JP2007333608A - Inspection device and inspection method of irregular flaw on sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection device capable of detecting irregular flaws generated on a surface of an inspection target along the longitudinal direction by means of an optical technique, and capable of accurately calculating the height and the width of the irregular flaw in a short time. <P>SOLUTION: A light irradiation means is disposed on one surface of a sheetlike article continuously conveyed which is the inspection target, and an imaging means is disposed on the other surface, and a data processing means is provided for detecting and quantifying the irregular flaw existing on the surface of the inspection target based on the transmission light imaged by the imaging means. In the data processing means, the height of the irregular flaw can be calculated in a short time by the product of the lateral width and the longitudinal amplitude of two peaks of an output signal wave of the irregular flaw part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inspection apparatus and an inspection method for uneven defects in a sheet.

  In the process of continuously producing sheets such as plastic films, local uneven thickness unevenness may occur continuously in the flow direction at the polymer discharge port. This uneven thickness becomes a streak-like defect when the height and width of the unevenness exceeds a predetermined size, and this streak-like defect becomes a problem in the user's processing process, so the sheet manufacturer has a streak-like defect. It must be avoided that the sheet is shipped as a product. Therefore, when discriminating between a non-defective product and a defective product with respect to a sheet having a streak-like defect, not only the presence or absence of the streak-like defect but also a non-defective product if the above-mentioned streak-like defect has a width of several mm or less and a height of several μm or less. Quantitative standards are established. Therefore, it is desirable to quantitatively evaluate the shape of the streak-like defect and determine a good product and a defective product. In addition, when the manufactured sheet is inspected, since the internal state of the roll is not known after winding up, it is not possible to inspect a part of the manufactured sheet by pulling out, but in-line full length inspection is performed. desired. Furthermore, since the sheet is conveyed at several meters to several hundred meters per minute in the length direction in the manufacturing process, it is desirable to perform quantitative evaluation in a short time in order to shorten the inspection interval in the sheet length direction.

  When quantifying the shape of the concave and convex defects present on the surface of the object to be inspected, the surface of the object to be inspected is detected by irradiating light to the object and referring to the state of the reflected light. A method of quantification is used. For example, methods described in Patent Literature 1, Patent Literature 2, and Patent Literature 3 are known.

  The method described in Patent Document 1 will be described with reference to FIG. FIG. 1 is a principle diagram of the inspection apparatus described in Patent Document 1. In FIG. 1, 1 denotes an object to be inspected, 2 denotes a light irradiation means, 3 denotes an imaging means, 9 denotes an uneven defect, and 8 denotes a data processing apparatus.

  The method described in Patent Document 1 irradiates light to the object 1 by using a planar light irradiation means 2 in which the intensity or wavelength of light to be irradiated gradually changes from large to small along the irradiation surface. Then, the reflected light on the surface of the inspection object is received by the imaging means 3. In this method, the imaging means 3 receives light from a different position of the light irradiating means 2 when there is an uneven defect in the inspection object 1 compared to when there is no uneven defect.

  Since the amount of light received by the imaging unit 3 changes according to the inclination of the surface of the object 1 to be inspected, the signal output from the imaging unit 3 is differentiated. Furthermore, based on the fact that the intensity or wavelength of the reflected light imaged is related to the slope of the slope of the uneven defect, by detecting the location and size of the uneven defect on the surface of the object to be inspected based on the value of the differential signal The height or depth of the irregular defect is measured.

  The method described in Patent Document 2 will be described with reference to FIG. 2A. FIG. 2A is a perspective view of the inspection apparatus described in Patent Document 2. FIG. In FIG. 2A, 1 is a to-be-inspected object, 2 is a light irradiation means, 3 is an imaging means, 4 is a retroreflection screen, 6 is a streak-like defect, 8 is a data processor.

  As shown in the figure, the surface of the object to be inspected 1 is arranged between the recursive reflection screen 4 and the light irradiating means 2, and the light of the light irradiating means 2 hits the surface of the object 1 to be inspected and is reflected to be recursive. An optical path toward the reflection screen 4 is formed. With the above arrangement, the light from the light irradiation means 2 is reflected by the inspection object 1 and enters the recursive reflection screen 4 and is reflected in the same direction as the incident optical axis, so that it is reflected again by the surface of the inspection object 1. It is captured by the image pickup means 3 disposed above the light irradiation means 2. With this configuration, an image in which the uneven defects on the surface of the object 1 to be inspected are optically emphasized can be captured by the imaging means 3, and the uneven defects on the surface that should be smooth can be easily found.

The detection principle of the surface inspection using the recursive reflection screen will be described with reference to FIG. 2B. FIG. 2B is an explanatory diagram showing the principle of surface inspection of the inspection apparatus of Patent Document 2. In FIG. 2B, 1 is a test object, 4 is a retroreflection screen, and 41 is a bead-like reflection sphere. The recursive reflection screen 4 has a bead-shaped reflection sphere 41 densely provided on the surface thereof, and each reflection sphere 41 has a directional reflection pattern as shown in the figure with respect to incident light. As shown in FIG. 2B, the light coming from the light source direction is reflected in the direction of the retroreflection screen 4 on the surface of the inspection object 1. On the other hand, the image pickup means 3 arranged above the light irradiation means 2 is directed to the surface of the inspection object 1 from the camera viewing direction in the figure, and the reflected light from the recursive reflection screen 4 is the inspection object 1. It captures the light that re-reflects. When viewing each point A, B, and C of the inspection object 1 from the camera, the imaging means 3 captures it as a surface having intermediate brightness on a plane that does not have an uneven defect like the point C. On the other hand, at point A, which is a downhill as viewed from the imaging means 3 side of the uneven defect, the reflection angle of the light from the recursive reflection screen 4 changes due to the uneven defect and captures strong light. At point B, which is an uphill as viewed from the imaging means 3 side of the uneven defect, the reflection angle of the light from the recursive reflection screen 4 changes due to the uneven defect, and weak light is captured. Therefore, the uneven defect on the surface of the inspection object 1 can be detected by the amount of light received by the imaging means 3.
The method described in Patent Document 2 irradiates the inspection object 1 with light using the light irradiation means 2, reflects the reflected light on the inspection object surface with the retroreflective screen 4, and again the inspection object. 1 and the reflected light on the surface of the object to be inspected is imaged by the imaging means 3.

  Further, since the gray value of the image picked up by the image pickup means 3 changes according to the slope of the unevenness on the surface of the object to be inspected, a gray value-gradient table corresponding to the type of the object to be inspected is created in advance. By using the table, the gray value of the image is converted to the slope of the streak defect, and the obtained slope is integrated to quantify the surface shape of the object 1 to be inspected.

  The method described in Patent Document 3 will be described with reference to FIG. FIG. 3 is a perspective view of the inspection apparatus described in Patent Document 3. In FIG. 3, 1 denotes an object to be inspected, 2 denotes a light irradiation means, 3 denotes an imaging means, 5 denotes a diffusion screen, and 9 denotes an uneven defect.

In the method described in Patent Document 3, light is irradiated on the inspection object 1 using the light irradiation means 2, and the reflected light on the surface of the inspection object is imaged by the imaging means 3. When the uneven defect 9 is present on the object 1 to be inspected, the reflection angle of the light from the light irradiation means 2 changes due to the uneven defect, and the gray value of the image captured by the imaging means 3 changes. In order to detect a change in the gray value due to the uneven defect, the luminance average value of one measurement line of the pixel data imaged by the imaging means 3 is obtained, and the difference between the luminance value of each pixel data and the luminance average value is integrated. (Cumulative addition). Thereby, the uneven defect on the surface of the object to be inspected is emphasized. Furthermore, using the integration value and the conversion coefficient for correcting the curvature and color of the object to be inspected, the shape of the unevenness on the surface of the object to be inspected is obtained.
Japanese Patent No. 2926365 JP 2006-003168 A Japanese Patent No. 3107628

  However, in the above background art, it is difficult to apply to a sheet-like object that is continuously running.

  In the method described in Patent Document 1, light from the light irradiation unit is reflected by an object to be inspected, and the reflected light is imaged by the imaging unit. However, the sheet-like object that is continuously running has large vertical and angular fluctuations, and the amount of light picked up by the imaging means changes due to the fluctuation of the sheet-like object.

  In other words, even when uneven defects with the same height occur, the amount of light picked up by the imaging means varies due to the vertical and angular fluctuations of the sheet-like material, and the height of the uneven defects to be obtained. Is a different value.

  As described above, there is a problem that the height of the uneven defect cannot be inspected with high accuracy.

  In the method described in Patent Document 2, the light from the light irradiation means and the reflected light from the retroreflective screen are reflected by the object to be inspected and imaged by the area sensor camera. Even if a streak-like defect with the same height occurs due to up-down fluctuations and angle fluctuations of a sheet that is continuously running, the amount of light captured by the area sensor camera varies, and the streak to be obtained The value is different from the height of the shape defect. Furthermore, since the image pickup means is an area sensor camera, it is difficult to inspect the full length of a continuously traveling sheet-like object.

  Also, a variety of varieties are manufactured on the plastic film production line, and the varieties and thickness are frequently changed. Therefore, it is necessary to create a gray value-slope table corresponding to the type of object to be inspected, and it is difficult to create a gray value-slope table for multiple varieties. .

  Furthermore, the height of the stripe defect is obtained by cumulatively adding pixel data of the stripe defect. Here, the sheet-like material may be transported by several hundred meters, and when a large number of streak defects occur on the surface of the object to be inspected, the height of the streak defect is quantified by cumulatively adding pixel data. There is a problem that it is not sufficient in terms of time to find out.

  In the method described in Patent Document 3, as in Patent Documents 1 and 2, the light from the light irradiation means is reflected by the object to be inspected, and the reflected light is imaged by the imaging means. In the production line, the problem is that the sheet cannot be quantified with high accuracy due to the vertical and angular fluctuations of the sheet-like material, and the time required to integrate (cumulatively add) the signal waveform of the uneven defect imaged by the imaging means. With regard to, when a large number of uneven defects occur on the sheet surface, it is not sufficient in time to apply to the production of a sheet such as a film, and the accuracy of quantification of the uneven defect shape on the surface of the object to be inspected is Depending on the conversion coefficient, there is a problem that the conversion coefficient must be obtained with high accuracy.

  An object of the present invention is to provide an inspection apparatus and an inspection method capable of solving the above-described problems of the prior art and accurately detecting and quantifying uneven defects in a sheet.

  In order to achieve the above object, according to the present invention, a light irradiating means for irradiating light from one side of an object to be inspected, and the object to be inspected disposed opposite to the other surface of the object to be inspected. An imaging unit having a plurality of photoelectric conversion elements for imaging the transmitted light from the light source and outputting the imaged light quantity as an output signal waveform; and a surface of the inspected object based on the signal waveform of the transmitted light imaged by the imaging unit And a data processing means for detecting uneven defects present in the sheet, wherein the light irradiation means is continuously in a longitudinal direction and a direction in a plane perpendicular to the imaging axis of the imaging means. A light-emitting unit that emits light to be output by the imaging unit so that the amount of emitted light changes, the imaging unit is disposed so that an imaging axis intersects the light irradiation unit, and the data processing unit Predetermined threshold value of output signal waveform A position detecting means for detecting the position of the concave / convex defect on the object to be inspected, and a difference between positions of two adjacent peaks in the output signal waveform of the photoelectric conversion element and the two peaks There is provided an inspection device for uneven defects in a sheet, comprising: quantification means for obtaining a shape of the uneven defects based on an output proportional to a product of a difference between output values.

  According to a preferred embodiment of the present invention, the light irradiating means includes a dimming member extending between the light irradiating means and the object to be inspected in a direction parallel to the longitudinal direction of the light irradiating means. In a sheet that uses a line-shaped light source, and the imaging means is configured such that light from the line-shaped light source is incident when the imaging axis intersects with the dimming unit and there is no defect in the inspection object An inspection device for uneven defects is provided.

  Moreover, according to the preferable form of this invention, the inspection apparatus of the uneven | corrugated shaped defect in the sheet | seat which uses what arranged the some photoelectric conversion element in parallel with the said light irradiation means as said imaging means is provided.

  Further, according to another aspect of the present invention, there is provided a method for inspecting a concave / convex defect that obtains the shape of the concave / convex defect present in a test object traveling in a traveling direction, wherein one surface of the test object is provided. The light is irradiated on the object to be inspected by the light irradiation means that irradiates the light quantity continuously changing in the axial direction perpendicular to the longitudinal direction and the imaging axis of the imaging means from the side, and the place where the light quantity changes monotonously is imaged Imaging the transmitted light from the object to be inspected by an imaging means having a plurality of photoelectric conversion elements, and detecting a peak exceeding a predetermined threshold of the output signal waveform of each photoelectric conversion element by the position detection means The concavo-convex shape is detected by a quantifying means that detects a position and is based on an output proportional to a product of a difference between positions of two adjacent peaks in the output signal waveform of the photoelectric conversion element and a difference value of the output values of the two peaks. Flawed Method of inspecting uneven defect in the seat to determine the Jo is provided.

  Further, according to a preferred embodiment of the present invention, the amount of light in the axial direction perpendicular to the longitudinal direction of the light irradiating means and the imaging axis of the imaging means changes continuously, and in a sheet where there is a monotonously changing portion. An inspection method for uneven defects is provided.

  Further, according to a preferred embodiment of the present invention, there is provided a method for inspecting concave and convex defects in a sheet from which the imaging unit obtains a one-dimensional image parallel to the light irradiation unit.

  Moreover, according to another form of this invention, the manufacturing method of the sheet | seat which test | inspects the uneven | corrugated defect of the said sheet | seat using the inspection method of the uneven | corrugated defect in the said sheet | seat is provided.

  In the present invention, the “concavo-convex defect” refers to a concave or convex defect present on the surface of the object to be inspected. For example, there are thickness unevenness continuously generated in the traveling direction of the uneven object to be inspected, and application unevenness generated when another object is applied to the object to be inspected.

  In the present invention, the “light irradiating means” refers to a light emitting body that is installed at a position facing the imaging means with the object to be inspected therebetween and can illuminate the imaging range of the imaging means on the object to be inspected. Say. The light irradiating means is preferably one in which a plurality of optical fibers are arranged in a line or a cylindrical rod illumination because a predetermined inspection range can be uniformly irradiated. In addition, the apparatus can be realized at low cost by using a columnar fluorescent lamp.

  In the present invention, “the amount of emitted light continuously changes” means that the light amount is maximized at the center of the light irradiating means in the axial direction perpendicular to the longitudinal direction of the light irradiating means and the imaging axis, and away from the center. The amount of light that changes from light to dark uniquely and linearly or curvedly. The continuous light amount may be a mountain shape, or may be a right-up type or a right-down type with a large amount of light on the one hand and a small amount of light on the other hand. Further, by providing the light irradiating means with a light reducing member that blocks light, a continuous change in the amount of light can be made steep, and uneven defects on the object to be inspected can be detected with higher accuracy.

  In the present invention, the “imaging means” is installed at a position facing the light irradiation means across the object to be inspected, has a plurality of photoelectric conversion elements, and the received light amount of each photoelectric conversion element is an electric signal. As output. When a line sensor camera in which a plurality of photoelectric conversion elements are arranged in a row is used as the imaging means, it is preferable because continuous film can be continuously imaged at high speed.

  In the present invention, the “light-reducing member” is disposed between the light-emitting portion of the light-irradiating means and the object to be inspected in parallel to the longitudinal direction of the light-emitting portion, and is directed to the amount of light from the light-irradiating means. It is a member for giving the property. As the light reducing member, it is preferable to use a material that does not transmit light, such as iron or aluminum, to block light in a cross section perpendicular to the longitudinal direction of the light irradiation means.

  According to the inspection device for uneven defects in the sheet of the present invention, uneven defects such as streak defects generated on the surface of the sheet-like object, which is an important criterion for discriminating between non-defective products and defective products of the sheet-like object. Thus, it is possible to realize an inspection apparatus and an inspection method for quantitatively evaluating the shape of a streak-like defect in a short time from an imaging signal waveform of the shape.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a diagram showing the shape of streak-like defects that occur in the plastic film that is the device under test 1. In FIG. 4, reference numeral 1 denotes a plastic film as an object to be inspected, and 6 denotes a streak-like defect. The streaky defects generated on the surface of the plastic film shown in FIG. 4 occur parallel to the flow direction of the plastic film 1 and form a minute convex shape in a cross section perpendicular to the film length direction. A case where the width and height of the streak-like defect are quantitatively evaluated by receiving transmitted light will be described as an example.

  FIG. 5 is a perspective view showing a configuration of a sheet inspection apparatus according to an embodiment of the present invention. In FIG. 5, 1 is a plastic film which is an object to be inspected, 2 is a light irradiation means, 3 is an imaging means, 7 is a slit, 8 is a data processing means, 10 is a dimming member, and θ is the width direction of the film and light irradiation. Angle formed by the longitudinal direction of the means The angle formed by the traveling direction of the film and the imaging axis of the imaging means, and θ2 represent the angle formed by the traveling direction of the film and the imaging axis of the imaging means. In the sheet inspection apparatus of FIG. 5, the light irradiation means 2 is arranged on one surface of the film 1 traveling in the film length direction, and the imaging means 3 is arranged on the other surface. The light is converted into an output signal waveform by the photoelectric conversion element and input to the data processing means. Here, by adopting the transmission type, it is possible to increase the vertical vibration and angle fluctuation of the continuously running film, and it is possible to perform quantification with high accuracy.

  The data processing means 8 quantitatively obtains the shape of the concavo-convex portions present on the film surface based on the input output signal waveform.

  The light irradiating means 2 is a line light source provided with a dimming member 10 for defining the slit portion 7, and the light quantity in the axial direction perpendicular to the longitudinal direction and the imaging axis of the imaging means is continuously changed. The visual field width of the imaging means 3 is arranged in parallel with the longitudinal direction of the light irradiation means 2, and the extension of the imaging axis of the imaging means 3 is the longitudinal direction of the light irradiation means and the imaging axis of the imaging means. It corresponds to the light-reducing member provided in the axial direction orthogonal to.

  FIG. 6A shows an axial direction orthogonal to the longitudinal direction of the light irradiation means and the imaging axis of the imaging means when the imaging axis of the imaging means is changed in the axial direction orthogonal to the longitudinal direction of the light irradiation means and the imaging axis of the imaging means. It is the schematic which shows the light quantity distribution received with the imaging means. In FIG. 6A, 2 represents a light irradiation means. The light quantity distribution received by the imaging unit in FIG. 6A is a mountain-shaped distribution in which the central part of the light emitting part of the light irradiating unit 2 is brightest and becomes darker at the periphery. The gradation value received by the image pickup means changes gently because the focus of the image pickup means is adjusted to the surface of the inspected object 1 and light is widely taken from the vicinity of the light irradiation means that is not in focus. .

  FIG. 6B shows the longitudinal direction of the light irradiating means when the imaging axis of the imaging means is changed in the longitudinal direction of the light illuminating means 2 provided with the dimming member for defining the slit and the axial direction orthogonal to the imaging means. It is the schematic which shows the light quantity distribution received with the imaging means of the axial direction orthogonal to the imaging axis of an imaging means. In FIG. 6B, 2 represents a light irradiation means, 7 represents a slit, and 10 represents a light reducing member. As shown in FIG. 6B, by installing the light reducing member 10 that defines the slit 7 in the light irradiation means 2, the image pickup means is arranged in the axial direction orthogonal to the longitudinal direction of the light irradiation means 2 and the image pickup axis of the image pickup means. When the imaging axis is changed, a steep light amount distribution can be obtained in the cross-sectional direction orthogonal to the longitudinal direction of the light irradiation means and the imaging axis of the imaging means. Since this dimming member 10 can obtain a steep light amount distribution as it is installed closer to the light emitting portion with respect to an axial direction orthogonal to the longitudinal direction of the light irradiation means 2 and the imaging axis of the imaging means, When a defect occurs, it is preferable because the amount of light received by the imaging means can be changed sufficiently. However, if it is installed too close, the required amount of light cannot be obtained, and the detection accuracy is reduced. In addition, when the dimming member 10 is separated from the light emitting unit, a steep light amount distribution cannot be obtained, and the detection accuracy is lowered. Therefore, an axis orthogonal to the longitudinal direction of the light irradiation unit and the imaging axis of the imaging unit. The position of the direction dimming member and the central part of the light emitting part is preferably between 5 mm and 30 mm.

  Hereinafter, the principle of detecting streak-like defects existing in the plastic film 1 from the light irradiation means 2 and the imaging means 3 facing each other with the plastic film 1 as an object to be inspected in between will be described. FIG. 7A is a schematic diagram illustrating the imaging axis of the imaging unit viewed from a direction parallel to the longitudinal direction of the light irradiation unit in one embodiment of the present invention. FIG. 7B is a schematic diagram of a change in the imaging axis of the imaging unit on the left slope of the streak when a streak occurs on the film viewed from a direction parallel to the longitudinal direction of the light irradiation unit in one embodiment of the present invention. . FIG. 7C is a schematic diagram of a change in the imaging axis of the imaging unit on the right slope of the streak when a streak occurs on the film viewed from a direction parallel to the longitudinal direction of the light irradiation unit in one embodiment of the present invention. .

7A, 7B, and 7C, 1 is a plastic film as an object to be inspected, 2 is a light irradiation means, 3 is an imaging means, 6 is a streak defect, 7 is a slit, 8 is a data processing means, and 10 is a reduction. The optical member, a is the intersection of the extension of the imaging axis of the imaging means and the plane of the dimming member 10 installed in the light irradiation means 2, and b is changed on the left slope of the streak-like defect when the streak-like defect occurs The intersection of the extension of the imaging axis of the imaging means and the plane of the dimming member 10 installed in the light irradiation means 2, c is the imaging axis of the imaging means changed on the right slope of the streak-like defect when the streak-like defect occurs And the intersection of the light-reducing member 10 installed on the light irradiating means 2 with the plane.
FIG. 8 shows changes in the amount of light imaged by the imaging means when streaks occur on the film. In FIG. 8, 2 represents a light irradiation means, and 10 represents a light reducing member. Note that a, b, and c correspond to a, b, and c in FIG. 7, respectively.

  As shown in FIGS. 7B and 7C, when the streak-like defect 6 occurs on the film, the refractive index changes on the slope of the streak-like defect, and the intersection between the extension of the imaging axis of the imaging means 3 and the light irradiation means changes. . As shown in FIG. 7B, on the left slope of the streak-like defect, the intersection of the imaging axis of the imaging unit and the light irradiation unit changes near the center of the light irradiation unit, and the amount of light captured by the imaging unit increases. On the other hand, as shown in FIG. 7C, on the right slope of the streak-like defect, the intersection of the imaging axis of the imaging unit and the light irradiation unit changes away from the center of the light irradiation unit, and the amount of light captured by the imaging unit is small. Become.

  In order to accurately quantify the height of the streak-like defect, as shown in FIGS. 7B and 7C, the light refraction changes due to the streak-like defect, and the longitudinal direction of the light irradiation means and the imaging axis of the imaging means are changed. When the imaging position in the orthogonal axial direction changes, it is preferable that the amount of light can be changed sufficiently as shown in FIG. For this reason, it is preferable that the imaging position in the case where there is no defect by the imaging means 3 is set so as to be between the maximum value and the minimum value of the light amount. In addition, when a dimming member that blocks light parallel to the longitudinal direction of the light irradiating means is disposed, the imaging position in the axial direction perpendicular to the longitudinal direction of the light irradiating means and the imaging axis of the imaging means changes. The amount of change in the amount of light of the output signal waveform picked up by the image pickup means increases, and the height of the streak-like defect can be quantified with high accuracy.

In FIG. 5, the smaller the angle θ ₂ formed by the film 1 and the image pickup means 3, the greater the angle change on the slope of the streak-like defect, and the greater the deviation of the optical axis when there is no streak-like defect. Therefore, the detection performance of streak-like defects is improved. However, as the angle θ ₂ becomes smaller, the space required for the device configuration becomes wider, so 30 ° <θ ₂ <75 ° is preferable.

  In the case where an uneven defect is generated on the film surface, when the film surface that transmits light is irradiated with light, the optical path of the irradiated light is deflected in a plane direction perpendicular to the slope of the uneven defect. Similarly, in the case of a streak-like defect that occurs on the film surface in the film length direction, light is refracted in a plane direction perpendicular to the slope of the streak. Here, the light irradiation means and the image pickup means are installed so that the longitudinal direction is perpendicular to the traveling direction of the film, and when the light from the light irradiation means is applied to the streak-like defect, the slope of the streak-like defect is Since the normal direction is only the direction perpendicular to the film running direction, the light refracted by the streak defect changes in a direction perpendicular to the film running direction. Since this direction is parallel to the longitudinal direction of the light irradiation means, the amount of light is the same when there is a streak-like defect on the film surface. Therefore, it is impossible to detect streak-like defects.

  Therefore, as shown in FIG. 5, the light irradiating means and the imaging means are installed at an angle θ that satisfies 0 ° <θ <90 ° from a direction perpendicular to the running direction of the film.

  Here, when θ is close to 0 °, the change in the imaging axis of the imaging means 3 in the axial direction orthogonal to the longitudinal direction of the light irradiation means and the imaging axis of the imaging means when a streak-like defect occurs in the film 1 Since the amount is small, the output signal waveform of the streak-like defect portion becomes small and the detection accuracy is low. For this reason, θ is preferably set to 15 ° or more. On the other hand, as it approaches 90 °, the amount of light refracted in the film running direction with streak-like defects increases and the detection signal increases, but the range that can be inspected in the film width direction is narrowed. It is preferable.

  Next, a method for detecting and quantifying the position of the streak-like defect from the signal waveform obtained by the imaging means will be described. FIG. 9 is a diagram illustrating an imaging signal waveform captured by the imaging unit according to the embodiment of the present invention. The place where the gray value of the signal imaged by the image pickup means 3 changes rapidly as shown in FIG. 9 is a streak-like defect in which the slope of the film surface changes abruptly.

  Further, the data processing means uses the position detection means of the streak-like defect by detecting the peak of the output signal waveform of each photoelectric conversion element, and the distance between the positions of the two peaks and the difference between the values of the streak-like defect. And quantifying means for obtaining the shape.

  FIG. 10 is a diagram showing a method for detecting a position of a streak-like defect from an imaging signal waveform according to an embodiment of the present invention. In the position detection means, as shown in FIG. 10, the transmitted light imaged by the imaging means is converted into a signal waveform by a photoelectric conversion element, and the influence of illumination unevenness and film fluttering is removed from the signal waveform. Furthermore, if two peaks of maximum value and minimum value are extracted from the waveform after removal of illumination unevenness and film flutter, and the absolute value of the difference value between the maximum value and the minimum value exceeds the threshold, the position Is detected as a streak-like defect portion. Here, the threshold value of the difference value between the adjacent maximum value and minimum value used for detecting the position of the streak-like defect is determined according to the height of the streak-like defect to be detected, and the minimum streak shape to be detected in advance. By detecting the defect and using the difference value between the adjacent maximum value and minimum value at that time as a threshold value, it becomes possible to detect a stripe defect having a height higher than the minimum stripe defect.

  As a method of removing the effects of illumination unevenness and film flutter, a method of recognizing the signal waveform pattern of illumination unevenness in advance and taking the difference from the imaging signal waveform, or taking a moving average of the imaging signal waveform, There is a method to take the difference of.

  FIG. 11 is a diagram showing an imaging signal waveform quantification unit obtained by cutting out a streak-like defect portion according to an embodiment of the present invention. In FIG. 11, w represents the difference value between the maximum and minimum pixel positions of the streak-like defect portion, and h represents the difference value between the maximum and minimum values of the streak-like defect portion. In the quantification means, as shown in FIG. 11, the height and width of the streak-like defect portion are obtained in a short time from the imaging signal waveform including one maximum value and one minimum value of the streak-like defect portion detected. It is what.

  In order to apply the quantification means, the present inventors have collected a large number of streak-like defects generated on the surface of the plastic film and measured the shape of the streak-like defects. As a result, the cross-section of the streak-like defects can be approximated to a cosine waveform. It was confirmed. Furthermore, the present inventors have taken an image of a streak-like defect on the film surface by the imaging means, and the imaging waveform changes depending on the slope of the film surface. It has been found that the degree can be approximated by a sine waveform that is a derivative of a cosine waveform.

FIG. 12 is a diagram showing streaky defects approximated by a cosine waveform. FIG. 13 is a diagram showing a signal waveform of a streak-like defect approximated by a cosine waveform. Here, the line types in FIGS. 12 and 13 correspond to each other, and the signal waveform of the streak-like defect (1) approximated to the cosine waveform in FIG. 12 is (1) in FIG. Similarly, the signal waveforms of the stripe-like defects (2) and (3) in FIG. 12 also correspond to (2) and (3) in FIG.
When comparing the streak-like defect (1) with (2) where the streak height is twice that of (1), the amplitude of (2) is twice that of (1) in the signal waveform. Further, when comparing the streak-like defect (1) with (3) where the width of the streak is twice that of (1), the amplitude of (3) is half of the amplitude of (1) in the signal waveform. The period of (3) is twice that of (1).

  Since the amplitude of the imaging signal waveform is proportional to the slope (first derivative) of the film surface, integrating the half period of the signal waveform of the streak-like defect portion of the imaging signal results in integration of the streak-like defect portion of the film surface. It is possible to calculate information proportional to the height.

  Since the signal waveform of the streak-like defect portion can be approximated as a sine wave, the height H of the film surface can be calculated by integrating with respect to the pixel position by the following equation. h is a difference value between the maximum value and the minimum value of the streak-like defect portion, and w is a difference value between pixel values of the maximum value and the minimum value of the stripe-like defect portion. The integration range is a half cycle of the signal waveform of the streak defect portion.

Furthermore, the unit of the height H of the streak-like defect portion in the mathematical expression is a pixel. Therefore, the actual streak height can be obtained by multiplying the conversion constant to be converted into an actual numerical value as in the following equation. Here, A and B are conversion constants, which are set according to the light amount distribution of the light irradiation means.
As a method for adjusting the conversion constant, it can be easily adjusted by imaging a streak-like uneven portion having a known height with an inspection device and obtaining the relationship between the height and the signal.

As described above, since the cross-sectional shape of the streak-like defect is approximated to a cosine shape, the height H of the streak-like defect on the film surface is a feature amount of the imaging signal waveform of the streak-like defect part without performing integral calculation. It can be obtained by a simple mathematical formula of multiplication of h and w. In actual calculation, the same result can be obtained by detecting an amount proportional to w or h from a signal and multiplying them. For example, instead of w, a difference between the start point and end point of the signal change can be used.
The height of the streak signal waveform of FIG. 13 is obtained by multiplying the amplitude of the waveform by a half cycle. When the waveform (1) is used as a reference, the height of the waveform (2) is twice that of (1). The height of (3) is the same as that of (1), and it can be confirmed that it coincides with FIG.

  The width W of the streak-like defect on the film surface can be obtained by multiplying the difference between the pixels at the two peak positions of the image signal waveform of the streak portion by the resolution of the image pickup means and multiplying it by two.

  The resolution is a range in which one photoelectric conversion element takes an image obtained by dividing the visual field width of the imaging unit by the number of photoelectric conversion elements arranged in a plurality of rows as the imaging unit.

  As an example of the present invention, a streak shape that occurs on the surface of a transparent plastic film before stretching during film formation, has a convex shape in a cross section perpendicular to the film length direction, and continues parallel to the length direction of the film. The height and width of the defects were quantitatively evaluated.

The line sensor camera as the image pickup means has 7500 image pickup elements arranged in a straight line, and the light irradiation means uses a columnar fluorescent lamp provided with a slit portion parallel to the longitudinal direction. The angle θ between the line sensor camera, the fluorescent lamp and the film width direction was 20 °. Further, the angle θ ₂ formed by the imaging axis of the line sensor camera and the film was set to 65 °. The distance between the central portion of the fluorescent lamp and the light reducing member in the axial direction orthogonal to the longitudinal direction of the fluorescent lamp and the imaging axis of the imaging means was 20 mm.

As a data processing means, from the output signal waveform from the line sensor camera, the effect of uneven illumination and film fluttering is removed by moving average, the difference value between the adjacent maximum value and minimum value is detected, and the streak-like defect to be detected is detected. The streak-like defect portion can be detected by comparing the difference between the maximum value and the minimum value adjacent to each other when the 1.0-μm streak-like defect, which is the minimum height, is detected, and comparing it with the output signal waveform. It was.
Furthermore, in the streak defect where the difference between the adjacent maximum value and the minimum value of the output signal waveform is greater than or equal to the threshold value, the distance between the adjacent maximum value and the minimum value is multiplied by the amplitude, and the film type, light source By multiplying and adding the constants determined from the above characteristics, the streak-like defects could be quantified in a short time and with high accuracy.

  Then, the film manufacturing process is managed based on the quantification information of the streak-like defects, the streak-like defects can be detected over the entire length of the film, and the size can be quantified and fed back to the film manufacturing process. The film production method could be improved.

  The present invention is not limited to an inspection apparatus for uneven defects that quantitatively evaluate streaky defects that occur on the surface of a continuously running plastic film, but the width and height of uneven defects that occur on a steel sheet surface, and the surface with a highly reflective material. Although it can be applied to the quantitative evaluation of the degree of local coating loss on the coated film surface, the application range is not limited thereto.

It is a principle figure of the inspection device of patent documents 1. It is a perspective view of the inspection device of patent documents 2. It is explanatory drawing which shows the principle of the surface inspection of the inspection apparatus of patent document 2. FIG. It is a perspective view of the inspection device of patent documents 3. It is a shape figure of a stripe-like fault. It is a perspective view which shows the test | inspection apparatus structure in one Embodiment of this invention. It is the schematic of the light quantity distribution of the axial direction orthogonal to the longitudinal direction of the light irradiation means in one Embodiment of this invention, and the imaging axis of an imaging means. It is the schematic of the light quantity distribution of the axial direction orthogonal to the longitudinal direction of the light irradiation means provided with the light reduction member for defining the slit in one Embodiment of this invention, and the imaging axis of an imaging means. It is the schematic showing the optical axis of the imaging means seen from the direction parallel to the longitudinal direction of the light irradiation means in one Embodiment of this invention. It is the schematic of the change of the optical axis of the imaging means in the left slope of a stripe, when a stripe has generate | occur | produced on the film seen from the direction parallel to the longitudinal direction of the light irradiation means in one Embodiment of this invention. It is the schematic of the change of the optical axis of the imaging means in the right slope of a streak when a streak has arisen on the film seen from the direction parallel to the longitudinal direction of the light irradiation means in one Embodiment of this invention. It is the schematic showing the change of the light and dark value imaged with the imaging means when a stripe generate | occur | produces on the film in one Embodiment of this invention. It is a conceptual diagram showing the imaging signal waveform in one Embodiment of this invention. It is a conceptual diagram showing the position detection method of the uneven | corrugated defect from the imaging signal waveform in one Embodiment of this invention. It is a conceptual diagram showing the quantification means of the imaging signal waveform by one Embodiment of this invention. It is a schematic diagram showing a stripe-like defect approximated by a cosine waveform. It is the schematic diagram showing the signal waveform of the stripe defect by which cosine waveform approximation was carried out.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 To-be-inspected object 2 Light irradiation means 3 Image pickup means 4 Retroreflective reflection screen 41 Bead type reflection sphere 5 Diffusion screen 6 Stripe defect 7 Slit 8 Data processing device 9 Uneven defect 10 Light reducing member θ Film width direction and light irradiation The angle formed by the longitudinal direction of the means θ _{2 The} angle formed by the traveling direction of the film and the imaging axis of the imaging means h The difference value between the maximum value and the minimum value of the stripe-like defect portion The pixel position of the maximum value and the minimum value of the stripe-like defect portion Of the imaging axis of the imaging means and the intersection of the light irradiation means b Extension of the imaging axis of the imaging means when the stripe defect occurs and intersection of the light irradiation means c of the imaging axis of the imaging means when the stripe defect occurs Intersection of extension and light irradiation means

Claims (7)

A light irradiating means for irradiating light from one surface side of the object to be inspected, and a plurality of photoelectric conversion elements arranged opposite to the other surface of the object to be inspected and imaging the transmitted light from the object to be inspected. An imaging unit that outputs an imaged light amount as an output signal waveform; and a data processing unit that detects an uneven defect on the surface of the object to be inspected based on a signal waveform of the transmitted light imaged by the imaging unit; A sheet inspection apparatus comprising: the imaging means so that the amount of emitted light continuously changes in a direction perpendicular to a longitudinal direction of the light irradiation means and an imaging axis of the imaging means. The imaging means is arranged so that the imaging axis intersects the light irradiation means, and the data processing means sets a predetermined threshold value of the output signal waveform of the imaging means. Detecting peaks that exceed A product of a position detecting means for detecting the position of the uneven defect on the object to be inspected, and a difference between the positions of two adjacent peaks in the output signal waveform of the imaging means and a difference between the output values of the two peaks An inspection device for uneven defects in a sheet, comprising: quantification means for obtaining a shape of the uneven defects based on an output proportional to The light irradiating means is a line light source including a dimming member extending in a direction parallel to the longitudinal direction of the light irradiating means between the light irradiating means and the object to be inspected. The light from the line-shaped light source is configured to be incident when the imaging axis intersects with the dimming unit and the test object has no defect. Inspection device for uneven defects in sheets. The inspection device for uneven defects in a sheet according to claim 1 or 2, wherein the imaging means comprises a plurality of photoelectric conversion elements arranged in parallel with the light irradiation means. A method for inspecting a concave / convex defect that obtains the shape of a concave / convex defect present in a traveling object to be inspected, comprising: a longitudinal direction of a light irradiation means and an imaging axis of an imaging means from one surface side of the inspection object; A plurality of photoelectric conversion elements arranged so that the object to be inspected is irradiated with light by a light irradiating unit that irradiates an amount of light that continuously changes in a direction perpendicular to the axis, and an imaging axis intersects the light irradiating unit The transmitted light from the object to be inspected is picked up by the image pickup means having the above, and the position of the concavo-convex defect is detected by the position detection means for detecting a peak exceeding a predetermined threshold of the output signal waveform of each photoelectric conversion element, Obtaining the shape of the uneven defect by quantification means based on an output proportional to the product of the difference between the positions of two adjacent peaks in the output signal waveform of the photoelectric conversion element and the difference between the output values of the two peaks. Features and Inspection method of uneven shortcomings in the sheet that. 5. The light irradiating means uses a light quantity that continuously changes in the amount of light orthogonal to the longitudinal direction of the light irradiating means and the imaging axis of the imaging means, and has a monotonously changing portion. A method for inspecting irregularities in the sheet according to claim 1. 6. The method for inspecting a concave-convex defect in a sheet according to claim 4 or 5, wherein the imaging means is one that obtains a one-dimensional image parallel to the light irradiation means. A method for producing a sheet, wherein the uneven defect of the sheet is inspected by using the method for inspecting an uneven defect in the sheet according to claim 4.

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