but has a feature that it is difficult to detect defects such as holes formed in the laminated sheet. On the other hand, a photographed image by the transmission method has a feature that it is easy to detect a defect such as a hole formed in the laminated sheet, but it is difficult to detect thin wrinkles attached to the photographing surface. By using the characteristics of each method, it is possible to estimate what the abnormalities appear in the images by comparing the captured images of the front and back illumination areas. be able to. For example, as shown in the upper part of FIG. 5B, when an abnormality is detected in both the front side illumination area and the back side illumination area, the abnormality has a large shadow that can be detected by both the reflection method and the transmission method. It can be assumed that it is a kimono. Also, as shown in the middle part of FIG. 5B, when an abnormality of the laminated sheet is detected in the front side illumination area but not in the back side illumination area, the abnormality is thinly attached to the imaging surface that is difficult to detect by the transmission method. It can be guessed that it is dirty. On the other hand, as shown in the lower part of FIG. 5B, when an abnormality of the laminated sheet is not detected in the front side illumination area but is detected in the back side illumination area, the abnormality is not detected in the reflection method. It can be inferred that this is a hole in one of the layers. As described above, the image analysis device 65 may compare the photographed image in the front illumination area with the photographed image in the back illumination area and use the result for defect inspection of the laminated sheet.

  In addition, in order to suppress the mixing of the light transmitted through the laminated sheet and the light reflected from the laminated sheet, particularly in the overlapping region, the light illumination direction is controlled by the first lighting device 62 and the second lighting device 64. It is preferable to attach a partition plate and a filter for this purpose. When transmitted light and reflected light are mixed, it becomes difficult to detect thin stains and the like generated on the surface of the laminated sheet. Therefore, it is preferable to adjust the overlapping region of these lights as narrow as possible.

  In the example illustrated in FIG. 5, an example of the inspection process based on the captured image of the first imaging device 61 has been described. However, the inspection process based on the captured image of the second imaging device 63 can be performed in the same manner. . As described above, the first photographing device 61 photographs the front side illumination area of the laminated sheet by the reflection method and photographs the back side illumination region by the transmission method, but the second photographing device 63, The front side illumination area of the laminated sheet is photographed by the transmission method, and the back side illumination area of the laminated sheet is photographed by the reflection method.

  In the case of sanitary thin paper made mainly of wood pulp, such as tissue paper or toilet paper, paper dust is generated during the manufacturing process, and the paper dust is scattered in the atmosphere where the photographing device is placed. It is predicted that For this reason, when analyzing the captured image, the image analysis device 65 ignores (cancels) the paper dust scattered around the laminated sheet and detects only the defects generated in the laminated sheet to be inspected. It is preferably programmed to do so. Specifically, since the laminated sheet is conveyed at a constant speed in one direction, it can be said that the defects occurring in the laminated sheet are moving at the same speed in the same direction as the laminated sheet. On the other hand, since paper dust flies in the atmosphere, the moving direction and moving speed are completely different from those of laminated sheets. Therefore, the image analysis device 65 detects only a defective portion moving at the same speed in the same direction as the laminated sheet from the photographed image of the laminated sheet, and ignores other paper dust and the like. It is possible to detect only foreign matter adhering to the sheet or abnormality occurring in the laminated sheet.

  In order to prevent malfunction due to paper dust, the cameras constituting the photographing devices 61 and 62 are accommodated inside the case, and clean air is introduced into the case to make positive pressure, so that the paper dust is inside the case. It is preferable to prevent intrusion. In this case, the camera may shoot the object through the air discharge port of the case. In this way, paper dust can be prevented from entering the case, and paper dust can be prevented from adhering to the camera lens.

  Further, in the defect inspection device 60 located between the perforation processing unit 50 and the log forming unit 70, the known perforation formed on the laminated sheet is ignored (cancelled) when the image analysis device 65 analyzes the captured image. ), And preferably programmed to detect only unknown defects excluding perforations generated in the laminated sheet to be inspected. For example, the image analysis device 65 may be programmed so as to hold information on the period in which the perforations are formed and not to recognize the perforations generated in that period as defects. In addition, the image analysis device 65 holds information on the shape characteristic of the perforation (the shape characteristic that is formed entirely along the size in the flow direction and the width direction). You may program so that the perforation which it has may not be recognized as a defect.

  As mentioned above, in this specification, in order to express the content of this invention, embodiment of this invention was described, referring drawings. However, the present invention is not limited to the above-described embodiments, but includes modifications and improvements obvious to those skilled in the art based on the matters described in the present specification.

DESCRIPTION OF SYMBOLS 11 ... 1st original fabric roll 12 ... 2nd original fabric roll 20 ... 1st overlapping part 21 ... Overlapping roller 30 ... Embossing process part 31 ... 1st embossing roller 32 ... 2nd embossing roller 33 ... 1st receiving roller 34 ... 2nd receiving roller 40 ... 2nd overlapping part 41 ... Overlapping roller 50 ... Perforation processing part 51 ... Cutter roller 52 ... Anvil roller 60 ... Defect inspection apparatus 61 ... 1st imaging | photography Device 62 ... First illumination device 63 ... Second imaging device 64 ... Second illumination device 65 ... Image analysis device 70 ... Log forming unit S1 ... First sheet S2 ... Second sheet

Claims (6)

A method of manufacturing a sheet product in which two or more sheets are laminated,
A superposition process of superposing two or more sheets to obtain a laminated sheet;
Illuminating the laminated sheet from at least one side of the front and back sides of the laminated sheet, photographing the laminated sheet from at least the other side, and obtaining an image of the laminated sheet;
An image analysis step of analyzing the image of the laminated sheet and inspecting the laminated sheet for the presence or absence of defects. The photographing step illuminates the laminated sheet from both the front side and the back side of the laminated sheet, and photographs the laminated sheet from at least one side of the front side and the back side of the laminated sheet. The manufacturing method according to claim 1, which is a step of obtaining an image of a sheet. In the photographing step, the front side illumination area in which the laminated sheet is illuminated by an illumination device located on the front side of the laminated sheet, and the laminated sheet is illuminated by the illumination device located on the back side of the laminated sheet. Forming a back side illumination area that is at least partially different from the area, and at least partially separating the front side illumination area and the back side illumination area by an imaging device located on at least one side of the front and back sides of the laminated sheet The manufacturing method according to claim 2, wherein an image of a region included in is taken. In the photographing step, the laminated sheet is photographed from both the front and back sides of the laminated sheet to obtain images of the front and back sides of the laminated sheet,
4. The manufacturing method according to claim 2, wherein in the image analysis step, images on the front side and the back side of the laminated sheet are analyzed to inspect for defects in the laminated sheet. During the image analysis process, the laminated sheet is conveyed at a constant speed in one direction,
The manufacturing method according to any one of claims 1 to 4, wherein the image analysis step detects, from the image of the laminated sheet, only an unknown defect portion that moves at the same speed in the same direction as the laminated sheet. . A stacking unit for stacking two or more sheets to obtain a laminated sheet;
An illumination unit that illuminates the laminated sheet from at least one side of the front side and the back side of the laminated sheet;
In a state in which the laminated sheet is illuminated by the illumination unit, a photographing unit that photographs the laminated sheet from at least the other side of the front surface side and the back surface side of the laminated sheet, and obtains an image of the laminated sheet;
An image analysis unit that analyzes an image of the laminated sheet and inspects for the presence or absence of a defect in the laminated sheet.

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