JP7739743B2 - Sanitary paper defect inspection device and manufacturing method - Google Patents

Description

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.

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 at high speed using rollers or other devices, and capturing images of the paper surface with a camera during transport to detect defects on the paper surface.

Regarding 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 irradiated from an illumination device and transmitted through the sheet material is detected by a camera, is also known as the "transmission method."

JP 2014-238304 A

In conventional "transmission type" defect inspection devices, an illumination device is positioned on the optical axis of the imaging device. However, when an illumination device is positioned on the optical axis of the imaging device in this way, if the sheet-like material has hole-like defects or perforation holes, diffraction of light occurs as 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, with sheets that have pre-formed perforations, when holes are formed on the paper surface, it is necessary to distinguish whether they are known perforations or unknown defects. However, if the size and shape of the holes cannot be accurately detected through light diffraction, it becomes difficult to determine whether the holes are perforations or defects.

The primary objective of the present invention is to provide a defect inspection technology that can more accurately detect the size and shape of holes that occur in sheet-like materials.

After extensive research into ways to solve the problems of the conventional inventions described above, the inventors of the present invention discovered that by positioning a light source outside the angle of view of the imaging device in a transmission-type defect inspection device, it is possible to more accurately detect the size and shape of holes formed in a sheet-like object. Based on this discovery, the inventors realized that the problems of the conventional technology could be solved, and completed the present invention. Specifically, the present invention has the following configuration or steps.

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 the inspected portion of the 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. In this case, 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 located outside the angle of view.

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

In the defect inspection device according to the present invention, it is preferable that the imaging device is arranged so that its optical axis is substantially perpendicular to the area to be inspected, and that one or more light sources are arranged so that their optical axes are tilted relative to the area to be inspected. By arranging the imaging device so that its optical axis is perpendicular to the area to be inspected on the sheet-like object in this way, the imaging device and the sheet-like object are essentially directly opposite each other, allowing accurate imaging of the shape of holes that have occurred in the sheet-like object. In this case, tilting the optical axis of the light source relative to the area to be inspected on the sheet-like object allows high illuminance at the area to be inspected. In particular, it is preferable that the imaging device and light source are arranged so that the optical axis of the imaging device and the optical axis of the light source intersect within the plane of the area to be inspected on the sheet-like object.

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

The defect inspection device according to the present invention preferably further comprises 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 on the sheet-like material in the captured image that match the characteristics of non-defective areas stored in the database and other defects. This makes it possible to prevent perforations or other holes from being detected as defects, even if they are formed in the sheet-like material. In particular, as described above, the present invention makes it possible to more accurately detect the size and shape of holes occurring in the sheet-like material, making it easier to distinguish between known perforation holes and other unknown hole-like defects.

A second aspect of the present invention relates to a method for manufacturing a sheet-like material. The method for manufacturing a sheet-like material according to the present invention 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 described above.

This invention makes it possible to more accurately detect the size and shape of holes that occur in sheet-like materials.

FIG. 1 shows a schematic diagram of a part of the manufacturing process of a sheet material. FIG. 2 shows an example of the configuration of a defect inspection device according to the first embodiment. FIG. 3 shows an example of the configuration of a defect inspection device according to the second embodiment. FIG. 4 shows an example of the configuration of a defect inspection device according to the third embodiment.

The following describes embodiments of the present invention using the drawings. The present invention is not limited to the embodiments described below, and also includes appropriate modifications of the embodiments below that would be obvious to a person skilled in the art.

1. First embodiment
A first embodiment of the present invention will be described with reference to FIGS. 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 paper and plastic objects. In particular, the sheet-like object is preferably sanitary paper for home use, such as tissue paper or toilet paper. "Sanitary paper" refers to "sanitary paper" as defined in the JIS "Terminology for Paper, Paperboard, and Pulp" (JISP 0001). "Sanitary paper" includes towels, sanitary tissue, tissue paper, toilet paper, and tissue paper. The sanitary paper manufactured by the present invention is preferably thin paper with a basis weight ranging from 10 to 25 g/ ^m² . Furthermore, the sanitary paper may be a single-ply product consisting of a single sheet, or a two-ply or three-ply or more product consisting of two or three or more overlapping sheets. In the example shown in FIG. 1, sanitary paper is obtained by overlapping two sheets to form a laminated sheet, and then embossing and perforating the laminated sheet. Furthermore, defect inspection of the sanitary paper is performed after the perforation process.

The process of manufacturing base paper for sanitary paper basically involves a preparation process in which raw pulp fiber (pulp slurry) is obtained, and a papermaking process in which raw pulp fiber is separated from the raw pulp fiber to form a fiber web and then dried. In the preparation process, the raw pulp slurry, which is the raw material for sanitary paper, is prepared. Papermaking raw material is primarily made 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 paper mulberry, mitsumata, hemp, kenaf, etc.; 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, one 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 pulp or may be beaten in whole or in part. 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, raw paper rolls for sanitary paper are produced, and the raw paper is pulled out from multiple raw paper rolls and stacked, and various processes (such as embossing and perforation) are performed to obtain sanitary paper.

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 base roll 11 and a second base roll 12 are located upstream of the device. A long first sheet S1 is wound around the first base roll 11, and a long second sheet S2 is wound around the second base roll 12. When the first sheet S1 and the second sheet S2 are unwound from the first base roll 11 and the second base roll 12, respectively, the sheets S1 and S2 are transported downstream of the device via driven-rotating transport rollers and driven-rotating guide rollers, 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.

The embossing unit 30 is located downstream of the first overlapping unit 20. In the example shown in Figure 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, for example, comprises embossing rollers 31 and 32 and receiving rollers 33 and 34 positioned opposite each other across the transport 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 embossing roller 31 and 32 has multiple protrusions corresponding to the embossing pattern to be imparted to each sheet S1 and S2. On the other hand, each receiving roller 33, 34 can be, for example, a metal roller with a recessed pattern formed on its outer surface that is complementary to the raised pattern of the embossing rollers 31, 32, or a rubber roller with a rubber-coated outer surface. In the embossing section 30, sheets S1, S2 are introduced between the embossing rollers 31, 32 and the receiving rollers 33, 34, and by sandwiching and pressing them, an embossment pattern corresponding to the raised portions of the embossing rollers 31, 32 can be applied to the surface of each sheet S, S2.

The 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, each of which has been separately embossed in the embossing section 30, are overlapped. 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.

The perforation processing unit 50 is located downstream of the second overlapping unit 40. The perforation processing unit 50 forms perforations at regular intervals in the laminated sheet, extending in the width direction (a direction perpendicular to the conveying direction in a plane). Forming the perforations makes it easier to separate the laminated sheet at specified 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 multiple blades arranged intermittently in a perforation pattern along the axial direction of its roller. When the laminated sheet is sandwiched between the fixed blade 51 and the rotary blade 52, the blades form perforations in the laminated sheet. Examples of sheet products that require perforations include toilet paper and kitchen paper.

The log forming unit 70 is located downstream of the perforation processing unit 50. In the log forming unit 70, after perforation processing, the laminated sheet is wound up to a predetermined length using a take-up roller to form a log. The laminated sheet log is then transported to a cutting unit (not shown) and cut to a predetermined width using a log saw or similar device to create individual sheet products. This process can produce roll-shaped sheet products such as toilet roll and kitchen roll. However, the present invention can also be applied to sheet products such as tissue paper.

As shown in FIG. 1, the camera 211 and light source 212 of the defect inspection device 200 are disposed between the perforation unit 50 and the log formation unit 70. In this embodiment, the defect inspection device 200 inspects a laminated sheet (hereinafter also referred to as sanitary paper S) made by overlapping two layers of sheets S1 and S2 for defects. Therefore, it is sufficient to provide at least one defect inspection device 200 downstream of the overlapping area 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 one immediately after the perforation unit 50.

The defect inspection device 200 includes a camera 211 (camera) installed on one side (front side) of the sanitary paper S so that it faces the paper surface, and an image analyzer 220 connected to the camera 211 via a wired or wireless connection. The defect inspection device 200 also includes a light source 212 located on the other side (back side) of the sanitary paper, i.e., the opposite side from the camera 211. The sanitary paper S is transported at a constant speed in a constant direction, particularly in the portion facing the camera 211. The back side of the sanitary paper S is illuminated by the light source 212, and light that passes through the sanitary paper S is introduced to the camera 211. In this way, the camera 211 captures the light emitted from the light source 212 that passes through the surface of the sanitary paper S, thereby acquiring the captured image. The captured image of the sanitary paper acquired by the camera 211 is input to the image analyzer 220, which then analyzes whether any defects have occurred 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.

Figure 2 shows an example of the arrangement of the imaging device 211 and light source 212 for the defect inspection device 200 according to the first embodiment. As shown in Figure 2, the imaging 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 Figure 2, "defects" that have occurred on the sanitary paper S are indicated by the symbol D. Examples of defects include holes, stains, streaks, foreign matter, and other quality defects that render the sanitary paper unsuitable for sale. Also, in Figure 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 imaging 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 Figure 2, the "angle of view" of the imaging device 211 is indicated by the symbol W, and the "angle of view range" of the imaging device 211 is indicated by a dashed line. Also, in Figure 2, the area on the surface of the sanitary paper S photographed by this photographing device 211 is referred to as the "photographing range."

The image capture device 211 is a camera for capturing still or video image data. The image data captured by the image capture device 211 is sent to the image analysis device 220 (see Figure 1), where a predetermined image analysis is performed for defect detection. The camera is realized, for example, by 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 charge from the photoelectric conversion element and generates image data, and IC memory. The camera may capture still images or videos at a predetermined frame rate.

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 sanitary paper S 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.

The light source 212 is a light that illuminates the imaging range of the sanitary paper S photographed by the imaging device 211. It is preferable that the light source 212 emits white light. Examples of light sources 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 use a spot light source, whose illumination range (spot size) and optical axis are easy to control. Using a spot light source allows light to be emitted in a limited direction and range from the light source. In Figure 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 dotted line. In the example shown in Figure 2, etc., a spot light source with an illumination range (diameter) that expands in a tapered shape around the optical axis is used as the light source 212. It should be noted that a spot light source with an illumination range that is the same at infinity can also be used.

As shown in Figure 2, the light source 212 is positioned to illuminate an area that includes 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 that is 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 the transmission method.

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

Furthermore, the angle of view W of the image capture 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 image capture device 211 is wide, it becomes difficult to position the light source 212 outside the range of the angle of view of the image capture device 211. For this reason, it is preferable that the angle of view of the image capture device 211 be 60 degrees or less, and particularly 50 degrees or less.

Furthermore, as shown in Figure 2, it is preferable that the photographing device 211 be positioned 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 positioning 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. Therefore, in order to narrow the illumination range of the light source 213 to some extent, it is preferable to use a spot light source as this light source 213.

Furthermore, as shown in FIG. 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 must 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.

It is also preferable to position 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.

The images captured by the photographing device 211 are analyzed by the image analysis device 220. The image analysis device 220 analyzes the images of the sanitary paper acquired by the photographing device 211 and inspects the sanitary paper for defects. A general-purpose computer may be used as the image analysis device 220. The image analysis device 220 is equipped with an interface for the photographing device, and receives image data acquired by the photographing device 211. The image analysis device 220 is equipped with, 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 memory unit. The control and calculation unit can be implemented by a processor such as a CPU or GPU. The memory unit can be implemented 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 accepts operational information from humans. The display unit may be a display device such as an LCD display or an organic EL display, and may display image data acquired from the imaging device 211.

The image analysis device 220 (specifically, the control and calculation unit) basically analyzes the captured image acquired by the imaging 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 group of pixels in the image data of the sanitary paper, and if there are any areas that are 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 area corresponding to the hole in the captured image will appear brighter. Also, if there is foreign matter (e.g., soot or oil stains) attached to the sanitary paper, the area containing the foreign matter will appear darker. In this way, the image analysis device 220 determines that an area where there is an abnormality in the brightness of the image data is a defective area 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.

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 in the captured image that may indicate defects, 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.

[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 configuration that differs from the first embodiment will be mainly described, and the configuration that is essentially the same as that of the first embodiment will be assigned the same reference numerals and detailed description will be omitted.

In the second embodiment shown in Figure 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. Like the first light source 212, the second light source 213 is arranged on the back side of the sanitary paper S, i.e., on the opposite side from the imaging device 211. In this way, it is possible to perform defect inspection using the transmission method using multiple light sources 212, 213. Also, in this second embodiment, as in the first embodiment, the first light source 212 and the second light source 213 are arranged outside the angle of view range of the imaging device 211. Furthermore, it is preferable to arrange the imaging 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.

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, 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, 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 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.

In addition, although not shown in the figures, as a modified example of the third embodiment, it is also possible to place 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 placing multiple light sources on the same side as the photographing device 211, floating matter (e.g., paper dust) present between the surface of the sanitary paper S and the photographing device 211 can be illuminated from multiple directions, making it 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 on the paper surface.

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 place another light source on the back side of the sanitary paper S, i.e., on the side opposite the photographing device 211, similar to the second light source 213 (see Figure 3) in the second embodiment described above. Furthermore, it is also possible to place multiple light sources on both the front and back sides of the sanitary paper S.

In the above, this specification has described embodiments of the present invention with reference to the drawings in order to express the content of the present invention. However, the present invention is not limited to the above embodiments, and includes modifications and improvements that would be obvious to a person skilled in the art based on the matters described in this specification.

DESCRIPTION OF SYMBOLS 11...First raw web roll 12...Second raw web roll 20...First overlapping section 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 section 41...Overlapping roller 50...Perforation processing section 51...Cutter roller 52...Anvil roller 200...Defect inspection device 211...Photographing 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-like material)

Claims (5)

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. The defect inspection device according to claim 1 , wherein the imaging device is disposed so that its optical axis is perpendicular to the portion to be inspected. 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. 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;
4. A defect inspection device according to claim 1, wherein, among the defects occurring on the sanitary paper in the captured image, the device distinguishes between defects that match the characteristics of non-defective areas stored in the database and other defects. 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.