Sanitary paper defect inspection device and manufacturing method

Abstract

To more accurately detect the size or the shape of a hole in a sheet-like material.SOLUTION: A device 200 for inspecting a sheet-like material S for detects includes: an imaging device 211 arranged on one surface side of an inspection target site of the sheet-like material S, the imaging device imaging a surface of the inspection target site; and a light source 212 arranged on another surface side of the inspection target site of the sheet-like material S, the light source irradiating an imaging range of the imaging device 211 with light from another surface side of the inspection target site. The light source 212 is arranged outside the range of the angle of view of the imaging device 211.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a defect inspection device for sheet-like materials such as sanitary paper, and a method for manufacturing sheet-like materials using the same. [Background technology]

[0002] A conventional method for inspecting household sanitary paper, such as toilet paper and tissue paper, for defects (holes, stains, streaks, foreign objects, etc.) that occur during the manufacturing process involves transporting the base paper for the sanitary paper at high speed using rollers or the like, and photographing the paper surface with a camera while transporting, thereby detecting defects on the paper surface.

[0003] For example, with regard to defect inspection technology for sheet-like objects such as paper and film, Patent Document 1 discloses an inspection device that includes an illumination device that irradiates light onto the sheet-like object and an imaging device that continuously captures images of the transmitted light that has passed through the sheet-like object, and analyzes the captured images of the sheet-like object to determine whether it is good or bad. This inspection method, in which light that has been irradiated from the illumination device and transmitted through the sheet object is detected by a camera, is also called the "transmission method." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-238304 Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional "transmission type" defect inspection devices, an illumination device is positioned on the optical axis of an imaging device. However, when an illumination device is positioned on the optical axis of an imaging device in this way, if hole-like defects or perforation holes are formed in a sheet-like material, diffraction of light occurs when the light emitted from the illumination device passes through the holes, causing the holes to appear larger than they actually are or their shapes to be unable to be accurately detected. In particular, in the case of a sheet-like material with pre-formed perforations, when a hole is formed on the paper surface, it is necessary to distinguish whether it is a known perforation or an unknown defect. However, if the size and shape of the hole cannot be accurately detected by light diffraction, it becomes difficult to determine whether the hole is a perforation or a defect.

[0006] Therefore, a main object of the present invention is to provide a defect inspection technique that can more accurately detect the size and shape of holes that occur in sheet-like objects. [Means for solving the problem]

[0007] The inventor of the present invention has diligently studied means for solving the problems of the above-mentioned conventional inventions, and has discovered that in a transmission-type defect inspection device, by arranging a light source outside the angle of view of the imaging device, it is possible to more accurately detect the size and shape of holes formed in a sheet-like material. Based on this discovery, the inventor has come to the realization that the problems of the conventional technology can be solved, and has completed the present invention. Specifically, the present invention has the following configuration or steps.

[0008] A first aspect of the present invention relates to a defect inspection device for sheet-like objects. The defect inspection device according to the present invention comprises an imaging device and one or more light sources. The imaging device is arranged on one side of an inspected portion of a sheet-like object and images the surface of the inspected portion. The light source is arranged on the other side of the inspected portion and illuminates the imaging range of the imaging device from the other side of the inspected portion. At this time, the one or more light sources are arranged outside the angle of view of the imaging device. In other words, in the present invention, no light sources are present within the angle of view of the imaging device, and the imaging range of the imaging device is illuminated by a light source arranged outside the angle of view.

[0009] As in the above configuration, since the light source is not positioned on the optical axis of the imaging device, even if a perforation hole or hole-like defect occurs in the sheet-like material, diffracted light passing through the hole can be prevented from directly entering the imaging device. This allows the imaging device to accurately capture holes in the sheet-like material. As a result, it also becomes easier to distinguish between perforation holes and hole-like defects from the image captured by the imaging device. Furthermore, by inspecting defects in sheet-like materials using a transmission method as in the present invention, even if the sheet-like material is stacked in two or more layers, hole-like defects that occur in only one layer and other defects such as the attachment of foreign matter can be effectively detected.

[0010] In the defect inspection device according to the present invention, it is preferable that the photographing device is arranged so that its optical axis is substantially perpendicular to the portion to be inspected, and that one or more light sources are arranged so that their optical axes are inclined relative to the portion to be inspected. By arranging the photographing device so that its optical axis is perpendicular to the portion to be inspected on the sheet-like object, the photographing device and the sheet-like object are substantially directly opposite each other, allowing accurate photographing of the shape of holes formed in the sheet-like object, etc. In this case, by inclining the optical axis of the light source relative to the portion to be inspected on the sheet-like object, high illuminance at the portion to be inspected can be maintained. In particular, it is preferable that the photographing device and the light source are arranged so that the optical axis of the photographing device and the optical axis of the light source intersect within the plane of the portion to be inspected on the sheet-like object.

[0011] The defect inspection device according to the present invention may further include one or more light sources arranged on one side of the inspected area (i.e., on the same side as the imaging device) to illuminate the imaging range of the imaging device from that side of the inspected area. By arranging a light source on the same side as the imaging device in this way, the above-mentioned transmission type inspection and reflection type inspection can be performed simultaneously. For example, by using the reflection type inspection in combination, thin soot stains adhering to a sheet-like object can be effectively detected.

[0012] The defect inspection device according to the present invention preferably further includes an image analysis device that analyzes the image captured by the imaging unit. This image analysis device includes a database that stores the characteristics of non-defective areas (e.g., perforation holes) that do not need to be detected as defects. The image analysis device then distinguishes between defects occurring in the sheet-like material in the captured image that match the characteristics of the non-defective areas stored in the database and other defects. This makes it possible to prevent perforations or other defects from being detected as defects, even if they are formed in the sheet-like material. In particular, according to the present invention, the size and shape of holes occurring in the sheet-like material can be detected more accurately as described above, making it easier to distinguish between known perforation holes and other unknown hole-like defects.

[0013] A second aspect of the present invention relates to a method for manufacturing a sheet-like material, which includes the steps of obtaining a sheet-like material and inspecting the sheet-like material for defects using the defect inspection device according to the first aspect. [Effects of the Invention]

[0014] According to the present invention, the size and shape of holes formed in a sheet-like material can be detected more accurately. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 shows a schematic diagram of a part of the manufacturing process for a sheet material. [Figure 2] FIG. 2 shows an example of the configuration of a defect inspection device according to the first embodiment. [Figure 3] FIG. 3 shows an example of the configuration of a defect inspection device according to the second embodiment. [Figure 4] FIG. 4 shows an example of the configuration of a defect inspection device according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] The following describes embodiments of the present invention with reference to the drawings. The present invention is not limited to the embodiments described below, and includes appropriate modifications of the embodiments described below within the scope obvious to those skilled in the art.

[0017] [1. First embodiment] A first embodiment of the present invention will be described with reference to Figures 1 and 2. The present invention relates to a defect inspection device for sheet-like objects and a method for manufacturing sheet-like objects using the defect inspection device. Examples of sheet-like objects include those made of paper or plastic. In particular, the sheet-like object is preferably sanitary paper for home use, such as tissue paper or toilet paper. "Sanitary paper" means "sanitary paper" as defined in JIS "Terminology for Paper, Paperboard and Pulp" (JISP 0001). "Sanitary paper" includes towels, sanitary paper, tissue paper, toilet paper, and tissue paper. The sanitary paper manufactured by the present invention has a basis weight of 10 to 25 g / m 2 It is preferable that the tissue paper is in the range of 0.01 to 0.01 mm. Furthermore, the sanitary paper may be a one-ply product consisting of one sheet, or a two-ply or three-ply or more product made by stacking two or three or more sheets. In the example shown in Figure 1, the sanitary paper is obtained by stacking two layers of sheets to form a laminated sheet, and then embossing and perforating this laminated sheet. Furthermore, the sanitary paper is inspected for defects after the perforation process.

[0018] The process of manufacturing base paper for sanitary paper basically involves a preparation process to obtain a papermaking raw material (pulp slurry), which is a suspension of raw pulp fiber, and a papermaking process to separate raw pulp fiber from the papermaking raw material to form a fiber web and dry it. In the preparation process, the papermaking raw material (pulp slurry), which is the raw material for sanitary paper, is prepared. Papermaking raw material is made primarily from pulp. Examples of raw pulp include kraft pulp (KP) such as bleached hardwood kraft pulp (LBKP) and bleached softwood kraft pulp (NBKP); chemical pulp such as sulfite pulp (SP) and soda pulp (AP); semi-chemical pulp such as semi-chemical pulp (SCP) and chemi-groundwood pulp (CGP); mechanical pulp such as groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP); non-wood pulp made from materials such as paper mulberry, mitsumata, hemp, and kenaf; cotton-based pulp such as cotton linter and cotton lint; and deinked pulp made from recycled paper. Depending on the application and required performance of the tissue paper, a single type of raw pulp may be used, or multiple types of raw pulp may be used in any ratio. The raw pulp may be unbeaten, or may be wholly or partially beaten. The papermaking raw materials prepared in the preparation process are then made into sanitary paper in the papermaking process. The papermaking process can be carried out using a known papermaking machine. In this way, sanitary paper is obtained by producing raw rolls of base paper for sanitary paper, pulling out the base paper from multiple raw rolls, stacking them, and performing various processes (e.g., embossing and perforation).

[0019] Specifically, sanitary paper base paper is transported from the upstream side of the device on the right side of Figure 1 to the downstream side of the device on the left side. A first raw roll 11 and a second raw roll 12 are located upstream of the device. A long first sheet S1 is wound around the first raw roll 11, and a long second sheet S2 is wound around the second raw roll 12. When the first sheet S1 and the second sheet S2 are unwound from the first raw roll 11 and the second raw roll 12, respectively, the sheets S1 and S2 are transported downstream of the device via a drivingly rotating transport roller and a drivenly rotating guide roller, and are superimposed on each other in the first overlapping section 20 (overlapping roller 21). Here, the multi-layered sheet formed by superimposing the first sheet S1 and the second sheet S2 is referred to as a laminated sheet. The laminated sheet is transported downstream of the device.

[0020] An embossing unit 30 is located downstream of the first overlapping unit 20. In the example shown in FIG. 1, the laminated sheet is again separated into a first sheet S1 and a second sheet S2 in the embossing unit 30, and each sheet is embossed. The embossing unit 30 includes, for example, embossing rollers 31 and 32 and receiving rollers 33 and 34 positioned opposite 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. Each of the embossing rollers 31 and 32 has a plurality of protrusions corresponding to the embossing pattern to be imparted to each of the sheets S1 and S2. On the other hand, each of the receiving rollers 33, 34 can be, for example, a metal roller having a recessed pattern formed on its outer periphery that is complementary to the pattern of the raised portions of the embossing rollers 31, 32, or a rubber roller having a rubber-coated outer periphery. In the embossing section 30, the sheets S1, S2 are introduced between the embossing rollers 31, 32 and the receiving rollers 33, 34, and by sandwiching and pressing them, the surface of each of the sheets S, S2 can be embossed in a pattern that corresponds to the raised portions of the embossing rollers 31, 32.

[0021] A second overlapping section 40 (overlapping roller 41) is located downstream of the embossing section 30. In the second overlapping section 40, the first sheet S1 and the second sheet S2, which have been separately embossed in the embossing section 30, are overlapped with each other. This results in a two-layer laminated sheet in which each layer is embossed. Furthermore, for example, when producing kitchen paper, an adhesive may be applied between the layers after embossing to adhere the two layers together.

[0022] The perforation processing unit 50 is located downstream of the second overlapping unit 40. The perforation processing unit 50 forms perforations extending in the width direction (a direction perpendicular to the conveying direction in a plane) at regular intervals in the laminated sheet. Forming the perforations makes it easier to separate the laminated sheet at predetermined lengths. The perforation processing unit 50 includes, for example, a fixed blade 51 and a rotary blade 52. The peripheral surface of the fixed blade 51 has a plurality of blades intermittently provided in a perforation pattern along the axial direction of its roller, and by sandwiching the laminated sheet between the fixed blade 51 and the rotary blade 52, perforations are formed in the laminated sheet by the blades. Examples of sheet products that require perforations include toilet paper and kitchen paper.

[0023] The log forming section 70 is located downstream of the perforation processing section 50. In the log forming section 70, after perforation processing, the laminated sheet is wound up to a predetermined length by a winding roller to form a log. The laminated sheet log is then transported to a cutting section (not shown) and cut to a predetermined width by a log saw or the like to form individual sheet products. In this process, roll-shaped sheet products such as toilet rolls and kitchen rolls can be manufactured. However, the present invention can also be applied to sheet products such as tissue paper.

[0024] 1, the image capturing device 211 and light source 212 of the defect inspection device 200 are disposed between the perforation unit 50 and the log forming unit 70. In this embodiment, the defect inspection device 200 inspects a laminated sheet (hereinafter also referred to as sanitary paper S) formed by overlapping two layers of sheets S1 and S2 for defects. Therefore, it is sufficient that at least one defect inspection device 200 is provided downstream of the overlapping portion of the two layers of sheets S1 and S2. However, when embossing or perforating each sheet, defects are likely to occur in the sheet during each processing step. Therefore, it is also possible to provide one defect inspection device 200 immediately after the embossing unit 30 and another defect inspection device 200 immediately after the perforation unit 50.

[0025] The defect inspection device 200 includes a photographing device 211 (camera) installed on one side (front side) of the sanitary paper S so as to face the paper surface, and an image analysis device 220 connected to the photographing device 211 by wire or wirelessly. The defect inspection device 200 also includes a light source 212 arranged on the other side (back side) of the sanitary paper, i.e., the opposite side from the photographing device 211. The sanitary paper S is transported at a constant speed in a constant direction, particularly in the portion facing the photographing device 211. The back side of the sanitary paper S is illuminated by the light source 212, and light that has passed through this sanitary paper S is introduced to the photographing device 211. In this way, the photographing device 211 captures the light that has passed through the surface of the sanitary paper S, of the light irradiated from the light source 212, to acquire a photographed image. The photographed image of the sanitary paper acquired by the photographing device 211 is input to the image analysis device 220, which then analyzes whether or not there are any defects on the surface of the sanitary paper. The image analysis device 220 also performs processing to determine the type of defects on the paper surface contained in the captured image.

[0026] FIG. 2 shows an example of the arrangement of the photographing device 211 and the light source 212 in the defect inspection device 200 according to the first embodiment. As shown in FIG. 2, the photographing device 211 is arranged on the front side (one side) of the sanitary paper S, and the light source 212 is arranged on the back side (other side) of the sanitary paper S. Also, in FIG. 2, a "defect" that has occurred on the sanitary paper S is indicated by the symbol D. Examples of defects include holes, stains, streaks, foreign matter, and other quality defects that make the sanitary paper unsuitable for sale. Also, in FIG. 2, the "optical axis" (axis of symmetry passing through the center of the optical imaging system, also referred to as the principal axis) of the photographing device 211 and the "optical axis" (central axis of the light illumination range) of the light source 212 are each indicated by a dashed-dotted line. Also, in FIG. 2, the "angle of view" of the photographing device 211 is indicated by the symbol W, and the "angle of view range" of the photographing device 211 is indicated by a dashed line. In addition, in FIG. 2, the range on the surface of the sanitary paper S photographed by this photographing device 211 is referred to as the "photographing range."

[0027] The photographing device 211 is a camera for acquiring image data of still images or videos. The image data acquired by the photographing device 211 is sent to the image analysis device 220 (see FIG. 1), where predetermined image analysis is performed for defect detection. The camera is realized by, 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 the amount of charge from the photoelectric conversion element and generates image data, an IC memory, etc. The camera may be one that captures still images or one that captures videos at a predetermined frame rate.

[0028] The photographing device 211 is preferably positioned so that its optical axis is approximately perpendicular to the surface of the sanitary paper S. In other words, if a straight line is drawn perpendicularly from the imaging surface of the photographing device 211, that line will intersect the surface of the paper at an approximately perpendicular angle. Specifically, the angle θ1 between the optical axis of the photographing device 211 and the surface of the sanitary paper S is preferably 80 to 100 degrees, and particularly preferably 85 to 95 degrees or 90 degrees. This allows the photographing device 211 to photograph the surface of the sanitary paper S without distortion.

[0029] The light source 212 is a light that illuminates the photographing range of the sanitary paper S photographed by the photographing device 211. The light source 212 preferably emits white light. Examples of the light source 212 include fluorescent lamps, LEDs (light-emitting diodes), OLEDs (organic light-emitting diodes), lamps, arc lamps, and incandescent bulbs. The light source 212 can be a spot light source, a parallel light source (surface light source), or a point light source. However, it is most preferable to employ a spot light source, whose illumination range (spot size) and optical axis are easy to control. The use of a spot light source allows light to be emitted in a limited direction and range from the light source. In FIG. 2, the illumination range of the light source 212 is indicated by a dashed line, and the optical axis of the light source 212 is indicated by a dashed line. In the example shown in FIG. 2, etc., a spot light source whose illumination range (diameter) expands in a tapered shape around the optical axis is employed as the light source 212. Note that a spot light source whose illumination range is the same at infinity can also be used.

[0030] 2, the light source 212 is positioned so as to illuminate an area including the area photographed on the surface of the sanitary paper S by the photographing device 211. That is, in this embodiment, the photographing device 211 photographs the inspection area on the front side of the sanitary paper S, and the light source 212 illuminates the inspection area of ​​the sanitary paper S being photographed by the photographing device 211 from the back side. For this reason, light emitted from the light source 212 and transmitted through the sanitary paper S is introduced into the photographing device 211. In this way, the photographing device 211 acquires a photographed image of the sanitary paper S using a transmission method.

[0031] Furthermore, in the present invention, no light sources, including light source 212, are located within the angle of view of photographing device 211. In other words, even when sanitary paper S is excluded, light source 212 will not appear in the image photographed by photographing device 211. In particular, light source 212 is not located on the optical axis of photographing device 211. By arranging photographing device 211 and light source 212 in this way, even if perforations or hole-like defects occur in sanitary paper S, it is possible to prevent diffracted light from passing through these holes and directly entering photographing device 211. As a result, the shape of the holes in sanitary paper S is accurately captured in the image photographed by photographing device 211, making it easier to identify the size and shape of the holes.

[0032] Furthermore, the angle of view W of the photographing device 211 is preferably 10 to 60 degrees, and particularly preferably 15 to 50 degrees or 20 to 30 degrees. If the angle of view of the photographing device 211 is made wide, it becomes difficult to position the light source 212 outside the range of the angle of view of the photographing device 211. For this reason, it is preferable that the angle of view of the photographing device 211 be 60 degrees or less, and particularly 50 degrees or less.

[0033] 2, it is preferable that the photographing device 211 is placed outside the illumination range of the light source 212. In other words, when the sanitary paper S is excluded, the light emitted from this light source 212 does not directly enter the imaging surface of the photographing device 211. In this way, by placing the photographing device 211 outside the illumination range of the light source 212, it is possible to more reliably prevent diffracted light that has passed through the holes in the sanitary paper S from directly entering the photographing device 211. Furthermore, if the illumination range of the light source 212 is too wide, the emitted light will directly enter the photographing device 211, so it is preferable to use a spot light source as the light source 213 in order to narrow the illumination range of the light source 213 to some extent.

[0034] 2, in a longitudinal cross-sectional view of the sanitary paper S, the optical axis of the light emitted from the light source 212 is inclined at a predetermined angle θ2 with respect to the surface of the sanitary paper S. The inclination angle θ2 of the optical axis of the light source 212 is preferably, for example, 30 to 120 degrees, 40 to 100 degrees, 50 to 90 degrees, or 60 to 80 degrees. In this embodiment, the photographing device 211 is assumed to be positioned so that its optical axis is approximately perpendicular to the sanitary paper S. Therefore, in order to position the light source 212 outside the angle of view of the photographing device 211, the optical axis of the light source 212 needs to be inclined with respect to the sanitary paper S. From this perspective, it is preferable that the inclination angle θ2 of the optical axis of the light source 212 be 80 degrees or less. In particular, in order to position the photographing device 211 outside the illumination range of the light source 212, it is preferable that the inclination angle θ2 of the optical axis of the light source 212 be 60 to 80 degrees.

[0035] Furthermore, it is preferable to arrange the optical axis of the photographing device 211 and the optical axis of the light source 212 so that they intersect on the surface of the sanitary paper S. This allows the light source 212 to illuminate the photographing range of the photographing device 211 with sufficient illuminance.

[0036] The image captured by the photographing device 211 is analyzed by the image analyzing device 220. The image analyzing device 220 analyzes the image of the sanitary paper acquired by the photographing device 211 and inspects the sanitary paper for defects. A general computer may be used as the image analyzing device 220. The image analyzing device 220 has an interface for the photographing device, and image data acquired by the photographing device 211 is input to it. The image analyzing device 220 has, for example, a control and calculation unit, a memory unit (database), an operation unit, and a display unit. The control and calculation unit performs image analysis processing of the image data acquired from the photographing device 211 in accordance with a computer program for defect inspection stored in the storage unit. The control and calculation unit can be realized by a processor such as a CPU or GPU. The storage unit can be realized by non-volatile memory such as an HDD or SSD, or volatile memory such as RAM or DRAM. The operation unit is composed of input devices such as a mouse, keyboard, touch panel, and microphone, and receives operation information from a person. The display unit may be a display device such as a liquid crystal display or an organic EL display, and may display image data acquired from the image capturing device 211.

[0037] The image analysis device 220 (specifically, the control and calculation unit) basically analyzes the captured image acquired by the photographing device 211 to determine whether there are any defects or faults on the surface of the sanitary paper. For example, the image analysis device 220 measures the brightness (density) of each pixel or pixel group of the image data of the sanitary paper, and if there is a part that is darker (or brighter) than the normal brightness range, it determines that the sanitary paper of that image data is defective. For example, in defect inspection using the transmission method, if there is a hole in the sanitary paper, the part corresponding to the hole in the captured image will appear brighter in brightness. Also, if there is foreign matter (e.g., soot or oil stains) attached to the sanitary paper, the part containing the foreign matter will appear darker in brightness. In this way, the image analysis device 220 determines that a part where there is an abnormality in the brightness of the image data is a defective part of the sanitary paper. The image analysis device 220 also determines that there is a defect in the sanitary paper if perforations are not formed where they should be.

[0038] The image analysis device 220 may also include a database that stores the characteristics (size, shape, color, periodicity, etc.) of non-defective areas that do not need to be detected as defects. In this case, the image analysis device 220 identifies the size, shape, and periodicity of feature points that may be defects from the captured image, and distinguishes between defects that match the features of non-defective areas stored in the database and other defects. In this way, by comparing feature points with the features of non-defective areas stored in the database, it is possible to distinguish non-defective areas from other areas. For example, sanitary paper S, such as toilet paper, may have periodic perforations. Even if perforations are visible in the captured image, the image analysis device 220 can identify them as defective areas by comparing them with the features of perforations stored in the database. This prevents perforations from being mistakenly recognized as defects.

[0039] [2. Second Embodiment] 3 shows an example of the configuration of a defect inspection device 200 according to the second embodiment. In the following embodiments, the configurations different from those of the first embodiment will be mainly described, and the configurations that are substantially the same as those of the first embodiment will be assigned the same reference numerals and detailed description thereof will be omitted.

[0040] In the second embodiment shown in FIG. 3, a second light source 213 is arranged in addition to the first light source 212, which is the same as in the first embodiment. The second light source 213, like the first light source 212, is arranged on the back side of the sanitary paper S, i.e., on the opposite side from the photographing device 211. In this way, it is possible to perform a defect inspection using a transmission method using multiple light sources 212, 213. Also, in this second embodiment, like the first embodiment, the first light source 212 and the second light source 213 are arranged outside the angle of view range of the photographing device 211. Furthermore, it is preferable to arrange the photographing device 211 outside the illumination range of the first light source 212 and the second light source 213. Furthermore, the number of light sources is not limited to the first light source 212 and the second light source 213, and it is of course possible to add more.

[0041] 3. Third Embodiment FIG. 4 shows an example configuration of a defect inspection device 200 according to the third embodiment. In the second embodiment shown in FIG. 4, a third light source 214 is arranged in addition to the same first light source 212 as in the first embodiment. Unlike the first light source 212, the third light source 214 is arranged on the front side of the sanitary paper S, i.e., on the same side as the photographing device 211. In this way, the light emitted from the first light source 212 passes through the sanitary paper S and enters the photographing device 211, as described above. On the other hand, the light emitted from the third light source 214 is reflected on the surface of the sanitary paper S and enters the photographing device 211. In this way, it is possible to inspect the sanitary paper S for defects by using both the transmission method using the first light source 212 and the reflection method using the third light source 214.

[0042] Furthermore, although not shown in the figures, as a modified example of the third embodiment, it is also possible to arrange another light source on the surface side of the sanitary paper S, similar to the third light source 214. In this way, when photographing the surface of the sanitary paper S using the light reflection method, by arranging multiple light sources on the same side as the photographing device 211, it is possible to illuminate floating matter (e.g., paper dust) present between the surface of the sanitary paper S and the photographing device 211 from multiple directions, and therefore it is possible to lighten the color of the shadow of the floating matter projected onto the paper surface. This makes it possible to analyze the photographed image acquired by the photographing device 211 and more clearly detect defects adhering to the paper surface.

[0043] Furthermore, as a further modification of the third embodiment, in addition to the first light source 212 and the third light source 214, it is also possible to arrange another light source on the back side of the sanitary paper S, i.e., on the opposite side from the photographing device 211, similar to the second light source 213 (see FIG. 3) of the second embodiment described above. Furthermore, it is also possible to arrange multiple light sources on both the front and back sides of the sanitary paper S.

[0044] In the above, in order to express the contents of the present invention, the present specification has described embodiments of the present invention with reference to the drawings. However, the present invention is not limited to the above embodiments, and includes modifications and improvements that are obvious to those skilled in the art based on the matters described in the present specification. [Explanation of symbols]

[0045] 11...First raw material roll 12...Second raw material roll 20...first overlapping portion 21...overlapping roller 30...embossing section 31...first embossing roller 32... Second embossing roller 33... First receiving roller 34... second receiving roller 40... second overlapping portion 41... Laminating roller 50... Perforation processing section 51...cutter roller 52...anvil roller 200... Defect inspection device 211... Imaging device 212...first light source 213...second light source 214...Third light source 220...Image analysis device S1...First sheet S2...Second sheet S... Sanitary paper (sheet-shaped)

Claims

1. A defect inspection device for sanitary paper, an imaging device disposed on one side of the inspection area of ​​the sanitary paper and configured to capture an image of the surface of the inspection area; one or more spot light sources arranged on the other side of the examination site and illuminating an imaging range of the imaging device from the other side of the examination site, the one or more spot light sources are arranged outside the angle of view range of the imaging device so that their optical axes are inclined with respect to the region to be examined, There is no light source within the angle of view of the imaging device, The image capturing device is disposed outside the illumination range of the spot light source. Defect inspection equipment.

2. The imaging device is arranged so that its optical axis is perpendicular to the region to be examined. The defect inspection device according to claim 1 .

3. further comprising one or more light sources arranged on the one side of the examination site and illuminating an imaging range of the imaging device from the one side of the examination site; 3. The defect inspection device according to claim 1 or 2.

4. Further provided is an image analysis device that analyzes the captured image of the imaging device, The image analysis device comprises: a database storing characteristics of non-defective portions that do not need to be detected as defects; Among the defects occurring on the sanitary paper in the photographed image, defects that match the characteristics of non-defective areas stored in the database are distinguished from other defects. The defect inspection device according to any one of claims 1 to 3.

5. A process for obtaining sanitary paper; and inspecting the sanitary paper for defects using the defect inspection device according to any one of claims 1 to 4. Sanitary paper manufacturing method.

Images