JP2023089140A - Device for inspecting sheet-like material for defects and method for manufacturing the same - Google Patents

Abstract

To provide a defect inspection device that can efficiently detect a foreign material on a sheet-like material even if the foreign material is only slightly colored.SOLUTION: A device 200 for inspecting a sheet-like material S includes: an imaging device 211 arranged on one surface side of an inspection target site of a sheet-like material S, the imaging device imaging a surface of the inspection target site; at least one of light sources 212, 213 arranged on one surface side of the inspection target site, the at least one light source illuminating the imaging range of the imaging device on the surface of the inspection target site; and a white member 214 arranged in a site which overlaps with the imaging range at least partially on the other surface side of the inspection target site. As the white member 214, a plate including a white curved part in contact with the inspection target site is employed.SELECTED DRAWING: Figure 5

Description

The present invention relates to a defect inspection apparatus for sheet-like articles such as sanitary paper and a method for manufacturing sheet-like articles using the same.

Conventionally, regarding household sanitary paper such as toilet paper and tissue paper, rollers have been used as a method for inspecting defects (holes, stains, streaks, foreign matter, etc.) that occur during the manufacturing process. It is known to detect defects occurring on a paper surface by photographing the paper surface with a camera while the paper surface is being conveyed at high speed by means of a camera.

For example, regarding defect inspection technology for a sheet-like object to be inspected such as paper, film, etc., Patent Document 1 discloses that illumination light is applied to the object to be inspected to create a shadow on the surface, and specular reflection or There is disclosed an apparatus for picking up an image of irregular reflection with a camera in a dark field sensitivity region and processing the image signal of the picked-up image to detect defects. In this way, the inspection method in which the camera detects the reflected light emitted from the lighting and reflected on the paper surface is also called the "reflection method."

Further, Patent Documents 1 and 2 disclose a defect inspection apparatus having a function of discriminating the types of detected defects. For example, in these patent documents, a photographed image is divided into blocks (lattice) consisting of a predetermined number of pixel matrices, and the types of defects (holes, stains, etc.) detected based on the density information (that is, brightness information) in each block. etc.) have been proposed.

Japanese Unexamined Patent Application Publication No. 2017-21003 JP-A-08-145907

By the way, as in the defect inspection apparatus described in Patent Document 1, in a "reflection type" apparatus in which an imaging device and a light source are arranged on one side of a sheet-like object to be inspected, dirt adhering to the sheet-like object It will be reflected in the state as shown in FIG. That is, assuming that the sheet-like material is almost white, stains (soot stains, machine oil stains, etc.) appear darker than the surface of the sheet-like material. Here, in the reflection method, the paper surface of the sheet-like object is also captured in the photographed image with a relatively low brightness. (difference between brightness and darkness) becomes small, and dirt adhering to the paper surface may not be detected. On the other hand, if you try to accurately detect dirt with low contrast, for example, you will need a high-performance imaging device, which will lead to an increase in equipment costs, and dust and paper dust that do not need to be detected as defects will appear on the paper surface. There is also a possibility that an error such as a shadow cast on the surface being detected as a defect may occur.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a defect inspection apparatus and method capable of efficiently detecting light-colored foreign matter adhered to a sheet.

The inventors of the present invention, as a result of intensive studies on means for solving the above-described problems of the prior art, found that a "reflection type" defect inspection apparatus in which an imaging device and a light source are arranged on one side of a sheet-shaped object has a sheet By providing a white member on the other side of the sheet, the contrast between the foreign matter adhering to the sheet and the paper surface is increased, and even if the foreign matter with a light color is adhered to the sheet, it can be effectively removed. I got the knowledge that it can be detected. Based on the above findings, the inventors of the present invention conceived that the problems of the prior art can be solved, and completed the present invention. Specifically, the present invention has the following configurations and steps.

A first aspect of the present invention relates to a sheet defect inspection apparatus. A defect inspection apparatus according to the present invention includes an imaging device, one or more light sources, and a white member. The imaging device is arranged on one side of the inspected portion of the sheet-like object, and captures the surface of the inspected portion to obtain an image of the sheet-like object. The light source is arranged on one side of the site to be inspected (that is, on the same side as the imaging device), and illuminates the imaging range of the imaging device on the surface of the site to be inspected. The white member is arranged on the other side of the site to be inspected at a position that at least partially overlaps with the imaging range of the imaging device. In the specification of the present application, "white" means a color with an L ^* value of 60 or more in the CIE-L ^* a ^* b ^* color system. In particular, the white member preferably has an L ^* value of 70 or more, more preferably 80 or more, and even more preferably 85 or more. The white member may be made of a material different from that of the sheet-shaped object to be inspected, or may be made of the same material. For example, if the sheet is white, another part of the sheet may be superimposed on the part to be inspected of the sheet and used as a white member, or another part of the sheet to be inspected may be used. It is also possible to stack sheets and use them as a white member. In this way, in a reflection-type defect inspection system, by arranging a white member on the back side of the inspected part of the sheet, the contrast between the paper surface of the inspected part and the foreign matter adhering to it in the photographed image can be improved. becomes larger, the foreign matter detection sensitivity can be increased.

In the defect inspection apparatus according to the present invention, the white member may be a plate including a white flat portion formed parallel to the inspected portion of the sheet. In this case, the flat portion of the plate is preferably arranged at a fixed distance from the site to be inspected. In addition, when the plate (white member) is arranged without contact with the sheet-like material, the distance between the plate and the sheet-like material is preferably close, for example, within 20 cm or within 10 cm, preferably within 5 cm. is particularly preferred. In this way, by making the plate non-contact with the sheet-like material, it becomes easier to arrange the plate. In addition, it is possible to avoid the generation of static electricity due to the contact between the plate and the sheet-like material and the formation of wrinkles on the sheet-like material.

In the defect inspection apparatus according to the present invention, the white member may be a plate including a white curved portion that contacts the inspected portion of the sheet. By arranging the plate including the curved surface portion in contact with the sheet-like material in this manner, the contrast between the paper surface of the sheet-like material and the foreign matter adhering thereto can be increased. Furthermore, since the plate and the sheet are always in contact with each other, it is difficult for paper dust and the like to accumulate on the plate.

In the defect inspection apparatus according to the present invention, the white member may be a roller including a white peripheral surface that comes into contact with the inspected portion of the sheet. By using the rollers in this manner, it is possible to efficiently inspect the adhesion of foreign substances or the like at the contact points between the rollers and the sheet-like material while conveying the sheet-like material. Further, by making the peripheral surface of the roller that contacts the sheet white, the contrast between the paper surface of the sheet and the foreign matter adhering thereto can be increased.

In the defect inspection apparatus according to the present invention, the sheet-like object to be inspected may be wound into a roll. In this case, it is preferable that the portion of the sheet to be inspected by the photographing device or the like is located on the outermost layer of the sheet wound into a roll. Moreover, it is preferable that the white member is another layer of the sheet-like material located on the inner layer side of the site to be inspected. In this way, by using the outermost layer of the roll body of the sheet material as the portion to be inspected, it is possible to use another layer located on the inner layer side as the white member. This makes it possible to easily increase the contrast between the paper surface of the sheet and the foreign matter adhering to it without using a device such as a plate or roller as described above. In addition, in the process of manufacturing a sheet, soot stains and the like are often deposited in streaks on the surface of the paper in a substantially straight line along the conveying direction. When the sheet-like material with such streak-like dirt adhered is wound into a roll, the streak-like dirt is piled up over a plurality of layers. In such a state where dirt is piled up, the outermost layer of the sheet roll body is used as the part to be inspected, so that the color of the dirt appears darker in the photographed image. It can be even bigger.

A second aspect of the present invention relates to a method for manufacturing a sheet-like material. A manufacturing method according to the present invention includes a step of obtaining a sheet-like material and a step of inspecting the presence or absence of defects in the sheet-like material using the above-described defect inspection apparatus according to the first aspect.

ADVANTAGE OF THE INVENTION According to this invention, even when the foreign material with a light color adheres to a sheet-like article, the said foreign material can be detected efficiently.

FIG. 1 shows an example of the configuration of a paper machine. FIG. 2 shows a configuration example of a defect inspection apparatus according to the first embodiment. FIG. 3 is a block diagram showing an example of the functional configuration of the defect inspection device. FIG. 4 schematically shows an example of a photographed image acquired by the defect inspection apparatus according to the present invention. FIG. 5 shows a configuration example of a defect inspection apparatus according to the second embodiment. FIG. 6 shows a configuration example of a defect inspection apparatus according to the third embodiment. FIG. 7 shows a configuration example of a defect inspection apparatus according to the fourth embodiment. FIG. 8 schematically shows an example of an image captured by a conventional "reflection type" defect inspection apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments for carrying out the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments described below, and includes appropriate modifications within the scope obvious to those skilled in the art from the following embodiments.
In the specification of the present application, "A to B" means "A or more and B or less."

[1. First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. The present invention relates to a sheet defect inspection apparatus and a method for manufacturing a sheet using the defect inspection apparatus. Examples of sheet materials include those made of paper and plastic. In particular, the sheet material is preferably sanitary paper for household use such as tissue paper or toilet paper. "Sanitary paper" means "sanitary paper" defined in JIS "Paper, Paperboard and Pulp Terminology" (JISP 0001). "Sanitary paper" includes towels, sanitary paper, tissues, toilet paper, and tissue paper. The sanitary paper produced by the present invention is preferably thin paper having a basis weight in the range of 10-25 g/m ² . The sanitary paper may be a one-ply product consisting of one sheet, or may be a two-ply or three-ply product in which two or three or more sheets are superimposed. In particular, in the present invention, the sheet material is preferably white with an L ^* value of 60 or more, 70 or more, 80 or more, or 85 or more in the CIE-L ^* a ^* b ^* color system. In the following description, one-ply white sanitary paper is taken as an example of the sheet material.

The manufacturing method of sanitary paper basically consists of a preparation process for obtaining a papermaking raw material (pulp slurry), which is a suspension of raw pulp fibers, and a papermaking process for forming a fiber web by drawing the raw pulp fiber from the papermaking raw material and drying it. including.

In the adjustment process, the raw material for papermaking (pulp slurry), which is the raw material for sanitary paper, is adjusted. Pulp is the main raw material for papermaking. Examples of raw material 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. (SCP) and semi-chemical pulp such as chemigroundwood pulp (CGP); mechanical pulp such as ground wood pulp (GP) and thermomechanical pulp (TMP, BCTMP); Examples include non-wood pulp, cotton pulp such as cotton linter and cotton lint, and deinked pulp made from waste paper. As the raw material for papermaking, one type of raw material pulp may be used, or a plurality of types of raw material pulp may be used in an arbitrary ratio, depending on the use and required performance of the thin paper. The raw material pulp may be unbeaten pulp, or may be wholly or partially beaten.

The papermaking raw material prepared in the preparation process is made into sanitary paper in the papermaking process. The paper making process can be performed using the paper machine 100 . As shown in FIG. 1, the paper machine 1000 includes a wire part 110, a press part 120, a dry part 130, a calendar part 140, and a reel part 150. As shown in FIG.

The wire part 110 is a part for squeezing water contained in the pulp slurry to form a thin wet paper web. The wire part 110 comprises a pair of two upper and lower wires 111 in which a paper net is formed into an endless track belt, and a head box 112 for spraying pulp slurry between the two wires 111 . The head box 112 sprays the pulp slurry thinly toward the nip portion of the wire 111 . Moisture contained in the pulp slurry is squeezed out from the mesh of the two wires 111 that are pressed against each other by pressure from the forming rolls 113 . The wire 111 is run by a forming roll 113 functioning as a drive roll and a drive roll 14 . The forming roll 113 and the drive roll 114 are arranged so as to contact the wire 111 , and the wire 111 is given a driving force by the rotational force of the forming roll 113 and the drive roll 114 being transmitted to the wire 111 .

The press part 120 is a part that further removes moisture from the thin wet paper web formed by the wire part 110 . The press part 120 includes a dryer felt 121 made of felt in the form of an endless track belt, and a plurality of felt rolls 122 that contact the dryer felt 121 and rotate as the dryer felt travels. In the press part 120, the wet paper fed from the wire part 110 is placed on the surface of the dryer felt 121, and the wet paper is permeated through the fibrous dryer felt 121 to further remove moisture contained in the wet paper.

The dry part 130 is a part that further dries the wet paper from which moisture has been removed in the press part 120 . The dry part 130 includes a heatable columnar Yankee dryer 131 and a hood 132 having a hot air jet nozzle. In the dry part 130, wet paper is pressed against the outer peripheral surface of the Yankee dryer 131 which is heated by blowing steam into it, and hot air is blown to the outer peripheral side of the Yankee dryer 131 from an injection port provided inside the hood 132. Dry the wet paper by Also, the dry base paper formed on the surface of the Yankee dryer cylinder 131 is creped by a doctor blade 133 and peeled off. The crepe ratio of the base paper is preferably 15 to 45% or 20 to 38%, for example. The crepe ratio is a value calculated by [(peripheral speed of Yankee dryer)−(peripheral speed of reel drum))/(peripheral speed of Yankee dryer)]×100(%).

The calender part 140 is a part where the base paper dried in the dry part 130 is calendered. The calender part 140 comprises a calender roll 141 and a receiving roll 142 . In the calender part 140, the base paper is sandwiched between a calender roll 141 and a receiving roll 142 and pressed to smooth the surface of the base paper, densify the structure, make the paper thickness uniform, and give gloss. . Although the types of the calender roll 141 and the receiving roll 142 are not particularly limited, for example, those made of metal can be preferably used.

The reel part 150 is a part for winding the calendered base paper. The reel part 150 has a reel drum 151 . In the reel part 150 , the core 152 is fixed to the reel drum 151 , the base paper is wound around the core 152 , and the base paper is wound around the core 152 by rotating the reel drum 151 . As a result, it is possible to obtain a raw fabric roll in which the raw paper is wound into a roll.

In this embodiment, a defect inspection device 200 is installed between the calendar part 140 and the reel part 150 of the paper machine 100 . The defect inspection apparatus 200 includes an imaging device 211 (camera) installed on one side (surface side) of the base paper of sanitary paper so as to face the paper surface, and an image analysis device connected to the imaging device 211 by wire or wirelessly. 220. Furthermore, the defect inspection device 200 includes a plurality of light sources 212 and 213 arranged on one side (surface side) of the base paper of the sanitary paper together with the photographing device 211, and a plurality of light sources 212 and 213 arranged on the other side (back side) of the base paper of the sanitary paper. white member 214 is provided. The paper machine 100 conveys the stencil sheet at a constant speed in a certain direction between the calendar part 140 and the reel part 150, particularly in the portion where the photographing device 211 faces the stencil sheet. Also, one side (surface side) of the original paper is illuminated by light sources 212 and 213 , and the light reflected on the paper surface is introduced into the photographing device 211 . In this manner, the image capturing device 211 acquires a captured image by capturing the light reflected from the paper surface of the original paper among the light emitted from the light sources 212 and 213 . The photographed image of the sanitary paper obtained by the photographing device 211 is input to the image analysis device 220, and the image analysis device 220 analyzes whether or not there is a defect on the surface of the sanitary paper. The image analysis device 220 also performs processing for determining the type of defects on the paper surface included in the captured image.

FIG. 2 shows an arrangement example of an imaging device 211, light sources 212 and 213, and a white member 214 in the defect inspection apparatus 200 according to the first embodiment. As shown in FIG. 2, a photographing device 211 and a plurality of light sources 212 and 213 are arranged on the front side (one side) of the sanitary paper S, and a white member 214 is arranged on the back side (the other side) of the sanitary paper. is placed. In addition, in FIG. 2, the defect generated on the sanitary paper S is denoted by D. As shown in FIG. Examples of defects include quality defects that make sanitary paper unsuitable for sale, such as stains, holes, streaks, and foreign matter.

The imaging device 211 is a camera for acquiring image data of still images or moving images. The image data acquired by the photographing device 211 is transmitted to the image analysis device 220 (see FIG. 3), and predetermined image analysis for defect detection is performed. A camera includes, 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 charge amount from the photoelectric conversion element and generates image data, an IC memory, and the like. is realized by Note that the camera may take a still image, or may take a moving image at a predetermined frame rate.

It is preferable that the imaging surface (lens) of the imaging device 211 is arranged substantially parallel to the surface of the sanitary paper S. As shown in FIG. Therefore, when a straight line is drawn perpendicularly from the imaging surface of the photographing device 211, the straight line intersects the plane of the paper substantially perpendicularly. As a result, the photographing device 211 can photograph the surface of the sanitary paper S without distortion. In FIG. 2, the imaging range of the imaging device 211 is indicated by a dashed line.

The light sources 212 and 213 are lights that illuminate the photographing range of the sanitary paper S photographed by the photographing device 211 . The light sources 212 and 213 preferably emit white light. Examples of light sources 212, 213 include fluorescent lamps, LEDs (light emitting diodes), OLEDs (organic light emitting diodes), lamps, arc lamps, incandescent lamps, and the like. Further, the light sources 212 and 213 can be spot light sources, parallel light sources (surface light sources), or point light sources. Most preferred. If a spot light source is used, it is possible to irradiate light in a limited direction and range from the light source. In FIG. 2, the illumination ranges of the light sources 212 and 213 are indicated by dashed lines, and the optical axes of the light sources 212 and 213 are indicated by dashed lines. The "optical axis" means a straight line passing through the center of the light emitting portion of the light source and perpendicular to the light emitting surface. In the example shown in FIG. 2 and the like, the light sources 212 and 213 are spot light sources whose illumination range (diameter) is tapered around the optical axis. As the spot light source, one having the same illumination range at infinity can also be used.

As shown in FIG. 2, each of the light sources 212 and 213 is arranged to illuminate a range including the imaging range of the imaging device 211 . That is, in the present embodiment, the photographing device 211 photographs the portion to be inspected on the surface of the sanitary paper S, and the light sources 212 and 213 photograph the portion to be inspected on the surface of the sanitary paper S photographed by the photographing device 211. Illuminate. Therefore, the light emitted from the light sources 212 and 213 and reflected by the surface of the sanitary paper S is introduced into the imaging device 211 . In this way, the photographing device 211 acquires a photographed image of the sanitary paper S by the “light reflection method”.

In addition, as shown in FIG. 2, in a cross-sectional view in the longitudinal direction of the sanitary paper S, the optical axes of the light emitted from the light sources 212 and 213 are inclined at a predetermined angle θ with respect to the surface of the sanitary paper S. there is The inclination angle θ of the optical axis of the main light sources 212 and 213 is preferably, for example, 30 degrees to 90 degrees, 35 degrees to 85 degrees, or 45 degrees to 80 degrees. In the example shown in FIG. 2, the inclination angles of the optical axes of the first light source 212 and the second light source 213 are equal, but the inclination angles of the optical axes of the respective light sources may be different.

In addition, in a cross-sectional view of the sanitary paper S in the longitudinal direction, the first light source 212 and the second light source 213 are arranged so as to sandwich the photographing device 211 . That is, the photographing device 211 is positioned between the first light source 212 and the second light source 213 in the sanitary paper transport direction. Also, the photographing device 211 is installed at a position higher than the light sources 212 and 213 . That is, the distance from the photographing device 211 to the surface of the sanitary paper S is greater than the distance from the light sources 212 and 213 to the surface of the sanitary paper S.

In this way, when the surface of the sanitary paper S is photographed by the “light reflection method”, by arranging the plurality of light sources 212 and 213 as described above, the light existing between the surface of the sanitary paper S and the photographing device 211 Floating matter (for example, paper dust) can be illuminated from multiple directions, making it possible to lighten the color of the shadow of the floating matter projected on the paper surface. This makes it possible to analyze the photographed image acquired by the photographing device 211 and more clearly detect the defects adhered to the paper surface.

As shown in FIG. 2, the white member 214 is arranged on the side (rear side) opposite to the photographing device 211 and the light sources 212 and 213 . The white member 214 is arranged on the back side of the white sanitary paper S for the purpose of increasing the brightness of the surface of the sanitary paper S in the photographed image. Specifically, the light emitted from the light sources 212 and 213 is partially transmitted through the surface of the sanitary paper S, and the transmitted light reaches the white member 214 arranged on the back side of the sanitary paper S. do. The white member 214 reflects all frequency components of transmitted light because at least the surface on the side of the sanitary paper S is white. Therefore, the inspected portion of the sanitary paper S on which the white member 214 is arranged on the back side has a high brightness in the photographed image. In this embodiment, a plate-shaped member having a surface parallel to the surface of the sanitary paper S is used as the white member 214 . The material forming the white member 214 is not particularly limited, and may be made of paper, plastic, or metal.

In addition, in the embodiment shown in FIG. 2, the white member 214 includes a white planar portion formed parallel to the paper surface of the sanitary paper S, and this planar portion is separated from the sheet-like material by a constant distance G. It is located in the The distance G between the plane portion of the white member 214 and the surface of the sanitary paper S is preferably as short as possible so that the white member 214 does not interfere with the transportation of the sanitary paper. Specifically, in FIG. 2, assuming that the sanitary paper S does not exist, the photographing range on the plane portion of the white member 214 by the photographing device 211 is indicated by P, and the first light source 212 , and the range where the irradiation light from the second light source 213 overlaps on the plane portion of the white member 214 is denoted by L. At this time, it is preferable that the length of the range L where the irradiation light overlaps is 80% or more or 90% or more of the length of the photographing range P in the transport direction of the sanitary paper S (horizontal direction in the figure). , 100% or more. That is, it is particularly preferable that the length of the range L is equal to or longer than the length of the photographing range P (L≧P). The distance G between the white member 214 and the sanitary paper S may be set so as to satisfy such conditions. For example, the gap G is preferably 1 cm to 20 cm or 2 to 10 cm. In this manner, by photographing the range where the light emitted from the light sources 212 and 213 overlaps on the plane portion of the white member 214 with the photographing device 211, the brightness of the surface of the sanitary paper S in the photographed image can be effectively increased. can do. It should be noted that such a plate-like white member 214 may be in contact with the sheet-like material (that is, the gap G is zero). In this case, the portion of the white member 214 that contacts the sheet should be rounded or made of a smooth material so that the sheet does not tear or wrinkle when it comes into contact with the plate-like white member 214 . Just do it.

Although not shown, the defect inspection apparatus 200 may further include removing means for removing dust (such as paper dust) adhering to the flat portion of the white member 214 . As the removal means, a blower that continuously or intermittently blows air between the surface of the sanitary paper and the flat surface of the white member 214, and a brush or wiper that automatically or manually wipes the flat surface of the white member 214 are used. can be used.

FIG. 3 shows a functional configuration example of the image analysis device 220 connected to the imaging device 211 . The image analysis device 220 analyzes the image of the sanitary paper acquired by the photographing device 211 with the above-described configuration, and inspects the presence or absence of defects in the sanitary paper. A general computer may be used for the image analysis device 220 . The image analysis device 220 has an interface for the imaging device, and receives image data acquired by the imaging device 211 . The image analysis device 220 includes a control calculation section 221 , a storage section 222 , an operation section 223 and a display section 224 . The control calculation unit 221 controls each element 222 to 224 and performs image analysis processing of the image data acquired from the imaging device 211 according to the computer program for defect inspection stored in the storage unit 222 . The control calculation unit 221 can be implemented by a processor such as a CPU or GPU. The storage unit 222 can be realized by a non-volatile memory such as HDD or SDD, or a volatile memory such as RAM or DRAM. The operation unit 223 is composed of an input device such as a mouse, keyboard, touch panel, microphone, etc., and receives operation information by a person. The display unit 224 may be a display device such as a liquid crystal display or an organic EL display, and may display image data acquired from the imaging device 211 . Note that the display unit 224 may be integrated with the operation unit 223 to form a touch panel display.

The control calculation unit 221 of the image analysis device 220 basically analyzes the photographed image acquired by the photographing device 211 and determines whether or not there is a defect on the surface of the sanitary paper. For example, the image analysis device 220 measures the brightness (density) for each pixel or pixel group of the image data of sanitary paper, and if there is a darker (or brighter) portion than the normal brightness range, the image data of sanitary paper is defective. For example, when a foreign substance (such as soot or oil) adheres to the sanitary paper, the brightness of the foreign substance appears dark. In this way, the control calculation unit 221 determines that the part where the brightness of the image data is abnormal is the defective part of the sanitary paper.

For example, as shown in FIG. 4, when foreign matter such as dirt adheres to the surface of the sanitary paper, the brightness of the area where the foreign matter adheres is low. In this way, it can be determined that a defect is attached to a portion with a lower brightness than the normal brightness of the paper surface. For example, a brightness range equivalent to the brightness of the paper surface may be regarded as normal, and a defect with a brightness lower than this normal brightness range may be determined as a foreign matter.

As shown in Fig. 8, even in the image captured by the conventional reflection method (when no white member is placed on the back side of the sanitary paper), when assuming that the sanitary paper is almost white, , Dirt appears darker than sanitary paper. However, with the conventional reflection method, if the stain on the sanitary paper is relatively light in color, the contrast between the paper surface and the stain (difference in light and shade) becomes small, and the stain on the paper surface may not be detected. . On the other hand, as shown in Fig. 4, in the reflection method of the present invention (when a white member is placed on the back side of the sanitary paper), the brightness of the paper surface of the sanitary paper is lower than that of the conventional reflection method (Fig. 8). can be raised. As a result, the contrast between the normal area and the soiled area on the sanitary paper increases, so even if the stain is relatively light in color, the presence of stains can be detected more reliably. becomes possible. When the sanitary paper is white and white light is emitted from the light sources 212 and 213, the effects of the present invention described here become more pronounced.

[2. Second Embodiment]
FIG. 5 shows a defect inspection device 200 according to the second embodiment. In the following embodiments, descriptions of configurations similar to those of the first embodiment will be omitted, and descriptions will be given of configurations that are different.

In the second embodiment, the white member 214 includes a white curved surface portion having a curved cross section in the sanitary paper conveying direction. Also, the curved surface portion of the white member 214 is in contact with the back surface of the sanitary paper. For this reason, the sanitary paper is conveyed in the longitudinal direction while a portion (specifically, the portion to be inspected) of the paper is always in contact with the curved surface portion of the white member 214 . The white member 214 having a curved surface portion may be a plate member having an arc-shaped cross section as shown in FIG. It may be a shaped member.

Further, in the second embodiment, a plurality of light sources 212 and 213 are arranged so as to illuminate the contact portion between the sanitary paper and the white member 214, respectively. Similarly, the photographing device 211 is arranged so as to photograph the contact portion between the sanitary paper and the white member 214 . As a result, the photographing device 211 can acquire a photographed image of the contact portion between the sanitary paper and the white member 214 by the “reflection method”.

As shown in FIG. 5, since the sanitary paper S and the white member 214 are in close contact with each other, the contrast between the normal surface of the sanitary paper S and the defective portion D to which dirt or the like is adhered can be further enhanced. Also, since the white member 214 and the sanitary paper are always in contact with each other, paper dust and the like are less likely to accumulate on the reflecting surface of the white member 214 . As a result, the reflecting surface of the white member 214 is always kept clean, and the intensity of the reflected light is maintained.

[3. Third Embodiment]
FIG. 6 shows a defect inspection device 200 according to the third embodiment. In the third embodiment, a roller having a white peripheral surface is used as the white member 214 . The white peripheral surface of the roller contacts the rear surface of the sanitary paper S, and rotates in the same direction as the direction in which the sanitary paper S is conveyed. For this reason, the sanitary paper is conveyed in the longitudinal direction while a portion (specifically, the portion to be inspected) of the paper is always in contact with the white peripheral surface of the roller. The roller may be a driving roller that actively rotates by itself provided with a driving device such as a motor, or a driven roller that passively rotates as the sanitary paper S is conveyed. Also in the third embodiment, a plurality of light sources 212 and 213 are arranged so as to illuminate the contact portion between the sanitary paper and the roller. Similarly, the photographing device 211 is arranged so as to photograph the contact portion between the sanitary paper and the roller. As a result, the photographing device 211 can acquire a photographed image of the contact portion between the sanitary paper and the roller (white member 214) by the “reflection method”.

[4. Fourth Embodiment]
FIG. 7 shows a defect inspection device 200 according to the fourth embodiment. In the fourth embodiment, the photographing device 211 and the light sources 212 and 213 included in the defect inspection device 200 are arranged so that a part of the outermost layer of the sanitary paper wound around the reel drum 151 is a portion to be inspected. It is That is, the sanitary paper is wound around the core 152 attached to the reel drum 151 to be wound in a roll shape, and the number of layers is sequentially increased. The photographing device 211 is arranged at a position where a part of the surface of the outermost layer of the roll-shaped sanitary paper whose diameter is gradually expanded can be photographed. placed in position.

By arranging the photographing device 211 and the light sources 212 and 213 in this manner, a portion of the outermost layer of the roll-shaped sanitary paper becomes a portion to be inspected, as shown in the enlarged view of FIG. Moreover, the roll-shaped sanitary paper is in a state in which white paper surfaces are laminated over a plurality of layers. For this reason, the single or multiple layers of white paper positioned immediately below (on the inner layer side of) the portion to be inspected of the outermost layer functions as a "white member 214" for increasing the brightness of the portion to be inspected. In other words, by winding the sanitary paper into a roll and setting the outermost layer thereof as the portion to be inspected, it is possible to use the sanitary paper itself as the white member 214 to be inspected for foreign matter adhesion and the like.

Sanitary paper is generally transported in one direction during the manufacturing process, as in the paper machine 100 shown in FIG. For this reason, as shown in FIG. 4, for example, foreign matter such as stains caused by adhesion of soot or machine oil tends to adhere linearly along the conveying direction of the sanitary paper. When the sanitary paper is wound up by the reel drum 151 when the dirt or the like adheres approximately linearly in this way, the dirt or the like is piled up in the roll-shaped sanitary paper in the stacking direction. In other words, when dirt adheres to the surface of the outermost layer of the sanitary paper, the same dirt often adheres to the surface of the lower layer, and the dirt overlaps the upper and lower layers. Then, when the part to be inspected on the outermost layer of the sanitary paper is photographed by the photographing device 211, the dirt or the like that overlaps over a plurality of layers appears dark in the photographed image. In other words, for the normal part of the paper surface in the photographed image, the brightness is relatively high by overlapping the white paper surface over multiple layers, and for the stained part in the photographed image, there are multiple colored stains. Overlapping over the layers results in a relatively low brightness. As a result, according to the present embodiment, the contrast between foreign substances such as stains that have adhered to the surface of the sanitary paper in a straight line and other normal areas is increased, so stains on the paper surface can be detected more reliably. be able to. In particular, even light-colored stains that are difficult to detect with only one layer of sanitary paper can be easily detected as foreign matter because the density of the color in the photographed image is increased by stacking multiple layers. .

As described above, in the specification of the present application, the embodiments of the present invention have been described 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 are obvious to those skilled in the art based on the matters described in the specification of the present application.

DESCRIPTION OF SYMBOLS 100... Paper machine 110... Wire part 111... Wire 112... Head box 113... Forming roll 114... Drive roll 120... Press part 121... Dryer felt 122... Felt roll 130... Dry part 131... Yankee dryer 132... Hood 133... Doctor blade 140... Calendar part 141... Calendar roll 142... Receiving roll 150... Reel part 151... Reel drum 152... Core 200... Defect inspection device 211... Photographing device 212... First light source 213... Second light source 214... White member 220 ... Image analysis device 221 ... Control calculation unit 222 ... Storage unit 223 ... Operation unit 224 ... Display unit

Claims (3)

A defect inspection device for a sheet-like object,
a photographing device arranged on one side of the part to be inspected of the sheet-shaped object for photographing the surface of the part to be inspected;
one or a plurality of light sources arranged on the one side of the site to be inspected and illuminating an imaging range of the imaging device on the surface of the site to be inspected;
a white member arranged at a position at least partially overlapping with the imaging range on the other side of the inspection site,
The defect inspection apparatus, wherein the white member is a plate including a white curved surface portion that contacts the inspected portion. The defect inspection apparatus according to claim 1, wherein the plate is a plate-shaped portion having an arc-shaped cross section. a step of obtaining a sheet-like material;
a step of inspecting the presence or absence of defects in the sheet-like material using the defect inspection apparatus according to claim 1,
A method for producing a sheet-like article.

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