Coil flaw inspection system and coil flaw inspection method

Abstract

To provide a coil flaw inspection system and a coil flaw inspection method, capable of detecting a flaw generated on a bottom surface of a metal strip coil at a high detection ratio while eliminating a risk of safety for an operator in a manufacturing site, and without causing uneven illuminance on the bottom surface of the metal strip coil.SOLUTION: A coil flaw inspection system 1, which detects a flaw on a bottom surface of a metal strip coil C obtained by winding up a metal strip in a coil form, includes: a light source 10 installed at an upper position of a lifted metal strip coil C; an imaging device 2 installed at a lower position of the lifted metal strip coil C, for imaging a bottom surface Ca of the metal strip coil C; and an image diagnosis device 4 that detects a flaw f in a captured image I captured by the imaging device 2. A diffuser panel 7 that reflects illumination light 10a from the light source 10 to irradiate the bottom surface Ca of the metal strip coil C at uniform illuminance is installed at an adjacent position below the imaging device 2 or horizontal to the imaging device 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a coil defect inspection system and a coil defect inspection method for detecting defects on the bottom surface of a metal strip coil obtained by winding a metal strip into a coil shape. [Background technology]

[0002] Generally, in a metal strip manufacturing line, for example, a cold rolling line or a hot rolling line, the metal strip is shipped in a coiled form. The manufactured coil, i.e., the metal strip coil wound into a coil, is placed on a coil stand. If a foreign object is attached to the coil stand or an equipment malfunction occurs, scratches will occur on the bottom surface of the metal strip coil that is in contact with the coil stand. Once a foreign object is attached to the coil stand or an equipment malfunction occurs, scratches will continue to occur on the bottom surface of the metal strip coil, so it is very important to correctly detect the scratches present on the bottom surface of the metal strip coil and notify the operator.

[0003] Here, as a steel plate defect inspection device for detecting surface defects of a steel plate, for example, a steel plate defect inspection device shown in Patent Document 1 has been proposed. The steel plate defect inspection device shown in Patent Document 1 irradiates illumination light from a light source onto the surface of a steel plate, captures a surface image of the steel plate irradiated with the illumination light by an imaging device, and detects surface defects in the steel plate based on the luminance value of the surface image. The steel plate defect inspection device includes a gloss meter that measures the glossiness of the steel plate, and a control device that adjusts the position and / or angle of at least one of the light source and the imaging device according to the glossiness of the steel plate measured by the gloss meter.

[0004] This steel plate defect inspection device can accurately detect surface defects even when the type of steel plate changes significantly in terms of surface properties, such as between GA steel plate and GI steel plate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-138900 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the steel plate defect inspection device shown in Patent Document 1 is a device that inspects surface defects on a traveling steel plate, and is not suitable for detecting scratches that occur on the bottom surface of a metal strip coil placed on a coil placement table. On the other hand, when detecting defects on the bottom surface of a metal strip coil, a method is considered in which an inspector checks the bottom surface of the metal strip coil from below while the metal strip is hoisted by a crane, but this method has safety risks such as the hoisting tool falling.

[0007] In addition, in order to avoid safety risks, a method is also conceivable in which the bottom surface of the metal strip coil is imaged from below by an imaging device while the metal strip is hoisted by a crane, and the image is detected by an imaging diagnostic device. In this case, there is no safety risk, but the illumination of the bottom surface of the metal strip coil by the illumination light from the light source is insufficient, and the bottom surface of the metal strip coil appears dark. This causes a problem that it is difficult to detect defects by the imaging diagnostic device in the image of the bottom surface of the metal strip coil. To address this problem, it is conceivable to irradiate the bottom surface of the metal strip coil from below. However, with this method, depending on the surface properties of the metal strip, uneven illumination occurs on the bottom surface of the metal strip coil, so that it is difficult to detect defects by the imaging diagnostic device in the image of the bottom surface of the metal strip coil.

[0008] Therefore, the present invention has been made to solve these conventional problems, and has as its object to provide a coil defect inspection system and coil defect inspection method that are capable of detecting defects on the bottom surface of a metal strip coil with a high detection rate, without causing uneven illuminance on the bottom surface of the metal strip coil, while eliminating safety risks to workers at manufacturing sites. [Means for solving the problem]

[0009] In order to solve the above problems, a coil defect inspection system according to one embodiment of the present invention is a coil defect inspection system that detects defects on the bottom surface of a metal strip coil formed by winding a metal strip into a coil, and includes a light source installed at a position above the lifted metal strip coil, an imaging device installed at a position below the lifted metal strip coil and imaging the bottom surface of the metal strip coil, and an image diagnostic device that detects defects on the image captured by the imaging device, and is characterized in that a diffuser plate is installed below the imaging device or in a position horizontally adjacent to the imaging device, which reflects illumination light from the light source and irradiates the bottom surface of the metal strip coil with uniform illuminance.

[0010] Furthermore, a coil defect inspection method according to another aspect of the present invention is a coil defect inspection method for detecting defects on the bottom surface of a metal strip coil formed by winding a metal strip into a coil, and includes an imaging step in which an imaging device installed at a position below the lifted metal strip coil images the bottom surface of the metal strip coil, and an image diagnosis step in which an image diagnostic device detects defects on the image captured in the imaging step, and the gist of the imaging step is that illumination light from a light source installed at a position above the lifted metal strip coil is reflected by a diffuser plate installed below the imaging device or in a position horizontally adjacent to the imaging device, and the bottom surface of the metal strip coil is irradiated with uniform illuminance by the imaging device. Effect of the Invention

[0011] The coil defect inspection system and coil defect inspection method of the present invention can provide a coil defect inspection system and coil defect inspection method that can detect defects on the bottom surface of a metal strip coil with a high detection rate, without causing uneven illuminance on the bottom surface of the metal strip coil, while eliminating safety risks to workers at the manufacturing site. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of a coil defect inspection system according to an embodiment of the present invention; [Diagram 2] 2 is a flowchart for explaining a process flow in the coil defect inspection system shown in FIG. [Diagram 3] 3 is a flowchart for explaining a detailed flow of processing in step S2 (image diagnosis step) in the flowchart shown in FIG. 2. [Figure 4] 4 is a flowchart for illustrating a detailed flow of processing in step S23 (flaw detection step) in the flowchart shown in FIG. 3. [Diagram 5] 2 is a diagram showing an image of the bottom surface of a metal strip coil captured by an imaging device in the coil defect inspection system shown in FIG. 1. FIG. [Figure 6] FIG. 1 is a diagram showing a schematic configuration of a coil defect inspection system according to a first reference example. [Figure 7] 7 is a diagram showing an image of the bottom surface of the metal strip coil captured by an imaging device in the coil defect inspection system according to the first reference example shown in FIG. 6. FIG. [Figure 8] FIG. 13 is a diagram showing a schematic configuration of a coil defect inspection system according to a second reference example. [Figure 9] 9 is a diagram showing an image of the bottom surface of the metal strip coil captured by an imaging device in the coil defect inspection system according to the second reference example shown in FIG. 8. FIG. [Figure 10] 1A and 1B are diagrams explaining the image determination range in an imaging image (imaging range) determined by an imaging diagnostic device, in which (a) is a diagram explaining the image determination range when the bottom surface of the metal strip coil is large, and (b) is a diagram explaining the image determination range when the bottom surface of the metal strip coil is small. [Figure 11] This explains the image judgment range when the imaging diagnostic device uses the entire captured image (imaging range) as the image judgment range, where (a) is a diagram explaining the image judgment range when the bottom surface of the metal strip coil is large, and (b) is a diagram explaining the image judgment range when the bottom surface of the metal strip coil is small. [Figure 12]5A and 5B are explanatory diagrams for explaining a detailed flow of processing in step S23 (defect detection step) in the flowchart shown in FIG. 4, in which (a) is an explanatory diagram of a state in which the image diagnostic device has acquired an image of the image judgment range, (b) is an explanatory diagram of a state in which the image diagnostic device has divided the image of the image judgment range into multiple images, (c) is an explanatory diagram of a state in which the image diagnostic device has performed image judgment on each of the multiple divided images and detected defects, and (d) is an explanatory diagram of a state in which the image diagnostic device has recombined each of the multiple images on which image judgment has been performed and detected defects. [Figure 13] 1A and 1B are explanatory diagrams for explaining a detailed flow of processing when an image diagnostic device detects defects without dividing an image in an image judgment range into multiple images, in which (a) is an explanatory diagram of a state in which the image diagnostic device acquires an image in the image judgment range, (b) is an explanatory diagram of a compressed image in which the image diagnostic device compresses the image in the image judgment range, (c) is an explanatory diagram of a state in which the image diagnostic device performs image judgment on the compressed image and detects defects, and (d) is an explanatory diagram of a state in which the image diagnostic device detects defects in the compressed image on which image judgment has been performed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments shown below are merely examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention is not limited to the following embodiments in terms of the materials, shapes, structures, arrangements, etc. of the components. In addition, the drawings are schematic, and therefore, it should be noted that the relationship between thickness and planar dimensions, ratios, etc. may differ from the actual relationship between thickness and planar dimensions, and the drawings may include parts in which the relationship between dimensions and ratios differ from one another.

[0014] FIG. 1 shows a schematic configuration of a coil defect inspection system according to one embodiment of the present invention. The coil defect inspection system 1 shown in FIG. 1 detects defects f (see FIG. 12) on a bottom surface Ca of a metal strip coil C formed by winding a metal strip into a coil in a cold rolling line which is a manufacturing line for the metal strip.

[0015] The manufactured metal strip coil C is placed on a coil stand (not shown), but if a foreign object is attached to the coil stand or an equipment malfunction occurs, scratches will occur on the bottom surface Ca of the metal strip coil C that is in contact with the coil stand. Once a foreign object is attached to the coil stand or an equipment malfunction occurs, scratches f will continue to occur on the bottom surface Ca of the metal strip coil C, so it is very important to correctly detect the scratches f present on the bottom surface Ca of the metal strip coil C and notify the worker.

[0016] Therefore, in this embodiment, during transportation by a crane (not shown) from the coil placement stand to shipping, the coil defect inspection system 1 is configured to detect defects f on the bottom surface Ca of the metal strip coil C, which is made by winding a metal strip into a coil shape. The coil defect inspection system 1 includes an imaging device 2, an imaging device control device 3, an image diagnostic device 4, a coil information PC 5, a display device 6, and a diffusion plate 7.

[0017] The imaging device 2 is installed on the floor F at a position midway along the transport path from a coil stand on which the metal strip coil C is hoisted by a hoisting tool 11 of a crane (not shown). In other words, the imaging device 2 is installed below (directly below) the hoisted metal strip coil C, and images the bottom surface Ca of the metal strip coil C from below. The imaging device 2 is an imaging device such as a CCD camera or a CMOS camera.

[0018] Here, in order for the imaging device 2 to image the bottom surface Ca of the metal strip coil C, it is necessary to illuminate the bottom surface Ca of the metal strip coil C with illumination light to make it bright. For this reason, in this embodiment, illumination light 10a from a plurality of light sources (indoor lighting) 10 installed in the factory is irradiated onto the bottom surface Ca of the metal strip coil C. Each light source 10 is composed of a light source such as a strobe light source, an LED light source, or a metal highland lamp.

[0019] Here, as shown in FIG. 1, each light source 10 is installed at a position above the suspended metal strip coil C, and the illumination light 10a from each light source 10 is unlikely to be irradiated onto the bottom surface Ca of the metal strip coil C. For this reason, if illumination light 10a is simply irradiated onto the bottom surface Ca of the metal strip coil C from multiple light sources 10 installed at a position above the suspended metal strip coil C, as in the coil defect inspection system 100 according to the first reference example shown in Fig. 6, the illuminance of the illumination light 10a is low and the bottom surface Ca becomes dark. In this case, the captured image I of the bottom surface Ca of the metal strip coil C captured by the imaging device 2 becomes dark due to insufficient illuminance as shown in Fig. 7, making it difficult to detect defects occurring on the bottom surface Ca of the metal strip coil C.

[0020] In response to this, as in the coil defect inspection system according to the second reference example shown in FIG. 8, a method is also conceivable in which illumination light 10a is directly irradiated onto the bottom surface Ca of the lifted metal strip coil C from a light source 10 installed at a position below the bottom surface Ca of the metal strip coil C to brighten the bottom surface Ca. However, when the bottom surface Ca of the metal strip coil C is brightly illuminated in this manner, illuminance unevenness occurs on the bottom surface Ca of the metal strip coil C depending on the surface properties of the metal strip. The captured image I of the bottom surface Ca of the metal strip coil C captured by the imaging device 2 in this case is as shown in FIG. 9. Since illuminance unevenness occurs on the bottom surface Ca of the metal strip coil C in this manner, it becomes difficult to detect defects occurring on the bottom surface Ca of the metal strip coil C.

[0021] 1, in the coil defect inspection system 1 according to this embodiment, a diffuser 7 is installed below the imaging device 2, which reflects illumination light 10a from a plurality of light sources (in-house lighting) 10 installed at a position above the hoisted metal strip coil C, and irradiates the bottom surface Ca of the metal strip coil C with uniform illuminance. Specifically, the diffuser 7 is installed on the floor F at a position midway along the transport path from the coil placement stand on which the metal strip coil C is hoisted by the hoisting tool 11 of a crane (not shown), and the imaging device 2 is installed on the diffuser 7.

[0022] Here, the "bottom surface Ca of the metal strip coil C" is an arc surface with a length of about 1 / 6 of the entire circumference of the bottom side of the metal strip coil C, as shown in Fig. 1. Also, "uniform illuminance" means that the illuminance of the illumination light 10a on the bottom surface Ca of the metal strip coil C is approximately uniform over the entire bottom surface Ca. For example, to be considered "uniform illuminance," the illuminance of the illumination light 10a on the bottom surface Ca may be within a range of ±50 lux with respect to a predetermined illuminance (100 lux).

[0023] Since the diffusion plate 7 needs to reflect the illumination light 10a with uniform illuminance, the surface is not a mirror surface but a flat rough surface, and the color is ideally non-glossy white. The size and shape of the diffusion plate 7 depend on the shape of the metal band coil C to be imaged, but is, for example, a rectangle of about 1.5 to 2.0 m x 2.0 to 3.0 m. The illumination light 10a from the light source 10 is reflected by the diffuser 7 and irradiated with uniform illuminance onto the bottom surface Ca of the metal strip coil C. The captured image I of the bottom surface Ca of the metal strip coil C captured by the imaging device 2 at this time is as shown in Fig. 5. In this way, by reflecting the illumination light 10a from the light source 10 by the diffuser 7 and irradiating the bottom surface Ca of the metal strip coil C with uniform illuminance, it is possible to brighten the bottom surface Ca of the metal strip coil C without uneven illuminance on the bottom surface Ca of the metal strip coil C, and it is possible to easily detect scratches that have occurred on the bottom surface Ca of the metal strip coil C.

[0024] In addition, the imaging device control device 3 of the coil defect inspection system 1 controls the operation of the imaging device 2 from the start to the end of the imaging operation of the imaging device 2 of the bottom surface Ca of the metal strip coil C, and is composed of a computer with calculation processing capabilities. The image diagnostic device 4 detects flaws f in the captured image I captured by the imaging device 2. The image diagnostic device 4 is a computer system having a calculation function for implementing the flaw detection function by executing a program on computer software. This computer system is configured with a ROM, a RAM, a CPU, etc., and realizes the above-mentioned functions on the software by executing various dedicated programs pre-stored in the ROM, etc.

[0025] Data of the captured image I captured by the imaging device 2 is input to the imaging device control device 3. The data of the captured image I input to the imaging device control device 3 is then output from the imaging device control device 3 to the image diagnostic device 4. Then, the image diagnostic device 4 obtains the data of the captured image I and then detects the flaw f in the captured image I.

[0026] Regarding the detection of flaw f by the imaging diagnostic device 4, specifically, after acquiring data of the captured image I, the imaging diagnostic device 4 determines an image judgment range JA in the captured image I (imaging range IA) as shown in Figures 10(a) and (b). Regarding the process of determining the image determination range JA in the captured image I (imaging range IA), the image diagnostic device 4 calculates the position of the bottom surface Ca of the metal strip coil C in the imaging range IA by the imaging device 2 based on the outer diameter information of the metal strip coil C and the position information of the metal strip coil C. Then, the image diagnostic device 4 determines the image determination range JA in the captured image I based on the calculated position of the bottom surface Ca of the metal strip coil C in the imaging range IA.

[0027] The outer diameter information of the metal band coil C is information on the outer diameter D (see FIG. 1) of the metal band coil C when performing defect detection, and is input from the coil information PC5 connected to the imaging diagnostic device 4 to the imaging diagnostic device 4. In addition, the position information of the metal band coil C is the position CL (x0, y0) of the center line CL of the metal band coil C on the xy coordinate system, the width of the metal band coil C in the direction along the center line CL, and the center position of the width of the metal band coil C in the direction along the center line CL in FIG. This position information of the metal band coil C is also input from the coil information PC5 to the imaging diagnostic device 4. The coil information PC5 stores information such as manufacturing information of the metal band, manufacturing conditions, shape information of the metal band coil C, the installation position of the imaging device 2, and information on the imaging range IA.

[0028] In this way, the image diagnostic device 4 calculates the position of the bottom surface Ca of the metal band coil C in the imaging range IA by the imaging device 2 based on the outer diameter information of the metal band coil C and the position information of the metal band coil C, and determines the image determination range JA in the captured image I (imaging range IA) based on the calculated position of the bottom surface Ca of the metal band coil C in the imaging range IA. The reason for this will be described below.

[0029] Since the imaging range IA by the imaging device 2 is constant, the ratio of the bottom surface Ca of the metal strip coil C to the captured image I varies depending on the size of the metal strip coil C. In such a case, if the entire captured image I (imaging range IA) is set as the image determination range JA, image information in a range other than the bottom surface Ca of the metal strip coil C may be erroneously detected as a defect. FIG. 11 shows a case where the imaging diagnostic device 4 sets the entire captured image I (imaging range IA) as the image determination range JA, where (a) shows the image determination range JA when the bottom surface Ca of the metal strip coil C is large, and (b) shows the image determination range JA when the bottom surface Ca of the metal strip coil C is small. In the case of FIG. 11(a), since the area of ​​the bottom surface Ca of the metal strip coil C is large, the difference between the area of ​​the image determination range JA and the area of ​​the bottom surface Ca of the metal strip coil C is small, and there is a relatively small possibility that image information in a range other than the bottom surface Ca of the metal strip coil C will be erroneously detected as a defect. In contrast, in the case of Figure 11 (b), the area of ​​the bottom surface Ca of the metal band coil C is small, so the difference between the area of ​​the image determination range JA and the area of ​​the bottom surface Ca of the metal band coil C is large, and there is a high risk that image information in the range other than the bottom surface Ca of the metal band coil C will be erroneously detected as a defect.

[0030] 10(a) and 10(b), the image diagnostic device 4 calculates the position of the bottom surface Ca of the metal band coil C in the imaging range IA of the imaging device 2 based on the outer diameter information of the metal band coil C and the position information of the metal band coil C, and determines the image determination range JA in the captured image I (imaging range IA) based on the calculated position of the bottom surface Ca of the metal band coil C in the imaging range IA. This reduces the difference between the area of ​​the image determination range JA and the area of ​​the bottom surface Ca of the metal band coil C, and can reduce the rate of erroneous detection of image information in a range other than the bottom surface Ca of the metal band coil C as a defect.

[0031] Then, the image diagnostic device 4 determines the image determination range JA in the captured image I (imaging range IA), and then detects flaws f in the image of the image determination range JA. The process of detecting flaws f in the image in the image judgment range JA will now be described. As shown in Figs. 12(a) and (b), the image diagnostic device 4 divides the image in the determined image judgment range JA into a plurality of images (four in this embodiment) I1 to I4. Then, as shown in Fig. 12(c), the image diagnostic device 4 performs image judgment on each of the divided images I1 to I4 to detect flaws f. Furthermore, as shown in Fig. 12(d), the image diagnostic device 4 recombines each of the images I1 to I4 that have been subjected to image judgment to generate a recombined image I1. (1+2+3+4) The defect f is detected in the determined image determination range JA. The reason for dividing the image in the determined image determination range JA into a plurality of images I1 to I4 and performing the defect f detection process in this manner will be described below.

[0032] FIG. 13 is an explanatory diagram for explaining a detailed flow of processing when the image diagnostic device 4 detects a flaw f without dividing the image in the image determination range JA into a plurality of images I1 to I4. In this case, as shown in Fig. 13(a), an image of the image determination range JA in the captured image I (imaging range IA) determined by the image diagnostic device 4 is acquired. Since the image of this image determination range JA has a large amount of data, the image of the image determination range JA is usually compressed in an image processing step to obtain a compressed image JAp, as shown in Fig. 13(b).

[0033] Next, as shown in Fig. 13(c), in the image judgment step, image judgment is performed on the compressed image JAp to detect flaws f. At this point, since the compressed image JAp is coarse, fine flaws f may not be detected. In the case of Fig. 13(c), even though there were three flaws f in the image in the image judgment range JA shown in Fig. 13(a), the fine flaws f could not be detected and only two flaws f were detected.

[0034] Then, as shown in Fig. 13(d), in the final judgment process, the detection of flaws f is performed on the compressed image JAp that has been subjected to image judgment. In the case of Fig. 13(d), since two flaws f are detected in the image judgment performed in Fig. 13(c), two flaws f are detected in the final judgment process. In this way, when the image diagnostic device 4 compresses the image without dividing the image of the image judgment range JA into multiple images I1 to I4 and detects the defect f, there is a problem that the defect detection rate will be low and the defect false detection rate will be high.

[0035] In contrast, as in the present embodiment, the image diagnostic device 4 divides the image of the determined image determination range JA into a plurality of images I1 to I4 (four in this embodiment), performs image determination on each of the divided images I1 to I4 to detect flaws f, and recombines each of the images I1 to I4 that have been subjected to image determination to generate a recombined image I (1+2+3+4) The defect f is detected in the image of the image judgment range JA shown in FIG. 12(a) to (d). In the example shown in FIG. 12(a) to (d), when there are three defects f in the image of the image judgment range JA shown in FIG. 12(a), three defects f are finally detected in FIG. 12(d).

[0036] Then, the image diagnostic device 4 outputs the detection result of the flaw f to the display device 6 together with information on the metal strip coil C and information on the time the flaw was detected. The display device 6 displays the detection result of the flaw f together with information on the metal strip coil C and the time of flaw detection, etc. The worker can know the information displayed on the display device 6, such as the detection result of the flaw f, the information on the metal strip coil C, and the time of flaw detection.

[0037] As described above, the coil defect inspection system 1 according to this embodiment includes the light source 10 installed at a position above the lifted metal strip coil C, the imaging device 2 installed at a position below the lifted metal strip coil C for imaging the bottom surface Ca of the metal strip coil C, and the image diagnostic device 4 for detecting defects f in the image I captured by the imaging device 2. In addition, a diffusion plate 7 is installed below the imaging device 2, which reflects illumination light 10a from the light source 10 and irradiates the bottom surface Ca of the metal strip coil C with uniform illuminance.

[0038] This makes it possible to brighten the bottom surface Ca of the metal band coil C without uneven illumination on the bottom surface Ca of the metal band coil C, and makes it easy to detect scratches on the bottom surface Ca of the metal band coil C. Therefore, scratches f on the bottom surface Ca of the metal band coil C can be detected with a high detection rate. In addition, while the metal strip coil C is hoisted by the lifting device 11 of a crane (not shown), the bottom surface Ca of the metal strip coil C is imaged from below by the imaging device 2, and defects f are detected on the captured image I by the image diagnostic device 4, so there is no need for workers to get around to the underside of the metal strip coil C, eliminating safety risks to workers at the manufacturing site.

[0039] Furthermore, according to the coil defect inspection system 1 of this embodiment, the image diagnostic device 4 calculates the position of the bottom surface Ca of the metal strip coil C in the imaging range IA by the imaging device 2 based on the outer diameter information of the metal strip coil C and the position information of the metal strip coil C, and determines the image determination range JA in the captured image I based on the calculated position of the bottom surface Ca of the metal strip coil C in the imaging range IA. Then, the image diagnostic device 4 detects defects f in the image in the determined image determination range JA.

[0040] This reduces the difference between the area of ​​the image determination range JA and the area of ​​the bottom surface Ca of the metal strip coil C, thereby reducing the rate of false detection in which image information in areas other than the bottom surface Ca of the metal strip coil C is mistakenly detected as a defect f. Moreover, according to the coil defect inspection system 1 of this embodiment, the image diagnostic device 4 divides the image of the determined image determination range JA into a plurality of images I1 to I4, performs image determination on each of the divided plurality of images I1 to I4 to detect defects f, and further, recombines each of the plurality of images I1 to I4 that have been subjected to image determination to generate a recombined image I (1+2+3+4) Detect flaw f on the surface.

[0041] This makes it possible to increase the detection rate of the flaw f and reduce the erroneous detection rate of the flaw f without using the compressed image JAp. Next, a process flow in the coil defect inspection system 1, which represents the coil defect inspection method according to this embodiment, will be described with reference to the flowchart shown in FIG. First, in step S1, the imaging device 2 of the coil defect inspection system 1 images the bottom surface Ca of the metal strip coil C from below at a position midway along the transport path from the coil placement stand on which the metal strip coil C is lifted by the lifting device 11 of a crane (not shown) (imaging step).

[0042] In this step S1 (imaging step), illumination light 10a from a light source 10 installed at a position above the suspended metal strip coil C is reflected by a diffuser 7 installed at a position below the imaging device 2, and the imaging device 2 images the bottom surface Ca of the metal strip coil C by irradiating it with uniform illuminance. Data of the captured image I (see FIG. 5) captured in step S1 (imaging step) is sent from the imaging device 2 to the imaging device control device 3.

[0043] Next, in step S2, the image diagnostic device 4 detects flaws f in the captured image I captured in step S1 (imaging step) (image diagnostic step). A specific process of step S2 (image diagnosis step) will be described with reference to FIG. First, in step S21, the image diagnostic apparatus 4 acquires data of the captured image I from the imaging device control device 3 (captured image acquisition step).

[0044] Next, in step S22, the image diagnostic apparatus 4 determines an image determination range JA in the captured image I (imaging range IA) as shown in FIGS. 10(a) and 10(b) (image determination range determination step). Specifically, this step S22 (image determination range determination step) will be described. The image diagnostic device 4 calculates the position of the bottom surface Ca of the metal strip coil C in the imaging range IA by the imaging device 2 based on the outer diameter information of the metal strip coil C and the position information of the metal strip coil C. Then, the image diagnostic device 4 determines the image determination range JA in the captured image I based on the calculated position of the bottom surface Ca of the metal strip coil C in the imaging range IA.

[0045] As described above, the outer diameter information of the metal band coil C is information on the outer diameter D (see FIG. 1) of the metal band coil C when flaw detection is performed, and is input from the coil information PC5 connected to the imaging diagnostic device 4 to the imaging diagnostic device 4. In addition, the position information of the metal band coil C is the position CL (x0, y0) of the center line CL of the metal band coil C on the xy coordinate system, the width of the metal band coil C in the direction along the center line CL, and the center position of the width of the metal band coil C in the direction along the center line CL. This position information of the metal band coil C is also input from the coil information PC5 to the imaging diagnostic device 4.

[0046] In this way, in step S22, the image diagnostic device 4 calculates the position of the bottom surface Ca of the metal band coil C in the imaging range IA by the imaging device 2 based on the outer diameter information of the metal band coil C and the position information of the metal band coil C, and determines the image determination range JA in the captured image I (imaging range IA) based on the calculated position of the bottom surface Ca of the metal band coil C in the imaging range IA. As a result, as described above, the difference between the area of ​​the image determination range JA and the area of ​​the bottom surface Ca of the metal band coil C becomes small, and the erroneous detection rate of erroneously detecting image information in a range other than the bottom surface Ca of the metal band coil C as a defect can be reduced.

[0047] Next, in step S23, the image diagnostic device 4 detects the flaw f in the image in the determined image determination range JA (flaw detection step). The process in step S23 (flaw detection step) will be described in detail with reference to FIG. First, in step S231, the image diagnostic apparatus 4 acquires image data of the image determination range JA determined in step S22 (image determination range determination step), as shown in FIG. 12(a).

[0048] Next, in step S232, the image diagnostic device 4 divides the image of the image determination range JA acquired in step S231 into a plurality of (four in this embodiment) images I1 to I4 as shown in FIG. 12(b). Next, in step S233, the image diagnostic device 4 performs image determination on each of the divided images I1 to I4 to detect a flaw f, as shown in FIG. 12(c).

[0049] Next, in step S234, the image diagnostic device 4 recombines each of the multiple images I1 to I4 that have been subjected to image determination to generate a recombined image I, as shown in FIG. (1+2+3+4) Detect flaw f on the surface. In this way, by dividing the image of the determined image determination range JA into multiple images I1 to I4 and performing the defect f detection process, the defect detection rate can be increased and the defect false detection rate can be reduced without using the compressed image JAp. In the example shown in Figures 12(a) to (d), if there are three defects f in the image of the image determination range JA shown in Figure 12(a), three defects f are ultimately detected in Figure 12(d).

[0050] When the process in step S234 is completed, step S23 ends and the process proceeds to step S24. In step S24, the image diagnostic device 4 outputs the detection result of the flaw f to the display device 6 together with information on the metal strip coil C and information on the flaw detection time. When the process in step S24 is completed, step S2 ends and the process proceeds to step S3.

[0051] Then, in step S3, the display device 6 displays the detection result of the flaw f together with information on the metal strip coil C and information such as the time of flaw detection. The worker can know the information displayed on the display device 6, such as the detection result of the flaw f, the information on the metal strip coil C, and the time of flaw detection. As described above, according to the coil defect inspection method according to this embodiment, The method includes an imaging step (step S1) in which the imaging device 2 installed at a position below the suspended metal strip coil C images the bottom surface Ca of the metal strip coil C, and an image diagnosis step (step S2) in which the image diagnosis device 4 detects flaws f in the image I captured in the imaging step (step S1). In the imaging step (step S1), the imaging device 2 images the bottom surface Ca of the metal strip coil C, which is illuminated with uniform illuminance by reflecting illumination light 10a from a light source 10 installed at a position above the suspended metal strip coil C by a diffusion plate 7 installed at a position below the imaging device 2.

[0052] This makes it possible to brighten the bottom surface Ca of the metal band coil C without uneven illumination on the bottom surface Ca of the metal band coil C, and makes it easy to detect scratches f on the bottom surface Ca of the metal band coil C. Therefore, scratches f on the bottom surface Ca of the metal band coil C can be detected with a high detection rate. In addition, while the metal strip coil C is hoisted by the lifting device 11 of a crane (not shown), the bottom surface Ca of the metal strip coil C is imaged from below by the imaging device 2, and defects f are detected on the captured image I by the image diagnostic device 4, so there is no need for workers to get around to the underside of the metal strip coil C, eliminating safety risks to workers at the manufacturing site.

[0053] Moreover, according to the coil defect inspection method of this embodiment, the image diagnosis step (step S2) includes an image judgment range determination step (step S22) in which the image diagnosis device 4 calculates the position of the bottom surface Ca of the metal strip coil C in the imaging range IA by the imaging device 2 based on the outer diameter information of the metal strip coil C and the position information of the metal strip coil C, and determines the image judgment range JA in the captured image I based on the calculated position of the bottom surface Ca of the metal strip coil C in the imaging range IA. The image diagnosis step (step S2) also includes a defect detection step (step S23) in which the image diagnosis device 4 detects defects in the image of the image judgment range JA determined in the image judgment range determination step (step S22).

[0054] This reduces the difference between the area of ​​the image determination range JA and the area of ​​the bottom surface Ca of the metal strip coil C, thereby reducing the rate of false detection in which image information in areas other than the bottom surface Ca of the metal strip coil C is mistakenly detected as a defect f. According to the coil defect inspection method of this embodiment, in the defect detection step (step S23) in the image diagnosis step (step S2), the image diagnosis device 4 divides the image of the image determination range JA determined in the image determination range determination step (step S22) into a plurality of images I1 to I4. In addition, in the defect detection step (step S23), image determination is performed on each of the divided plurality of images I1 to I4 to detect defects f, and further, a recombined image I1 is generated by recombining each of the plurality of images I1 to I4 that have been subjected to image determination. (1+2+3+4) Detect flaw f on the surface.

[0055] This makes it possible to increase the detection rate of the flaw f and reduce the erroneous detection rate of the flaw f without using the compressed image JAp. Although the embodiment of the present invention has been described above, the present invention is not limited to this and various modifications and improvements can be made. For example, the coil defect inspection system 1 is not limited to detecting defects f on the bottom surface Ca of a metal strip coil C in which a metal strip is wound into a coil shape in a cold rolling line, but may also be configured to detect defects f on the bottom surface Ca of a metal strip coil C in which a metal strip is wound into a coil shape in a metal strip manufacturing line other than a cold rolling line, such as a hot rolling line.

[0056] Furthermore, the diffusion plate 7 may be installed not only below the imaging device 2, but also horizontally adjacent to the imaging device 2. The diffusion plate 7 installed in this manner can also reflect the illumination light 10a from the light source 10 to irradiate the bottom surface Ca of the metal strip coil C with uniform illuminance. [Explanation of symbols]

[0057] 1 Coil defect inspection system 2. Imaging device 3. Imaging device control device 4. Diagnostic imaging equipment 5 Coil information PC 6 Display device 7 Diffuser 10 light source 10a Illumination light 11 Lifting equipment C Metal strip coil Ca bottom F floor f Flaw I Captured image IA Imaging Range JA Image Judgment Range JAp Compressed Image Images divided into I1 to I4 I (1+2+3+4) Recombined Image

Claims

1. A coil defect inspection system for detecting defects on a bottom surface of a metal strip coil obtained by winding a metal strip into a coil, comprising: a light source installed at a position above the suspended metal strip coil; an imaging device that is installed at a position below the lifted metal strip coil and captures an image of a bottom surface of the metal strip coil; an image diagnostic device that detects defects in the captured image captured by the imaging device; A coil defect inspection system characterized in that a diffusion plate is installed below the imaging device or in a position horizontally adjacent to the imaging device, which reflects illumination light from the light source and irradiates the bottom surface of the metal strip coil with uniform illuminance.

2. 2. The coil defect inspection system according to claim 1, wherein the imaging diagnostic device calculates a position of a bottom surface of the metal band coil in an imaging range by the imaging device based on outer diameter information of the metal band coil and position information of the metal band coil, determines an image determination range in the captured image based on the calculated position of the bottom surface of the metal band coil in the imaging range, and detects defects in an image within the determined image determination range.

3. 3. The coil defect inspection system according to claim 2, wherein the image diagnostic device divides an image in the determined image judgment range into a plurality of images, performs image judgment on each of the plurality of divided images to detect defects, and further detects defects on a recombined image obtained by recombining each of the plurality of images that have been subjected to image judgment.

4. A coil defect inspection method for detecting defects on a bottom surface of a metal strip coil obtained by winding a metal strip into a coil shape, comprising: an imaging step of imaging a bottom surface of the metal strip coil by an imaging device installed at a position below the lifted metal strip coil; and an image diagnosis step in which an image diagnostic device detects defects in the captured image captured in the imaging step, This coil defect inspection method is characterized in that, in the imaging step, illumination light from a light source installed at a position above the suspended metal strip coil is reflected by a diffuser plate installed below the imaging device or in a position horizontally adjacent to the imaging device, and the bottom surface of the metal strip coil is irradiated with uniform illuminance, and the imaging device images the bottom surface of the metal strip coil.

5. 5. The coil defect inspection method according to claim 4, wherein the image diagnosis step includes an image determination range determination step in which the image diagnostic device calculates a position of a bottom surface of the metal band coil in an imaging range by the imaging device based on outer diameter information and position information of the metal band coil, and determines an image determination range in the captured image based on the calculated position of the bottom surface of the metal band coil in the imaging range, and a defect detection step in which the image diagnostic device detects defects in an image within the image determination range determined in the image determination range determination step.

6. 6. The coil defect inspection method according to claim 5, wherein, in the defect detection step in the image diagnosis step, the image diagnostic device divides the image of the image judgment range determined in the image judgment range determination step into a plurality of images, performs image judgment on each of the plurality of divided images to detect defects, and further detects defects on a recombined image obtained by recombining each of the plurality of images that have been subjected to image judgment.

Images