Metal foil inspection method and inspection system used therefor
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- MITSUI MINING & SMELTING CO LTD
- Filing Date
- 2025-10-21
- Publication Date
- 2026-06-25
Smart Images
Figure JP2025036937_25062026_PF_FP_ABST
Abstract
Description
Method for inspecting metal foil and inspection system used therefor
[0001] The present disclosure relates to a method for inspecting a metal foil and an inspection system used therefor.
[0002] Conventionally, for copper foil that is roll-conveyed at high speed, detection of foreign matter that may be present on the surface of the copper foil has been carried out. This foreign matter detection is performed, for example, as disclosed in Patent Document 1 (Japanese Patent No. 4136938), by scanning the surface of the copper foil with a CCD to detect portions that are considered defective, and by performing detailed foreign matter verification with a verification device installed downstream of the CCD.
[0003] Conventional foreign matter inspection machines such as those disclosed in Patent Document 1 have two types of optical systems, and foreign matter is detected based on information obtained from two types of reflections. That is, one is an optical system for regular reflection measurement in which a light source and a CCD sensor are arranged at the same angle with respect to the perpendicular line to the foil surface. The other is an optical system for diffuse reflection measurement in which a CCD sensor is arranged at a position perpendicular to the foil surface, and two light sources are arranged at the same angle with respect to the foil surface. In regular reflection, light does not reflect in the direction of the CCD sensor from the roughened foil surface, whereas a large amount of light reflects to the CCD sensor from a portion with low roughness such as the surface of a foreign object. Therefore, the rubbed portion of the foreign object appears white, and the foreign object can be discovered by the difference in brightness. On the other hand, in diffuse reflection, contrary to regular reflection, a large amount of light reflects in the direction of the CCD sensor from the roughened foil surface, whereas light does not reflect in the direction of the CCD sensor from a portion with low roughness such as a foreign object. Therefore, the rubbed portion of the foreign object appears black, and the foreign object can be discovered by the difference in brightness. And when these two characteristics are detected at the same position, it is determined as a problematic foreign object.
[0004] Japanese Patent No. 4136938
[0005] Conventional foreign object inspection methods, as described above, rely on differences in roughness between the foreign object and its surroundings to determine if it is a foreign object. This is a so-called two-dimensional method, and its detection accuracy can be poor depending on the degree of roughness and the size of the foreign object. In particular, with the recent trend towards lowering the roughness of copper foil, conventional detection methods based on differences in roughness are reaching their limits. Furthermore, in order to improve productivity, there is a need to detect foreign objects in copper foil that has undergone high-speed surface treatment, and currently, this requires a large number of high-precision inspection devices.
[0006] The present inventors have now discovered that by detecting foreign matter that may be present on the surface of a metal foil during transport, transmitting the positional information of the foreign matter to an imaging device and / or displacement meter located downstream in the transport direction, and by performing not only the acquisition of a two-dimensional image by the imaging device but also the measurement of the height profile of the metal foil surface in the area containing the foreign matter by the displacement meter, it is possible to detect foreign matter that may be present on the surface of a metal foil during transport with higher accuracy.
[0007] Therefore, the object of the present invention is to provide an inspection method or inspection system that can detect foreign matter that may be present on the surface of metal foil during transport with higher accuracy.
[0008] The following embodiments are provided according to this disclosure: [Embodiment 1] A method for inspecting a metal foil, comprising: (a) detecting a foreign object that may be present on the surface of the metal foil during transport and acquiring location information of the foreign object; (b) transmitting the location information of the foreign object to an imaging device and / or displacement meter located downstream in the transport direction of the metal foil; (c) using the imaging device to photograph the foreign object identified by the location information and acquiring a two-dimensional image of the region on the metal foil surface that includes the foreign object; (d) using the displacement meter to measure the height profile of the region on the metal foil surface that includes the foreign object identified by the location information, either before or after step (c); and (e) evaluating the foreign object based on the two-dimensional image and / or the height profile. [Aspect 2] The metal foil inspection method according to Aspect 1, wherein step (e) includes: determining whether the two-dimensional shape of the foreign object is within a first tolerance range based on the two-dimensional image; determining whether the displacement of the foreign object in the height direction is within a second tolerance range based on the height profile; and recognizing the foreign object as defective if the two-dimensional shape of the foreign object is determined to be outside the first tolerance range and / or the displacement of the foreign object in the height direction is determined to be outside the second tolerance range. [Aspect 3] The metal foil inspection method according to Aspect 2, wherein step (d) is performed after step (c), and in step (b), the position information of the foreign object is transmitted to the imaging device. [Aspect 4] The metal foil inspection method according to Aspect 2, wherein step (c) is performed after step (d), and in step (b), the position information of the foreign object is transmitted to the displacement meter. [Aspect 5] The method for inspecting metal foil according to any one of aspects 1 to 4, wherein the imaging device moves in the width direction across the transport direction to photograph the foreign object, and the displacement meter moves in the width direction to acquire the height profile of the metal foil surface in the area containing the foreign object. [Aspect 6] The method for inspecting metal foil according to aspect 5, wherein the imaging device and the displacement meter move simultaneously toward the foreign object in the width direction to acquire the two-dimensional image and measure the height profile for the same foreign object.[Aspect 7] The method for inspecting metal foil according to aspect 6, wherein the imaging device and the displacement meter are fixed to each other at the same position in the width direction and at a certain distance apart in the transport direction. [Aspect 8] The method for inspecting metal foil according to any one of aspects 1 to 7, wherein the measurement of the height profile by the displacement meter is performed at a position where the back side of the metal foil is supported by a support member. [Aspect 9] The method for inspecting metal foil according to any one of aspects 2 to 8, further comprising the step of marking the location of the metal foil where the defect has been identified or at a location suggesting such a defect. [Aspect 10] The method for inspecting metal foil according to any one of aspects 1 to 9, wherein the displacement meter is a laser displacement meter. [Aspect 11] A method for manufacturing metal foil, comprising the steps of: manufacturing a long metal foil; and carrying out the method for inspecting metal foil according to any one of aspects 1 to 10 while transporting the metal foil. [Aspect 12] Metal foil obtained by the method for manufacturing metal foil according to aspect 11. [Aspect 13] An inspection system used in the metal foil inspection method described in any one of aspects 1 to 10, comprising: a foreign matter detection device that detects foreign matter that may be present on the surface of the metal foil and acquires positional information of the foreign matter; an imaging device disposed downstream in the transport direction of the metal foil, which photographs the foreign matter identified by the positional information of the foreign matter and acquires a two-dimensional image of the region on the surface of the metal foil that includes the foreign matter; a displacement meter disposed downstream in the transport direction of the metal foil, which measures the height profile of the surface of the metal foil that includes the foreign matter identified by the positional information of the foreign matter; and an information transmission unit that transmits the positional information of the foreign matter to the imaging device and / or the displacement meter. [Aspect 14] The inspection system according to aspect 13, further comprising: a first determination unit that determines whether the two-dimensional shape of the foreign object is within the first tolerance range; a second determination unit that determines whether the displacement of the foreign object in the height direction is within a second tolerance range; and a defect determination unit that determines the foreign object is defective if the two-dimensional shape of the foreign object is determined to be outside the first tolerance range and / or the displacement of the foreign object in the height direction is determined to be outside the second tolerance range.
[0009] This is a schematic diagram showing an example of an inspection system used in the inspection method of this disclosure. This diagram schematically shows two-dimensional images acquired by an imaging device and height profiles measured by a displacement meter for three types of foreign objects that differ only in their height profile, along with their evaluation results. This is a schematic block diagram showing the configuration of the signal processing unit. This is a perspective view showing an example of the arrangement and movement direction of the imaging device and displacement meter. This is a schematic block diagram showing the configuration of the data evaluation unit. This is a flowchart showing an example of the inspection flow in the inspection method of this disclosure, showing the part related to the foreign object detection device. This is a flowchart showing an example of the inspection flow in the inspection method of this disclosure, showing the part related to the imaging device. This is a flowchart showing an example of the inspection flow in the inspection method of this disclosure, showing the part related to the displacement meter.
[0010] Inspection Method and Inspection System The inspection method for metal foil according to this disclosure is performed on metal foil during transport. The metal foil may be any type of metal foil, but is preferably copper foil, and may be electrolytic copper foil or rolled copper foil. The metal foil may be a long length of metal foil transported by a roll-to-roll system, or it may be metal foil pieces cut to a predetermined size transported by a sheet-type transport means (e.g., a belt conveyor). The inspection method according to this disclosure is preferable when the metal foil is subjected to tension, as this makes it easier to detect foreign objects with high accuracy; therefore, the roll-to-roll system is more preferable. Accordingly, when using a sheet-type transport means, it is preferable to improve the detection accuracy by applying tension to the metal foil.
[0011] The inspection method for metal foil according to this disclosure includes the following steps: (a) detection of foreign matter and acquisition of its position information; (b) transmission of foreign matter position information to an imaging device and / or a displacement meter; (c) acquisition of a two-dimensional image by the imaging device; (d) measurement of the height profile by the displacement meter; and (e) evaluation of the foreign matter. The order of steps (c) and (d) is irrelevant, and either may be performed first (or last). Figure 1 shows an example of an inspection system 10 used in the inspection method of this disclosure. The direction of transport of the metal foil M in the figure is indicated by the arrow. The inspection system 10 shown in Figure 1 comprises a foreign matter detection device 12, an imaging device 14, a displacement meter 16, and an information transmission unit 18. The illustrated inspection system 10 is applied to a configuration in which metal foil M supplied from a supply roller 20 is conveyed in the conveying direction indicated by the arrow via a plurality of guide rollers 22 and wound up by a winding roller 24. However, it is not limited to this configuration and may be applied to a configuration in which the foil is conveyed by a sheet-type conveying means (e.g., a belt conveyor) as described above. The supply roller 20 may be a roller that supplies metal foil M, which is continuously conveyed from the foil manufacturing process in a roll-to-roll manner, to the inspection system 10, but it may be replaced by a metal foil roll in which the metal foil is wound into a roll shape. The imaging device 14 and the displacement meter 16 only need to be positioned downstream of the foreign object detection device 12 in the conveying direction, and either the imaging device 14 or the displacement meter 16 may be on the upstream (or downstream) side.
[0012] As mentioned above, conventional foreign object inspection is a so-called two-dimensional judgment, as it determines whether an object is foreign based on the difference in roughness between the foreign object and its surroundings, and the detection accuracy was sometimes poor depending on the degree of roughness and the size of the foreign object. In particular, in recent years, the roughness of copper foil has been decreasing, so the conventional detection method based on differences in roughness is reaching its limits. In contrast, the method or apparatus of this disclosure can detect foreign objects that may be present on the surface of metal foil M during transport, transmit the positional information of the foreign object to an imaging device 14 and / or displacement meter 16 located downstream in the transport direction, and not only acquire a two-dimensional image with the imaging device 14, but also measure the height profile of the metal foil M surface in the area containing the foreign object with the displacement meter 16, thereby enabling more accurate detection of foreign objects that may be present on the surface of metal foil M during transport. In other words, the method or apparatus of this disclosure can accurately measure the height (displacement in the height direction) of the foreign object by using the displacement meter 16, and can realize a three-dimensional evaluation that is more reliable than conventional two-dimensional evaluations.
[0013] The advantages of three-dimensional evaluation will be explained below using specific examples. Figure 2 shows three types of foreign objects that differ only in their height profiles: two-dimensional images acquired by the imaging device 14, height profiles measured by the displacement meter 16, and their evaluation results (determination of whether or not they are defects). In types 1 to 3 shown in Figure 2, the shape of the foreign object F observed from the two-dimensional images (X-axis - Y-axis direction) acquired by the imaging device 14 is the same. However, the height profiles (Z-axis direction) measured by the displacement meter 16 are all different. That is, foreign object F of type 1 has a convex shape, while foreign object F of type 2 has a concave shape. For this reason, these foreign objects F can be determined to be defects (if the displacement in the height direction is outside the acceptable range). On the other hand, foreign object F of type 3 is not observed in the height profile (Z-axis direction) and can be determined not to be a defect. Therefore, objects that appear to be foreign objects F, which would have been determined to be defects based solely on the acquisition of two-dimensional images by the imaging device 14, can be determined to be problem-free. In other words, in the imaging device 14, there are cases where there are no actual irregularities in the area that appears to be a foreign object F. Conventionally, it was difficult to detect such cases, but with the method or apparatus of this disclosure, it is possible to accurately determine that there is no problem even if there is no actual harm. In this way, by taking into account not only the two-dimensional image (X-axis-Y-axis direction) but also the height profile (Z-axis direction), it is possible to perform a three-dimensional evaluation of the foreign object F, and as a result, the detection accuracy of the foreign object F can be improved. That is, it becomes possible to distinguish between convex foreign objects F and concave foreign objects F, which are difficult to judge with two-dimensional information alone, improving inspection accuracy and product yield. Furthermore, in conventional methods, it was ultimately necessary to visually identify defects, and identifying defects based only on two-dimensional images acquired by the imaging device was not easy for inexperienced people, leading to the problem of inconsistency in judgment. However, this problem can also be resolved with the method or apparatus of this disclosure, making it possible to identify defects without inconsistency in judgment. Moreover, because three-dimensional evaluation is possible by combining the imaging device 14 and the displacement meter 16, foreign objects can be detected with high accuracy even on metal foil M that is being transported at high speed.In this regard, as mentioned above, in order to improve productivity, there is a need to detect foreign matter on copper foil that has been surface-treated at high speed. Currently, this requires a large number of high-precision inspection devices. However, according to the method or apparatus of the present disclosure, it is possible to detect foreign matter that may be present on the surface of metal foil M during transport with higher precision without requiring a large number of high-precision inspection devices, and it can also handle increased transport speeds. For example, the method or apparatus of the present disclosure makes it possible to detect foreign matter with a height of about 10 micrometers even on metal foil M being transported at a speed of 30 m / min or more.
[0014] The following describes each of the steps (a) through (e).
[0015] (a) In the step of detecting foreign matter and acquiring its location information, foreign matter F that may be present on the surface of the metal foil M during transport is detected and its location information is acquired. This step can be performed using a foreign matter detection device 12. The foreign matter detection device 12 is not particularly limited as long as it is configured to detect foreign matter F that may be present on the surface of the metal foil M and to acquire its location information, and a foreign matter detection device with a conventional configuration, such as the CCD detector disclosed in Patent Document 1, may be used. Preferably, foreign matter F can be detected and its location information can be acquired by irradiating the metal foil M with light and receiving the resulting specular reflected light and / or scattered light. In the subsequent steps (c) and (d), the imaging device 14 and displacement meter 16 will photograph and measure the foreign matter F, but the foreign matter detection device 12 aims to determine the location of the foreign matter F by measuring a wide area as a preliminary step to these steps.
[0016] The foreign object detection device 12 shown in Figure 1 is configured to detect foreign objects F and acquire their positional information by irradiating a metal foil M with light and receiving the resulting specularly reflected light, and by irradiating the metal foil M with light and receiving the resulting scattered light. The foreign object detection device 12 may be equipped with two types of optical systems as disclosed in Patent Document 1 (Japanese Patent No. 4136938), and may be equipped with (i) a first optical system consisting of a light 26a that irradiates light onto a predetermined reading portion P on the surface of the metal foil M supported by a guide roller 22, and a CCD sensor 28a that receives specularly reflected light from the reading portion P, and (ii) a second optical system consisting of two lights 26b, 26c that irradiate light onto a predetermined reading portion Q on the surface of the metal foil M supported by a guide roller 22, and a CCD sensor 28b that receives scattered light from the reading portion Q. However, the foreign object detection device 12 may be configured so that the two optical systems are handled by a single CCD sensor.
[0017] In the first optical system, the light 26a is positioned to illuminate the reading portion P of the metal foil M, which is located below the horizontal center of the guide roller 22 (for example, at an incident angle of 30°), and irradiates the reading portion P with light. The CCD sensor 28a is positioned on the optical axis of the specularly reflected light from the reading portion P irradiated by the light 26a, and receives the reflected light from the reading portion P. Multiple CCD sensors 28a (for example, six) may be provided along the axial direction of the guide roller 22.
[0018] In the second optical system, the light 26b is positioned to illuminate the reading portion Q of the metal foil M, which is located below the horizontal center of the guide roller 22 (for example, from an incident angle of 45°), and irradiates the reading portion Q with light. The light 26c is positioned in the direction opposite to the position where the light 26b is installed, with respect to the normal to the reading portion Q, and irradiates the reading portion Q with light. The CCD sensor 28b is installed in the direction normal to the reading portion Q and receives scattered light from the reading portion Q. Multiple CCD sensors 28b may also be provided (for example, six) along the axial direction of the guide roller 22.
[0019] A rotary encoder 23 that outputs a pulse signal corresponding to the rotation of the guide roller 22 may be connected to the rotation axis of the guide roller 22.
[0020] The foreign object detection device 12 may include a signal processing unit 30 for processing signals from the rotary encoder 23 and the CCD sensors 28a and 28b, respectively. As shown in Figure 3, the signal processing unit 30 may include a determination unit 32, a reflected light processing unit 34, and a scattered light processing unit 36. The reflected light processing unit 34 is connected to the CCD sensor 28a and the determination unit 32, and the scattered light processing unit 36 is connected to the CCD sensor 28b and the determination unit 32. The rotary encoder 23 is connected to the guide roller 22 and the determination unit 32. The reflected light processing unit 34, the scattered light processing unit 36, and the determination unit 32 can be configured as a microcomputer equipped with hardware such as a CPU, ROM, and RAM.
[0021] The method for determining foreign matter F in the foreign matter detection device 12 equipped with the two types of optical systems and signal processing unit 30 described above is publicly known, as detailed in Patent Document 1, and can be carried out appropriately based on the publicly known method disclosed in Patent Document 1, but the outline is explained below.
[0022] First, the CCD sensors 28a and 28b convert each pixel into a brightness signal according to the intensity of the received light and transmit the resulting image data to the reflected light processing unit 34 and the scattered light processing unit 36, respectively.
[0023] In the reflected light processing unit 34, when image data is received from the CCD sensor 28a, reflected light processing is performed. Specifically, the process is as follows: The average brightness of the received image data is calculated, and a threshold value that is a first predetermined multiple greater than this average brightness is set. Here, in the case of the metal foil M being copper foil, experiments have shown that the amount of reflected light is greater in the defective copper parts of the copper foil compared to the copper foil surface that is not defective. That is, the brightness of the defective copper parts is greater than that of the parts without defective copper, and it appears whitish to the human eye. Therefore, in the received image data, parts with high brightness are likely to be defective copper parts. For each region composed of pixels with brightness greater than the above threshold, a white label is applied to indicate that it is a region with high brightness. After that, a filter is performed to extract only the labeling regions of a predetermined size or larger, and the white labeling regions that constitute labeling regions smaller than the predetermined size are excluded. Furthermore, only the white labeling areas that constitute a labeling area of a predetermined size or larger and contain pixels with a brightness greater than a second predetermined multiple of the average brightness value (which is greater than a first predetermined multiple), are extracted, and the white labeling areas that do not contain such high-brightness pixels are excluded. In this way, the image with white labeling is output to the determination unit 32.
[0024] In the scattered light processing unit 36, when image data is received from the CCD sensor 28b, scattered light processing is performed. Specifically, the following is done: The average value of the brightness of the received image data is calculated. Here, if the metal foil M is copper foil, experiments have shown that the amount of scattered light is smaller in the defective copper parts of the copper foil compared to the copper foil surface that is not defective. In other words, the brightness of the defective copper parts is lower than that of the non-defective copper parts, and it appears black to the human eye. Therefore, in the received image data, parts with low brightness are likely to be defective copper parts. So, the calculated average brightness is used as a threshold, and black labeling is performed for each region composed of pixels whose brightness is smaller than the average brightness. After that, a filter is performed to extract only the labeling regions of a predetermined size or larger, and black labeling regions that constitute labeling regions smaller than the predetermined size are excluded. The image with black labeling applied in this way is output to the determination unit 32.
[0025] The determination unit 32 receives image data A from the reflected light processing unit 34 and image data B from the scattered light processing unit 36, and performs a defect extraction process for the copper foil. The metal foil M (copper foil in this case) is transported by the guide roller 22 and read by the CCD sensors 28a and 28b at the reading section P and reading section Q, respectively. Therefore, there is a time difference in the timing of reading the same part of the copper foil. This time difference is measured by counting the pulse signals corresponding to the rotation speed of the guide roller 22 obtained by the rotary encoder 23, and the image data B received with a predetermined time difference after receiving image data A is determined to be the image data of the same part of the copper foil, and the image data A and image data B of the same part of the copper foil are paired. Next, the paired image data A and image data B are compared, and the area that is white-labeled in image data A and black-labeled in image data B is extracted as a defective copper part, and the extracted part is output. In this way, the determination unit 32 can identify the foreign object F as the imaging target and acquire its position information.
[0026] (b) In step (b) of transmitting foreign object position information to the imaging device and / or displacement meter, the position information of the foreign object F obtained above is transmitted to the imaging device 14 and / or displacement meter 16. That is, the inspection system 10 includes an information transmission unit 18 that transmits the position information of the foreign object F to the imaging device 14 and / or displacement meter 16. As shown in Figure 1, the information transmission unit 18 is connected to the imaging device 14 and / or displacement meter 16 and can be configured to transmit the position information acquired by the signal processing unit 30 to the imaging device 14 and / or displacement meter 16. For example, if step (d) is performed after step (c), the position information of the foreign object F should be transmitted to the imaging device 14 in step (b). On the other hand, if step (c) is performed after step (d), the position information of the foreign object F should be transmitted to the displacement meter 16 in step (b). However, the position information of the foreign object F may be transmitted to both the imaging device 14 and the displacement meter 16 in step (b). Furthermore, the signal processing unit 30 may be incorporated into the information transmission unit 18, or the information transmission unit 18 may be incorporated into the signal processing unit 30.
[0027] (c) In the step of acquiring a two-dimensional image using an imaging device, the imaging device 14 photographs the foreign object F identified by the position information obtained from the information transmission unit 18, and acquires a two-dimensional image of the region on the surface of the metal foil M that includes the foreign object F. By using the imaging device 14, a two-dimensional image of the region (X-axis-Y-axis direction) on the surface of the metal foil M that includes the foreign object F can be acquired, as illustrated in Figure 2. The imaging device 14 is not particularly limited as long as it has a configuration that can photograph the foreign object F identified by the position information of the foreign object F and acquire a two-dimensional image of the region on the surface of the metal foil M that includes the foreign object F, but it is preferably a verify device. Various verify devices for visual inspection are commercially available and can be used as appropriate. The imaging device 14 or the verify device is equipped with a camera such as a CCD camera or a CMOS camera, and can acquire a high-precision two-dimensional image of the region on the surface of the metal foil M that includes the foreign object F.
[0028] The imaging device 14 may take a photograph of the foreign object F at any angle with respect to the surface of the metal foil M, but it is preferable to take the photograph from an angle above within the range of 70° to 110° (i.e., within ±20° of the perpendicular), and more preferably from an angle above 90° (i.e., perpendicular to the surface of the metal foil M).
[0029] The imaging device 14 is preferably configured to be movable in the width direction W that crosses the transport direction in order to photograph the foreign object F. In this way, the foreign object F can be photographed from the optimal position or angle based on the position information of the foreign object F. Here, the width direction W is typically perpendicular to the transport direction, but it may be moved diagonally to the transport direction. That is, the width direction W may be at any angle with respect to the transport direction, but it is preferably in a direction within the range of 70° to 110° with respect to the transport direction (i.e., within ±20° of the perpendicular), and more preferably in a direction of 90° (i.e., perpendicular to the transport direction).
[0030] (d) In step (d) measuring the height profile using a displacement meter, the displacement meter 16 measures the height profile of the surface of the metal foil M in the region containing the foreign object F identified by the position information transmitted from the information transmission unit 18. The height profile of the surface of the metal foil M is the height profile in the Z-axis direction perpendicular to the surface when the surface captured by the imaging device 14 is assigned the X-axis and Y-axis directions. The displacement meter 16 is not particularly limited as long as it is capable of measuring the height profile of the surface of the metal foil M, but it is preferably a laser displacement meter. By using a laser displacement meter, the height profile of the surface of the metal foil M can be measured with high accuracy even for metal foil M that is being transported at high speed. That is, with a laser displacement meter, height profile data can be stably acquired not only at low transport speeds but also at high transport speeds (e.g., 30 m / min or more).
[0031] The height profile measurement by the displacement gauge 16 may be performed at a position where the metal foil M is not supported by a support member such as the guide roller 22, as shown in Figure 1. However, as shown in Figure 4, it is preferable to perform the measurement at a position where the back side of the metal foil M is supported by a support member such as the guide roller 22, as this allows the metal foil M to be measured in a state free from tension, distortion, and deflection, and as a result, more accurate height profile information can be obtained. The support member is not limited to the guide roller 22, but may be any member that can reduce distortion and deflection of the metal foil M by supporting it. For example, the support member may be a stage having a flat surface for supporting the back side of the metal foil M, and this is also preferably applicable to embodiments using a sheet-fed conveying system.
[0032] The displacement meter 16 is preferably configured to be movable in the width direction W across the transport direction in order to obtain the height profile of the surface of the metal foil M in the area containing the foreign object F. In this way, the displacement of the foreign object F can be measured from an optimal position or angle based on the position information of the foreign object F. Here, as mentioned above, the width direction W is typically perpendicular to the transport direction, but it may also be moved diagonally to the transport direction. That is, the width direction W is preferably in the range of 60° to 120° with respect to the transport direction (i.e., within ±30° of the perpendicular to the transport direction), more preferably in the range of 80° to 100° (i.e., within ±10° of the perpendicular to the transport direction), and even more preferably in the range of 90° (i.e., perpendicular to the transport direction).
[0033] Preferably, as shown in Figure 4, the imaging device 14 moves in the width direction W to photograph the foreign object F, and the displacement meter 16 moves in the width direction W to acquire the height profile of the surface of the metal foil M in the area containing the foreign object. In this way, the imaging device 14 and the displacement meter 16 can work together to efficiently acquire information about the same foreign object F. From this viewpoint, it is particularly preferable that the imaging device 14 and the displacement meter 16 move simultaneously toward the foreign object F in the width direction W to acquire a two-dimensional image and measure the height profile of the same foreign object F. In this case, it is preferable that the imaging device 14 and the displacement meter 16 are fixed to each other at the same position in the width direction W and at a certain distance in the transport direction. Therefore, it is preferable that the imaging device 14 and the displacement meter 16 are fixed to the same base. The distance between the imaging position by the imaging device 14 and the measurement position by the displacement meter 16 in the transport direction is not particularly limited, but is preferably 5 cm to 30 cm, more preferably 10 cm to 25 cm, even more preferably 15 cm to 21 cm, and particularly preferably 19 cm to 21 cm.
[0034] The inspection system 10 may be equipped with multiple sets of imaging devices 14 and displacement meters 16. For example, multiple sets of imaging devices 14 and displacement meters 16 may be provided in the width direction W as described above. In this case, the range of movement in the width direction W of the sets of imaging devices 14 and displacement meters 16 can be narrowed, so that the position for photographing or measuring foreign matter F can be reached more quickly and reliably, and foreign matter that may be present on the surface of the metal foil M during transport can be detected with even higher accuracy. Alternatively, multiple sets of imaging devices 14 and displacement meters 16 may be provided in the transport direction. In this case, foreign matter F that the first set of imaging devices 14 and displacement meters 16 failed to photograph or measure can be photographed or measured by another set of imaging devices 14 and displacement meters 16 located further downstream, and foreign matter that may be present on the surface of the metal foil M during transport can be detected with even higher accuracy. Furthermore, multiple sets of imaging devices 14 and displacement meters 16 may be provided in the width direction W and also in the transport direction.
[0035] (e) In the foreign object evaluation step (e), the foreign object F is evaluated based on the two-dimensional image and / or height profile obtained above. That is, it is typical to evaluate the foreign object F based on both the two-dimensional image and the height profile, but in some cases it is sufficient to evaluate the foreign object F based on only one of the two-dimensional image or the height profile. Examples of the latter include cases where there is a clearly large foreign object F in the two-dimensional image (for example, one that can be determined by visual inspection), or where there is an extremely large convex foreign object F in the height profile.
[0036] Preferably, step (e) may include a determination step based on a two-dimensional image, a determination step based on a height profile, and a defect identification step. The order of the determination step based on the two-dimensional image and the determination step based on the height profile is irrelevant.
[0037] In the two-dimensional image-based determination process, it is determined whether the two-dimensional shape of the foreign object F falls within a first acceptable range based on the two-dimensional image. The first acceptable range refers to the range in which the two-dimensional shape and size of the foreign object F do not pose a problem, and can be appropriately determined based on previously acquired data.
[0038] In the height profile-based determination step, it is determined whether the height displacement of the foreign object F is within a second tolerance range based on the height profile. The second tolerance range means the range in which the height displacement of the foreign object F does not pose a problem, and can be appropriately determined based on previously acquired data. In this two-dimensional image-based determination step, it may be possible to determine whether or not there are irregularities caused by the foreign object based on the height profile, and if irregularities exist, to determine whether or not the height displacement of the irregularities is within the second tolerance range.
[0039] In the defect identification process, a foreign object F is identified as a defect if its two-dimensional shape is determined to be outside the first acceptable range and / or its displacement in the height direction is determined to be outside the second acceptable range. Typically, a foreign object F is identified as a defect when both its two-dimensional shape and its displacement in the height direction are determined to be outside the acceptable range. However, as mentioned above, there may be cases where a foreign object F can be identified as a defect based on only one of the two-dimensional shape or the displacement in the height direction. For example, if the size of the two-dimensional shape of the foreign object F exceeds a predetermined threshold set at a level significantly higher than the first acceptable range, or if the displacement in the height direction of the foreign object F exceeds a predetermined threshold set at a level significantly higher than the second acceptable range, the foreign object F may be identified as a defect without considering the other factor (height displacement or two-dimensional shape).
[0040] The evaluation in process (e) may be performed by a human, or it may be performed automatically by a data evaluation unit 38 installed in or separately provided in the inspection system 10. Alternatively, it may be performed in a way that a human intervenes in the judgment or evaluation by the data evaluation unit 38. An example of the data evaluation unit 38 is shown in Figure 5. As shown in Figure 5, the data evaluation unit 38 comprises a first judgment unit 40, a second judgment unit 42, and a defect certification unit 44. The first judgment unit 40 determines whether the two-dimensional shape of the foreign object F is within a first tolerance range and transmits the result to the defect certification unit 44. The second judgment unit 42 determines whether the displacement of the foreign object F in the height direction is within a second tolerance range and transmits the result to the defect certification unit 44. The defect certification unit 44 certifies the foreign object F as a defect if its two-dimensional shape is determined to be outside the first tolerance range and / or its displacement in the height direction is determined to be outside the second tolerance range. The first determination unit 40, the second determination unit 42, and the defect identification unit 44 can be configured as microcomputers equipped with hardware such as a CPU, ROM, and RAM. The inspection system 10 may include a labeler 46, as will be described later. In this case, it is preferable that the defect identification unit 44 transmits the location information of the foreign object F to the labeler 46 when it identifies the foreign object F as a defect.
[0041] (f) Marking (Optional step) It is preferable to mark the location where a defect has been identified in the metal foil M or a location that suggests such a defect. This serves as a guide when removing the defective portion of the metal foil M by cutting or other means. Examples of methods for marking include attaching a label sticker, engraving (e.g., laser engraving), perforation (e.g., punching or laser perforation), printing (e.g., inkjet printing), and marking with a writing instrument (e.g., an oil-based marker). Furthermore, the location where the mark is applied is not limited to the location where a defect has been identified in the metal foil M, but may also be a location that suggests such a defect. A typical example of a location that suggests a location where a defect has been identified in the metal foil M is the end in the width direction of the metal foil M. If a mark is applied to the end in the width direction of the metal foil M, even if the metal foil M is wound in a roll, the location of the defect in the metal foil M can be inferred simply by looking at the end of the roll. In this case, if a mark is applied to the end at the same location in the transport direction or longitudinal direction as the location where the defect has been identified in the metal foil M, it becomes easier to identify the location of the defect from the end. In particular, if a label sticker is attached to the edge of the metal foil M in the width direction so that a portion of it protrudes, the presence of a defect in the metal foil M can be immediately noticed simply by looking at the edge of the roll, and the location of the defect can be easily identified. In this regard, the inspection system 10 shown in Figure 1 is equipped with a labeler 46 on the downstream side in the transport direction of the imaging device 14 and displacement meter 16, and the labeler 46 may be configured to attach a label sticker or the like to the metal foil M based on the defect location information received from the defect identification unit 44.
[0042] (g) Detection of pinholes (optional process) In the method or system of the present disclosure, pinholes in the metal foil M may be detected at any stage. This is because pinholes in the metal foil M can also be defects. Therefore, the inspection system 10 may include a pinhole detector. The pinhole detector may be configured to irradiate light from a light source onto one surface of the metal foil M and detect the light transmitted through the pinhole with a light receiving element such as a CCD provided on the opposite side of the metal foil M. The pinhole detector may be provided in any section of the conveyance path of the metal foil M, including a section upstream of the foreign object detection device 12, a section between the foreign object detection device 12 and the imaging device 14 or the displacement meter 16, a section between the imaging device 14 and the displacement meter 16, a section between the displacement meter 16 and the labeler 46, and a section downstream of the labeler 46. When a pinhole is detected, a pinhole detection signal can be transmitted to the defect determination unit 44 to assist in the defect determination of the foreign object F.
[0043] Manufacturing method and metal foil As described above, the metal foil M to be inspected according to the present disclosure can be a long metal foil that has been conveyed in a roll-to-roll manner from the foil manufacturing process. Therefore, the inspection method of the present disclosure can be a series of processes associated with the foil manufacturing process. That is, according to a preferred embodiment of the present disclosure, there is provided a method for manufacturing a metal foil including a process of manufacturing a long metal foil and a process of implementing the inspection method of the metal foil of the present disclosure while conveying the metal foil. Further, according to another preferred embodiment of the present disclosure, there is provided a metal foil obtained by such a method for manufacturing a metal foil.
[0044] Inspection flow An example of the inspection flow in the inspection method of the present disclosure using the inspection system 10 will be described using the flowcharts of FIGS. 6A to 6C. The inspection flow shown in FIGS. 6A to 6C is merely an example, and the method and inspection system 10 of the present disclosure are not limited thereto.
[0045] Figure 6A shows the inspection flow in the foreign object detection device 12. First, the foreign object detection device 12 is activated. When the foreign object detection device 12 detects a foreign object F (step 60), it determines whether or not the foreign object F is a target for imaging (step 62). The method for determining foreign object F in the foreign object detection device 12 is as described above. If the determination unit 32 determines that the foreign object F is a target for imaging, it acquires its position information and transmits an imaging instruction to the imaging device 14 via the information transmission unit 18 (step 64). The imaging instruction may include the position information of the foreign object F. The foreign object detection device 12 waits until it detects the next foreign object F, that is, it continues the detection operation, regardless of the operation of the imaging device 14 (step 66). Even if the determination unit 32 does not determine that the foreign object F is a target for imaging, the foreign object detection device 12 waits until it detects the next foreign object F, that is, it continues the detection operation (step 68).
[0046] Figure 6B shows the inspection flow in the imaging device 14. Upon receiving an imaging instruction from the foreign object detection device 12, the imaging device 14 determines whether or not a foreign object F is approaching the imaging position (step 70). If a foreign object F is approaching the imaging position, the imaging device 14 moves toward the foreign object F (step 72), photographs the target foreign object F, and sends a trigger signal to the displacement meter 16 (step 74). The imaging device 14 waits until the next imaging instruction is received, regardless of the operation of the displacement meter 16 (step 76). If the movement of the imaging device 14 cannot keep up with the transported foreign object F and the target foreign object F passes by, an error is displayed and imaging is postponed (step 78). In this case as well, the imaging device 14 waits until the next imaging instruction is received (step 80).
[0047] In step 70, it is preferable that the imaging device 14 determines whether it has finished imaging the previous foreign object F when it receives an imaging instruction from the foreign object detection device 12. In this case, if it has finished imaging the previous foreign object F, it is preferable that the imaging device 14 starts moving (step 72), and if it has not finished imaging the previous foreign object F, it is preferable that the imaging device 14 starts moving when it has finished imaging that foreign object F (step 72).
[0048] Fig. 6C shows the inspection flow in the displacement meter 16. First, when the displacement meter 16 receives a trigger signal from the imaging device 14 (step 82), the displacement meter 16 starts measuring the height profile of the foreign object F (step 84) and outputs the measurement result (step 86). Then, it waits until the next trigger signal is received (step 88).
[0049] Through such a series of inspection flows, foreign objects F that may exist on the surface of the metal foil M during conveyance can be detected with high precision. In particular, by using not only the foreign object detection device 12 and the imaging device 14 but also the displacement meter 16, the height (displacement in the height direction) of the foreign object F can be accurately measured, and a three-dimensional evaluation with higher reliability than the conventional two-dimensional evaluation can be realized.
[0050] 10: Inspection system, 12: Foreign object detection device, 14: Imaging device, 16: Displacement meter, 18: Information transmission unit, 20: Supply roller, 22: Guide roller, 23: Rotary encoder, 24: Take-up roller, 26a, 26b, 26c: Lights, 28a, 28b: CCD sensors, 30: Signal processing unit, 32: Determination unit, 34: Reflected light processing unit, 36: Scattered light processing unit, 38: Data evaluation unit, 40: First determination unit, 42: Second determination unit, 44: Defect identification unit, 46: Labeler, M: Metal foil, F: Foreign object, P, Q: Reading parts, W: Width direction
Claims
1. A method for inspecting metal foil, comprising: (a) detecting foreign matter that may be present on the surface of metal foil during transport and acquiring location information of the foreign matter; (b) transmitting the location information of the foreign matter to an imaging device and / or displacement meter located downstream in the transport direction of the metal foil; (c) using the imaging device to photograph the foreign matter identified by the location information and acquiring a two-dimensional image of the region on the surface of the metal foil containing the foreign matter; (d) using the displacement meter to measure the height profile of the region on the surface of the metal foil containing the foreign matter identified by the location information, either before or after step (c); and (e) evaluating the foreign matter based on the two-dimensional image and / or the height profile.
2. The method for inspecting metal foil according to claim 1, wherein step (e) includes: determining whether the two-dimensional shape of the foreign object is within a first tolerance range based on the two-dimensional image; determining whether the displacement of the foreign object in the height direction is within a second tolerance range based on the height profile; and recognizing the foreign object as defective if the two-dimensional shape of the foreign object is determined to be outside the first tolerance range and / or the displacement of the foreign object in the height direction is determined to be outside the second tolerance range.
3. The method for inspecting metal foil according to claim 2, wherein step (d) is performed after step (c), and in step (b), the position information of the foreign object is transmitted to the imaging device.
4. The method for inspecting metal foil according to claim 2, wherein step (c) is performed after step (d), and in step (b), the position information of the foreign object is transmitted to the displacement meter.
5. The method for inspecting a metal foil according to claim 1, wherein the imaging device moves in the width direction across the transport direction to photograph the foreign object, and the displacement meter moves in the width direction to acquire the height profile of the metal foil surface in the area containing the foreign object.
6. The method for inspecting metal foil according to claim 5, wherein the imaging device and the displacement meter move simultaneously toward the foreign object in the width direction to acquire the two-dimensional image and measure the height profile of the same foreign object.
7. The method for inspecting metal foil according to claim 6, wherein the imaging device and the displacement meter are fixed to each other at the same position in the width direction and at a certain distance apart in the transport direction.
8. The method for inspecting a metal foil according to claim 1, wherein the measurement of the height profile by the displacement meter is performed at a position where the back side of the metal foil is supported by a support member.
9. The method for inspecting a metal foil according to claim 2, further comprising the step of marking the location of the defect identified on the metal foil or a location suggesting such defect.
10. The method for inspecting metal foil according to claim 1, wherein the displacement meter is a laser displacement meter.
11. A method for manufacturing a metal foil, comprising the steps of: manufacturing a long metal foil; and carrying out the metal foil inspection method described in any one of claims 1 to 10 while transporting the metal foil.
12. A metal foil obtained by the method for manufacturing a metal foil according to claim 11.
13. An inspection system used in a method for inspecting metal foil according to any one of claims 1 to 10, comprising: a foreign matter detection device for detecting foreign matter that may be present on the surface of the metal foil and acquiring positional information of the foreign matter; an imaging device disposed downstream in the transport direction of the metal foil, which photographs the foreign matter identified by the positional information of the foreign matter and acquires a two-dimensional image of the region on the surface of the metal foil that includes the foreign matter; a displacement meter disposed downstream in the transport direction of the metal foil, which measures the height profile of the surface of the metal foil that includes the foreign matter identified by the positional information of the foreign matter; and an information transmission unit for transmitting the positional information of the foreign matter to the imaging device and / or the displacement meter.
14. The inspection system according to claim 13, further comprising: a first determination unit for determining whether the two-dimensional shape of the foreign object is within the first allowable range; a second determination unit for determining whether the displacement of the foreign object in the height direction is within a second allowable range; and a defect determination unit for determining that the foreign object is defective if the two-dimensional shape of the foreign object is determined to be outside the first allowable range and / or the displacement of the foreign object in the height direction is determined to be outside the second allowable range.