JP2024036007A - Metal strip surface inspection device, surface inspection method, and metal strip manufacturing method - Google Patents

Abstract

An object of the present invention is to provide a surface defect detection device that can accurately detect defects in a metal strip. SOLUTION: A metal strip surface inspection device includes a plurality of light emitting elements whose optical axes are arranged toward a metal strip that is conveyed in one direction, an optical axis whose optical axis is arranged toward the metal strip, and an imaging unit having a plurality of imaging elements provided to be paired with the plurality of light emitting elements; and a determination unit that determines a defect in the metal band based on imaging data generated by the imaging unit. . Each of the plurality of light emitting elements is provided so that it emits emitted light having a mutually distinguishable wavelength, and an irradiation range of the emitted light includes the width direction of the metal band. The imaging range of each of the plurality of image sensors is set to include the irradiation range of the paired light emitting element. Each of the imaging ranges has a line shape along the width direction of the metal band, and is provided at different angles with respect to the one direction. [Selection diagram] Figure 1

Description

The present invention relates to a metal strip surface inspection apparatus, a surface inspection method, and a metal strip manufacturing method for inspecting surface defects of a metal strip.

Metal strips, such as thin steel sheets, are manufactured through various processes. In the manufacturing process of a metal strip, for example, a slab is first cast in a steel manufacturing process. The slab becomes a hot rolled metal strip in a hot rolling process. Oxides on the surface of the hot-rolled metal strip are removed in a pickling process. The hot rolled metal strip from which oxides have been removed is cold rolled to a predetermined thickness in a cold rolling process. The metal strip hardened in these processing steps is softened in an annealing step. The metal strip that has undergone the annealing process is subjected to multiple treatments such as plating and temper rolling.

Between these steps, the metal strip is inspected for defects. When a defect in the metal strip is detected, action is taken depending on the degree of the defect. For example, in the case of a serious defect, measures such as marking and removal of the defect are performed. Furthermore, in the case of a minor defect, the operator is notified that a minor defect has been detected. Furthermore, in the case of very minor defects, settings are made so that they are not detected as defects.

In the manufacturing process of metal strips, when a defect is detected, its degree of importance is also determined. For example, when a flaw caused by a roll or the like is transferred to a metal band, an uneven defect occurs in which unevenness occurs on the surface. Since such uneven defects are transferred to the metal band each time the roll rotates, the quality is greatly affected. Therefore, uneven defects are set to have a higher degree of importance than other types of defects. Various efforts have been made to detect such uneven defects with high precision.

For example, in Patent Document 1, light of different wavelengths from three or more line light sources is irradiated in parallel from different directions, and the irradiated lines are scanned with a line scan camera.

JP 2019-39798 Publication

In Patent Document 1, scanning is performed with one line scan camera. That is, since the inspection is performed using only the imaging information of the scan camera, there is a problem in that it is difficult to obtain the minute shape of the uneven defect. For this reason, for example, there is a problem that the detection accuracy is lowered for uneven defects having a gentle slope.

The present invention has been made in view of the above-mentioned problems, and provides a metal strip surface inspection device and a metal strip surface inspection method that can accurately detect uneven defects formed on the surface of a metal strip. Another object of the present invention is to provide a method for manufacturing a metal strip.

In order to solve the above problems, the present invention has the following features.

[1]
a plurality of light-emitting elements having optical axes facing a metal strip that is conveyed in one direction; and a plurality of light-emitting elements having optical axes facing the metal belt and being paired with the plurality of light-emitting elements. an imaging unit having a plurality of imaging elements;
a determination unit that determines a defect in the metal band based on imaging data generated by the imaging unit;
Each of the plurality of light emitting elements is provided so that it emits emitted light of a mutually distinguishable wavelength, and the irradiation range of the emitted light includes the width direction of the metal band,
Each of the plurality of image sensors has an imaging range set to include the irradiation range of the paired light emitting element,
In the metal band surface inspection apparatus, each of the imaging ranges is provided in a line shape along the width direction of the metal band, and is provided at different angles with respect to the one direction.
[2]
The metal band according to [1], wherein the angle that the optical axes of the pair of image sensors make in the one direction is equal to the angle that the optical axes of the pair of light emitting elements make in the one direction. Surface inspection equipment.
[3]
The metal band according to [1], wherein the angle that the optical axes of the pair of image sensors make in the one direction is different from the angle that the optical axes of the pair of light emitting elements make in the one direction. Surface inspection equipment.
[4]
The determination unit includes an angle correction unit that corrects the image data captured by the image sensor so that the angle of the imaging range with respect to the one direction approaches a reference angle,
The metal strip surface inspection device according to any one of [1] to [3], wherein the determination unit determines a defect in the metal belt based on the imaging data corrected by the angle correction unit.
[5]
The determination unit selects a plurality of pieces of imaging data in which a part of the metal band included in one of the imaging data matches a part of the metal band included in another of the imaging data. Including a position correction section that selects from data,
The metal strip surface inspection device according to [4], wherein the determination section determines a defect in the metal strip based on the imaging data selected by the position correction section.
[6]
The metal strip surface inspection apparatus according to any one of [1] to [5], wherein each of the image pickup elements is arranged so that at least two of the image pickup ranges intersect at one point.
[7]
The metal strip surface inspection device according to any one of [1] to [6], wherein the imaging range of at least one image sensor extends in the width direction of the metal strip.
[8]
a conveyance step of conveying the metal strip in one direction;
an irradiation step of irradiating a plurality of emitted lights with mutually distinguishable wavelengths toward a plurality of irradiation ranges set along the width direction of the metal band;
a setting step of setting a plurality of line-shaped imaging ranges that are set to be paired with the irradiation range and extend along the width direction of the metal band so as to form mutually different angles with respect to the one direction; and,
an imaging data generation step of generating imaging data of the metal band imaged to include the irradiation range that is paired with the imaging range, according to the imaging range set in the setting step;
A method for inspecting the surface of a metal strip, comprising: determining a defect in the metal strip based on a plurality of the image data.
[9]
The determination step includes:
an angle information acquisition step of acquiring an angle made by each of the imaging ranges in the one direction;
The surface inspection method according to [8], including an angle correction step of correcting the imaging data so that the angle acquired in the angle information acquisition step approaches a reference angle.
[10]
The determining step includes selecting a plurality of pieces of imaging data in which the part of the metal band included in the one imaging data matches the part of the metal band included in the other imaging data. The surface inspection method according to [9], including a position correction step of selecting from among the captured image data.
[11]
A method of manufacturing a metal strip using the metal strip surface inspection device according to any one of [1] to [6].

According to the surface inspection device for a metal strip according to the present invention, an object to be inspected is irradiated with a plurality of imaging data whose imaging ranges have different angles with respect to one direction, and which are irradiated with emitted light of mutually distinguishable wavelengths. The presence or absence of a defect can be determined using a plurality of pieces of imaging data. Thereby, the surface inspection device can acquire detailed data regarding the shape of the uneven defect, and therefore can accurately detect the uneven defect on the metal strip.

FIG. 2 is an explanatory diagram showing the configuration of a metal strip surface inspection device. FIG. 2 is a block diagram of a defect detection section in FIG. 1. FIG. FIG. 3 is an explanatory diagram showing the arrangement relationship between the first light emitting element and the first image sensor in FIG. 2; FIG. 3 is an explanatory diagram showing the arrangement of the first light emitting element, the first image sensor, and other arrangement relationships in FIG. 2; FIG. 4 is an explanatory diagram illustrating the first light emitting element, the first image sensor, and other arrangement relationships in FIG. 3; FIG. 2 is an explanatory diagram showing an arrangement of a first light emitting element and a first imaging element as seen from above a metal band. FIG. 3 is an explanatory diagram showing an example of the arrangement of the first to third light emitting elements and the first to third image pickup elements. It is an explanatory view showing each aspect of the irradiation range in a metal band. It is an explanatory view showing each other aspect of the irradiation range in a metal belt. It is an explanatory view showing each other aspect of the irradiation range in a metal band. It is a flowchart of the surface inspection of a metal strip. FIG. 12 is a flow diagram showing a subroutine of the determination step in FIG. 11; FIG. 3 is a schematic diagram in which image data generated by the first image sensor during a predetermined period is associated with a position on the surface of a metal band. FIG. 3 is a schematic diagram in which image data generated by the first image sensor during a predetermined period is associated with a position on the surface of a metal band. This is an example in which imaging data acquired at a predetermined time is associated with the position of a metal band. FIG. 6 is an explanatory diagram showing an example of angle correction by an angle correction section. 13 is a flow diagram showing a subroutine of the position correction step of FIG. 12. FIG. 7 shows a mode of position correction of a plurality of correction data by a position correction unit. FIG. 2 is a cross-sectional view of a metal band showing an aspect of uneven defects. It is an example of the imaging data of the uneven|corrugated defect of FIG. FIG. 3 is an explanatory diagram showing a mode in which specularly reflected light is received at a flat portion of a metal band. FIG. 3 is an explanatory diagram showing a mode in which specularly reflected light is reflected at a negative slope portion of the metal band. FIG. 3 is an explanatory diagram showing a mode in which specularly reflected light is reflected at a positively inclined portion of a metal band. FIG. 20 is an explanatory diagram showing an example of image data obtained by capturing specularly reflected light from the uneven defect in FIG. 19; FIG. 6 is an explanatory diagram showing a mode in which diffusely reflected light is received at a flat portion of a metal band. FIG. 3 is an explanatory diagram showing a mode in which diffusely reflected light is reflected at a negative slope portion of a metal band. FIG. 3 is an explanatory diagram showing a mode in which diffusely reflected light is reflected at a positively inclined portion of a metal band. FIG. 20 is an explanatory diagram showing an example of imaging data obtained by imaging diffusely reflected light from the uneven defect in FIG. 19; FIG. 2 is a cross-sectional view of a metal band showing an aspect of uneven defects. This is an example of imaging data of the uneven defect shown in FIG. 29. FIG. 3 is an explanatory diagram showing composite data obtained by combining three pieces of imaging data. This is another example of imaging data of an uneven defect. FIG. 7 is an explanatory diagram showing other data of composite data obtained by combining three imaging data.

FIG. 1 shows the configuration of a metal strip surface inspection device. The metal strip 10 is conveyed in one direction D, which is the direction of the arrow shown in FIG. The metal strip 10 is conveyed, for example, by a conveyance section 20 provided in a production line for the metal strip 10. The surface inspection device 100 detects defects in the metal strip 10 transported in one direction D in this way.

Note that the conveyance section 20 is a conveyance roller provided in the production line of the metal strip 10. In this embodiment, the conveyance unit 20 is configured by two conveyance rollers provided along one direction D.

The surface inspection device 100 can be used to detect defects on the surface of the metal strip 10 that has been subjected to any manufacturing process. Specifically, the surface inspection apparatus 100 performs each process of a hot rolling process, a pickling process, a cold rolling process, an annealing process, a plating process, a temper rolling process, and a final inspection process for ensuring the quality of the metal strip. Among them, it can be used for the metal strip 10 that has undergone any of the manufacturing processes. The surface inspection device 100 can be installed at any position from the input side to the output side of the equipment for these processes.

The metal strip 10 is not particularly limited, but for example, a thin steel plate can be used. More specifically, as the metal strip 10 to be inspected, any process after the hot rolling process, for example, each process of a pickling process, a cold rolling process, an annealing process, a plating process, a temper rolling process, and A thin steel plate that has undergone a process such as a final inspection process can be used. Note that, after the hot rolling process, the thin steel plate serving as the metal strip 10 is wound into a coil shape during the above steps.

The metal band 10 is not limited to a coil-shaped thin steel plate, and may be a sheet-shaped material such as a thick steel plate on which the above-described steps are performed. Further, the metal band 10 is not limited to steel material, and may be a metal material including aluminum, copper, or the like.

The surface inspection apparatus 100 for the metal strip 10 includes an imaging unit 31 that images the surface of the metal strip 10, and a determination section 32 that determines defects based on the image data captured by the imaging unit 31.

The determination unit 32 can determine, for example, a concavo-convex defect formed of a concave portion, a convex portion, or a combination thereof. Examples of the uneven defect include defects whose uneven shape can be visually recognized.

Specifically, when viewed from the direction perpendicular to the surface of the metal strip 10, circular, elliptical, striped, or irregularly shaped irregular defects with a diameter of approximately 0.1 to 1.0 mm may be inspected. can. Further, as for uneven defects, for example, those having a depth (or height) of about 5 to 1000 μm from the surface can be inspected.

Incidentally, uneven defects are conventionally classified into more detailed categories. Specifically, there are dents, dull baldness, crimp scratches, scratches, etc. Dents are defects that are formed in a concave shape when the metal strip 10 is caught by some kind of hard foreign matter during the line passage.

Dull baldness is a defect in a portion where the irregularities (dulls) of a rolling roll are not transferred to the metal band 10 during a rolling process (cold rolling process or temper rolling process) using a rolling roll that has been subjected to dull processing. Dull baldness occurs due to wear of the rolling rolls, adhesion of foreign matter to the rolling rolls, and the like.

A crimp flaw is a defect that occurs when a part of the bonded interlayer of the metal strip 10 is peeled off when the coiled metal strip 10 is batch annealed. A scratch is a defect that is generated as a sliding trace on the surface of the metal band 10 when the metal band 10 comes into contact with a foreign object such as an equipment component.

In this way, the uneven defects that occur on the surface of the metal strip 10 take on various shapes depending on the cause of their occurrence. Therefore, in order to take appropriate measures corresponding to the cause of the occurrence, it is important that the determining section 32 determines the shape of the uneven defect.

FIG. 2 shows the configuration of a surface inspection apparatus 100 for a metal strip 10. As shown in FIG. As shown in FIG. 2, the imaging unit 31 includes a first light emitting element 311, a second light emitting element 312, and a third light emitting element 313.

Each of the first light emitting element 311, the second light emitting element 312, and the third light emitting element 313 can emit light having wavelengths that are distinguishable from each other. More specifically, each of the first light emitting element 311, the second light emitting element 312, and the third light emitting element 313 can emit emitted light in different color tones, for example.

In this embodiment, the first light emitting element 311 is capable of emitting light having a wavelength having a peak in an arbitrary band of 435 to 500 nm, that is, blue light, for example. The second light emitting element 312 is capable of emitting light having a wavelength having a peak in an arbitrary band of 600 to 800 nm, that is, red light, for example. The third light emitting element 313 can emit light having a wavelength having a peak in an arbitrary band of 500 to 580 nm, that is, green light, for example.

Note that each emitted light may be in any form as long as it can be identified by an image sensor described later. For example, even if each of the first light emitting element 311 to the third light emitting element 313 emits emitted light of the same color tone, the peak band of each emitted light is different, and each of the respective bands is different. It is sufficient if the signals can be separated by a BPF (Band Pass Filter). This is because by doing so, an image sensor, which will be described later, can identify each emitted light.

For each of the first light emitting element 311, the second light emitting element 312, and the third light emitting element 313, for example, LEDs arranged in a row along a predetermined direction can be used. For example, each of the first light emitting element 311, the second light emitting element 312, and the third light emitting element 313 are LEDs arranged in a row along the width direction of the metal strip 10 when viewed from one direction D. can be used.

The imaging unit 31 includes a first imaging device 314, a second imaging device 315, and a third imaging device 316. Each of the imaging elements 314 to 316 is provided to be paired with each of the light emitting elements 311 to 313.

Specifically, the first image sensor 314 is provided to be paired with the first light emitting element 311. The first image sensor 314 can selectively receive the light emitted from the first light emitting element 311. The first image sensor 314 can selectively receive the emitted light emitted from the first light emitting element 311, for example, by using a BPF that passes through a band corresponding to the emitted light.

The second image sensor 315 is provided to be paired with the second light emitting element 312. The second image sensor 315 can selectively receive light emitted from the second light emitting element 312. The second image sensor 315 can selectively receive the emitted light emitted from the second light emitting element 312, for example, by using a BPF that passes through a band corresponding to the emitted light.

The third image sensor 316 is provided as a pair with the third light emitting element 313. The third image sensor 316 can selectively receive the light emitted from the third light emitting element 313. The third image sensor 316 can selectively receive the emitted light emitted from the third light emitting element 313, for example, by using a BPF that passes through a band corresponding to the emitted light.

As each of the first image sensor 314 to third image sensor 316, for example, a line scan camera equipped with a CCD imaging sensor element or a CMOS imaging element can be used.

Since the line scan camera has a higher scan rate than other imaging sensors, it can image the reflected light reflected by the metal band 10 at high speed. For example, the scan rate of the line scan camera is preferably 10 MHz or more, more preferably 50 MHz or more for a metal strip manufacturing line. The upper limit of the scan rate of the line scan camera is preferably about 640 MHz. With such setting values, sufficient imaging data can be obtained to determine defects in the metal band 10.

The surface inspection apparatus 100 for the metal strip 10 includes a determination section 32 that determines defects in the metal strip 10 based on imaging data generated by the imaging unit 31.

The determination unit 32 has an input unit 321 that is an interface that receives input of imaging data from the imaging unit 31.

The determination unit 32 includes a storage unit 322 that stores imaging data and the like transmitted from the imaging unit 31. The storage unit 322 is not particularly limited, but for example, a nonvolatile memory such as an HDD (hard disk drive) or an SSD (solid state drive) can be used.

The determination unit 32 has an output unit 323 that is an interface that outputs display data to the display unit 33 that displays the determination result.

The determination unit 32 includes a control unit 324 that controls the entire surface inspection apparatus 100 for the metal strip 10. The control unit 324 is configured by a computer including a CPU, ROM, and RAM (not shown). The control unit 324 includes an angle correction unit 324a that corrects the imaging data input from the input unit 321. The control unit 324 includes a position correction unit 324b that selects imaging data suitable for processing from a plurality of imaging data. The control unit 324 includes a defect determination unit 324c that determines defects based on imaging data. The angle correction section 324a, the position correction section 324b, and the defect determination section 324c are executed by the CPU reading out software stored in the ROM.

The angle correction unit 324a corrects the image data captured by each of the first to third image sensors 314 to 316. Specifically, the angle correction unit 324a specifies an imaging range determined by the arrangement of each of the first to third imaging elements 314 to 316, and each of the imaging ranges is configured with respect to one direction D. The imaging data is corrected so that the angle becomes a predetermined reference angle.

The position correction unit 324b selects imaging data from among the plurality of imaging data in which the part of the metal band included in one imaging data matches the part of the metal band included in another imaging data. select. More specifically, the position correction unit 324b selects data that includes a specific part of the metal band 10 from among the plurality of imaging data. For example, the position correction unit 324b performs position correction on a plurality of angle-corrected image data to distinguish between a specific part of the metal band 10 included in one image data and that of other image data. The positions of the specific region on the imaging data can be matched.

Thereby, the imaging data acquired by the imaging unit is associated as data at the same position within the plane of the metal band. That is, it is possible to obtain information on reflected light when the same position on the surface of the metal band is irradiated with light of different wavelength bands at different angles with respect to the conveyance direction of the metal band.

By including the position correction section 324b, the surface inspection apparatus 100 eliminates the need to adjust the positional relationship to match the irradiation range of each of the first to third light emitting elements 311 to 313. That is, it is possible to use image data obtained by imaging the same part of the metal band 10 for determination without adjusting the imaging ranges of the first to third image sensors 314 to 316.

Therefore, by including the position correction unit 324b, the surface inspection apparatus 100 includes the first to third light emitting elements 311 to 313 and the first to third image pickup elements 314 to 316 paired with these elements. The degree of freedom in the arrangement can be increased.

The defect determination unit 324c determines whether or not an uneven defect is formed in the inspection target based on the imaging data. For example, the defect determination unit 324c can determine that an uneven defect is formed in the inspection target when a contrast equal to or higher than a predetermined threshold is detected.

The display unit 33 displays the determination result output from the determination unit 32. For example, a display such as a liquid crystal display can be used as the display unit 33. Furthermore, the display section 33 may include a speaker that outputs audio. That is, the display unit 33 may notify the worker of the determination result using audio according to the received determination result.

3 to 5 show the arrangement relationship between the first light emitting element 311 and the first imaging element 314. Specifically, the first image sensor 314 is arranged at a position where it can image the reflected light that is emitted from the first light emitting element 311 and reflected on the surface of the metal band 10 .

As shown in FIG. 3, the first image sensor 314 and the first light emitting element 311 are arranged to face each other when viewed from above the transport section 20. The optical axis AX1 of the first light emitting element 311 forms an angle β1 with the axis AX2 perpendicular to the surface of the metal band 10. Further, the optical axis AX3 of the first image sensor 314 forms an angle β2 with the axis AX2 in the direction perpendicular to the surface of the metal band 10. In the example shown in FIG. 3, the angle β1 is approximately the same as the angle β2.

In other words, the angle that the optical axis AX1 of the first light emitting element 311 as a pair makes in one direction D, and the angle that the optical axis AX3 of the first image sensor 314 as a pair makes in one direction D. They are placed at similar positions. By arranging the first image sensor 314 in this way, it is possible to clearly image the uneven defect on the metal band 10.

In this way, the first image sensor 314 can be placed at a position where it can image the specularly reflected light of the first light emitting element 311. In other words, in the example shown in FIG. 3, the imaging range of the first image sensor 314 is set to be able to image specularly reflected light.

Furthermore, in the example shown in FIG. 4, the angle β1 that the optical axis AX1 of the first light emitting element 311 makes with the axis AX2 is smaller than the angle β2 that the optical axis AX3 of the first image sensor 314 makes with the axis AX2. small.

In other words, the angle that the optical axis AX1 of the first light emitting element 311 as a pair makes in one direction D, and the angle that the optical axis AX3 of the first image sensor 314 as a pair makes in one direction D. They may be arranged at different positions. By arranging the first image sensor 314 in this way, it is possible to clearly image the uneven defect on the metal band 10.

The attenuation behavior of the reflected light reflected by the inclined surface of the uneven defect changes depending on the difference between the angle β1 and the angle β2. Therefore, the determination unit 32 can obtain detailed information including the contour shape of the slope of the uneven defect, and can discriminate the uneven defect in detail. Note that, in order to ensure that the amount of reflected light received by the first image sensor 314 is sufficient, the difference between the angle β1 and the angle β2 is preferably 15 to 45 degrees.

In this way, the first image sensor 314 may be arranged at a position where it can image the forward scattering of the diffusely reflected light from the first light emitting element 311. In other words, the imaging range of the first image sensor 314 may be set to be able to image forward scattered light among the diffusely reflected light.

Furthermore, in the example shown in FIG. 5, the angle β1 that the optical axis AX1 of the first light emitting element 311 makes with the axis AX2 is smaller than the angle β2 that the optical axis AX3 of the first image sensor 314 makes with the axis AX2. It is small and smaller than the example shown in FIG.

In this way, the first image sensor 314 may be arranged, for example, at a position where backscattered light of the diffusely reflected light from the first light emitting element 311 can be imaged. In other words, the imaging range of the first image sensor 314 may be set to be able to image backscattered light among the diffusely reflected light.

By arranging the first image sensor 314 in this way, it is possible to receive reflected light in a manner different from the example shown in FIG. Obtainable.

Note that the second light emitting element 312 and the second image sensor 315 may be arranged in the same manner as the first light emitting element 311 and the first image sensor 314, or may be arranged in a different manner. Good too. Further, the third light emitting element 313 and the third image sensor 316 have the same configuration as the first light emitting element 311 and the second light emitting element 312, and the first image sensor 314 and the second image sensor 315. It may be arranged in this manner, or it may be arranged in a different manner. That is, each of the first light emitting element 311, the second light emitting element 312, and the third light emitting element 313 has an optical axis facing the conveyance section 20, and each of the optical axes and the same direction. The angles may be different from each other.

FIG. 6 shows the arrangement of the first light emitting element 311 and the first imaging element 314 as seen from above the transport section 20. As shown in FIG. 6, when viewed from above the transport section 20, the light emitted from the first light emitting element 311 is irradiated onto the metal band 10 so as to include the width direction of the metal band 10. In this embodiment, the light emitted from the first light emitting element 311 is irradiated across the width direction of the metal band 10 .

That is, in this embodiment, when viewed from above the conveyance unit 20, the irradiation range AR1 of the emitted light is formed on the surface of the metal band 10 in the width direction thereof. Specifically, the irradiation range AR1 of the emitted light is formed in a line shape extending along the width direction of the metal band 10. The irradiation range AR1 of the emitted light forms an angle α with one direction D. Note that the angle α is preferably set in advance. Furthermore, the positional relationship between the first light emitting element 311 and the first imaging element 314 can be specified based on the angle α, the angle β1, and the angle β2.

The first image sensor 314 is installed so that the imaging range includes the irradiation range AR1 of the emitted light. Therefore, the first image sensor 314 is provided so as to be able to receive the reflected light reflected in the irradiation range AR1. In this embodiment, since the irradiation range AR1 and the imaging range are the same, they will be described with the same reference numerals hereinafter.

Note that the second light emitting element 312, the second image sensor 315, the third light emitting element 313, and the third image sensor 316 are the same as the first light emitting element 311 and the first image sensor 314. can be placed in

FIG. 7 shows an example of the arrangement of the first to third light emitting elements 311 to 313 and the first to third image sensors 314 to 316. In FIG. 7, the irradiation range AR1 of the first light emitting element 311 is shown. An irradiation range AR2 of the second light emitting element 312 is shown. An irradiation range AR3 of the third light emitting element 313 is shown.

The first light emitting element 311 to the third light emitting element 313 and the first image sensor 314 to the third image sensor 316 are arranged such that, for example, at least two of the irradiation ranges AR1 to AR3 intersect with each other. Preferably. In other words, each of the first to third light emitting elements 311 to 313 is preferably arranged such that the irradiation ranges of at least two emitted lights intersect at one point.

As in the embodiment shown in FIG. 7, each of the first to third light emitting elements 311 to 313 is preferably arranged so that the irradiation ranges of the three emitted lights intersect at one point. In FIG. 7, the irradiation ranges AR1 to AR3 intersect with each other at the widthwise center of the metal band 10 when viewed from one direction D.

Note that the first to third light emitting elements 311 to 313 and the first to third imaging elements 314 to 316 can be freely provided depending on the embodiment.

8 to 10 show the irradiation ranges AR1 to AR3 in the metal band 10, respectively. For example, as shown in FIG. 8, the first to third light emitting elements 311 to 313 may be arranged so that the irradiation ranges AR1 to AR3 do not intersect with each other.

Further, for example, as shown in FIG. 9, each of the irradiation ranges AR1 to AR3 may have one intersection. In FIG. 9, the irradiation ranges AR2 and AR3 intersect with each other at the center of the width direction of the metal band 10 when viewed from one direction D.

Furthermore, as shown in FIG. 10, each of the irradiation ranges AR1 to AR3 may have two intersections. In FIG. 10, the irradiation ranges AR1 and AR3 intersect with each other at one end side in the width direction of the metal band 10 when viewed from one direction D. Further, the irradiation ranges AR2 and AR3 intersect with each other at the other end side in the width direction of the metal band 10 when viewed from one direction D. Note that the intersection of the irradiation ranges AR1 and AR3 is located upstream in one direction D than the intersection of the irradiation ranges AR2 and AR3.

For example, each of the irradiation ranges AR1 to AR3 can be set to have a different angle with respect to one direction D. The angle that each of the irradiation ranges AR1 to AR3 makes with respect to one direction D is preferably set in advance and stored in the storage unit 322.

Note that, as described above, in this embodiment, the imaging ranges of the first to third imaging elements 314 to 316 match the irradiation ranges AR1 to AR3. Therefore, the imaging ranges of the first image sensor 314 to the third image sensor 316 will be described using the same symbols as the irradiation ranges AR1 to AR3. Further, it is preferable that the angle that each of the imaging ranges AR1 to AR3 makes with respect to one direction D is set in advance and stored in the storage unit 322.

In the embodiment shown in FIG. 7, the angle that the irradiation range AR1 makes with respect to one direction D is 90°. The angle that the irradiation range AR2 makes with respect to one direction D is 135°. The angle that the irradiation range AR3 makes with respect to one direction D is 45°. In other words, the irradiation range AR1 of the first light emitting element 311 has a linear shape extending in the width direction of the metal band 10 when viewed from one direction D.

Note that any one of the first to third light emitting elements 311 to 313 and the first to third image pickup elements 314 to 316 may be located on the upstream side in one direction D.

The first to third light emitting elements 311 to 313 each emit light in a line shape, each selected from different wavelength bands of RGB, for example. In this embodiment, the first light emitting element 311 emits light in a blue wavelength band.

The first image sensor 314 images the light emitted from the first light emitting element 311 in the blue wavelength band. The second light emitting element 312 emits light in the red wavelength band. The second image sensor 315 images the light emitted from the second light emitting element 312 in the red wavelength band. The third light emitting element 313 emits light in the green wavelength band. The third image sensor 316 images the light emitted from the third light emitting element 313 in the green wavelength band.

As described above, according to the surface inspection apparatus 100 for the metal strip 10 according to the present embodiment, the imaging range is set to include the irradiation range of the emitted light of wavelengths that are mutually distinguishable. It becomes possible to visually inspect the metal strip 10 for defects.

Moreover, the surface inspection apparatus 100 for the metal strip 10 includes at least one of the angle correction section 324a and the position correction section 324b, so that each image pickup is performed as if the data were at the same position on the surface of the metal strip 10. Able to process data. This makes it possible for the defect determination unit 324c to determine uneven defects using more detailed data.

The surface inspection apparatus 100 for the metal strip 10 is preferably used after at least one step is performed in the manufacturing process of the metal strip 10, which includes a plurality of steps. In other words, the metal strip 10 is preferably manufactured using the surface inspection apparatus 100 for the metal strip 10.

The manufacturing process for the metal strip 10 includes, for example, a steel manufacturing process in which a slab is cast, a hot rolling process in which the slab becomes a hot-rolled metal band, and a pickling process in which oxides on the surface of the hot-rolled metal band are removed. , a cold rolling process in which a hot-rolled metal strip from which oxides have been removed is cold-rolled to a predetermined thickness. In addition to these steps, manufacturing steps include a plurality of steps such as an annealing step for softening the metal strip 10, plating, and temper rolling.

A method for inspecting the surface of the metal strip 10 using the surface inspection apparatus 100 for the metal strip 10 described above will be described. FIG. 11 is a flow diagram of the surface inspection of the metal strip 10. Routine R1 of the method for inspecting the surface of the metal strip 10 is started, for example, with detection of the start of the conveyance unit 20 as a trigger.

As shown in FIG. 11, when the routine R1 of the surface inspection method for the metal strip 10 is started, the control section 324 transports the metal strip 10 in one direction D by operating the transport section 20 (step S101).

When the conveyance step of step S101 is performed, the control unit 324 causes the metal band 10 to be irradiated with light emitted from the first to third light emitting elements 311 to 313 at mutually distinguishable wavelengths (step S102).

In the irradiation step of step S102, the control unit 324 causes each output light to be emitted toward the irradiation ranges AR1 to AR3 set along the width direction of the metal band 10. For example, the control unit 324 causes the first light emitting element 311 to emit blue light. The control unit 324 causes the second light emitting element 312 to emit red light. The control unit 324 causes the third light emitting element 313 to emit green light.

The control unit 324 controls a plurality of linear imaging ranges AR1 to AR3, which are set to be paired with the irradiation ranges AR1 to AR3 and extend along the width direction of the metal band 10, to each other in one direction D. They are set to form different angles (step S103).

The setting step of step S103 may be performed in advance before routine R1 of the surface inspection method is started. The control unit 324 may set the imaging ranges AR1 to AR3 by reading out the imaging ranges AR1 to AR3 stored in the storage unit 322, for example.

The first to third image sensors 314 to 316 generate image data using the received light in a specific band (step S104). Specifically, the first image sensor 314 generates image data of the metal band 10 imaged so as to include the irradiation range AR1 paired with the image capture range AR1. The second image sensor 315 generates image data of the metal band 10 imaged to include the irradiation range AR2 that is paired with the image capture range AR2. The third image sensor 316 generates image data of the metal band 10 that is imaged to include the irradiation range AR3 that is paired with the image capture range AR3. The imaging unit 31 transmits each piece of imaging data generated in the imaging data generation step of step S103 to the determination unit 32.

Upon receiving the imaging data, the control unit 324 stores it in the storage unit 322 in chronological order. The control unit 324 determines a defect in the metal band 10 based on the received imaging data (step S105).

The determination step of step S105 is executed as subroutine R2. FIG. 12 shows the subroutine R2 of the determination step. As shown in FIG. 12, the control unit 324 refers to the storage unit 322 and obtains the angle that the imaging ranges AR1 to AR3 make with respect to one direction D (step S201).

The angle correction unit 324a corrects the imaging data so that the angle acquired in the angle information acquisition step of step S201 approaches the reference angle (step S202).

For example, in the example shown in FIG. 6, the first image sensor 314 generates image data tilted by an angle α with respect to one direction D. Furthermore, in the example shown in FIG. 7, the first to third image sensors 314 to 316 each generate image data tilted at different angles with respect to one direction D.

In the angle correction step of step S202, the angle correction unit 324a corrects these imaging data so that they approach the reference angle. For example, the angle correction unit 324a takes the imaging range AR1 as a reference angle and corrects the imaging ranges AR2 and AR3 so that they approach the reference angle.

FIG. 13 is a schematic diagram in which image data generated by the first image sensor 314 during a predetermined period is associated with the position of the surface of the metal band 10. For example, the imaging data at time t0 is generated with the position of the metal band 10 in the width direction shifted when viewed from one direction D. Specifically, the imaging data is generated at a position where the lower side of FIG. 13 is shifted in one direction D side from the upper side.

FIG. 14 schematically shows how the angle correction section 324a performs angle correction of detection data at each time. The angle correction unit 324a selects the image data to be processed (in this embodiment, the second image sensor 315 and the third image sensor 316) among the image data generated by the first image sensor 314 to the third image sensor 316. (imaging data of the image sensor 316) are arranged in chronological order. The angle correction unit 324a moves each pixel to the same position in the width direction of the metal band 10 with respect to the imaging data for each time series (relocation data).

For example, the angle correction unit 324a uses the detection data at time t0 as a reference pixel at the center of the plate width, and adjusts the detection data so that the data extends in the width direction of the metal band 10 from the reference (extends in the vertical direction in the figure). ) to move pixels. In other words, the angle correction unit 324a corrects the image data captured by the image sensor so that, for example, the angle formed with respect to one direction D of the imaging ranges AR2 and AR3 becomes the reference angle (90°).

Imaging data is generated at each preset scan rate in the first to third imaging elements 314 to 316. That is, the angle correction unit 324a can associate the position of the surface of the metal band 10 with the imaging data by reading out the scan rate and the transport speed of the transport unit 20 from the storage unit 322.

Further, it is preferable to synchronize the imaging timing of the first to third imaging elements 314 to 316 and the conveyance speed of the metal band 10. Specifically, the timing at which the metal band 10 reaches each of the imaging ranges AR1 to AR3 may be synchronized with the imaging timing of the first to third imaging elements 314 to 316. By synchronizing these, the imaging data is generated at a constant pitch with respect to the surface of the metal band 10, so that it is possible to easily associate the imaging data with the position of the surface of the metal band 10.

The angle correction unit 324a preferably performs angle correction on the image data acquired from the first to third image sensors 314 to 316. For example, when the reference angle is 90°, the imaging data is converted to data arranged in the width direction of the metal strip 10 on the surface thereof.

For example, if the angle that the imaging range AR1 makes with respect to one direction D is 90°, the imaging data of the imaging ranges AR2 and AR3 may be corrected by using the imaging data of the imaging range AR1 as a reference. good.

Further, as shown in FIGS. 7, 9, and 10, when at least one intersection is provided by each of the imaging ranges AR1 to AR3, the angle correction unit 324a rotates the imaging data around the intersection of the imaging ranges. It is preferable to perform angle correction as follows. This eliminates the need for position correction processing, making it possible to simplify the correction processing.

The angle correction unit 324a may perform complementation processing to rearrange data according to the timing of generation of imaged data. FIG. 15 is an example in which imaging data acquired at a predetermined time is associated with the position of the surface of the metal band 10. The angle correction unit 324a uses, for example, pixel data a1 at the first position at time t1 as a reference. The angle correction unit 324a moves the pixel data b1 at the second position, the pixel data c1 at the third position, and the pixel data d1 at the fourth position at time t1 to the position of the reference pixel data a1. let That is, in the width direction of the metal band 10, the pixel data b1, c1, and d1 are moved to the position of the pixel data a1. Imaging data in the second and subsequent columns may be selected in such a manner that they straddle adjacent pixels. In this case, the angle correction unit 324a may weight the brightness of adjacent pixels depending on the degree to which the pixel positions overlap, and obtain a new brightness value.

For example, in the example of FIG. 15, when pixel data a1 at the first position is used as a reference, the same position as a1 in the board width direction is a range that straddles pixels b1 and b2 in the second column. At this time, the weighting coefficients for the pixels b1 and b2 in the second row can be determined from the interval in the plate width direction between the pixels in the first row and the pixels in the second row and the angle α of the irradiation range. Therefore, the sum of the weighting coefficients multiplied by the pixels b1 and b2 in the second column can be used as the brightness value of the rearrangement data.

FIG. 16 shows an example of angle correction by the angle correction section 324a. Similar to the example shown in FIG. 8, FIG. 16 shows an example in which the imaging ranges AR1 to AR3 do not intersect with each other in the metal band 10.

In this figure, an example will be described in which the angle correction unit 324a corrects the imaging data using 90° as a reference angle. The imaging range AR1 has an angle α of 90° and has a line shape extending in the board width direction. The angle correction unit 324a does not correct the imaging data obtained in the imaging range AR1 because it does not require correction.

The angle correction unit 324a corrects the angle that the imaging range AR2 makes with respect to one direction D to be 90°, thereby generating a virtual imaging range AR21. The angle correction unit 324a corrects the angle that the imaging range AR3 makes with respect to one direction D to be 90°, thereby generating a virtual imaging range AR31.

By performing the angle correction in this manner, each pixel value of the imaging data can be arranged in the width direction of the metal strip 10 on the surface of the metal strip 10. Thereby, a plurality of imaging data at the same position in the longitudinal direction of the metal band 10 can be generated.

For example, the position correction unit 324b determines, from the plurality of image data corrected by the angle correction unit 324a, the part of the metal band 10 included in one image data and the part of the metal band 10 included in the other image data. Select imaging data that matches the region. (Step S203). The position correction step of step S203 is executed as subroutine R3.

FIG. 17 shows the subroutine R3 of the position correction step of step S203. As shown in FIG. 17, the position correction unit 324b acquires correction data that is the imaging data corrected in the angle correction step of step S202 (step S301).

When the correction data acquisition step of step S301 is executed, the position correction unit 324b selects imaging data that includes a specific part of the metal band 10 from among the plurality of acquired correction data (step S302). .

FIG. 18 shows a mode of position correction of a plurality of correction data by the position correction section 324b. As shown in FIG. 18, the imaging range AR1 and the virtual imaging ranges AR21 and AR31 form an angle of 90° with respect to one direction D.

The imaging range AR1 and the virtual imaging ranges AR21 and AR31 are arranged offset from each other in one direction D. That is, the correction data of the virtual imaging ranges AR21 and AR31 is data at a position shifted in one direction D from the imaging data of the imaging range AR1 generated at the same time.

The position correction unit 324b selects imaging data including a specific part of the metal band 10 imaged in the imaging range AR1 from among the imaging data in the virtual imaging range AR21. Similarly, the position correction unit 324b selects imaging data including a specific part of the metal band 10 imaged in the imaging range AR1 from among the imaging data in the virtual imaging range AR31. Thereby, all the imaging data are arranged in the board width direction on the surface of the metal strip 10, and a set of imaging data at the same position with respect to the longitudinal direction of the metal strip can be generated.

Note that the position correction unit 324b stores in advance the distances between the imaging range AR1, the virtual imaging ranges AR21 and AR21, AR21, and the reference position in the storage unit 322, and calculates the distance and the transport speed of the transport unit 20, for example. By referring to it, position correction can be performed.

FIG. 19 is a cross-sectional view of the metal strip 10 showing an example of an uneven defect. As shown in FIG. 19, the metal strip 10 has uneven defects 11 that are recessed from the surface. FIG. 20 is an example of imaging data of the uneven defect 11 in FIG. 19. As shown in FIG. 20, the region having the uneven defect has a darker (darker) color than the surrounding region.

The defect determination unit 324c determines whether the uneven defect 11 is formed on the metal band 10, for example, based on the imaging data corrected by the position correction unit 324b. Hereinafter, a case where the metal strip 10 shown in FIG. 19 has a circular uneven defect 11 will be described.

21 to 23 show modes in which the imaging range of the first image sensor 314 is set at a position where specularly reflected light from the first light emitting element 311 can be imaged. FIG. 24 is an example of imaging data of the uneven defects shown in FIGS. 21 to 23.

In a flat region where no uneven defects are formed as shown in FIG. 21, imaging data with uniform brightness is obtained as shown in FIG. 24(a).

As shown in FIG. 22, when the inclination of the uneven defect 11 is along the optical axis of the first light emitting element 311 (negative inclination: inclination in the direction in which the recess becomes deeper with respect to the conveyance direction of the metal band 10) , the reflected light is scattered according to the inclination of the uneven defect 11. Therefore, as shown in FIG. 24(b), the amount of reflected light received by the first image sensor 314 is lower than the amount of reflected light reflected from a flat portion.

As shown in FIG. 23, when the inclination of the uneven defect 11 is not along the optical axis of the first light emitting element 311 (positive inclination: inclination in the direction in which the recess becomes shallow with respect to the conveyance direction of the metal strip), The reflected light is scattered according to the inclination of the uneven defect 11. Therefore, as shown in FIG. 24(c), the amount of reflected light received by the first image sensor 314 is lower than the amount of reflected light reflected from a flat portion.

As shown in FIG. 24, the defect determination unit 324c determines the presence or absence of an uneven defect based on imaging data in which the contrast between the area corresponding to the uneven defect and the surrounding area is high. Therefore, the defect determination unit 324c can clearly detect the uneven defect.

25 to 27 show modes in which the imaging range of the first image sensor 314 is set at a position where diffusely reflected light from the first light emitting element 311 can be imaged. FIG. 28 is an example of imaging data of the uneven defects shown in FIGS. 25 to 27.

In a flat region where no uneven defects are formed as shown in FIG. 25, imaging data with uniform brightness is obtained as shown in FIG. 28(a).

As shown in FIG. 26, when the inclination of the uneven defect 11 is along the optical axis of the first light emitting element 311 (negative inclination: inclination in the direction in which the recess becomes deeper with respect to the conveyance direction of the metal band 10) , the reflected light is scattered according to the inclination of the uneven defect 11. Therefore, as shown in FIG. 28(b), the amount of reflected light received by the first image sensor 314 is lower and darker than the reflected light reflected from a flat area.

As shown in FIG. 27, when the inclination of the uneven defect 11 is not along the optical axis of the first light emitting element 311 (positive inclination: inclination in the direction in which the recess becomes shallow with respect to the conveyance direction of the metal strip), The reflected light is scattered according to the inclination of the uneven defect 11. Specifically, since the direction of the reflected light approaches the optical axis of the diffusely reflected light, the amount of reflected light received by the first image sensor 314 is as shown in FIG. 28(c). It becomes higher and brighter than the reflected light reflected from a flat area.

In this manner, when the first to third image sensors 314 to 316 are provided to be able to image diffusely reflected light, the amount of light that receives the diffusely reflected light changes depending on the inclination of the slope of the uneven defect. Therefore, the defect determination unit 324c can determine the inclination of the slope of the uneven defect based on the change in the amount of reflected light.

As shown in FIG. 28, by providing the first image sensor 314 to the third image sensor 316 so as to be able to image diffusely reflected light, the defect determination unit 324c acquires information regarding the inclination of the slope part of the uneven defect. can do.

Next, a case will be described in which the first to third light emitting elements 311 to 313 emit light of different tones. Specifically, the first light emitting element 311 emits light of a blue tone, the second light emitting element 312 emits light of a red tone, and the third light emitting element 313 emits light of a green tone. Let me explain the case.

As shown in FIG. 7, when the first light emitting element 311 to the third light emitting element 313 and the first image sensor 314 to the third image sensor 316 are arranged, the imaging ranges AR1 to AR3 are arranged in one direction D. make different angles to each other. Furthermore, each of the imaging ranges AR1 to AR3 intersects at the center of the metal band 10 in the width direction when viewed from one direction D. Note that an example will be described in which the first image sensor 314 to the third image sensor 316 are arranged so as to be able to receive specularly reflected light from the first light emitting element 311 to the third light emitting element 313.

FIG. 29 is a cross-sectional view of the metal strip 10 showing an example of an uneven defect. As shown in FIG. 29, the metal strip 10 has uneven defects 11 that are recessed from the surface. FIG. 30 is an example of imaging data of the uneven defect 11 in FIG. 29. As shown in FIG. 30, the region having the uneven defect has a deeper (darker) color than the surrounding region.

FIG. 31 shows composite data obtained by combining the image data captured by the first to third image sensors 314 to 316 after being subjected to angle correction and position correction processing. In FIG. 31, the shading of each color is schematically shown. The uneven defect is formed in a circular shape when viewed from above. In uneven defects, emitted light in a specific wavelength band is attenuated in a specific direction. In the example shown in FIG. 31, imaging data is generated based on specularly reflected light. Therefore, the intensity of the reflected light of the uneven defect is about the same for both the positive slope and the negative slope. Note that in the flat part of the metal band 10, the color tones of blue, red, and green are mixed, so that the color becomes white. However, in the field of surface inspection technology for metal strips, if flat parts are displayed in white, unevenness such as metallic luster may not be detected. For this reason, imaging data is often corrected so that the brightness is adjusted so that flat areas are displayed in gray. Therefore, the image is shown in which the flat portion of the metal band 10 in FIG. 31 is adjusted to be gray instead of white.

For example, in FIG. 31, in the image area IM1 located in the left-right direction, the influence of the blue color among the light emitted from the first to third light-emitting elements 311 to 313 is small. Therefore, the image area IM1 is colored yellow.

In the image area IM2 located from the upper left to the lower right, the influence of the green color among the light emitted from the first to third light emitting elements 311 to 313 is small. Therefore, the image area IM2 is colored pink.

In the image area IM3 located from the lower left to the upper right, the influence of the red color among the light emitted from the first to third light emitting elements 311 to 313 is small. Therefore, the image area IM3 is colored pale (bright) blue.

In this way, in the region where the uneven defect is formed, the intensity of the specularly reflected light received by the first to third image sensors 314 to 316 changes. Therefore, the defect discrimination unit 324c can discriminate uneven defects based on color.

Next, an example will be described in which the first image sensor 314 to the third image sensor 316 are arranged so as to be able to receive diffusely reflected light from the first light emitting element 311 to the third light emitting element 313. Note that the cross-sectional shape of the metal band 10 is the same as that in FIG. 29, so the explanation will be omitted.

FIG. 32 is an example of imaging data of the uneven defect 11 in FIG. 29. As shown in FIG. 32, the region having the uneven defect has a lighter (brighter) color in the region to the left of the center than in the surrounding region.

In a region having a concave-convex defect, the region to the right from the center has a darker (darker) color than the surrounding region.

FIG. 33 shows composite data obtained by combining the image data captured by the first to third image sensors 314 to 316 after being subjected to angle correction and position correction processing. In FIG. 33, the shading of each color is schematically shown. The uneven defect is formed in a circular shape when viewed from above. In uneven defects, emitted light in a specific wavelength band is attenuated in a specific direction. In the example shown in FIG. 33, imaging data is generated based on diffusely reflected light. Note that in the flat part of the metal band 10, the color tones of blue, red, and green are mixed, resulting in a white color.

For example, in the image area IM4 located to the left in FIG. 33, the influence of the blue color among the light emitted from the first to third light emitting elements 311 to 313 is large. Therefore, the image area IM4 is colored blue.

In the image area IM5 located at the upper left, the influence of the green color among the light emitted from the first to third light emitting elements 311 to 313 is large. Therefore, the image area IM5 is colored green.

In the image area IM6 located at the lower left, the influence of the red color among the light emitted from the first to third light emitting elements 311 to 313 is large. Therefore, the image area IM6 is colored red.

In the image area IM7 located in the right direction, the influence of the blue color among the light emitted from the first to third light emitting elements 311 to 313 is reduced. Therefore, the image area IM7 is colored pale (bright) yellow.

In the image area IM8 located in the upper right direction, the influence of the red color among the light emitted from the first to third light emitting elements 311 to 313 is small. Therefore, the image area IM8 is colored pale (bright) blue.

In the image area IM9 located in the lower right direction, the influence of the green color among the light emitted from the first to third light emitting elements 311 to 313 is small. Therefore, the image area IM9 is colored pink.

As shown in FIG. 33, the intensity of the diffusely reflected light received by the first image sensor 314 to the third image sensor 316 varies depending on whether the slope is positive or negative with respect to one direction D. Change. Therefore, the defect determination unit 324c can determine the presence or absence of an uneven defect based on the color. Furthermore, the defect determining unit 324c can determine information regarding the inclination direction of the inclined surface of the uneven defect, that is, whether it is a positive inclination or a negative inclination, based on the color.

Specifically, depending on the degree of inclination of the uneven defect with respect to one direction D, a specific color of the emitted light is emphasized and imaged. Therefore, the defect determination unit 324c can determine the degree of inclination of the uneven defect with respect to one direction D based on the color of the image data.

In this way, by providing the first to third image pickup elements 314 to 316 to image the diffusely reflected light, it is possible to determine the direction of inclination of the slope part of the uneven defect. That is, in this aspect, it is possible to acquire not only the contour shape of the uneven defect when viewed from above, but also information regarding the shape of the inclined surface thereof.

As described above, according to the method for inspecting the surface of the metal strip 10 of the present invention, uneven defects on the metal strip 10 can be detected with high precision. Therefore, even fine-shaped uneven defects and gentle uneven-shaped uneven defects can be detected with high precision.

Furthermore, more detailed information can be obtained by using data that has been subjected to angle correction processing and position correction processing for each of the imaging data generated in the imaging ranges AR1 to AR3 for determining uneven defects. can. Thereby, the detection accuracy of uneven defects can be improved. That is, by using the composite data obtained by combining these data for determining the uneven defect, it is possible to detect not only the contour shape of the uneven defect but also the shape and degree of inclination of its sloped surface.

Note that it is preferable to store a composite image detected using the surface inspection apparatus of this embodiment in the storage unit 322 as a sample for a typical example of the uneven defect to be determined. The defect determination unit 324c may determine the uneven defect by comparing the representative example with the imaging data (including composite data). By performing the determination in this manner, the defect determination unit 324c can further improve the accuracy in determining uneven defects.

As described above, by manufacturing the metal strip 10 using the surface inspection apparatus 100 for the metal strip 10 of the present invention, it is possible to provide the metal strip 10 to a customer in a state with few uneven defects. Thereby, it is possible to improve customer satisfaction.

100 Metal band surface inspection device 10 Metal band 20 Conveyance unit 30 Defect detection unit 31 Imaging unit 311-313 Light-emitting element 314-316 Imaging element 32 Judgment unit 324a Angle correction unit 324b Position correction unit 324c Defect determination unit AR1-AR3 Imaging range (irradiation range)

Claims (15)

a plurality of light-emitting elements having optical axes facing a metal strip that is conveyed in one direction; and a plurality of light-emitting elements having optical axes facing the metal belt and being paired with the plurality of light-emitting elements. an imaging unit having a plurality of imaging elements;
a determination unit that determines a defect in the metal band based on imaging data generated by the imaging unit;
Each of the plurality of light emitting elements is provided so that it emits emitted light of a mutually distinguishable wavelength, and the irradiation range of the emitted light includes the width direction of the metal band,
Each of the plurality of image sensors has an imaging range set to include the irradiation range of the paired light emitting element,
In the metal band surface inspection apparatus, each of the imaging ranges is provided in a line shape along the width direction of the metal band, and is provided at different angles with respect to the one direction. The metal band according to claim 1, wherein the angle that the optical axes of the pair of image sensors make in the one direction is equal to the angle that the optical axes of the pair of light emitting elements make in the one direction. Surface inspection equipment. The metal band according to claim 1, wherein the angle that the optical axes of the paired image sensors make in the one direction is different from the angle that the optical axes of the paired light emitting devices make in the one direction. Surface inspection equipment. The determination unit includes an angle correction unit that corrects the image data captured by the image sensor so that the angle of the imaging range with respect to the one direction approaches a reference angle,
The metal strip surface inspection apparatus according to claim 1, wherein the determination section determines a defect in the metal strip based on the imaging data corrected by the angle correction section. The determination unit includes an angle correction unit that corrects the image data captured by the image sensor so that the angle of the imaging range with respect to the one direction approaches a reference angle,
The metal strip surface inspection apparatus according to claim 2, wherein the determination section determines a defect in the metal strip based on the imaging data corrected by the angle correction section. The determination unit includes an angle correction unit that corrects the image data captured by the image sensor so that the angle of the imaging range with respect to the one direction approaches a reference angle,
The metal strip surface inspection apparatus according to claim 3, wherein the determination section determines a defect in the metal strip based on the imaging data corrected by the angle correction section. The determination unit selects a plurality of pieces of imaging data in which a part of the metal band included in one of the imaging data matches a part of the metal band included in another of the imaging data. Including a position correction section that selects from data,
The metal strip surface inspection apparatus according to claim 4, wherein the determination section determines a defect in the metal strip based on the imaging data selected by the position correction section. The determination unit selects a plurality of pieces of imaging data in which a part of the metal band included in one of the imaging data matches a part of the metal band included in another of the imaging data. Includes a position correction unit that selects from data,
The metal strip surface inspection apparatus according to claim 5, wherein the determination section determines a defect in the metal strip based on the imaging data selected by the position correction section. The determination unit selects a plurality of pieces of imaging data in which a part of the metal band included in one of the imaging data matches a part of the metal band included in another of the imaging data. Includes a position correction unit that selects from data,
The metal strip surface inspection apparatus according to claim 6, wherein the determination section determines a defect in the metal strip based on the imaging data selected by the position correction section. 10. The metal strip surface inspection apparatus according to claim 1, wherein each of the imaging elements is arranged so that at least two of the imaging ranges intersect at one point. The metal strip surface inspection apparatus according to any one of claims 1 to 9, wherein the imaging range of at least one image sensor extends in the width direction of the metal strip. a conveyance step of conveying the metal strip in one direction;
an irradiation step of irradiating a plurality of emitted lights with mutually distinguishable wavelengths toward a plurality of irradiation ranges set along the width direction of the metal band;
a setting step of setting a plurality of line-shaped imaging ranges that are set to be paired with the irradiation range and extend along the width direction of the metal band so as to form mutually different angles with respect to the one direction; and,
an imaging data generation step of generating imaging data of the metal band imaged to include the irradiation range that is paired with the imaging range, according to the imaging range set in the setting step;
A method for inspecting the surface of a metal strip, the method comprising: determining a defect in the metal strip based on a plurality of pieces of the imaging data. The determination step includes:
an angle information acquisition step of acquiring an angle that each of the imaging ranges makes in the one direction;
13. The surface inspection method according to claim 12, further comprising: an angle correction step of correcting the imaging data so that the angle obtained in the angle information obtaining step approaches a reference angle. The determining step includes selecting a plurality of pieces of imaging data in which the part of the metal band included in the one imaging data matches the part of the metal band included in the other imaging data. 14. The surface inspection method according to claim 13, further comprising a position correction step of selecting from among the captured image data. A method for manufacturing a metal strip using the metal strip surface inspection apparatus according to any one of claims 1 to 9.

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