JP2011085521A - Surface flaw inspection device for sheet-shaped article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface flaw inspection device for detecting recess and projection flaws on the surface of a transparent sheet-shaped article without missing flaw, determining the direction of the recess and projection surface of the sheet-shaped article by a simple signal in real time, and performing quality control with high reliability. <P>SOLUTION: The surface flaw inspection device includes an illumination means for emitting a parallel light onto a running transparent sheet-shaped article from an oblique direction; and a photographic means and processing means for continuously detecting the light reflected from the surface of the sheet-shaped article. The device also for sheet-shaped articles is able to solve problems, by determining the presence or absence of a recess and projection flaw on the surface of the sheet-shaped article, and whether the detected surface is a recess flaw or a projection flaw. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus for detecting an irregularity defect on the surface of a transparent sheet and simultaneously inspecting the direction of the irregular surface.

  In recent years, optical film used for liquid crystals, etc., and high-functional films used for electronic equipment parts, etc., are becoming increasingly demanding standards for foreign substances, and these sheet-like materials are manufactured in a clean room, and are inspected for defects in the production line. Quality control regarding defects in sheet-like materials is performed by the machine. However, environment-related foreign matter generated by the operator's work, etc., and sheet-like chips generated in the slitting process, etc. may be scattered in the process, and these foreign matter may be scattered on the surface of the sheet-like material or in the line. May adhere to other rolls. For this reason, in the production line, a static eliminator for suppressing foreign matter from adhering to the sheet-like material, a dust removing device, an adhesive roll, etc. for removing the foreign material adhering to the sheet-like material are installed. Yes. Generally, the foreign matter adhering to the surface of the sheet-like material does not cause a problem if it is removed before winding up as a final product. However, when the sheet material passes over the foreign material adhering to the roll with a strong tension or when the sheet material passes with the foreign material biting into the nip roll, the surface of the sheet material presses the foreign material. Indentation is caused by this, and the opposite surface may be deformed into a convex shape. Moreover, when the state where the foreign matter has adhered to the roll continues, irregular defects may occur periodically at the outer peripheral pitch of the roll. Such irregularities have a problem that they become harmful defects due to the depth, height, area, periodicity, etc. of the irregularities, and are discarded out of quality standards. Furthermore, when this irregularity defect occurs, there is a problem that if it is discovered early and the foreign matter causing it is not removed, a huge loss of waste will occur.

  In order to solve this problem, a defect inspection machine using light transmission and refraction is installed in the line of transparent sheet material to detect uneven defects and foreign matters, and it is generated from the occurrence cycle of defects, etc. Measures such as estimating a source roll or the like and removing foreign matter adhering to the roll or the like are widely performed.

  However, uneven defects are hard to be detected by the method using light transmission and refraction because the difference from the formation of the sheet-like material having no defect is small, and harmless formation noise when the detection sensitivity is increased. There was a problem of over-detection due to false detection.

  In general, as a method of detecting irregularities on the surface of a sheet-like object that is difficult to detect, a comparison is made between the reflected light image that illuminates the sheet-like object obliquely and the reflected light image that illuminates the sheet-like object from the vertical direction. Thus, a method for detecting irregularities in the irregularities of the sheet-like material (for example, see Patent Document 1) has been proposed.

  However, the above-described conventional methods require two types of illumination devices, imaging devices, and dedicated image processing devices, which are costly and may not be compatible with high-speed production lines. It was.

  In addition, as a method of detecting the convex defect of the sheet-like material, the traveling sheet-like material is pressure-bonded to the inspection roll, and the amount of light scanned from the tangential direction of the roll is detected to detect the presence or absence of the convex defect. A method of discriminating (see, for example, Patent Document 2) has been proposed.

  However, the above-described conventional method is affected by vibration of the inspection roll, the thickness distribution in the width direction of the sheet-like material, and the variation in thickness of the sheet-like material over time, and thus there is a problem that there is a risk of detection omission and excessive detection. there were.

JP2001-201445 JP 08-128967 A

  The present invention solves the above-mentioned problems of the prior art, detects irregularities on the surface of a transparent sheet-like material without omission, and performs simple signal processing to determine which of the sheet-like material has a dent or projection. A defect inspection system for determining quality in real time, and presuming and dealing with rolls with foreign particles that cause them on the basis of the surface where concave defects or convex defects are generated, and performing reliable quality control. It is intended to provide.

  As a result of intensive studies, the present inventors have found that the above problems can be solved, and have completed the present invention. That is, the present invention includes an illuminating unit that irradiates parallel light from an oblique direction to a traveling transparent sheet surface, and an imaging unit and a processing unit that continuously detect reflected light from the sheet surface. The present invention also relates to an apparatus for inspecting a surface defect of a sheet-like material, wherein the presence or absence of an uneven defect portion on the surface of the sheet-like material and whether a detected surface is a concave defect or a convex defect are determined.

  As a preferred embodiment, when the pretreatment means has a concave defect on the surface of the sheet-like object, the pretreatment means detects that the luminance signal of the reflected light is higher than the luminance signal of the part without the defect, A signal processing means for determining and detecting a convex defect by detecting that the luminance signal of the reflected light is lower than the luminance signal of a portion having no defect when the surface of the sheet-like object has a convex defect; It is related with the surface defect inspection apparatus of the sheet-like material characterized by including.

  As a preferred embodiment, when the processing means has a concave defect on the surface of the sheet-like material, it is determined that the reflected light image is brighter than a part without the defect, and is determined as a concave defect. A sheet-like shape including image processing means for detecting that the image of the reflected light is darker than a portion having no defect when the surface of the object has a convex defect, and determining that the defect is a convex defect The present invention relates to a surface defect inspection apparatus for objects.

  As a preferred embodiment, the distance between the light source of the illuminating means and the sheet-like object, and the incident angle are such that the concave defect and the convex defect are optically different from the non-defect portion on the light receiving surface of the imaging means of reflected light. The present invention relates to an apparatus for inspecting a surface defect of a sheet-like material, wherein the density difference is set so as to be close to the maximum.

  According to the present invention, irregularities on the surface of a transparent sheet are detected without omission, and it is determined in real time by simple signal processing whether a sheet has depressions or protrusions. Based on the occurrence surface of the convex defect, it is possible to estimate and deal with the roll with the foreign material that causes it at an early stage, and it is possible to perform highly reliable quality control.

It is a figure which shows an example of the defect inspection apparatus of the uneven | corrugated shape of the transparent body sheet-like surface which concerns on embodiment of this invention. It is a figure which shows an example of the apparatus which consists of a some detection optical system in the uneven | corrugated shaped defect inspection of the transparent body sheet-like object surface concerning embodiment of this invention. It is a figure which shows the distribution of the brightness in a light-receiving surface, showing the path | route of the incident light and reflected light of illumination when the transparent body sheet-like material surface which concerns on embodiment of this invention has a concave defect. It is a figure which shows the distribution of the brightness in a light-receiving surface, showing the path | route of the incident light and reflected light of illumination when there exists a convex defect in the transparent body sheet-like object surface concerning embodiment of this invention. It is a figure which shows an example of an image in case there exists a concave defect in the transparent body sheet-like material surface which concerns on embodiment of this invention. It is a figure which shows an example of an image when there exists a convex defect in the transparent body sheet-like material surface which concerns on embodiment of this invention.

  The defect inspection apparatus for a transparent sheet according to the present invention continuously illuminates the traveling surface of a transparent sheet with illumination means for irradiating parallel light from an oblique direction and reflected light from the surface of the sheet. The image pickup means and the processing means are detected, and the presence or absence of uneven defects on the surface of the sheet-like object and whether the detected surface is a concave defect or a convex defect are characterized.

  Here, the parallel light refers to light composed of light components that are nearly parallel to the optical axis in the illumination direction without overlapping each light beam.

  According to the above configuration, by continuously detecting the reflected light of the parallel light from the oblique direction, when the uneven defect passes through the light irradiation position, the luminance signal is generated by the change of the light refraction or the reflection direction. Thus, it is possible to detect the presence or absence of uneven defects by a preset threshold value.

  Here, the concavo-convex defect refers to a defect in which a surface on which a foreign material or the like is pressed against a sheet-like object is curved and recessed, and the opposite surface bulges in a convex shape. In contrast to the irregular defect, the concave surface is called a concave defect, and the convex surface is called a convex defect.

  In the defect inspection apparatus for a transparent sheet according to the present invention, when the preprocessing means has a concave defect on the surface of the sheet, the luminance signal of the reflected light is higher than the luminance signal of the part having no defect. If there is a convex defect on the surface of the sheet-like material, it is detected that the reflected light luminance signal is lower than the luminance signal of the part without the defect. It is preferable to include signal processing means for determining a defect.

When there is a concave defect on the surface of the sheet-like object, the direction of the reflected light is changed by the curved surface and is partially condensed like a concave mirror. It can be determined as a concave defect by becoming higher than the value,
If there is a convex defect on the surface of the sheet-like material, a part of the incident light is refracted without being reflected by the convex part and enters the sheet-like material, and a part of the reflected light is lost. It becomes possible to determine a convex defect by lowering the luminance signal.

  Here, the threshold value on the bright side refers to the upper limit of the luminance on the high side that is not regarded as a defect on the basis of the luminance signal level including the ground noise of the reflected light without any defects on the sheet-like object, and the dark side The threshold value is a lower limit of luminance on the lower side which is not regarded as a defect with reference to a luminance signal level including a ground noise of reflected light having no defect in the sheet-like material.

  Therefore, the surface of the traveling sheet is irradiated with parallel light from an oblique direction, the brightness distribution in the width direction of the reflected light is continuously detected, and the bright side threshold and the dark side threshold of the brightness signal are detected. This determination is preferable in that the presence / absence of a defect can be detected in real time, and a concave defect and a convex defect can be distinguished in real time, so that a roll causing a defect can be estimated quickly.

  In the defect inspection apparatus for a transparent sheet according to the present invention, the pre-processing means detects that the image of the reflected light becomes brighter than the area having no defect when the surface of the sheet has a concave defect. Image processing means for determining that the defect is a concave defect and detecting that the image of the reflected light is darker than the part having no defect when there is a convex defect on the surface of the sheet-like material. In addition, it is preferable to determine whether or not there are uneven defects on the surface of the sheet-like object and whether the detected surface is a concave defect or a convex defect.

  According to the above-described configuration, by continuously capturing an image irradiated with parallel light from an oblique direction as an image continuously from the reflection direction, when an uneven defect passes through the light irradiation range, The brightness distribution of the irradiation range changes due to the change in the reflection direction, and appears as the shading of the image. The range exceeding the preset shading threshold is extracted as a defect image, and the area and maximum diameter of the image are preset. By checking with the value, it is possible to detect the presence or absence of uneven defects.

  Furthermore, when there is a concave defect on the surface of the sheet-like material, the direction of the reflected light changes in the range of the curved surface and is partially condensed like a concave mirror. A part exceeding the threshold value is extracted as an image of a bright defect, and when the area or maximum diameter of the bright defect image exceeds a preset value, it can be determined as a concave defect, and the surface of the sheet-like object If there is a convex defect on the surface, a part of the incident light is not reflected but refracts and enters the sheet-like material within the convex surface, and a part of the reflected light is lost. A part exceeding the threshold on the side is extracted as an image of a dark defect, and when the area or maximum diameter of the dark defect image exceeds a preset value, it can be determined as a convex defect.

  Therefore, by collimating the traveling sheet surface with parallel light from an oblique direction and comparing the image of the reflection surface with the image detection means for continuously capturing images of the irradiation range from the reflection direction, It is preferable in that it can detect the presence / absence of a defect and discriminate between a concave defect and a convex defect in real time, and can quickly estimate a roll causing the defect.

  In the defect inspection apparatus for a transparent sheet according to the present invention, the illumination unit uses a parallel light source, and the distance and the incident angle between the light source and the sheet are concave on the light receiving surface of the reflected light imaging unit. It is preferable that the defect and convex defect sites be set so that the difference in optical density between the defect-free site and the optical density difference is close to the maximum.

  According to the above configuration, by using a parallel light source, the difference in luminance signal at the defect is clarified because it accurately reflects or refracts even when the uneven curvature of the defect portion is small. It is excellent in that the contrast of the uneven defect image is clear.

  Here, the distance between the illumination means and the sheet-like object and the incident angle are such that the portion of the concave defect and the convex defect is the difference between the optical density and the portion having no defect, that is, the difference in the luminance signal at the portion is the maximum. Adjust in the state.

  In the defect inspection apparatus for a transparent sheet according to the present invention, the signal processing unit detects a luminance signal from the imaging unit, and the luminance signal in the width direction of the sheet has a predetermined width and exceeds the threshold value. If it occurs, it is determined as a concave defect, and it is determined as a convex defect when the luminance distribution in the width direction of the sheet-like material falls with a predetermined width exceeding a threshold value.

  According to the above configuration, it is possible to detect an elliptical or streaky concave defect or convex defect that is long in the width direction.

  Here, the width range in which the luminance distribution in the width direction of the sheet-like material exceeds the threshold is preferably set between the minimum defect size that needs to be detected and 1/3 of the size.

  In the defect inspection apparatus for a transparent sheet-like object according to the present invention, the signal processing means detects a luminance signal from the imaging means, and the luminance signal in the width direction of the sheet-like object has a predetermined length in the traveling method. When a rise exceeding the value occurs, it is judged as a concave defect, and when the brightness signal in the width direction of the sheet-like material falls below a threshold value with a predetermined length in the running method, it is judged as a convex defect. It is characterized by doing.

  According to the above configuration, it is possible to detect an elliptical or streaky concave defect or convex defect that is long in the traveling direction.

  Here, the length range in which the luminance distribution in the width direction of the sheet-like material exceeds the threshold value is preferably set between the minimum defect size that needs to be detected and 1/3 of the size.

  In the defect inspection apparatus for a transparent sheet according to the present invention, the image processing means sequentially accumulates an image within the effective visual field from the imaging means in the image memory without interruption, and based on the image, When an image having a predetermined area or length is detected in the bright area exceeding the threshold, it is determined as a concave defect, and based on the image, the dark area exceeding the threshold is an image having the predetermined area or length. It is characterized in that it is determined as a convex defect when is detected.

  According to the above configuration, since the defect is determined based on the image, the determination accuracy does not depend on the shape of the defect, which is excellent in that false detection is reduced.

  Here, the range of the area of the bright part or the dark part exceeding the threshold in the image detected by the image processing means can be set between the area of the minimum defect that needs to be detected and 1/3 of the area. Preferably, the image length range is set between the maximum diameter of the smallest defect that needs to be detected and 1/3 of the maximum diameter.

  Here, the image of the bright part due to the concave defect is a part condensed at the concave surface part, which is smaller than the area of the actual concave defect and often has a different shape. Is preferably set systematically small, and more preferably determined by the pattern of the shape of the image.

  Moreover, since the image of the dark part due to the convex defect is an image in which incident light is refracted at the convex part and enters the sheet-like material and a part of the reflected light is lost, it is smaller than the area of the actual concave defect. It is preferable to systematically set the value of the area or length determined as a defect to be small.

  Below, the defect inspection apparatus of the transparent body sheet-like material surface concerning this invention is demonstrated based on FIG. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

  FIG. 1 is a schematic diagram showing a schematic configuration of a defect inspection apparatus for a surface of a transparent sheet according to an embodiment of the present invention.

  In FIG. 1, the illumination means 1 for irradiating parallel light from the oblique direction θ to the surface of the transparent sheet W traveling in the direction A, and the luminance distribution in the width direction of the reflected light in the reflection direction θ ′ are shown. In the defect detection apparatus for detecting the uneven defect portion of the sheet-like material based on the imaging means 2 for continuously detecting and the difference in the brightness of the reflected light, it is not shown at the inspection position 3 on the surface of the sheet-like material. When there is a concave defect, it is determined that the reflected light has a higher luminance signal than the luminance signal of the part having no defect, and is determined as a concave defect, which is not shown in the inspection position 3 on the surface of the sheet-like object. When there is a convex defect, there is provided signal processing means 5 for detecting that the luminance signal of the reflected light is lower than the luminance signal of the part having no defect and determining as a convex defect.

  In addition, the inspection position 3 of the transparent sheet W is preferably a position close to the roll 4 that is less affected by vibrations and deflection in the width direction of the sheet, and an encoder is installed on the roll 4. It is possible to convert the traveling speed of the sheet-like material.

  With the above-described configuration, the reflected light of parallel light is continuously detected from the oblique direction by the imaging unit 2, so that when a concave defect or a convex defect passes through the light irradiation position, the light refraction and the change in the reflection direction are detected. As a result, the luminance signal changes, and it is possible to detect the presence or absence of uneven defects using a preset threshold value.

  Here, as the parallel light illuminating means 1, a point light source or a device in which a light source condensed in a spot shape is collimated by a collimator lens can be used.

  Here, the irregular defect is a sheet-like material such as a slit piece or fiber attached to a roll, the foreign matter attached to the roll is pressed against the sheet-like material, the surface is curved and dents, A defect in which the opposite surface bulges into a convex shape. In contrast to the irregular defect, the concave surface is called a concave defect, and the convex surface is called a convex defect.

  This uneven defect occurs when passing through a roll nipped with a rubber roll or a roll with high tension, and usually has unevenness of a height difference of several percent or less with respect to the average thickness of the sheet-like material. In many cases, it is in a very gently curved state. For this reason, in many cases, an uneven defect cannot be detected by an inspection method in which illumination is performed from the lower surface of a sheet-like object and the transmitted light is detected.

  Further, in the above configuration, when there is a concave defect on the surface of the sheet-like object, the direction of the reflected light is changed by the curved surface as shown in FIG. 3, and the light is partially condensed like a concave mirror. Therefore, in the brightness distribution on the light receiving surface DD ′, the luminance signal is higher than the threshold value L1 on the bright side in the defective portion, and it can be determined as a concave defect.

Furthermore, in the above configuration, when there is a convex defect on the surface of the sheet-like object, as shown in FIG. Since some of the reflected light is lost, the brightness distribution on the light receiving surface DD ′ is
In the defect portion, the luminance signal becomes lower than the dark side threshold value L2, and it can be determined as a convex defect.

  Here, the threshold value on the bright side refers to the upper limit of the luminance on the high side that is not regarded as a defect on the basis of the luminance signal level including the ground noise of the reflected light without any defects on the sheet-like object, and the dark side The threshold value is a lower limit of luminance on the lower side which is not regarded as a defect with reference to a luminance signal level including a ground noise of reflected light having no defect in the sheet-like material.

  The above-mentioned threshold values on the bright side and dark side are set from the level of the luminance signal at the concave and convex defects that are out of quality standards, and the luminance signal fluctuation range due to the surface roughness of the sheet-like material and vibration during running That is, it is preferable to set a value that is twice or more the formation noise.

  Thus, according to the above configuration, the traveling sheet surface is irradiated with parallel light from an oblique direction, the brightness distribution in the width direction of the reflected light is continuously detected, and the brightness signal is brightened. By the determination based on the threshold value and the threshold value on the dark side, it is possible to detect the presence / absence of a defect and to distinguish between a concave defect and a convex defect in real time. As a result, it becomes easy to find a roll that causes a defect, foreign matters adhering to the roll can be removed at an early stage, and it becomes possible to prevent the uneven defect from expanding.

  In FIG. 1, the illumination means 1 which irradiates parallel light from diagonal direction (theta) with respect to the surface of the transparent sheet-like object W which drive | works to A direction, and the image detection which images continuously the image of an irradiation range from a reflection direction In the defect inspection apparatus for detecting a concave and convex defect portion of the sheet-like material based on the difference between the means and the image of the reflected light in the reflection direction θ ′, a concave shape not shown at the inspection position 3 on the surface of the sheet-like material. When there is a defect, it is determined that the reflected light image is brighter than the part without the defect and is determined as a concave defect, and there is a convex defect (not shown) at the inspection position 3 on the surface of the sheet-like object. In this case, a signal processing means 5 and an image accumulation processing means 6 are provided which detect that the reflected light image is darker than a portion having no defect and determine a convex defect.

  With the above-described configuration, the range irradiated with parallel light from the oblique direction is continuously captured as an image from the reflection direction and is continuously captured and stored in the image storage processing unit 6 via the signal processing unit 5. When a concave defect or convex defect passes through, the brightness distribution in the irradiation range changes due to changes in the light refraction or reflection direction, and appears as light and shade of the image, and the defect exceeds the preset light and shade threshold. An image is extracted, and the image accumulation processing means 6 can detect the presence or absence of uneven defects by comparing the area and maximum diameter of the defect image with preset values.

  Further, in the above configuration, when there is a concave defect on the surface of the sheet-like object, the direction of the reflected light is changed by the curved surface as shown in FIG. 3, and the light is partially condensed like a concave mirror. Therefore, the image accumulation processing means 6 extracts a portion of the defective portion exceeding the bright side threshold L1 as an image of a bright defect, and the area and maximum diameter of the bright defect image are equal to or larger than a preset value. When it becomes, it can be determined as a concave defect.

  Furthermore, in the above configuration, when there is a convex defect on the surface of the sheet-like object, as shown in FIG. Since part of the reflected light is lost, the image accumulation processing means 6 extracts a portion of the defective portion that exceeds the dark side threshold value L2 as a dark defect image, and the area of the dark defect image. If the maximum diameter exceeds a preset value, it can be determined as a convex defect.

  Thus, according to the above configuration, the traveling surface of the sheet-like object is irradiated with parallel light from an oblique direction, images of the irradiation range are continuously captured from the reflection direction, and the images of the reflection surfaces are collated. The determination of the presence / absence of a defect and the determination of a concave defect and a convex defect can be performed in real time. As a result, it becomes easy to find a roll that causes a defect, foreign matters adhering to the roll can be removed at an early stage, and it becomes possible to prevent the uneven defect from expanding.

  In FIG. 1, the illuminating means 1 uses a parallel light source, and the distance between the light source and the sheet-like object and the incident angle θ are a concave defect and a convex defect on the light receiving surface of the imaging means 2 for the reflected light in the reflection direction θ ′. This is set so that the difference in optical density is close to the maximum with the part having no defect.

  According to the above configuration, by using a parallel light source, the difference in luminance signal at the defect is clarified because it accurately reflects or refracts even when the uneven curvature of the defect portion is small. The contrast of the uneven defect image becomes clear. A metal halide lamp, an LED array, or the like can be used as the light source of the illumination unit 1, and a collimator or the like is preferably installed on the output side of the light source in order to improve directivity and parallelism.

  Here, the distance between the illuminating means 1 and the sheet-like object and the incident angle θ are determined by the difference in optical density between the concave defect portion and the convex defect portion and the portion having no defect, that is, the difference in luminance signal at that portion. In order to detect thin uneven defects that are difficult to detect with an optical defect inspection machine with oblique transmission optical system, the incident angle and the reflection angle should be set in the range of 5 ° to 30 °. Is preferred. In addition, the distance between the illumination unit 1 and the sheet-like object is preferably set so as to be close to parallel light in consideration of the focal point such as a collimator, and is adjusted in the range of 0.3 m to 2.0 m.

  In FIG. 1, the signal processing means 5 detects the luminance signal from the imaging means 2, and if the rising of the luminance signal in the width direction of the transparent sheet W exceeds a threshold value with a predetermined width, A convex defect is determined when the brightness distribution in the width direction of the sheet-like material falls with a predetermined width exceeding a threshold value.

  According to the above configuration, it is possible to detect an elliptical or streaky concave defect or convex defect that is long in the width direction.

  Here, when a sheet-like object has a defect, the width where the luminance signal exceeds the threshold value is often narrower than the actual defect width, and the range of the width exceeding the threshold value needs to be detected. It is preferable to set between the smallest defect size and 1/3 of that size.

  Further, in FIG. 1, the signal processing means 5 detects the luminance signal from the imaging means 2, and the rising of the luminance signal in the width direction of the transparent sheet W has a predetermined length and exceeds the threshold value. When it occurs, it is determined as a concave defect, and when the brightness signal in the width direction of the sheet-like material falls in the traveling method with a predetermined length exceeding a threshold value, it is determined as a convex defect.

  According to the above configuration, it is possible to detect an elliptical or streaky concave defect or convex defect that is long in the traveling direction.

  Here, when the sheet-like object has a defect, the length of the luminance signal exceeding the threshold value is often shorter than the actual defect length, and the range of the length exceeding the threshold value is detected. Is preferably set between the required minimum defect size and 1/3 of the size.

  In FIG. 1, the image processing means 6 sequentially accumulates images in the effective field of view from the imaging means 2 in the image memory without interruption of the transparent sheet W, and based on the accumulated images, the brightness exceeding the threshold value is stored. When an image having a predetermined area or length is detected, the portion is determined as a concave defect, and when a dark portion exceeding the threshold is detected as an image having a predetermined area or length, it is determined as a convex defect.

  Here, when there is a defect in the sheet-like material, the area of the image detected by the image processing means is often smaller than the area of the image of the actual defect, and the range of the area of the bright part or the dark part can be detected. It is preferable to set between the area of the minimum required defect and 1/3 of the area.

  In addition, when the sheet-like object has a defect, the length of the image detected by the image processing unit is often smaller than the actual defect image length, and the range of the image length of the bright part or the dark part is Preferably, it is set between the maximum diameter of the smallest defect that needs to be detected and 1/3 of the maximum diameter.

  According to the above configuration, since the defect is determined based on the image, the determination accuracy does not depend on the shape of the defect, which is excellent in that false detection is reduced.

  As the continuously picked up image, a two-dimensional image obtained by superimposing one-dimensional data for each raster using the one-dimensional CCD camera on the image pickup means 2 can be used. For example, it is possible to use an image detected by releasing the shutter so that the sheet-like object can be continuously imaged without being cut in synchronization with the line speed.

  Here, the image of the bright part due to the concave defect is a part condensed at the concave surface part, which is smaller than the area of the actual concave defect and often has a different shape. Is preferably set systematically small, and more preferably determined by the pattern of the shape of the image.

  Moreover, since the image of the dark part due to the convex defect is an image in which incident light is refracted at the convex part and enters the sheet-like material and a part of the reflected light is lost, it is smaller than the area of the actual concave defect. It is preferable to systematically set the value of the area or length determined as a defect to be small.

  FIG. 2 shows a plurality of illumination units 1a to 1c and a plurality of imaging units when the inspection range in the width direction of the transparent sheet W is larger than the visual field width of the imaging unit in the above-described defect inspection apparatus for uneven defects. It is the figure which showed an example which provided 2a-2c and respond | corresponded.

  According to the above configuration, it is possible to detect uneven defects without omission over the entire surface of the traveling sheet.

Example 1
PC-type transparent film with three types of concave defects with an average thickness of about 50 μm, maximum depth of about 1 μm to 2 μm, maximum diameter of about 0.5 to 2.0 mm, and moving at 100 mm / second In the configuration shown in FIG. 1, the illumination unit and the film are configured with a cylindrical lens on the LED unit, the angle between the illumination unit and the film is set to 20 °, and can be regarded as parallel light. A distance of about 500 mm was used, and a one-dimensional CCD sensor camera with an effective pixel of 4000 bits was used as an image pickup means, and an image was taken from the regular reflection direction, and a luminance distribution and an image when passing through a concave defect were detected.

  As a result of evaluation under the above-mentioned conditions, it was confirmed that the luminance signal showed a rise of about 10 to 15% from the ground in the concave defect portion. FIG. 5 shows an example of a two-dimensional image near the concave defect (arrow). In FIG. 5, it was confirmed that the defect portion had high brightness and could be recognized as a bright defect that was a feature of the concave defect, and the presence / absence of the defect and the determination of the concave defect could be achieved as intended.

(Example 2)
A sample of a PC-based transparent film with three types of convex defects having an average thickness of about 50 μm, a maximum height of about 1 μm to 1.5 μm, and a maximum diameter of about 0.5 to 2.5 mm, and 100 mm / second. In order to obtain a state in which the illumination unit is formed of a cylindrical lens on the LED array and the angle between the illumination unit and the film is 20 °, and can be regarded as parallel light, in the configuration shown in FIG. The distance between the film and the film was set to a distance of about 500 mm, and a one-dimensional CCD sensor camera with an effective pixel of 4000 bits was used as the image pickup means, and the image was taken from the regular reflection direction.

  As a result of evaluation under the above-mentioned conditions, it was confirmed that the luminance signal showed a rise of about 15 to 23% from the formation in the convex defect portion. FIG. 6 shows an example of a two-dimensional image near the convex defect portion (arrow). In FIG. 6, it was confirmed that the defect portion had low luminance and could be recognized as a dark defect that is a feature of the convex defect, and the presence / absence of the defect and the determination of the convex defect could be achieved as intended.

DESCRIPTION OF SYMBOLS 1 Illuminating means 2 Imaging means 3 Inspection position 4 Signal processing part 5 Roll 5 Signal processing apparatus 6 Image accumulation processing apparatus 7 Encoder W Sheet-like object A Traveling direction of sheet-like object θ Incident angle of illumination means θ ′ Reflected light by imaging means Detection angle L1 Bright side threshold L2 Dark side threshold

Claims (4)

Illuminating means for irradiating parallel light from an oblique direction on the traveling sheet-like surface of the transparent body, and imaging means and processing means for continuously detecting reflected light from the sheet-like surface,
An apparatus for inspecting a surface defect of a sheet-like material, characterized by determining the presence or absence of an uneven defect portion on the surface of the sheet-like material and whether the detected surface is a concave defect or a convex defect. When the pre-processing means has a concave defect on the surface of the sheet-like material, it is determined that the reflected light has a higher luminance signal than the luminance signal of the part having no defect, and is determined as a concave defect.
When there is a convex defect on the surface of the sheet-like material, it is determined that the luminance signal of the reflected light is lower than the luminance signal of the part having no defect, and determined as a convex defect.
2. The surface defect inspection apparatus for a sheet-like object according to claim 1, further comprising a signal processing means. When the processing means has a concave defect on the surface of the sheet-like material, it is determined that the reflected light image is brighter than a portion without a defect and is determined as a concave defect.
When there is a convex defect on the surface of the sheet-like material, it is determined that the reflected light image is darker than the part without the defect, and determined as a convex defect.
The surface defect inspection apparatus for a sheet-like object according to claim 1, further comprising an image processing unit. The distance between the light source of the illuminating means and the sheet-like object and the incident angle are such that, on the light receiving surface of the imaging means for reflected light, the difference between the concave defect and the convex defect is not a defect and the optical density is maximum. The surface defect inspection apparatus for a sheet-like object according to any one of claims 1 to 3, wherein the surface defect inspection apparatus is set so as to be in a state close to.