JP7524878B2 - Surface defect inspection system and surface defect inspection method - Google Patents

Description

The present invention relates to a surface defect inspection system and a surface defect inspection method.

In general, in the manufacturing line of steel plates, which are metal plates, quality assurance and quality control are performed by inspecting the surface of the steel plate with a surface defect inspection device. Most surface defect inspection devices are composed of an optical system using lighting and a camera, and an image processing system. The lighting and camera angles are adjusted so that the contrast (S/N ratio = signal-to-noise ratio) of the surface defect part to the normal part in the acquired image is increased, so that the target surface defect can be detected. These conventional surface defect inspection devices have excellent detection capabilities for uneven defects with large unevenness, but have difficulty detecting pattern-like defects with small unevenness and small S/N ratios. In order to detect such pattern-like defects with small unevenness, the image processing system generally corrects the brightness unevenness of the input image caused by uneven illuminance of the lighting, and then detects the surface defect part by comparing it with a predetermined threshold value, or if the noise in the normal part is large, applies a low-pass filter to reduce noise, or applies a differential filter to emphasize the edge of the surface defect part, thereby improving the S/N ratio of the surface defect part. However, many of these techniques are often only effective for specific types of defects or textures.

In the surface defect inspection device described in Patent Document 1, multiple feature images are generated by processing the original image with multiple spatial filters, and the degree of abnormality is calculated by performing statistical analysis processing, making it possible to detect pattern defects with small unevenness as defective areas.

JP 2018-155690 A

As mentioned above, there are many types of surface defects, such as uneven defects and pattern defects, but it is difficult to develop a surface defect inspection device that can detect all of them. Therefore, it is desirable to use a different surface defect inspection device for each type of defect, that is, to use multiple surface defect inspection devices in combination. Generally, each of multiple surface defect inspection devices has a defect display function and a defect rate tally function, so using multiple surface defect inspection devices in combination means that a display tally device corresponding to the number of surface defect inspection devices is required. In the production line, a person who inspects the quality of the steel plate surface (hereinafter referred to as the inspector) performs the inspection using the information displayed on the display tally device as guidance, but when there are multiple surface defect inspection devices, there are a number of display tally devices corresponding to the number of surface defect inspection devices, so the inspector has to monitor many display tally devices, which increases the workload and is inconvenient. In addition, the person who makes the final decision on whether the inspected steel plate passes or fails (hereinafter referred to as the "processor") checks the defect rate and defect locations from the information displayed on the display and tallying device, but if there are multiple surface defect inspection devices, there will be a corresponding number of display and tallying devices, which means the processer has to check many display and tallying devices, which increases the workload and is inconvenient. Furthermore, managing multiple devices entails a quality assurance risk due to the inspector or processer overlooking important defects.

The present invention has been made in consideration of the above problems, and its purpose is to provide a surface defect inspection system and a surface defect inspection method that can reduce quality assurance risks.

In order to solve the above-mentioned problems and achieve the object, the surface defect inspection system according to the present invention is characterized by comprising a single imaging means for imaging the surface of a metal plate being transported in a predetermined direction, a plurality of image processing means for processing image information of the surface of the metal plate imaged by the imaging means and capable of detecting surface defects of different forms, and a single display aggregation means for aggregating and displaying information regarding the surface defects detected by each of the plurality of image processing means.

The surface defect inspection system according to the present invention is characterized in that, in the above invention, when the surface defects detected by the multiple image processing means are located at the same position on the surface of the metal plate, the display counting means compares the defect types and harmfulness of the surface defects detected by the multiple image processing means, and selects and displays the surface defects with the highest severity.

The surface defect inspection method according to the present invention is characterized by comprising the steps of: imaging the surface of a metal plate being transported in a predetermined direction by a single imaging means; processing the image information of the surface of the metal plate imaged by the imaging means by a plurality of image processing means, which detect surface defects of different shapes; and collating and displaying information about the surface defects detected by each of the plurality of image processing means in a single display collating means.

The surface defect inspection method according to the present invention is characterized in that, in the above invention, when the surface defects detected by the multiple image processing means are located at the same position on the surface of the metal plate, the display counting means compares the defect types and harmfulness of the surface defects detected by the multiple image processing means, and selects and displays the surface defects with the highest severity.

The surface defect inspection system and surface defect inspection method according to the present invention have the effect of reducing quality assurance risks.

FIG. 1 is a schematic diagram showing the configuration of a surface defect inspection system according to an embodiment. FIG. 2 is a schematic diagram showing the configuration of a surface defect inspection system according to a conventional example. FIG. 3 is a flowchart showing an example of control relating to defect acceptance performed by the first display and tallying device of the surface defect inspection system according to the embodiment.

The following describes an embodiment of a surface defect inspection system and a surface defect inspection method according to the present invention. Note that the present invention is not limited to this embodiment.

Figure 1 is a schematic diagram showing the configuration of a surface defect inspection system 1 according to an embodiment. As shown in Figure 1, the surface defect inspection system 1 according to an embodiment includes a first surface defect inspection device 10 and a second surface defect inspection device 20 for inspecting surface defects such as uneven defects and pattern defects on the surface of a steel plate S, which is a metal plate. The first surface defect inspection device 10 is a surface defect inspection device that is excellent at detecting uneven defects on the surface of the steel plate S, and the second surface defect inspection device 20 is a surface defect inspection device that is excellent at detecting pattern defects on the surface of the steel plate S. In addition, the surface defect inspection system 1 according to an embodiment includes two surface defect inspection devices, the first surface defect inspection device 10 and the second surface defect inspection device 20, but the number of the multiple surface defect inspection devices is not limited to two.

The first surface defect inspection device 10 is composed of an illumination device 2, an imaging device 3, a first image processing device 11, and a first display and tallying device 12. The second surface defect inspection device 20 is composed of an illumination device 2, an imaging device 3, a second image processing device 21, and a second display and tallying device 22. That is, in the surface defect inspection system 1 according to the embodiment, the first surface defect inspection device 10 and the second surface defect inspection device 20 share a single imaging device 3 and illumination device 2.

The lighting device 2 illuminates the surface of the steel sheet S to be inspected with light to brighten it. The imaging device 3 images the area to be inspected on the surface of the steel sheet S illuminated by the lighting device 2, and outputs the obtained raw image data, which is image information of the surface of the steel sheet S, to the first image processing device 11 and the second image processing device 21. The imaging device 3 may be either a so-called line sensor camera having a one-dimensional imaging element or a so-called area camera having a two-dimensional imaging element, and in either case, imaging is performed in synchronization with the transport of the steel sheet S. When the imaging device 3 is a line sensor camera, for example, a continuous lighting device is used as the lighting device 2. Also, when the imaging device 3 is an area camera, for example, a flash lighting device is used as the lighting device 2, which emits a flash of light every time the steel sheet S advances a certain distance.

The first image processing device 11 and the second image processing device 21 analyze the raw image data of the surface of the steel sheet S received from the imaging device 3. If the analysis results in a surface defect on the surface of the steel sheet S, the surface defect is detected, and the type and harmfulness of the detected surface defect are determined, and the information is output to the first display and calculation device 12 and the second display and calculation device 22, respectively.

The second display and counting device 22 displays detection information (images of surface defect areas and positions of surface defects), judgment information (type and harmfulness), and statistical information (number of defects in the entire steel sheet S or total number of defects by defect type and harmfulness, occurrence rate, etc.) regarding the surface defects detected by the second image processing device 21. The second display and counting device 22 also outputs the detection information, judgment information, and statistical information regarding the surface defects detected by the second image processing device 21 to the first display and counting device 12, which is higher than the second display and counting device 22.

The first display and counting device 12 displays the detection information, the judgment information, and the statistical information about the surface defects detected by the first image processing device 11. The first display and counting device 12 also displays the detection information, the judgment information, and the statistical information about the surface defects detected by the second image processing device 21, which are received from the second display and counting device 22.

In this way, in the surface defect inspection system 1 according to the embodiment, the detection information, the judgment information, and the statistical information about the surface defects detected by the first image processing device 11 and the second image processing device 21, respectively, are displayed on the first display and tallying device 12, which is a single display and tallying device. Therefore, the inspector and the person in charge of the procedure need only check the first display and tallying device 12 to see the various information about the surface defects detected by the first image processing device 11 and the second image processing device 21, respectively.

Figure 2 is a schematic diagram showing the configuration of a surface defect inspection system 101 according to a conventional example. As shown in Figure 2, the surface defect inspection system 101 according to the conventional example includes a first surface defect inspection device 110 and a second surface defect inspection device 120.

The first surface defect inspection device 110 is composed of a first lighting device 102A, a first imaging device 103A, a first image processing device 111, and a first display and tallying device 112. The second surface defect inspection device 120 is composed of a second lighting device 102B, a second imaging device 103B, a second image processing device 121, and a second display and tallying device 122.

The physical configurations of the first lighting device 102A and the second lighting device 102B are the same as the lighting device 2 of the surface defect inspection system 1 according to the embodiment. The physical configurations of the first imaging device 103A and the second imaging device 103B are the same as the imaging device 3 of the surface defect inspection system 1 according to the embodiment. The physical configurations of the first image processing device 111 and the second image processing device 121 are the same as the first image processing device 11 and the second image processing device 21 of the surface defect inspection system 1 according to the embodiment. The physical configurations of the first display and tally device 112 and the second display and tally device 122 are the same as the first display and tally device 12 and the second display and tally device 22 of the surface defect inspection system 1 according to the embodiment.

The first surface defect inspection device 110 performs processing such as analysis, detection, and judgment on the raw image data of the surface of the steel sheet S obtained by the first lighting device 102A and the first imaging device 103A in the first image processing device 111, and then outputs the detection information, judgment information, and statistical information about the surface defects to the first display and tallying device 112. The second surface defect inspection device 120 performs processing such as analysis, detection, and judgment on the raw image data of the surface of the steel sheet S obtained by the second lighting device 102B and the second imaging device 103B in the second image processing device 121, and then outputs the detection information, judgment information, and statistical information about the surface defects to the second display and tallying device 122. The inspector and the operator then check the various information about the surface defects displayed on both the first display and tallying device 112 and the second display and tallying device 122. Therefore, in the conventional surface defect inspection system 101, multiple management places a heavy workload on inspectors and processors, and is inconvenient, resulting in a quality assurance risk due to important defects being overlooked.

In contrast, in the surface defect inspection system 1 according to the embodiment, in a production line where quality assurance of steel sheets S is performed using multiple surface defect inspection devices (first surface defect inspection device 10 and second surface defect inspection device 20), it is sufficient for an inspector to check only one display tally device (first display tally device 12) as guidance, instead of multiple display tally devices (first display tally device 12 and second display tally device 22). Similarly, in the surface defect inspection system 1 according to the embodiment, it is sufficient for a processor to check the defect rate and defect occurrence position using one display tally device (first display tally device 12) instead of multiple display tally devices (first display tally device 12 and second display tally device 22). Therefore, the surface defect inspection system 1 according to the embodiment can reduce the workload of inspectors and processors, improve convenience, and reduce quality assurance risks.

Here, in the surface defect inspection system 1 according to the embodiment, when displaying defects and counting the defect failure rate are performed using only one display/tallying device (first display/tallying device 12) among the multiple display/tallying devices (first display/tallying device 12 and second display/tallying device 22), a positional shift of the steel plate S in the steel plate transport direction may cause the longitudinal positions (positions in the steel plate transport direction) of the defects detected by the first surface defect inspection device 10 and the second surface defect inspection device 20 to shift, resulting in an incorrect failure rate being counted and a lower pass rate.

In the surface defect inspection system 1 according to the embodiment, the system is configured to share the raw image data used for processing with the first surface defect inspection device 10 and the second surface defect inspection device 20, and surface defect information is integrated in the first surface defect inspection device 10 (first image processing device 11) that has a positional deviation monitoring function. This makes it possible to display defects and tally up defect failure rates without causing deviations (positional deviations) in the longitudinal positions (positions in the steel plate transport direction) of defects detected by the first surface defect inspection device 10 and the second surface defect inspection device 20, respectively.

The position deviation monitoring function refers to, for example, a function that adjusts the timing of the start of inspection by starting front and back tracking upon detecting the welding position where the preceding steel plate S and the following steel plate S are joined in the steel plate transport direction, or a function that monitors the length of the coil around which the steel plate S is wound and outputs an alarm if the steel plate S is misaligned in the steel plate transport direction.

In addition, in the surface defect inspection system 1 according to the embodiment, when the first surface defect inspection device 10 and the second surface defect inspection device 20 each detect the same defect on the surface of the steel sheet S, if the same defect is counted twice as different defects (double counted), it may be erroneously calculated as a defective rate and the pass rate may decrease. On the other hand, if the person in charge tries to check whether the same defect is not counted twice as different defects (double counted), multiple management is required, which increases the person in charge's workload and ultimately leads to a quality assurance risk due to overlooking a significant defect.

Therefore, in the surface defect inspection system 1 according to the embodiment, when the first surface defect inspection device 10 and the second surface defect inspection device 20 detect a defect at the same steel plate position (the same position on the surface of the steel plate S), the defect type and the degree of harmfulness of the defect detected by the first surface defect inspection device 10 and the second surface defect inspection device 20 are compared. The defect detected by the first surface defect inspection device 10 refers to the surface defect of the steel plate S detected by the first image processing device 11 by processing the raw image data of the surface of the steel plate S imaged by the imaging device 3. The defect detected by the second surface defect inspection device 20 refers to the surface defect of the steel plate S detected by the second image processing device 21 by processing the raw image data of the surface of the steel plate S imaged by the imaging device 3. In the surface defect inspection system 1 according to the embodiment, the defect with the higher degree of severity is adopted from the defects detected by the first surface defect inspection device 10 and the second surface defect inspection device 20. As a result, the surface defect inspection system 1 according to the embodiment can prevent the same defect detected at the same position on the surface of the steel sheet S from being counted twice (double counting) as different defects, and can prevent a decrease in the pass rate due to an erroneous defective rate.

In addition, since the operator does not need to check whether the same defect is being double-counted, the risk of overlooking a significant defect due to multiple management can be reduced. It is desirable to provide a function for separately tallying up the defects detected by the first surface defect inspection device 10 and the second surface defect inspection device 20 and determining the defect rate, as well as a function for integrating (adding up) the defects and tallying them up and determining the defect rate. It is also desirable to provide a function for selecting the defect type to be integrated when integrating the defects detected by the first surface defect inspection device 10 and the second surface defect inspection device 20.

In addition, in the surface defect inspection system 1 according to the embodiment, when the first surface defect inspection device 10 and the second surface defect inspection device 20 detect a surface defect at the same steel plate position (the same position on the surface of the steel plate S), the harmfulness of the defects detected by the first surface defect inspection device 10 and the second surface defect inspection device 20 may be compared, and the more serious defect may be adopted. Note that, when the harmfulness of the defects is the same, the defect that is preset as the more serious defect type may be adopted.

Figure 3 is a flowchart showing an example of the control regarding defect adoption performed by the first display and counting device 12 of the surface defect inspection system 1 according to the embodiment.

First, the first display and counting device 12 judges whether the defects detected by the first surface defect inspection device 10 and the second surface defect inspection device 20 are at the same steel plate position (the same position on the surface of the steel plate S) (step S1). Next, if the first display and counting device 12 judges that the defects are at the same steel plate position (Yes in step S1), it judges whether the harmfulness of the defect satisfies the relationship of first surface defect inspection device 10 = second surface defect inspection device 20 (step S2). In other words, it judges whether the harmfulness of the defect detected by the first surface defect inspection device 10 is equal to the harmfulness of the defect detected by the second surface defect inspection device 20.

When the first display and tallying device 12 judges that the harmfulness of the defect satisfies the relationship of the first surface defect inspection device 10 = the second surface defect inspection device 20 (Yes in step S2), it judges whether the type of defect is more serious in the first surface defect inspection device 10 than in the second surface defect inspection device 20 (step S3). When the first display and tallying device 12 judges that the first surface defect inspection device 10 is more serious (Yes in step S3), it adopts the defect of the first surface defect inspection device 10 (step S4). Then, the first display and tallying device 12 ends this control. On the other hand, when the first display and tallying device 12 judges that the first surface defect inspection device 10 is not more serious, in other words, that the second surface defect inspection device 20 is more serious (No in step S3), it adopts the defect of the second surface defect inspection device 20 (step S5). Then, the first display and tallying device 12 ends this control.

In addition, in step S2, if the first display/tallying device 12 determines that the harmfulness of the defect does not satisfy the relationship of first surface defect inspection device 10 = second surface defect inspection device 20 (No in step S2), it determines whether the harmfulness of the defect satisfies the relationship of first surface defect inspection device 10 > second surface defect inspection device 20 (step S6). In other words, it determines whether the harmfulness of the defect detected by the first surface defect inspection device 10 is greater than the harmfulness of the defect detected by the second surface defect inspection device 20.

If the first display and tallying device 12 determines that the harmfulness of the defect satisfies the relationship of first surface defect inspection device 10 > second surface defect inspection device 20 (Yes in step S6), it adopts the defect of the first surface defect inspection device 10 (step S7). Then, the first display and tallying device 12 ends this control. On the other hand, if the first display and tallying device 12 determines that the harmfulness of the defect does not satisfy the relationship of first surface defect inspection device 10 > second surface defect inspection device 20 (No in step S6), it adopts the defect of the second surface defect inspection device 20 (step S8). Then, the first display and tallying device 12 ends this control.

In addition, in step S1, if the first display and counting device 12 determines that the steel plate positions are not the same (No in step S1), it uses both the defects from the first surface defect inspection device 10 and the defects from the second surface defect inspection device 20 (step S9). Then, the first display and counting device 12 ends this control.

In the surface defect inspection system 1 according to the embodiment, the first surface defect inspection device 10 and the second surface defect inspection device 20 can be integrated into a single surface defect inspection system 1 without misalignment of defects of different shapes detected by the first surface defect inspection device 10 and the second surface defect inspection device 20, and without double counting the same defect.

Table 1 shows the evaluation results of quality assurance risk (QA (Quality Assurance) risk). (1) in Table 1 shows the case where only the first surface defect inspection device 110 of the surface defect inspection system 101 according to the conventional example is used. (2) in Table 1 shows the case where only the second surface defect inspection device 120 of the surface defect inspection system 101 according to the conventional example is used. (3) in Table 1 shows the case where the surface defect inspection system 101 according to the conventional example is used. (4) in Table 1 shows the case where the surface defect inspection system 1 according to the embodiment is used.

As shown in Table 1, when only the first surface defect inspection device 110 of the conventional example is used, when only the second surface defect inspection device 120 of the conventional example is used, and when the surface defect inspection system 101 of the conventional example is used, it is difficult to detect either the uneven defect or the pattern defect, and the inspector and the person in charge of handling the problem must check multiple display and tally devices (the first display and tally device 112 and the second display and tally device 122), which increases the quality assurance risk (QA risk). On the other hand, when the surface defect inspection system 1 of the embodiment is used, it is possible to detect both the uneven defect and the pattern defect, and it is sufficient for the inspector and the person in charge of handling the problem to check one display and tally device (the first display and tally device 12), which reduces the quality assurance risk (QA risk).

1, 101 Surface defect inspection system 2 Illumination device 3 Imaging device 10, 110 First surface defect inspection device 11, 111 First image processing device 12, 112 First display and tallying device 20, 120 Second surface defect inspection device 21, 121 Second image processing device 22, 122 Second display and tallying device 102A First illumination device 102B Second illumination device 103A First imaging device 103B Second imaging device

Claims (2)

A single imaging means for imaging a surface of a metal plate being transported in a predetermined direction;
a plurality of image processing means for processing image information of the surface of the metal plate captured by the imaging means and detecting surface defects having different shapes;
a single display/counting means for collating and displaying information about the surface defects detected by each of the plurality of image processing means;
A surface defect inspection system comprising:
the display/counting means determines whether the surface defects detected by the plurality of image processing means are located at the same position on the surface of the metal plate,
When it is determined that the surface defects are not at the same position, the display counting means adopts and displays the surface defects detected by each of the plurality of image processing means,
When it is determined that the surface defects are located at the same position , the display/counting means further determines whether the harmfulness of the surface defects detected by each of the plurality of image processing means is equal or not;
When it is determined that the harmfulness is equal, the display counting means compares the types of the surface defects detected by the plurality of image processing means, and adopts and displays the surface defect having a higher degree of severity ,
When it is determined that the harmfulness levels are different, the display counting means compares the harmfulness levels of the surface defects detected by the plurality of image processing means, and adopts and displays the surface defect having a higher harmfulness level.
A surface defect inspection system comprising: A step of imaging a surface of a metal plate being transported in a predetermined direction by a single imaging means;
a step of processing image information of the surface of the metal plate captured by the imaging means using a plurality of image processing means, and the plurality of image processing means detect surface defects having different forms from each other;
a step of collecting and displaying information about the surface defects detected by each of the plurality of image processing means in a single display collecting means;
A surface defect inspection method comprising:
the display/counting means determines whether the surface defects detected by the plurality of image processing means are located at the same position on the surface of the metal plate,
When it is determined that the surface defects are not at the same position, the display counting means adopts and displays the surface defects detected by each of the plurality of image processing means,
When it is determined that the surface defects are located at the same position , the display/counting means further determines whether the harmfulness of the surface defects detected by each of the plurality of image processing means is equal or not;
When it is determined that the harmfulness is equal, the display counting means compares the types of the surface defects detected by the plurality of image processing means, and adopts and displays the surface defect having a higher degree of severity ,
When it is determined that the harmfulness levels are different, the display counting means compares the harmfulness levels of the surface defects detected by the plurality of image processing means, and adopts and displays the surface defect having a higher harmfulness level.
A surface defect inspection method comprising:

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