JP2020027066A - Defect inspection device for sheet-like object and manufacturing method - Google Patents

Abstract

To provide a defect inspection device capable of discriminating the kind of a defect that occurs to a sheet-like object in simple configuration and algorithm.SOLUTION: A defect inspection device comprises: an imaging apparatus 211 which is disposed at one face side of a sheet-like object and images a surface of the sheet-like object to obtain an image of the sheet-like object; one or more light sources 212 and 213 which are disposed at least at one face side of the sheet-like object and illuminate an imaging range of the imaging apparatus 211 on the surface of the sheet-like object; and an irregular reflection member 214 which is disposed at a position at least partially overlapped with the imaging range of the imaging apparatus 211 at the other face side of the sheet-like object and irregularly reflects radiation light from the light sources 212 and 213. In a case where a hole is formed on the sheet-like object, the light irregularly reflected by the irregular reflection member 214 is led through the hole into the imaging apparatus 211, such that the hole is represented bright in the picked-up image. Therefore, it is easily discriminated whether a defect which occurs in the sheet-like object is a hole or any other defect.SELECTED DRAWING: Figure 2

Description

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

  2. Description of the Related Art Conventionally, as a method for inspecting defects (holes, dirt, streaks, foreign substances, etc.) generated in a manufacturing process of household sanitary paper such as toilet paper and tissue paper, a base paper of the sanitary paper is used for a roller or the like. It is known to detect a defect that has occurred on the paper surface by photographing the paper surface with a camera while the paper is being transported at a high speed.

  For example, with respect to a defect inspection technique for a sheet-like inspection object such as a paper or a film, Patent Document 1 discloses that a shadow is formed on a surface by illuminating the inspection object with illumination light and specular reflection or reflection within the shadow. An apparatus is disclosed in which a diffuse reflection image is captured by a camera in a dark field sensitivity region, and an image signal of the obtained captured image is subjected to image processing to detect a defect. The inspection method of detecting the reflected light emitted from the illumination and reflected on the paper surface by the camera as described above is also called a “reflection method”.

  Patent Documents 1 and 2 disclose a defect inspection apparatus having a function of determining the type of a detected defect. For example, in these patent documents, a photographed image is divided into blocks (lattices) each including a predetermined number of pixel matrices, and the types of defects (holes and stains) detected based on density information (that is, brightness information) in each block. It has been proposed to determine

JP, 2017-21003, A JP-A-08-145907

  By the way, as in a defect inspection apparatus described in Patent Document 1, a “reflection type” apparatus in which an image pickup device and a light source are arranged on one surface side of a sheet-like object to be inspected, dirt adhering to the sheet-like object and the sheet The hole formed in the object is reflected in a state as shown in FIG. 7, for example. That is, assuming that the sheet is almost white, dirt (such as stains to which machine oil has adhered) appears in a darker color with a lower brightness than the sheet, and the holes have the same level as the dirt. The image is taken as a dark color or a darker color having a lower brightness. As described above, when the photographed image of the sheet-like object includes dirt and holes, each of these has lower brightness than the substantially white sheet-like object. Therefore, in order to determine the type of a defect generated in a sheet by the reflection method, a complicated algorithm for analyzing the brightness of the defect is required as shown in Patent Document 1 and Patent Document 2. There was a problem of becoming.

  Therefore, an object of the present invention is to determine the type of a defect generated in a sheet by a simple configuration and an algorithm.

  The inventor of the present invention has intensively studied means for solving the above-mentioned problems of the prior art, and as a result, in a "reflection type" defect inspection apparatus in which an imaging device and a light source are arranged on one side of a sheet-like material, By providing a diffuse reflection member on the other side of the object, which irregularly reflects the light emitted from the light source, it has been found that defects (especially holes and other defects) in the sheet can be easily identified. Was. The inventor has conceived that it is possible to solve the problems of the prior art based on the above findings, and has completed the present invention. More specifically, the present invention has the following configurations and steps.

  A first aspect of the present invention relates to a sheet-like defect inspection apparatus. A defect inspection apparatus according to the present invention includes an imaging device, one or a plurality of light sources, and a diffuse reflection member. The photographing device is arranged on one side of the sheet-like object, and photographs the surface of the sheet-like object to obtain an image of the sheet-like object. The light source is arranged on at least one surface side of the sheet-like material, and illuminates a photographing range of the photographing device on the surface of the sheet-like material. The diffuse reflection member is arranged on the other surface side of the sheet-like object at a position at least partially overlapping the photographing range of the photographing device, and irregularly reflects the irradiation light from the light source. Note that “diffuse reflection” is a phenomenon in which light reaching a reflecting surface is reflected in random directions. That is, the light that is irregularly reflected includes light having a different incident angle and a different reflection angle. Therefore, “diffuse reflection” is distinguished from specular reflection in which the incident angle of light is equal to the reflection angle, and retroreflection in which the incident light returns to the incident direction again. In this way, by installing the irregular reflection member on the back side of the sheet-like object, even if there is a defect (especially a hole) in the inspection area of the sheet-like object by the imaging device, the light emitted from the light source is And reaches the diffuse reflection member, where it is diffusely reflected and enters the camera again. For this reason, a diffuse reflection member is required.

  As in the above configuration, in the present invention, for example, a light source and a photographing device are arranged on the front side of a sheet-like material, and a diffuse reflection member is arranged on the back side thereof. Accordingly, when a hole is formed in the sheet-like object, the irradiation light from the light source passes through the hole of the sheet-like object, reaches the irregular reflection member, and is irregularly reflected there, and is guided to the imaging device. Then, in the captured image acquired by the image capturing device, the holes appear in the sheet-like object with a brightness higher than the normal brightness range of the paper surface. On the other hand, when a defect other than a hole, such as dirt or a foreign substance, is attached to the sheet-like material, the defect in the photographed image acquired by the photographing apparatus is lower than the lightness range when the sheet surface is normal. Reflected in For this reason, the defect inspection device analyzes the photographed image and compares the normal brightness range of the paper surface itself with the brightness of the defect occurring on the paper surface to determine whether the defect is a hole or not. Whether it is a defect (dirt, foreign matter, or the like) can be easily determined. Also, assuming that the sheet is sanitary paper, paper dust generated during the manufacturing process of the sanitary paper floats between the photographing device and the sanitary paper, and the paper dust and its shadow appear in the captured image. May be reflected. The paper dust and its shadow appear in the photographed image with low brightness, but the holes in the sanitary paper appear in bright brightness as described above. For this reason, according to the above configuration, it is possible to more reliably detect a hole formed in a sheet-like material (sanitary paper) while avoiding malfunction due to the influence of paper dust and its shadow.

  In the defect inspection apparatus according to the present invention, the irregular reflection member may include a flat portion formed in parallel with the sheet-like material. In this case, the flat portion may be arranged at a position separated from the sheet-like material at a constant interval. When the irregular reflection member is arranged in non-contact with the sheet, the distance between the irregular reflection member and the sheet is preferably short, for example, preferably within 20 cm or 10 cm, and preferably within 5 cm. Particularly preferred. As described above, by making the diffuse reflection member non-contact with the sheet-like material, the diffuse reflection member can be easily arranged. In addition, it is possible to avoid generation of static electricity due to contact between the irregular reflection member and the sheet-like material and formation of wrinkles on the sheet-like material.

  It is preferable that the defect inspection apparatus according to the present invention further includes a removing unit that removes dust (for example, paper dust) adhered to the plane portion of the irregular reflection member. If there is a certain space between the sheet-like material and the irregular reflection member, dust may adhere to the flat surface. When dust accumulates on the flat surface, the intensity of light that has been irregularly reflected is weakened, and there is a possibility that lightness in a captured image is reduced. Therefore, such a problem can be avoided by providing a removing means for removing dust from the flat surface of the irregular reflection member.

  In the defect inspection apparatus according to the present invention, the irregular reflection member may include a curved portion that comes into contact with the sheet-like material. In this way, by arranging the irregular reflection member in contact with the sheet-like material, for example, when a hole is formed in the sheet-like material, light emitted from a light source is surely irregularly reflected through the hole of the sheet-like material. The light reaches the member and becomes irregularly reflected. This improves the hole detection accuracy. Furthermore, since the irregular reflection member and the sheet-like material are always in contact with each other, it is difficult for paper dust or the like to accumulate on the reflection surface of the irregular reflection member, so that the reflection surface is always kept clean and the intensity of the reflected light is maintained. You.

  A second aspect of the present invention relates to a method for manufacturing a sheet-like material. The manufacturing method according to the present invention includes a step of obtaining a sheet and a step of inspecting the sheet for defects. In the inspection step, the presence or absence of a defect in the sheet is inspected using the defect inspection apparatus according to the first aspect described above. In particular, when a defect has occurred in a sheet-like material, it is possible to determine whether the defect is a hole formed in the sheet-like material or another defect (dirt, foreign matter, etc.). preferable.

  According to the present invention, it is possible to determine the type of a defect that has occurred in a sheet by a simple configuration and an algorithm.

FIG. 1 shows an example of the configuration of a paper machine. FIG. 2 shows a configuration example of the defect inspection apparatus according to the first embodiment. FIG. 3 is a block diagram showing an example of a functional configuration of the defect inspection device. FIG. 4 is a flowchart illustrating an example of a defect detection process in the image analysis device. FIG. 5 schematically shows an example of a photographed image acquired by the defect inspection apparatus according to the present invention. FIG. 6 shows a configuration example of a defect inspection apparatus according to the second embodiment. FIG. 7 schematically shows an example of a photographed image acquired by a conventional “reflection type” defect inspection apparatus.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, but also includes those which are appropriately modified by 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”.

The present invention relates to a sheet-like defect inspection apparatus and a method for manufacturing a sheet-like substance using the defect inspection apparatus. Examples of the sheet material include those made of paper and plastic. In particular, the sheet-like material is preferably household sanitary paper used as tissue paper or toilet paper. The “sanitary paper” means “sanitary paper” defined in JIS “Terms of paper, paperboard and pulp” (JISP 0001). “Sanitary paper” includes towels, menstrual paper, tissue paper, toilet paper, and dustpaper. The sanitary paper manufactured according to the present invention is preferably a thin paper having a basis weight in the range of 10 to 25 g / m ² . The sanitary paper of the present invention may be a single-ply product consisting of one sheet, or a two-ply or three-ply or more product obtained by laminating two or three or more sheets. In the following, a description will be given by taking a one-ply sanitary paper as an example of a sheet.

  Basically, the method of manufacturing sanitary paper 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 raw fiber pulp fibers from papermaking raw materials to form a fibrous web and drying. including.

  In the adjusting step, a papermaking raw material (pulp slurry) as a raw material for sanitary paper is adjusted. The main raw material for papermaking is pulp. Raw pulp includes, for example, kraft pulp (KP) such as hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP); chemical pulp such as sulfite pulp (SP) and soda pulp (AP); semi-chemical pulp Semi-chemical pulp such as (SCP) or chemical ground wood pulp (CGP); Mechanical pulp such as groundwood pulp (GP) or thermomechanical pulp (TMP, BCTMP); or raw materials such as mulberry, mitsumata, hemp, kenaf, etc. Examples include non-wood pulp, cotton pulp such as cotton linter and cotton lint, and deinked pulp made from waste paper. As the papermaking raw material, 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 of the thin paper and the required performance. The raw pulp may be unbeaten pulp or may be beaten in whole or in part.

  The papermaking raw material adjusted in the adjustment step is made in the papermaking step to become sanitary paper. 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.

  The wire part 110 is a part that squeezes water contained in the pulp slurry to form a thin layer of wet paper. The wire part 110 includes a pair of upper and lower two wires 111 in which a paper net is formed into an annular endless track belt, and a head box 112 for spraying pulp slurry between the two wires 111. The head box 112 sprays a thin pulp slurry toward the nip of the wire 111. The water contained in the pulp slurry is squeezed from the mesh of the two wires 111 that are pressed against each other by the pressure from the forming roll 113. The wire 111 is caused to travel by a forming roll 113 and a drive roll 14 functioning as a drive roll. The forming roll 113 and the drive roll 114 are arranged so as to be in contact with the wire 111, and the rotational force of the forming roll 113 and the drive roll 114 is transmitted to the wire 111 to apply a propulsive force to the wire 111.

  The press part 120 is a part for further removing the moisture of the thin paper web formed by the wire part 110. The press part 120 includes a dryer felt 121 in which the felt is formed into an annular endless track belt, and a plurality of felt rolls 122 that abut on 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 is passed through the fibrous dryer felt 121 to further remove moisture contained in the wet paper.

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

  The calendar part 140 is a part for performing calendering on the base paper dried in the dry part 130. The calendar part 140 includes a calendar roll 141 and a receiving roll 142. In the calendar part 140, the base paper is sandwiched between the calendar roll 141 and the receiving roll 142 and pressed to smooth the surface of the base paper, to densify the structure, to make the paper thickness uniform, to impart gloss, and the like. . The types of the calendar roll 141 and the receiving roll 142 are not particularly limited, but for example, a metal roll can be suitably used.

  The reel part 150 is a part for winding the calendered base paper. The reel part 150 includes a reel drum 151. In the reel part 150, after 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. This makes it possible to obtain a raw roll in which the base paper is wound in a roll shape.

  In the present embodiment, a defect inspection device 200 is provided 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 of the base paper of the sanitary paper so as to face the paper surface, and an image analysis device 220 connected to the imaging device 211 by wire or wirelessly. Further, the defect inspection apparatus 200 includes a plurality of light sources 212 and 213 arranged on one side of the base paper of the sanitary paper, together with the photographing apparatus 211, and a diffuse reflection member 214 arranged on the other side of the base paper of the sanitary paper. The paper machine 100 conveys the base paper at a constant speed in a certain direction between the calendar part 140 and the reel part 150, particularly in a portion where the base paper faces the photographing device 211. The one side of the base paper is illuminated by the light sources 212 and 213, and the light reflected on the paper is introduced into the photographing device 211. As described above, the photographing device 211 acquires a photographed image by photographing the light reflected from the paper surface of the base paper among the irradiation light from the light sources 212 and 213. The photographed image of the sanitary paper acquired by the photographing device 211 is input to the image analyzing device 220, and the image analyzing device 220 analyzes whether a defect has occurred on the paper surface of the sanitary paper. In addition, the image analysis device 220 performs a process of determining the type of a defect on the paper included in the captured image.

  FIG. 2 shows an example of the arrangement of the photographing device 211, the light sources 212 and 213, and the irregular reflection member 214 in the defect inspection device 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 the irregular reflection member 214 is disposed on the back side (the other side) of the sanitary paper. Is arranged. Further, in FIG. 2, a defect generated on the sanitary paper S is indicated by a symbol D. Examples of defects include defects in quality that are not suitable for selling sanitary paper, such as holes, dirt, streaks, and foreign matter.

  The photographing device 211 is a camera for acquiring image data of a still image or a moving image. The image data acquired by the imaging device 211 is transmitted to the image analysis device 220 (see FIG. 3), and predetermined image analysis for defect detection is performed. The camera is, for example, a lens, a mechanical shutter, a shutter driver, a photoelectric conversion element such as a CCD image sensor unit or a CMOS image sensor unit, a digital signal processor (DSP) that reads out an amount of charge from the photoelectric conversion element and generates image data, an IC memory, and the like. Is realized. Note that the camera may be configured to capture a still image, or may be configured to capture a moving image at a predetermined frame rate.

  It is preferable that the imaging device 211 has an imaging surface (lens) arranged substantially parallel to the paper surface of the laminated sheet. For this reason, when a straight line is drawn vertically from the imaging surface of the imaging device 211, the straight line intersects the paper surface almost perpendicularly. This allows the photographing device 211 to photograph the sheet surface of the laminated sheet without distortion. In FIG. 2, the photographic range of the photographic device 211 is indicated by a broken line.

  The light sources 212 and 213 are lights that illuminate a photographing range of the sanitary paper S photographed by the photographing device 211. It is preferable that the light sources 212 and 213 emit white light. Examples of the light sources 212 and 213 include a fluorescent lamp, an LED (light emitting diode), an OLED (organic light emitting diode), a lamp, an arc lamp, an incandescent lamp, and the like. Further, as the light sources 212 and 213, a spot light source, a parallel light source (surface light source), or a point light source can be adopted, but a spot light source that can easily control the illumination range (spot size) and the optical axis can be adopted. Most preferred. If a spot light source is used, light can be emitted from the light source in a limited direction and range. In FIG. 2, the illumination ranges of the light sources 212 and 213 are indicated by broken 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, a spot light source whose illumination range (diameter) spreads in a tapered shape around the optical axis is adopted as each of the light sources 212 and 213. In addition, as the spot light source, a light source having the same illumination range at infinity can be used.

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

  As shown in FIG. 2, in the longitudinal section of the sanitary paper S, the optical axis of the light emitted from each of the light sources 212 and 213 is inclined at a predetermined angle θ with respect to the paper surface of the sanitary paper S. I have. The inclination angle θ of the optical axes 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. Note that, 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.

  Further, the first light source 212 and the second light source 213 are arranged so as to sandwich the photographing device 211 in a longitudinal sectional view of the sanitary paper S. That is, the image capturing device 211 is located between the first light source 212 and the second light source 213 in the transport direction of the sanitary paper. Further, the photographing device 211 is installed at a position higher than each of the light sources 212 and 213. That is, the distance from the photographing device 211 to the paper surface of the sanitary paper S is longer than the distance from each of the light sources 212 and 213 to the paper surface of the sanitary paper S.

  As described above, when the paper 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 source exists between the paper surface of the sanitary paper S and the photographing device 211. Since a floating substance (for example, paper powder) can be illuminated from a plurality of directions, the color of the shadow of the floating substance projected on the paper surface can be reduced. As a result, it is possible to analyze the photographed image acquired by the photographing device 211 and more clearly detect a defect attached to the paper surface.

  As shown in FIG. 2, the irregular reflection member 214 is disposed on the side opposite to the imaging device 211 and the light sources 212 and 213. The irregular reflection member 214 is arranged to irregularly reflect the irradiation light from the light sources 212 and 213 and introduce a part of the reflected light to the imaging surface of the imaging device 211. As the irregular reflection member 214, for example, a member that has fine irregularities formed on a surface (reflection surface) to which light from the light sources 212 and 213 is irradiated and reflects incident light in a random direction may be used. As the irregular reflection member 214, a known reflection plate can be appropriately used. In the present embodiment, a plate-like member having a surface parallel to the surface of the sanitary paper S is used as the irregular reflection member 214.

  More specifically, when the defect D formed in the sanitary paper S is a hole penetrating from the front surface to the back surface, the irradiation light from each of the light sources 212 and 213 reaches the reflection surface of the irregular reflection member 214 through the hole. I do. When the irradiation light is irregularly reflected by the irregular reflection member 214, at least a part thereof passes through the hole of the sanitary paper S again and is introduced to the imaging surface of the imaging device 211. In this manner, the reflected light of the irregular reflection member 214 is introduced into the photographing device 211 through the hole of the sanitary paper S, so that the photographed image of the photographing device 211 shows the hole of the sanitary paper S as a region with high brightness. Becomes

  Further, in the embodiment shown in FIG. 2, the irregular reflection member 214 includes a flat portion formed in parallel with the paper surface of the sanitary paper S, and the flat portion is located at a position separated from the sheet by a predetermined distance G. It is located in. It is preferable that the gap G between the plane portion of the irregular reflection member 214 and the paper surface of the sanitary paper S is as close as possible so that the diffuse reflection member 214 does not hinder the conveyance of the sanitary paper. More specifically, in FIG. 2, when it is assumed that the sanitary paper S does not exist, a photographing range on the plane portion of the irregular reflection member 214 by the photographing device 211 is indicated by a symbol P, and the first light source 212 The range where light and the irradiation light from the second light source 213 overlap on the plane portion of the irregular reflection member 214 is indicated by a symbol L. At this time, it is preferable that the length of the range L where the irradiation light overlaps in the transport direction of the sanitary paper S (the left-right direction in the figure) is 80% or more or 90% or more of the length of the imaging range P. , 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 shooting range P (L ≧ P). The distance G between the irregular reflection member 214 and the sanitary paper S may be set so as to satisfy such a condition. For example, the interval G is preferably set to 1 cm to 20 cm or 2 to 10 cm. As described above, by photographing the range where the irradiation lights from the light sources 212 and 213 overlap on the plane portion of the irregular reflection member 214 by the photographing device 211, the reflected lights from the light sources 212 and 213 are introduced into the photographing device 211, respectively. Will be done. For this reason, the intensity of the reflected light introduced into the photographing device 211 increases, and the brightness of the hole of the sanitary paper S in the photographed image increases.

  Although not shown, the defect inspection apparatus 200 may further include a removing unit that removes dust (for example, paper dust or the like) attached to the flat surface of the irregular reflection member 214. As the removing means, a blower for continuously or intermittently sending air between the paper surface of the sanitary paper and the flat portion of the irregular reflection member 214, a brush or a wiper for automatically or manually wiping the flat portion of the irregular reflection member 214 is used. Can be used. If there is a gap between the sanitary paper and the irregular reflection member 214, dust may accumulate on the flat surface and the intensity of the irregularly reflected light may be weakened. Therefore, by providing a removing unit and removing dust continuously or periodically from the plane portion of the irregular reflection member 214, the light intensity of the reflected light introduced into the imaging unit 211 can be maintained.

  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 sanitary paper for defects. A general computer may be used for the image analysis device 220. The image analysis device 220 includes an interface for a photographing device, and receives image data acquired by the photographing device 211. The image analysis device 220 includes a control operation unit 221, a storage unit 222, an operation unit 223, and a display unit 224. The control calculation unit 221 controls each of the elements 222 to 224 and performs an image analysis process on the image data acquired from the imaging device 211 according to a computer program for defect inspection stored in the storage unit 222. The control operation unit 221 can be realized by a processor such as a CPU or a GPU. The storage unit 222 can be realized by a nonvolatile memory such as an HDD or an SDD, or a volatile memory such as a RAM or a DRAM. The operation unit 223 includes an input device such as a mouse, a keyboard, a touch panel, and a microphone, and receives operation information by a person. The display unit 224 is 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 operation unit 221 of the image analysis device 220 basically analyzes the photographed image acquired by the photographing device 211 and determines whether there is a defect on the surface of the sanitary paper. For example, the image analyzer 220 measures the lightness (density) for each pixel or pixel group of the image data of the sanitary paper, and when there is a darker or lighter part than the normal lightness range, the image data sanitization is performed. Judge that the paper is defective. For example, when a foreign substance is attached to the sanitary paper, the brightness of the foreign substance part appears dark. When a hole is formed in the sanitary paper, the brightness of the hole is brighter in the image data obtained by the reflection method using the irregular reflection member 214. As described above, the control calculation unit 221 determines that a part where the brightness of the image data has an abnormality is a defective part of the sanitary paper.

  FIG. 4 shows an example of the flow of the defect detection processing by the image analysis device 220. FIG. 5 schematically shows an image of the paper surface of the sanitary paper acquired by the photographing device 211, in which foreign matters such as holes and dirt exist on the paper surface. As shown in FIG. 4, first, a captured image is input from the imaging device 211 to the image analysis device 220 (step S1). The image analysis device 220 analyzes the captured image and determines whether or not a defect exists on the paper (step S2). As described above, a defect on a paper surface tends to have a lightness in a captured image deviating from a normal lightness range on the paper surface. Therefore, the image analysis device 220 determines the presence or absence of a defect based on the brightness of the captured image. If no abnormal lightness portion exists in the captured image, it is determined that the image is normal (step S3). On the other hand, if there is a high brightness portion or a low brightness portion exceeding a certain threshold value in the captured image, the image analysis device 220 determines that a defect exists on the paper, and The process proceeds to the process of determining the type (step S4).

  Next, the image analysis device 220 determines whether or not the brightness of the defect in the captured image is higher than the normal brightness range of the paper (step S4). That is, as shown in FIG. 5, when a hole is formed on the paper surface of the sanitary paper, the area where the hole is formed has a higher brightness. This is because the irregular reflection member 214 is arranged on the back surface of the sanitary paper as described above. On the other hand, when foreign matter such as dirt adheres to the paper surface of the sanitary paper, the area to which the foreign matter adheres has low brightness. Thus, a defect having a higher brightness than the normal brightness of the paper is determined to be a hole (step S5), and a defect having a lower brightness is determined to be a foreign matter (a defect other than a hole). (Step S6). For example, a lightness range similar to the lightness of the paper is regarded as normal, a defect with a lightness exceeding the normal lightness range is determined as a hole, and a defect with a lightness lower than the normal lightness range is determined as a foreign matter (defect other than a hole). do it.

  As shown in FIG. 7, in an image captured by the conventional reflection method (when the irregular reflection member is not disposed on the back side of the sanitary paper), holes and other foreign matter appear at a lower brightness than the paper surface. Becomes Therefore, in order to determine whether the defect on the paper is a hole or a foreign matter, a complicated algorithm for analyzing the brightness (density) of the defect is required. On the other hand, as shown in FIG. 5, according to the method of the present invention using the irregular reflection member, holes on the paper surface appear with a higher brightness than the paper surface, and other defects such as foreign matter have a lower brightness than the paper surface. appear. Therefore, as in the flow shown in FIG. 6, it is possible to determine the type of defect by a simple algorithm that only compares the lightness of the defect with the normal lightness range on the paper.

  FIG. 6 shows a defect inspection apparatus 200 according to the second embodiment. In the second embodiment, a description of the same configuration as that of the first embodiment will be omitted, and a different configuration will be described.

  In the second embodiment, as the irregular reflection member 214, a member including a curved portion having a curved cross section in the conveyance direction of the sanitary paper is used. The curved surface of the irregular reflection 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 part thereof always contacts the curved surface of the irregular reflection member 214. The irregular reflection member 214 having a curved surface portion may be a plate-like member having a circular cross section as shown in FIG. 6, a member having a circular cross section, a member having a semicircular cross section, or a cylindrical cross section. It may be a shaped member.

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

  As shown in FIG. 6, when the defect D generated on the paper surface of the sanitary paper is a hole, the light emitted from each of the light sources 212 and 213 is reliably emitted because the sanitary paper and the diffuse reflection member 214 are in close contact. Then, the light reaches the irregular reflection member 214 through the hole, and the reflected light is introduced into the imaging device 211. For this reason, according to the second embodiment, a hole formed on the paper surface can be detected more reliably. Furthermore, since the irregular reflection member 214 is always in contact with the sanitary paper, paper dust and the like hardly accumulate on the reflection surface of the irregular reflection member 214. Thereby, the reflection surface of the irregular reflection member 214 is always kept clean, and the intensity of the reflected light is maintained.

  As described above, the embodiments of the present invention have been described with reference to the drawings in order to express the contents of the present invention. However, the present invention is not limited to the above-described embodiment, but includes modifications and improvements obvious to those skilled in the art based on the matters described in the present specification.

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 Food 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 imaging device 212 first light source 213 second light source 214 diffuse reflection member 220 … Image analysis device 221 control arithmetic unit 222 storage unit 223 operation unit 224 display unit

Claims (5)

A sheet defect inspection apparatus,
A photographing device arranged on one side of the sheet-like object, for photographing the surface of the sheet-like object to obtain an image of the sheet-like object;
One or more light sources that are arranged on at least one surface side of the sheet-like object and illuminate an imaging range of the imaging device on the surface of the sheet-like object;
And a diffuse reflection member that is disposed on the other surface side of the sheet-like object at least partially overlaps a photographing range of the photographing device, and that irregularly reflects irradiation light from the light source. The irregular reflection member includes a flat portion formed in parallel with the sheet-like material,
The defect inspection device according to claim 1, wherein the flat portion is arranged at a position separated from the sheet by a predetermined distance. The defect inspection apparatus according to claim 2, further comprising a removing unit configured to remove dust attached to a plane portion of the irregular reflection member. The defect inspection device according to claim 1, wherein the irregular reflection member includes a curved surface portion that contacts the sheet-shaped object. Obtaining a sheet-like material;
Inspecting presence or absence of a defect of the sheet-like object using the defect inspection device according to any one of claims 1 to 4.
A method for producing a sheet.

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