JP4511978B2 - Surface flaw inspection device - Google Patents

Description

  The present invention relates to a wrinkle inspection device for a surface of a strip-like body such as a metal plate, and more particularly to a technique suitable for a wrinkle inspection device for inspecting various wrinkles on the surface of a steel plate such as a thin steel plate using a photographed image. is there.

  In the manufacturing process of strips such as steel sheets, it is necessary to detect defects that may impair the quality of the product at an early stage in the manufacturing stage and to prevent generation of defects in subsequent products by changing manufacturing conditions. . For example, a flaw is inspected while moving a steel plate in a production line. Numerous inspection methods, such as electromagnetic and optical, have been developed as inspection methods for wrinkles. Among them, optical inspection methods can detect wrinkles without contact with steel sheets, and can easily obtain wrinkle images. Widely used.

  In the optical inspection method, wrinkles on the surface of the steel plate are detected based on an image signal obtained by photographing the surface of the steel plate through which the steel plate is passed by an imaging device such as a CCD camera.

  Generally, as such a surface defect inspection method, two types of optical systems, a regular reflection optical system and a scattering reflection optical system, are known. It is known that the specular reflection optical system is effective for detecting irregular wrinkles on the surface, and the scattering reflection optical system is effective for detecting colored foreign matters and dirt defects on the surface of the steel sheet.

  In recent years, it has become more and more important to detect line-shaped line wrinkles with slight differences in color tone and unevenness from the viewpoint of quality inspection at the time of shipment and wrinkle prevention measures by early detection of wrinkles. However, when applied to steel plates with particularly high gloss, regular reflected light from the normal part is directly incident on the imaging device, so the brightness changes that occur due to slight irregular reflections that occur on the surface of the minute eyelids and the angle dependence of the reflectance. There is a problem that it is often difficult to detect line-shaped linear wrinkles (thick wrinkles in the flow direction of a plate such as a thread or a oyster wrinkle) with minute irregularities.

  Therefore, as a conventional surface flaw inspection of steel plates or the like, for example, as in the technique disclosed in Patent Document 1, a plurality of lights and cameras are arranged for each type of wrinkles, and the illumination photographing direction is An apparatus arranged at right angles or parallel to the line direction, as in the technique disclosed in Patent Document 2, a linear light source for irradiating illumination light on the surface of a steel sheet is inclined with respect to a line orthogonal to the line direction. As in the technique disclosed in Patent Document 3 and an apparatus arranged to capture a reflected light image, the surface of the steel plate is irradiated at a large angle near an incident angle of 90 degrees, and the incident direction of the irradiated light An apparatus for detecting uneven wrinkles is known by disposing the steel plate so as to be in the middle direction between the longitudinal direction of the steel plate and the width direction.

Japanese Patent Laid-Open No. 7-218451 JP 2000-121574 A JP 2000-314707 A

  However, the above prior art has the following problems.

  Since the technique disclosed in Patent Document 1 requires three sets of illumination photographing systems including a lighting device and a photographing device as one set, it takes time for on-site adjustment, and maintenance costs and equipment costs. There is a problem that becomes high.

  In the technique disclosed in Patent Document 2, the illumination light source that irradiates the strip light is arranged obliquely without being orthogonal to the line direction of the steel sheet, so that the illumination light is not parallel to the line width direction, and the production line direction By irradiating the linear wrinkles extending in a slanting direction, a shadow is formed in the reflected light image from the linear wrinkles to improve detection sensitivity. However, since it cannot be installed on the roll winding part, there is a problem that unevenness occurs in the reflected light intensity due to the vibration of the steel sheet, and a shaded line is generated on the photographed image. In addition, since the scanning line at the time of imaging is inclined with respect to the plate passing direction, image conversion is required when displaying the detected wrinkle position or hail image, and time is required for subsequent data processing. There is also a problem that a load occurs.

  The technique disclosed in Patent Document 3 is such that the light irradiation direction is an intermediate direction between the direction along the line width direction of the steel plate and the direction along the line longitudinal direction, thereby causing a point defect and the longitudinal direction of the steel plate. Long defects and long results in the width direction are detected. In addition, this technique allows the ratio of the cosine value of the incident angle to the wavelength of the illumination light to be less than or equal to a predetermined value determined from the surface roughness of the steel sheet, so that a minute depth equivalent to the surface roughness can be obtained. This is to detect uneven wrinkles. However, since the principle of wrinkle detection is a technique that detects wrinkles by creating a magic mirror phenomenon by creating a condition in which specular reflection is dominant in the reflected light, color change without irregularities (dirt, discoloration) , Scale remaining, etc.) cannot be detected.

  In order to solve the above problems, the object of the present invention is to detect linear wrinkles extending in the production line direction, minute irregularities wrinkles, wrinkles crossing the production line direction, and color change wrinkles with a simple configuration. An object of the present invention is to provide a steel sheet inspection apparatus that can perform such a process.

Flaw inspection apparatus of the present invention for solving the aforementioned problems is irradiated with strip light across the surface to the surface of the moving steel sheet, flaw inspection apparatus for inspecting defects of the surface of the image pickup to steel the reflected light from the surface in the irradiation area on the steel surface of the strip-shaped light is band-shaped parallel to the width direction of the steel sheet, incident on the steel sheet surface of the belt-shaped light, steel sheets less than 30 degrees 60 degrees with respect to the direction of movement of An illuminating device having a horizontal incident angle θ in the range and a vertical incident angle α with respect to the normal direction of the steel sheet surface in the range of 15 degrees to 70 degrees; and the illuminating apparatus with respect to the normal direction of the steel sheet ; An imaging device is provided that images the irradiation area at a vertical light receiving angle β that is α ± 5 degrees from the opposite side.

  The illuminating device includes a light source and a prism sheet that refracts the band-shaped light emitted from the light source at a predetermined angle in a direction in which the band-shaped light propagates in a plane in which the band-shaped light propagates, and is disposed so as to cross the steel plate width direction. You can also.

  The lighting device may include a light source and an optical fiber unit that aligns a plurality of optical fibers and emits incident light from the light sources.

  Further, in addition to the imaging device, a second imaging device that images the irradiation region at a vertical light receiving angle γ larger than the vertical light receiving angle β may be provided, and the vertical light receiving angle β and the vertical light receiving angle β may be provided. The difference in the direction light reception angle γ is preferably in the range of 20 degrees or more.

  With the apparatus configured as described above, illumination light tilted by a predetermined angle in the horizontal direction with respect to the moving direction of the band is irradiated with a uniform light intensity to the irradiation area on the band surface with a simple configuration. Therefore, it is possible to reduce the amount of regular scattering and the regular reflection component of the reflected light, which is a normal part of the belt-like body, and to efficiently receive the luminance modulation due to the scattered light of the minute concavo-convex shape with the imaging device. Further, since the linear wrinkles extending in the production line direction are irradiated from an oblique direction, a shadow is easily formed in the reflected light image from the linear wrinkles. As a result, it is possible to detect the wrinkle-shaped wrinkles at the same time as the wrinkles extending in the production line direction with high accuracy. If the second imaging device is provided, a scattering reflection optical system is formed, so that it is possible to further improve the sensitivity of detecting a color tone change at the same position and at the same time.

  According to the present invention, uneven wrinkles, particularly line wrinkles in the line direction, can be detected with good contrast, and color change wrinkles and dirt wrinkles can be reliably detected. Furthermore, the apparatus can be reduced in size and cost, and can be applied to a portion that is attached to the roll, so that accurate wrinkle inspection that is not affected by fluctuations in the pass line can be performed.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an embodiment of the present invention, and is a schematic configuration diagram of a steel plate wrinkle inspection apparatus.

  The eyelid inspection apparatus mainly includes an illumination device 10, an imaging device 20, an eyelid image processing device 30, and an operator eyelid display device 31. The portion where the steel plate 1 is wound around the roll 2 is measured, and inspection can be performed with less error due to variations in the pass line. In addition, the perpendicular direction of the steel plate surface curved in this application refers to the perpendicular direction of a tangent plane.

  The illuminating device 10 includes a light source 11 made of a fluorescent lamp or an incandescent lamp and an optical fiber bundle 12. The light source 11 is close to the input end 13 of the optical fiber bundle 12. At the output end 14, the irradiated band-like light L 1 is parallel light, and is inclined at a horizontal incident angle θ with respect to the line direction of the steel plate 1. A number of optical fibers are aligned to be illuminated.

  The imaging device 20 is composed of an imaging element such as a CCD or a CMOS, is located at a position facing the illumination device 10, and one or a plurality of the imaging devices 20 are arranged along the plate width direction. The number of imaging devices 20 is determined according to the inspection width and resolution. Since there are various types of steel plates 1 and the width is about 1 m to 4 m, three or four image pickup devices are usually arranged in parallel accordingly. In addition, the distance from the imaging device 20 to the strip | belt-shaped light irradiation surface LA on the steel plate surface of the strip | belt-shaped light L1 is about 800-1200 mm.

  The imaging device 20 captures a reflection image of the strip light reflected from the steel plate surface, and outputs a haze image signal. The pixel size in the steel plate line direction is equal to the length of the steel plate moving during one line scan (exposure time). Each time one line scan is performed in synchronization with the pulse signal PLG, the haze image signal is output to the haze image processing device 30.

  The image processing apparatus 30 is composed of a computer (all not shown) including an input interface and an image memory. The haze image processing device 30 accumulates haze image signals for each line scan input from the imaging device 20, generates a frame image, and performs image processing such as image quality improvement, image analysis, and image compression.

  The operator heel display device 31 superimposes the heel image sent from the heel image processing device 30 and a signal including the feature amount extracted from the heel image, and displays the heel image and the feature amount. Here, the feature amount includes data such as the type, position, size, and harmfulness of the eyelids.

  FIG. 2 shows a planar arrangement state of the illumination device 10 and the imaging device 20 viewed from above the roll surface, and FIG. 3 shows an arrangement state of the illumination device 10 and the imaging device 20 viewed from the roll axis direction. The output end of the illuminating device 10 is parallel to the width direction of the steel sheet as shown in FIG. 2, and the strip-shaped light is irradiated with being inclined at a horizontal direction incident angle θ and at a vertical direction incident angle α as shown in FIG. It is installed as follows. The distance from the output end 14 of the optical fiber bundle 12 to the incident point on the steel plate surface of the strip light L1 is about 200 to 400 mm. The width of the strip-shaped light irradiation surface LA on the steel plate is about 80 to 200 mm, and the length is irradiated over the entire width of the steel plate. Further, the vertical light receiving angle β of the optical axis of the imaging device 20 is installed so as to satisfy a range of ± 5 degrees with respect to the vertical incident angle α of the strip light L1.

  According to the embodiment of the present invention, since the output end 14 of the lighting device 10 is set so that the band-shaped light is irradiated with the horizontal incident angle θ inclined, the scattered and reflected light due to the formation that is a normal part of the steel sheet. Therefore, the imaging device can efficiently receive the luminance modulation by the scattered light of the fine ridges having a minute uneven shape. Moreover, since the linear wrinkles extending in the production line direction are irradiated from an oblique direction, shadows are easily formed in the reflected light image from the linear wrinkles. As the horizontal angle θ approaches 90 degrees, the specular reflection component can be removed. However, the ability to reveal wrinkles with respect to uneven horizontal lines such as chatter marks and lateral folds decreases, and the imaging device 20 However, it is difficult to secure a sufficient amount of received light. For this reason, when the horizontal direction angle is about 30 to 60 degrees, the result is that wrinkles are manifested with respect to uneven wrinkles and linear wrinkles extending in the production line direction.

  The vertical incident angle α of the band-shaped light L1 with respect to the steel plate surface is preferably about 15 ° to 70 °, although it depends on the shape of the ridge to be inspected and the surface roughness of the steel plate. If the incident angle is reduced, it is less likely to be adversely affected by the surface roughness of the steel sheet, and if the incident angle is increased, minute irregularity defects are easily detected.

  FIG. 4 is a configuration diagram of an illuminating device of a wrinkle inspection device according to another embodiment of the present invention. In this embodiment, the prism sheet 40 is disposed so as to cross the steel plate width direction in the illumination light source that irradiates the strip light parallel to the horizontal direction, and the irradiation of the strip light of the horizontal angle θ is realized. The device configuration other than the illumination device is the same as that shown in FIG. As shown in FIG. 5, the prism sheet 40 is a set pair in which saw-shaped prisms 41 are aligned in the horizontal direction. The prism sheet 40 is disposed so as to be perpendicular (vertical direction) to the steel plate width direction (lateral direction) of the output end 14 of the illuminating device that irradiates the strip-shaped light in parallel with the horizontal direction.

  When the prism sheet 40 is used, as shown in FIG. 6, a light beam incident in parallel to the line direction is irradiated as a light beam inclined by θ due to refraction based on Snell's law by the prism.

  In this embodiment, an acrylic prism sheet in which prisms having a prism angle φ of 28 degrees are arranged at a pitch of 0.5 mm may be used in order to irradiate at a horizontal angle of about 40 degrees. In order to change the horizontal angle of the strip light from the illumination device, it is sufficient to prepare prism sheets having different prism angles φ, and the illumination device can be easily improved.

  In addition, a condensing lens such as a rod lens is inserted or installed between the exit surface of the output end 14 and the prism sheet, or on the exit surface of the prism sheet, thereby condensing the zonal light to be irradiated in the vertical direction. You may let them.

  FIG. 7 is a configuration diagram of a wrinkle inspection apparatus according to another embodiment of the present invention. In this embodiment, an imaging device 20 and a second imaging device 21 are provided as imaging devices. As in the first embodiment, the imaging device 20 is installed so that the vertical light receiving angle β of the optical axis of the imaging device 20 satisfies the range of the vertical incident angle α ± 5 degrees of the strip light L1. . The second imaging device 21 is installed such that the vertical light receiving angle γ of the optical axis is large. In this way, by installing the second imaging device 21, it becomes possible to receive only irregularly reflected light, and the irregularly reflected light at the buttocks and the regular reflected light at the normal part can be clearly separated, and the contrast is clear. Can be obtained. Therefore, it is possible to detect a color tone change with low contrast, which was difficult to detect with the imaging device 20. Further, it is possible to distinguish a wrinkle that can be detected only by the imaging device 20, a wrinkle that can be detected by both the image capturing device 20 and the second image capturing device 21, and a wrinkle that can be detected only by the second image capturing device 21. Can be useful for detection classification. The vertical light receiving angle γ of the optical axis of the second imaging device 21 for receiving only the irregularly reflected light is preferably about 20 degrees or more different from the vertical light receiving angle β of the imaging device 20.

As an example, the apparatus shown in FIG. 1 was used. The width of the steel plate is 1500 mm.

  The imaging apparatus is three line sensor cameras of 2048 pixels, and the optical conditions are set in advance so that the visual field size of each camera is 2048 mm. Accordingly, the visual field of one line sensor camera is 512 mm, the pixel size in the plate width direction is 0.5 mm, and the pixel size in the line direction is 0.5 mm.

  The illuminating device is an illuminating device at the output end of a 2000 mm fiber bundle using three 180 W halogen lamps as light sources, and is set to irradiate at a horizontal angle of 40 degrees. It is set to irradiate the steel sheet surface at a vertical angle of 20 degrees. Further, the optical axes of the line sensor cameras are set equally at a vertical light receiving angle of 20 degrees.

  When a surface inspection of a steel sheet traveling at a speed of 300 m / min was performed using the wrinkle inspection apparatus with the above configuration, uneven wrinkles, uneven wrinkles, and color tone could be reliably detected.

It is a figure which shows the outline of the wrinkle inspection apparatus of one Embodiment of this invention. It is a top view which shows the arrangement | positioning condition of the illuminating device and imaging device seen from the upper direction of FIG. It is a front view which shows the arrangement | positioning condition of the illuminating device and imaging device seen from the front of FIG. Another embodiment of the present invention is shown, and is a schematic view of a lighting device. The example of the prism sheet | seat used in FIG. 4 is shown, (a) is sectional drawing, (b) is a front view. FIG. 6 is a side view schematically showing refraction of illumination light by the prism sheet shown in FIG. 5. The other embodiment of this invention is shown and it is a front view which shows the arrangement | positioning condition of an illuminating device and an imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel plate 2 Roll 10 Illuminating device 11 Light source 12 Optical fiber bundle 13 Optical fiber bundle input end 14 Light is a fiber bundle output end 20 Imaging device 21 Second image imaging device 30 疵 Image processing device 31 Operator 疵 display device 40 Prism sheet 41 Sawtooth shape Prism L1 Band light LA Band light irradiation surface

Claims (4)

In the wrinkle inspection apparatus that inspects the surface of the steel sheet by irradiating the surface of the moving steel sheet with a band-shaped light crossing the surface, imaging the reflected light from the surface,
Irradiation region on the steel sheet surface of the belt-shaped light is band-shaped parallel to the width direction of the steel sheet, incident on the steel sheet surface of the belt-shaped light, the range of less than 30 degrees 60 degrees with respect to the direction of movement of the steel sheet A lighting device having a vertical incident angle α in a range of 15 degrees or more and 70 degrees or less with respect to a normal direction of the steel sheet surface at a certain horizontal direction incident angle θ, and a side opposite to the lighting apparatus with respect to the normal direction of the steel sheet A wrinkle inspection apparatus comprising: an imaging device that images the irradiation region at a vertical light receiving angle β that is in a range of α ± 5 degrees from. The lighting device includes a light source and a prism sheet that refracts the band-shaped light emitted from the light source at a predetermined angle in a direction in which the band-shaped light propagates in a plane in which the band-shaped light propagates, and is arranged so as to cross in the steel plate width direction. The wrinkle inspection apparatus according to claim 1 . The lighting device includes a light source, and to align the plurality of optical fibers, aligned to incident light from a light source comprising an optical fiber unit for emitting, according to claim 1, characterized in that for emitting the belt-shaped light Sputum inspection device. In addition to the imaging device, the imaging device includes a second imaging device that images the irradiation region at a vertical light receiving angle γ that is larger than the vertical light receiving angle β, and the vertical light receiving angle β and the vertical light receiving angle γ The wrinkle inspection apparatus according to any one of claims 1 to 3 , wherein the difference is in a range of 20 degrees or more.

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