Defect detection device and defect detection assembly

Abstract

The present invention provides a defect detection device (100) for detecting defects on the surface of a flexible sheet-like material (S). The defect detection device (100) includes: a support roller (110) that has a cylindrical surface and provides a curved transfer path to the sheet-like material, and that supports the sheet-like material; a light emission unit (120) arranged on one side, in the direction in which the sheet-like material is transferred, of a portion in which the sheet-like material is curved along the circumference of the cylindrical surface of the support roller; a first image acquisition unit (130) which is arranged on the other side, in the direction in which the sheet-like material is transferred, of the portion in which the sheet-like material is curved; and an image processing unit (150) for image processing light received by the first image acquisition unit. The light emission unit (120) emits light toward a tangent part (112L) in which the sheet-like material is curved. The first image acquisition unit (130) line-scans and detects the light emitted toward and projected on the tangent part of the sheet-like material.

Description

Defect detection device and defect detection assembly

[0001] The present invention relates to a defect detection device and a defect detection assembly in which a plurality of such defect detection devices are arranged in parallel along the width of a sheet, and more particularly, to a defect detection device for detecting minute defects existing on the surface of a flexible sheet-shaped material wound and supplied in a roll form, and a defect detection assembly including the same.

[0002] In various manufacturing industries that handle sheet-like materials (e.g., electrode substrates, resin films, paper, metal plates, etc.), inspection is necessary to find defects, including fine foreign substances attached to the surface of materials used or products using such materials, in order to improve product quality and stability.

[0003] In the case of sheet materials, since they are supplied in rolls and are continuously supplied, there is a problem that if it is discovered later that a defect exists in a portion of the material, especially if there is a minute defect protruding from the surface, a significant amount of the entire sheet material must be discarded.

[0004] To address these issues, surface defect inspection of sheet materials is performed. Optical imaging is typically used to detect defects, including foreign matter. Specifically, defects within the material under test are captured by illuminating the test object and using a lens system to capture the corresponding area. The resulting image is evaluated by a computer unit, and based on the image information, it is determined whether a defect exists in the sheet material, and optionally, which type of defect it is.

[0005] However, in a situation where sheet-like material is continuously supplied in a rolled state, when a predetermined area of ​​the surface of the sheet-like material is continuously photographed with an area imaging camera, there is a problem in that the defect detection rate is low because there is not much time for the camera photographing the surface area to capture defects compared to the speed at which the sheet-like material is supplied.

[0006] In particular, micrometer-sized defects are directly related to performance and safety in electronic devices and batteries, making them a top priority for management. In this regard, there is a growing need for a detection method that can achieve height and lateral resolutions of 5 micrometers or less at speeds exceeding 120 m / min, as required in actual manufacturing environments.

[0007] The background technology described above is technical information that the inventor possessed for the purpose of deriving the present invention or acquired in the process of deriving the present invention, and cannot necessarily be said to be publicly known technology disclosed to the general public prior to the application for the present invention.

[0008] The present invention is intended to solve the above-mentioned problem, and an object of the present invention is to provide a defect detection device that can detect defects on the surface of a sheet-like material in real time, and can detect defects on the surface of a sheet-like material with high precision even in a situation where the sheet-like material is wound on a roll and then continuously supplied.

[0009] In addition, an object of the present invention is to provide a defect detection device capable of detecting protruding minute defects on the surface of a sheet-like material in sufficient time while reducing the processing time of the entire detection device by integrating and processing a line scan image for detecting such defects.

[0010] However, these tasks are merely exemplary, and the challenges addressed by the present invention are not limited thereto. Any challenges not mentioned will be readily apparent to those skilled in the art from this specification and the accompanying drawings.

[0011] One embodiment of the present invention relates to a defect detection device for detecting a defect on the surface of a flexible sheet-like material.

[0012] The above defect detection device includes a support roller having a cylindrical surface to provide a curved transport path for the sheet-like material, a light irradiation unit arranged on one side of the transport direction of the sheet-like material with respect to a portion where the sheet-like material is curved along the circumference of the cylindrical surface of the support roller, and a first image acquisition unit arranged on the other side of the transport direction of the sheet-like material with respect to the portion where the sheet-like material is curved.

[0013] The above light irradiation unit irradiates light toward the tangent portion where the sheet-like material is curved.

[0014] The above first image acquisition unit detects light projected onto a tangential portion of the sheet-like material by scanning the line.

[0015] The above defect detection device further includes a second image acquisition unit spaced apart from and arranged on the upper side of the sheet-like material, and the second image acquisition unit is arranged to be inclined at a predetermined angle in a direction toward the light irradiation unit from a vertical axis perpendicular to the tangent portion on the surface of the sheet-like material, and detects light reflected from the tangent portion by line scanning.

[0016] The above light irradiation unit includes a lighting unit and a telecentric lighting optical system that passes only straight light parallel to the optical axis toward the portion where the sheet-like material is curved among the light irradiated from the lighting unit.

[0017] The first image acquisition unit includes a first camera unit and a first telecentric lens that passes only straight light parallel to the optical axis obtained from a portion where the sheet-like material is curved among the light obtained by the first camera unit.

[0018] The above defect detection device further includes a speedometer arranged coaxially with the support roller and measuring the conveying speed of the sheet-like material conveyed by the support roller.

[0019] The light irradiation unit includes a plurality of lighting units that irradiate light obliquely toward a portion where the sheet-like material is curved, and a plurality of telecentric lighting optical systems that allow only straight light parallel to an optical axis toward a portion where the sheet-like material is curved to pass through the light irradiated from each of the plurality of lighting units, but are arranged to correspond to each of the plurality of lighting units.

[0020] The plurality of above lighting units are configured to irradiate light in opposite directions at a predetermined angle based on a direction perpendicular to the extension direction of the above tangent portion.

[0021] The first image acquisition unit includes a plurality of first camera units that acquire light at an angle to each other toward a portion where the sheet-like material is curved, and a plurality of first telecentric lenses that allow only straight light parallel to an optical axis acquired from a portion where the sheet-like material is curved among the light acquired by each first camera unit of the plurality of first camera units to pass therethrough, and are arranged to correspond to each first camera unit of the plurality of first camera units.

[0022] The plurality of first camera units are configured to obtain light in opposite directions at a predetermined angle relative to a direction perpendicular to the extension direction of the tangent portion.

[0023] The second image acquisition unit includes a second camera unit and a second telecentric lens that passes only straight light parallel to the optical axis obtained from a portion where the sheet-like material is curved among the light obtained by the second camera unit.

[0024] The second image acquisition unit is configured to generate a one-dimensional reflection image displayed as a brightness intensity at a predetermined point in time for a tangential portion of a curved portion of the sheet-like material illuminated with dark field illumination.

[0025] The above first image acquisition unit generates a one-dimensional projection image displayed as a brightness intensity at a predetermined point in time with respect to a tangent portion of a portion where the sheet-like material is curved.

[0026] The above defect detection device includes an image processing unit configured to process an image generated from at least one of the first image acquisition unit and the second image acquisition unit.

[0027] The above image processing unit performs a step of generating a two-dimensional array image in time sequence from one-dimensional projection images generated at each of a plurality of predetermined points in time.

[0028] The above image processing unit additionally performs a differentiation processing step of extracting only images with a predetermined change in brightness compared to the surroundings from the two-dimensionally arranged images according to the above time sequence.

[0029] The above image processing unit additionally performs a BLOB step (Binary Large Object step) to identify objects judged to be one object in the extracted image.

[0030] The above image processing unit additionally performs a step of obtaining location and size information for individual objects and generating an information map.

[0031] Another aspect of the present invention provides a defect detection assembly having a plurality of the aforementioned defect detection devices.

[0032] The plurality of defect detection devices includes a plurality of defect detection devices in a first row arranged in parallel along the width direction of the sheet-like material, and a plurality of defect detection devices in a second row arranged opposite to the plurality of defect detection devices in the first row in the length direction of the sheet-like material.

[0033] The individual defect detection devices of the plurality of defect detection devices of the first row and the individual defect detection devices of the plurality of defect detection devices of the second row are arranged to be staggered in the width direction of the sheet-like material.

[0034] The above defect detection assembly includes a second image acquisition unit extending in the width direction of the sheet-like material.

[0035] The second image acquisition unit is arranged between the plurality of defect detection devices of the first row and the plurality of defect detection devices of the second row.

[0036] The second image acquisition unit is arranged on the upper side of the surface of the sheet-like material and scans the line of light reflected from the surface of the sheet-like material or light transmitted from the lower side to detect defects on the surface of the sheet-like material.

[0037] The second image acquisition unit includes a second camera unit extending in the width direction of the sheet-like material, and a second rod lens array that focuses light acquired by the second camera unit.

[0038] The second image acquisition unit further includes a pair of upper light irradiation units arranged on each side of the second camera unit, wherein the pair of upper light irradiation units obliquely illuminate the surface of the sheet-like material.

[0039] The second image acquisition unit is configured to generate a one-dimensional reflection image displayed as a brightness intensity at a predetermined point in time for the surface of the sheet-like material illuminated with dark field illumination.

[0040] The second image acquisition unit further includes a lower light irradiation unit positioned opposite the second camera unit with respect to the sheet-like material, wherein the lower light irradiation unit illuminates the surface of the sheet-like material from below, and the second image acquisition unit generates a one-dimensional transmission image displayed as a brightness intensity at a predetermined point in time for the surface of the sheet-like material irradiated by the lower light irradiation unit (246).

[0041] Each of the plurality of defect detection devices of the first row and the plurality of defect detection devices of the second row each includes an optical path control element that controls an optical path.

[0042] The above defect detection assembly further includes an image processing unit configured to process an image generated from at least one of the first image acquisition unit and the second image acquisition unit.

[0043] Other aspects, features and advantages other than those described above will become apparent from the following detailed description, claims and drawings for carrying out the invention.

[0044] According to a defect detection device according to one embodiment of the present invention, a defect on the surface of a sheet-like material is detected in real time, and even in a situation where the sheet-like material is wound on a roll and then continuously supplied, the defect on the surface of the sheet-like material can be detected with high precision.

[0045] In addition, according to a defect detection device according to an embodiment of the present invention, by integrating a line scan image for detecting a defect and processing the image through a Time Delayed Integration (TDI) method, when detecting a protruding minute defect on the surface of a sheet-like material, it is possible to precisely detect a minute defect moving at high speed without missing it while projecting the defect for a sufficient amount of time.

[0046] By acquiring images of defects at low speeds, the amount of images acquired is reduced, which in turn reduces the load on the system required for image processing and analysis. This reduces the system's hardware requirements and improves its efficiency.

[0047] Furthermore, according to a defect detection assembly according to one embodiment of the present invention, surface defects can be continuously detected across the entire width of a sheet-like material having a predetermined width. Furthermore, since real-time analysis is possible, the causes of periodic defects can be identified and eliminated at an early stage.

[0048] In addition, according to the defect detection device and defect detection assembly according to one embodiment of the present invention, since a defect on the surface of a sheet-like material is detected in a projection manner, information on the size of the defect as well as the presence of a bond can be obtained without causing physical damage to the inspection object during the measurement process.

[0049] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person skilled in the art to which the present invention pertains from this specification and the attached drawings.

[0050] Figure 1 is a schematic diagram of a defect detection device according to one embodiment of the present invention.

[0051] FIG. 2 is an explanatory diagram showing a side view of a protruding defect on the surface of a sheet-like material moving at predetermined intervals according to the movement of a support roller in a defect detection device according to one embodiment of the present invention.

[0052] FIG. 3 is an explanatory diagram showing a correlation between images of defects projected at each time and integrated with respect to time in a defect detection device according to an embodiment of the present invention.

[0053] FIG. 4 is an explanatory diagram illustrating the relationship between the height of a protruding defect on the surface of a sheet-like material and the radius of a support roller in a defect detection device according to one embodiment of the present invention.

[0054] Figure 5 is a perspective view of a defect detection device according to one embodiment of the present invention.

[0055] Figure 6 is a side view of a defect detection device according to one embodiment of the present invention.

[0056] Fig. 7 is a perspective view of a defect detection device according to another embodiment of the present invention.

[0057] Figure 8 is a perspective view of a defect detection device according to another embodiment of the present invention.

[0058] Fig. 9 is a flowchart showing an image processing sequence of a defect detection device according to an embodiment of the present invention.

[0059] FIG. 10a and FIG. 10b are explanatory diagrams illustrating two profile generation methods of an image acquisition unit in a defect detection device according to one embodiment of the present invention.

[0060] FIG. 11 is an explanatory diagram illustrating a processing process of an image obtained from a first image acquisition unit of a defect detection device according to an embodiment of the present invention.

[0061] FIG. 12 is an explanatory diagram illustrating a processing process by combining images obtained from a first image acquisition unit and a second image acquisition unit of a defect detection device according to one embodiment of the present invention.

[0062] Fig. 13 is a flowchart showing an image processing sequence of a defect detection device according to another embodiment of the present invention.

[0063] FIG. 14 is a perspective view of a defect detection assembly according to one embodiment of the present invention.

[0064] FIG. 15 is an exploded perspective view of an individual defect detection device among the defect detection devices of the first row of the defect detection assembly of FIG. 14.

[0065] Figure 16 is a side view of the defect detection assembly of Figure 14.

[0066] Fig. 17 is a plan view of the defect detection assembly of Fig. 14.

[0067] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail in the description. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. In describing the present invention, identical components are identified by the same reference numerals even when illustrated in different embodiments.

[0068] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. When describing with reference to the drawings, identical or corresponding components are given the same reference numerals and redundant descriptions thereof will be omitted.

[0069] In the examples below, the terms first, second, etc. are not used in a limiting sense, but are used for the purpose of distinguishing one component from another.

[0070] In the examples below, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0071] For convenience of explanation, the sizes of components in the drawings may be exaggerated or reduced. For example, the sizes and thicknesses of each component shown in the drawings are arbitrarily shown for convenience of explanation, and therefore the present invention is not necessarily limited to the drawings.

[0072] In some embodiments, where implementations are otherwise feasible, specific process sequences may be performed in a different order than described. For example, two processes described in succession may be performed substantially simultaneously, or in a reverse order from the described order.

[0073] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. In this application, terms such as "comprise" or "have" are intended to indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but should be understood to not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0074] In the following examples, when regions, components, etc. are said to be connected, this includes not only cases where the regions, components, etc. are directly connected, but also cases where other regions, components, etc. are interposed between the regions, components, etc. and thus indirectly connected. For example, when it is said in this specification that regions, components, etc. are electrically connected, this includes not only cases where the regions, components, etc. are directly connected, but also cases where other regions, components, etc. are interposed between them and thus indirectly connected.

[0075] Hereinafter, a defect detection device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 17.

[0076] FIG. 1 is a schematic diagram of a defect detection device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a side view in which a protruding defect on the surface of a sheet-like material moves at predetermined intervals according to the movement of a support roller in the defect detection device according to an embodiment of the present invention, FIG. 3 is an explanatory diagram showing a correlation in which an image of a defect projected at each interval is integrated with respect to time in the defect detection device according to an embodiment of the present invention, FIG. 4 is an explanatory diagram explaining a relationship between a height of a protruding defect on the surface of a sheet-like material and a radius of a support roller in the defect detection device according to an embodiment of the present invention, FIG. 5 is a perspective view of a defect detection device according to an embodiment of the present invention, and FIG. 6 is a side view of a defect detection device according to an embodiment of the present invention.

[0077] Referring to FIGS. 1 and 5, a defect detection device (100) according to one embodiment of the present invention is configured to detect a defect on the surface of a flexible sheet-like material (S).

[0078] The above sheet-like material (S), although not shown in the drawing, is wound on a roll and then supplied to the defect detection device (100), and after the defect detection device (100) detects whether there is a defect on the surface of the sheet-like material, it is wound on a roll again.

[0079] The above defect detection device (100) has a cylindrical surface to provide a curved transport path for the sheet-like material (S), and includes a support roller (110) that supports the sheet-like material, a light irradiation unit (120) arranged on one side of the direction in which the sheet-like material is transported with respect to a portion where the sheet-like material is curved along the circumference of the cylindrical surface of the support roller, and a first image acquisition unit (130) arranged on the other side of the direction in which the sheet-like material is transported with respect to a portion where the sheet-like material is curved.

[0080] The above light irradiation unit (120) irradiates light toward a tangent portion corresponding to a vertex where the sheet-like material is bent by the support roller (110), and the first image acquisition unit (130) detects the light irradiated and projected onto the tangent portion of the sheet-like material by performing a line scan.

[0081] Accordingly, the light emitted from the light irradiation unit (120) irradiates the tangent portion of the curved portion of the sheet-like material (S), and the first image acquisition unit (130) is positioned on the opposite side of the light irradiation unit (120) with the tangent portion, which is the vertex of the sheet-like material (S), as the center.

[0082] Meanwhile, a defect detection device (100) according to an embodiment of the present invention includes a second image acquisition unit (140) arranged spaced apart from the upper side of a curved portion of the sheet-like material (S). The second image acquisition unit (140) is arranged to be inclined at a predetermined angle in a direction toward the light irradiation unit from a vertical axis perpendicular to the tangent portion (112l) on the surface of the sheet-like material, so as to detect light reflected from the tangent portion by line scanning.

[0083] As illustrated in FIG. 1, a defect detection device (100) according to one embodiment of the present invention includes an image processing unit (150) configured to process images generated from the first image acquisition unit (130) and the second image acquisition unit (140).

[0084] Referring to FIGS. 1 and 5, the sheet-like material (S) is conveyed from right to left in the drawings. Accordingly, the first image acquisition unit (130) acquires an image of the surface of the sheet-like material (S) at the vertex of the portion where the sheet-like material (S) curves and approaches the support roller (110). The arrangement relationship between the supply direction of the sheet-like material (S) and the first image acquisition unit (130) is not limited to the relationship illustrated in FIG. 1, and the first image acquisition unit (130) may also acquire an image of the surface of the sheet-like material (S) at the vertex of the portion where the sheet-like material curves and moves away from the support roller (110).

[0085] Referring to FIGS. 2 to 4, the principle of the defect detection device (100) according to the present invention detecting a protruding defect on a sheet-like material (S) and further detecting its height will be described. Referring to FIG. 2, the protruding defect present on the surface of the sheet-like material (S) wrapped around the cylindrical surface of the support roller (110) changes its position based on five predetermined points in time (indicated by strings T1 to T5 in FIGS. 2 and 3).

[0086] When the defect is at the position (T1) at time point 1, the top of the defect is lower than the apex of the surface of the curved sheet-like material, so it is not projected onto the first image acquisition unit, and only the curved portion of the sheet-like material is projected onto the first image acquisition unit. Thereafter, when the defect moves from the position (T1) at time point 1 to the position (T2) at time point 2, the top portion of the defect protrudes above the apex of the surface of the sheet-like material, and a portion of the entire height of the defect is projected onto the first image acquisition unit. When the defect reaches the position (T3) at time point 3, the entire protruding height of the defect is projected onto the first image acquisition unit, and when the defect reaches the position (T4) at time point 4, the defect is positioned lower than the apex of the sheet-like material. Subsequently, when the defect reaches the position (T5) at time point 5, the top portion of the defect is positioned lower than the apex of the sheet-like material.

[0087] When the two-dimensional data is converted into a one-dimensional form using the integration method or the averaging method for the projected two-dimensional defect images of the curved portion of the sheet-like material line-scanned at five viewpoints, as shown in the image on the left side of Fig. 3, a two-dimensionally reconstructed image is obtained using the projected images of the protruding defects over time, as shown on the right side of Fig. 3.

[0088] Here, since the first image acquisition unit (130) acquires an image in which the straight light irradiated from the light irradiation unit (120) is projected onto the vertex of the curved portion of the sheet-like material (S), the surface or protruding defect of the sheet-like material (S) is acquired as an image that is displayed as black in the first image acquisition unit (130). Since the first image acquisition unit (130) does not capture the light scattered by the irradiated light on the defect but acquires the light projected by the irradiated light on the defect, according to the defect detection device according to one embodiment of the present invention, information on the size of the defect can also be calculated and acquired in a situation in which the irradiated light becomes straight light with respect to the optical axis.

[0089] The height of the defect (length in the Z-axis direction) can be calculated using the following equation 1.

[0090] [Formula 1] Z-axis size of defect (㎛) = Luminance deviation from adjacent pixels (intensity) × Conversion factor (㎛ / intensity)

[0091] Here, the conversion factor can vary depending on the intensity of the light output, and can be measured using a reference sample whose height information is known.

[0092] The width of the defect (length in the X-axis direction) can be calculated using the following equation 2.

[0093] [Formula 2] X-axis size of defect (㎛) = vertical line width (pixel) × pixel resolution (㎛ / pixel)

[0094] The length of the defect (length in the Y-axis direction) can be calculated using Equations 3 and 4 below.

[0095] [Formula 3] Y-axis size of defect (㎛) = (Expected length of vertical line (pixel) - Observed length of vertical line (pixel) + 1) × pixel resolution (㎛ / pixel)

[0096] The expected length of the vertical line can be calculated by using the height h of the defect calculated in Equation 1 with reference to Fig. 4. Here, since R is much larger than h, the length of the chord can be assumed to be equal to the length of the arc.

[0097] The length L of the arc can be calculated using the Pythagorean theorem using R and h. Here, the expected length (pixel) of the vertical line can be calculated using Equation 4 below.

[0098] [Formula 4] Expected length of vertical line (pixel) = (arc length L (㎛) / sheet feed speed (㎛ / s)) × camera line acquisition speed (pixel / s)

[0099] Referring to FIGS. 5 and 6, the light irradiation unit (120) of the defect detection device (100) according to one embodiment of the present invention includes a lighting unit (122) and a telecentric illumination optical system (124) that allows only the straight light (L1a) parallel to the optical axis (LA) toward the portion where the sheet-like material is curved to pass through, among the light irradiated from the lighting unit (122). Meanwhile, the first image acquisition unit (130) includes a first camera unit (132) and a first telecentric lens (134) that allows only the straight light (L1b) parallel to the optical axis (LA) obtained from the portion where the sheet-like material is curved to pass through, among the light acquired by the first camera unit (132). Therefore, all straight light (L1) that reaches the first image acquisition unit (130) from the light irradiation unit (120) becomes parallel to the optical axis (LA).

[0100] Referring to Fig. 5, a pair of guide rollers (118a, 118b) are arranged at predetermined positions on the left and right sides of the support roller (110) to provide an appropriate level of tension to the sheet-like material being transported and to control the transport direction. An appropriate number of guide rollers may be used to control the transport path of the sheet-like material (S) and to provide the necessary tension to the sheet-like material. The guide rollers (118a, 118b) rotate around the guide roller rotation axis (117a, 117b).

[0101] The above support roller (110) has a circumferential surface (112), and the sheet-like material (S) comes into contact with the circumferential surface (112) of the support roller (110) at a predetermined angle (θ). The support roller (110) rotates around a support roller rotation axis (114) that is coaxial with the horizontal axis direction (HA). The back surface of the sheet-like material (S) comes into contact with the circumferential surface (112), and an anti-slip coating may be provided on the circumferential surface (112) so that the sheet-like material does not slip on the circumferential surface (112) and can be conveyed by a precisely controlled conveying distance.

[0102] In a state where the rotation speed of the support roller (110) and the conveying speed of the sheet-like material (S) are the same, a speedometer (116) for measuring the rotation speed of the support roller (110) is provided at one end of the support roller rotation shaft (114) of the support roller (110). The speedometer (116) measures the rotation speed of the support roller (110) and thus the conveying speed of the sheet-like material (S).

[0103] The second image acquisition unit (140) is arranged spaced apart from the upper side of the sheet-like material (S), and the second image acquisition unit (140) detects light reflected from the tangent portion (112l) by scanning the line along the inclined axis (IA) that is arranged to be inclined at a predetermined angle (α) in the direction toward the light irradiation unit from the vertical axis (VA) that is perpendicular to the tangent portion (112l) corresponding to the vertex of the curved portion on the surface of the sheet-like material (S). Accordingly, the inclined axis (IA), which is the optical axis of the straight light (L2) entering the second image acquisition unit (140), forms an angle of 90-α with respect to the optical axis (LA) of the straight light (L1a) irradiated from the light irradiation unit (120). If the α angle is, for example, 10 degrees, the oblique axis (IA), which is the optical axis of the straight light (L2) entering the second image acquisition unit (140), forms an angle of 80 degrees with respect to the optical axis (LA) of the straight light (L1a) irradiated from the light irradiation unit (120), and since the light irradiation unit (120) irradiates the sheet-like material, which is the subject, with light at a low angle, dark field illumination is achieved. In dark field illumination, a defective part (a protruding part or a sunken part) is displayed brightly and a part without a defect is displayed darkly.

[0104] The second image acquisition unit (140) above generates a one-dimensional reflection image displayed as brightness intensity at a predetermined point in time for the tangent portion (112l) of the curved portion of the sheet-like material irradiated with dark field illumination.

[0105] Fig. 7 is a perspective view of a defect detection device according to another embodiment of the present invention. Referring to Fig. 7, the optical axis (LA) of light projected from the light irradiation unit (120) to the first image acquisition unit (130) is arranged to be inclined at a predetermined angle with respect to the horizontal axis direction of the rotation axis (114) of the support roller (110).

[0106] FIG. 8 is a perspective view of a defect detection device according to another embodiment of the present invention. Referring to FIG. 8, the light irradiation unit and the first image acquisition unit, which irradiate light obliquely as shown in FIG. 7, are arranged as a pair at an angle to each other. Accordingly, the light irradiation unit (120a, 120b) of the defect detection device of the embodiment illustrated in FIG. 8 includes a plurality of lighting units (122a, 122b) that irradiate light obliquely to each other toward a portion where the sheet-like material (S) is curved, and a plurality of telecentric illumination optical systems (124a, 124b) that allow only straight light parallel to the optical axis (LA) toward the portion where the sheet-like material is curved among the light irradiated from each of the plurality of lighting units to pass therethrough, and are arranged to correspond to each of the plurality of lighting units. The plurality of light irradiation units (120a, 120b) are configured to irradiate light in opposite directions at a predetermined angle based on a direction perpendicular to the extension direction of the tangent unit (112l) on the XY plane.

[0107] The first image acquisition unit (130a, 130b) of the defect detection device of the embodiment illustrated in FIG. 8 comprises a plurality of first camera units (132a, 132b) that acquire light at an angle to each other toward a portion where the sheet-like material is curved, and a plurality of first telecentric lenses (134a, 134b) that are arranged to correspond to each first camera unit of the plurality of first camera units and that allow only straight light parallel to the optical axis (LA) acquired from the portion where the sheet-like material is curved to pass through the light acquired by each first camera unit of the plurality of first camera units. The plurality of first image acquisition units (130a, 130b) acquire light at an angle to each other in opposite directions at a predetermined angle based on a direction perpendicular to the extension direction of the tangent portion (112l) in the XY plane.

[0108] The second image acquisition unit (140) illustrated in Fig. 8 includes a second camera unit (142) and a second telecentric lens (144), similar to the second image acquisition units illustrated in Figs. 5 and 7. In addition, the second image acquisition unit generates a one-dimensional reflection image displayed as a brightness intensity at a predetermined point in time for a tangent portion (112l) of a portion where the sheet-like material is curved and illuminated with dark field illumination.

[0109] Meanwhile, the image processing unit (150) illustrated in FIG. 1 is configured to image process light received by at least one of the first image acquisition unit and the second image acquisition unit in the embodiments illustrated in FIGS. 5, 7, and 8.

[0110] FIG. 9 is a flowchart showing the image processing sequence of a defect detection device (100) according to an embodiment of the present invention as illustrated in FIG. 5.

[0111] Referring to FIG. 9, as described above, the first image acquisition unit (130) performs a step (S1) of acquiring a two-dimensional projection image of a tangent portion of a sheet-like material, and a step (S2) of generating a one-dimensional projection image in which the brightness intensity of light projected for each column according to each time is accumulated is performed.

[0112] In step (S2), a one-dimensional projection image can be generated by integrating the brightness intensity of the projected light, or a one-dimensional projection image can be generated by averaging the brightness intensity of the projected light.

[0113] With regard to integrating or averaging projected brightness intensities, FIGS. 10A and 10B are explanatory diagrams illustrating two profile generation methods of an image acquisition unit in a defect detection device according to an embodiment of the present invention. FIG. 10A illustrates a profile generation method in which the brightness intensity of projected light is integrated, and FIG. 10B illustrates a profile generation method in which the brightness intensity of projected light is processed as an average value.

[0114] Figure 10a illustrates a case where the image is scanned vertically to calculate the accumulated brightness intensity of each column line. Figure 10b illustrates a case where the image is scanned vertically to calculate the average brightness intensity of each column line. When the number of columns to be accumulated is 8, if the sum of all rows exceeds 255 when the brightness intensities are accumulated, it is considered overexposure, and the output of the light illumination unit's brightness intensity needs to be lowered. Therefore, in this case, it is preferable to select the averaging method rather than the accumulation method.

[0115] Referring again to FIG. 9, the image processing unit (150) performs a step (S3) of sequentially generating a two-dimensional array of images in chronological order from the one-dimensional projection images generated at each of a plurality of predetermined points in time. Thereafter, the image processing unit (150) performs a step (S4) of correcting problems such as uneven lighting or tilted images.

[0116] Next, the image processing unit (150) performs a differentiation processing step (S5) of extracting only images with a predetermined brightness change compared to the surroundings from the two-dimensionally arranged images in time sequence. Thereafter, the image processing unit (150) additionally performs a BLOB step (Binary Large Object step) (S6) of identifying an object determined to be one object from the extracted image, and then performs a step (S7) of classifying the type of defect, and a step (S8) of generating and storing a map of the generated size information for the type of defect is performed. The image processing unit (150) performs a step (S9) of analyzing the periodicity of a defect that meets the criteria for being determined to be a defect using a fast Fourier transform (FFT) to detect whether there is an abnormality.

[0117] After the step (S10) of obtaining a one-dimensional reflection image through line scanning at multiple viewpoints in the second image acquisition unit (140) is performed, the obtained one-dimensional reflection image is sent to the image processing unit (150). Meanwhile, the image processing unit (150) performs the step (S11) of sequentially allocating the values ​​of each one-dimensional reflection image in a two-dimensional array from the one-dimensional reflection image obtained through line scanning at multiple viewpoints in the second image acquisition unit (140). Next, the image processing unit (150) performs the step (S12) of correcting the problem when the lighting is uneven. Thereafter, the image processing unit (150) additionally performs the BLOB step (Binary Large Object step) (S13) of identifying an object determined to be one object in the extracted image.

[0118] In the S7 step described above, a logical operation is performed on two images that have passed through the S6 step in the first image acquisition unit (130) and the S13 step in the second image acquisition unit (140) to classify the defect type.

[0119] FIG. 11 is an explanatory diagram explaining a process of processing an image obtained from a first image acquisition unit of a defect detection device according to an embodiment of the present invention, and FIG. 12 is an explanatory diagram explaining a process of matching and processing images obtained from a first image acquisition unit and a second image acquisition unit of a defect detection device according to an embodiment of the present invention.

[0120] Referring to Fig. 11, the process of obtaining an information map for information such as the size of an object detected in an image from an image generated by an image processing unit after performing steps (S1, S2, S3) of Fig. 9, an image after undergoing steps (S4, S5) corresponding to a preprocessing step, and an image (S6) after BLOB processing is described.

[0121] Referring to Fig. 12, by matching and combining the images obtained from the first image acquisition unit and the images obtained from the second image acquisition unit, protruding defects and sunken defects or holes can be identified. Although sunken defects or holes cannot be detected from the images obtained from the first image acquisition unit, by combining the images obtained from the first image acquisition unit and the images obtained from the second image acquisition unit, protruding defects, sunken defects, and holes can all be distinguished and detected.

[0122] FIG. 13 is a flowchart showing the steps of processing an image by an image processing unit in the defect detection device according to the embodiment of FIG. 8. In the case of the defect detection device illustrated in FIG. 8, when the light that is irradiated to a predetermined point of the tangent part of the sheet-like material at an angle to each other and projected respectively intersects, the images obtained from each of the first image acquisition units (130a, 130b) are each processed, and after the step (S5a, S5b) in which the straight line component is emphasized using the differentiation method, the step (S5-5) in which the two images from each of the first image acquisition units (130a, 130b) are merged with each other by logical OR is performed. The steps after the images are merged are the same as the steps described in relation to FIG. 9, and therefore, a redundant description thereof will be omitted. In FIG. 13, the same steps performed in each first image acquisition unit (130a, 130b) and the same steps in which the image signals obtained from each first image acquisition unit (130a, 130b) are processed in the image processing unit (150) are distinguished by adding 'a' or 'b' to the drawing symbols indicating each step in FIG. 9.

[0123] Fig. 14 is a perspective view of a defect detection assembly including an array of multiple defect detection devices according to one embodiment of the present invention. Fig. 15 is an exploded perspective view of an individual defect detection device among the defect detection devices of the first row of the defect detection assembly of Fig. 14, and Fig. 16 is a side view of the defect detection assembly of Fig. 14. Fig. 17 is a plan view of the defect detection assembly of Fig. 14.

[0124] The sheet-like material has a considerable width, and the defect detection devices shown in FIGS. 5 to 8 are suitable for performing local detection work at a predetermined point. Therefore, in order to detect defects on the surface of a sheet-like material having a wider width, a defect detection assembly (200) having a plurality of individual defect detection devices arranged in parallel is required.

[0125] Referring to FIG. 14, the defect detection assembly (200) has a plurality of defect detection devices based on the defect detection device of the above-described structure, including a plurality of defect detection devices (250a) of a first row (260a) arranged in parallel in the width direction of the sheet-like material and a plurality of defect detection devices (250b) of a second row (260b) arranged correspondingly thereto.

[0126] In FIGS. 5 to 8, the light irradiation unit and the first image acquisition unit in each defect detection device are arranged vertically on the ground, but in order to efficiently utilize space, the plurality of defect detection devices (250a) of the first row (260a) of the defect detection assembly (200) illustrated in FIGS. 14 to 17 and the defect detection devices (250b) of the second row (260b) arranged correspondingly thereto are arranged so that the optical axes of the straight light (La, Lb) between each light irradiation unit (220a, 220b) and each first image acquisition unit (230a, 230b) are inclined with respect to the ground, as illustrated in FIG. 16 in particular.

[0127] The defect detection devices of the first row (260a) and the second row (260b) are arranged to face each other in the longitudinal direction (Y) of the sheet-like material, and a plurality of individual defect detection devices (250a, 250b) are arranged side by side in the width direction (X direction) of the sheet-like material.

[0128] Each of the defect detection devices of the first row (260a) and the second row (260b) is provided with a respective support roller (210a, 210b). Guide rollers (218a, 218b) are arranged on the left and right sides of the support rollers (210a, 210b) to provide a predetermined tension to the sheet-like material and control the transport direction of the sheet-like material.

[0129] Referring to Fig. 15, the individual defect detection device (250a) of the defect detection device of the first row (260a) is provided with a light irradiation unit (220a) and a first image acquisition unit (230a) inside a casing (251a). The light irradiation unit (220a) of the defect detection device of the first row (260a) includes an illumination unit (222a) and a telecentric illumination optical system (224a), and the first image acquisition unit (230a) of the defect detection device of the first row (260a) includes a first camera unit (232a) and a telecentric lens (234a). The light irradiation unit (220a) and the first image acquisition unit (230a) of the defect detection device of the first row (260a) are not arranged to face each other, but interact optically through the light control unit (261a).

[0130] The above light control unit (261a) includes a light irradiation unit through-hole (262a) open to the light irradiation unit (220a) and a light acquisition unit through-hole (264a) open to the first image acquisition unit (230a). The side surface of the light control unit (261a) is provided with a concave portion (266a) corresponding to the profile of the curved portion of the sheet-like material. The light irradiation unit through-hole (262a) and the light acquisition unit through-hole (264a) are each provided with a light irradiation port light path control element (263a) and a light acquisition unit light path control element (265a) for controlling the light path along which light generated from the light irradiation unit is irradiated to the tangent portion (212la, 212lb) of the curved portion of the sheet-like material and then projected and received by the first image acquisition unit (230). The same configuration is applied to the defect detection device of the second column (260b), and redundant description is omitted.

[0131] Meanwhile, as illustrated in Fig. 17, the individual defect detection devices of the plurality of defect detection devices of the first row (260a) and the individual defect detection devices of the plurality of defect detection devices of the second row (260b) are arranged to be staggered in the width direction of the sheet-like material. Accordingly, defect detection on the surface of the sheet-like material corresponding to the width (w) of the individual defect detection devices is not missed.

[0132] Referring again to FIGS. 14 to 16, a defect detection assembly (200) according to one embodiment of the present invention includes a second image acquisition unit (240) extending in the width direction of the sheet-like material. The second image acquisition unit is positioned between the plurality of defect detection devices of the first row (260a) and the plurality of defect detection devices of the second row (260b).

[0133] The second image acquisition unit (240) is positioned spaced apart from the upper surface of the sheet-like material and detects defects on the surface of the sheet-like material by line scanning light reflected from the surface of the sheet-like material. The second image acquisition unit (240) includes a second camera unit (242) extending in the width direction of the sheet-like material and a second rod lens array (244) that focuses light onto the second camera unit.

[0134] In addition, the second image acquisition unit (240) includes a pair of upper light irradiation units (248a, 248b) arranged on both sides of the second camera unit (242). The pair of upper light irradiation units (248a, 248b) obliquely illuminate the surface of the sheet-like material, and the second image acquisition unit generates a one-dimensional reflection image displayed as a brightness intensity at a predetermined point in time for the surface of the sheet-like material illuminated with dark field illumination.

[0135] The second image acquisition unit (240) further includes a lower light irradiation unit (246) positioned opposite the second camera unit with respect to the sheet-like material. When light irradiated from the lower light irradiation unit (246) is detected by the second camera unit, it can be seen that a hole has been formed in the sheet-like material.

[0136] The above defect detection assembly (200) further includes an image processing unit configured to process an image generated from at least one of the first image acquisition unit of the individual defect detection device and the second image acquisition unit disposed between the first and second rows of defect detection devices.

[0137] While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely examples. Those skilled in the art will readily appreciate that various modifications and equivalent alternative embodiments are possible based on the embodiments described herein. Therefore, the true scope of technical protection of the present invention should be determined based on the appended claims.

[0138] The terms "said" or similar designators used in the description and claims of the invention can refer to both the singular and the plural, unless specifically limited. Furthermore, unless there is an explicit description of the order or the contrary regarding the steps constituting the method according to the embodiment, the steps can be performed in any suitable order. The embodiments are not necessarily limited by the order in which the steps are described. The use of all examples or exemplary terms (e.g., "for example," etc.) in the embodiments is merely to further illustrate the embodiments, and the scope of the embodiments is not limited by the examples or exemplary terms, unless otherwise defined by the claims. Furthermore, those skilled in the art will appreciate that various modifications, combinations, and variations can be made according to design conditions and factors within the scope of the appended claims or their equivalents.

Claims

1. In a defect detection device for detecting a defect on the surface of a flexible sheet material, the defect detection device comprises: A support roller having a cylindrical surface to provide a curved transport path for the sheet-like material and supporting the sheet-like material; A light irradiation unit disposed on one side of the direction in which the sheet-like material is transported, with respect to a portion where the sheet-like material is curved along the circumference of the cylindrical surface of the support roller; and Including a first image acquisition unit arranged on the other side of the direction in which the sheet-like material is transported with respect to the portion where the sheet-like material is bent; The above light irradiation unit irradiates light toward the tangent portion where the sheet-like material is curved, A defect detection device characterized in that the first image acquisition unit detects light projected onto a tangential portion of the sheet-like material by line scanning.

2. In paragraph 1, It further includes a second image acquisition unit spaced apart from and arranged on the upper side of the sheet-like material, A defect detection device characterized in that the second image acquisition unit is arranged to be inclined at a predetermined angle in a direction toward the light irradiation unit from a vertical axis perpendicular to the tangent portion on the surface of the sheet-like material, and detects light reflected from the tangent portion by line scanning.

3. In paragraph 1, The above light irradiation unit, lighting unit; and A telecentric lighting optical system that passes only the straight light parallel to the optical axis toward the portion where the sheet-like material is curved among the light irradiated from the lighting unit; The above first image acquisition unit, First camera unit; and A defect detection device characterized by including a first telecentric lens that passes only straight light parallel to the optical axis obtained from a portion where the sheet-like material is curved among the light obtained by the first camera unit.

4. In paragraph 1, The above light irradiation unit includes a plurality of lighting units that irradiate light obliquely toward a portion where the sheet-like material is curved, and a plurality of telecentric lighting optical systems that allow only straight light parallel to the optical axis toward the portion where the sheet-like material is curved to pass through the light irradiated from each of the plurality of lighting units, and are arranged to correspond to each of the plurality of lighting units. The plurality of above lighting units are configured to irradiate light in opposite directions at a predetermined angle based on a direction perpendicular to the extension direction of the above tangent portion, The first image acquisition unit comprises a plurality of first camera units that acquire light at an angle to each other toward a portion where the sheet-like material is curved, and a plurality of first telecentric lenses that pass only straight light parallel to the optical axis acquired from the portion where the sheet-like material is curved among the light acquired by each first camera unit of the plurality of first camera units, and are arranged to correspond to each first camera unit of the plurality of first camera units. A defect detection device characterized in that the plurality of first camera units are configured to obtain light in opposite directions at a predetermined angle based on a direction perpendicular to the extension direction of the tangent portion.

5. In paragraph 2, The above second image acquisition unit, Second camera unit; and A second telecentric lens that passes only the straight light parallel to the optical axis obtained from the portion where the sheet-like material is curved among the light obtained by the second camera unit; A defect detection device characterized in that the second image acquisition unit generates a one-dimensional reflection image displayed as a brightness intensity at a predetermined point in time for a tangential portion of a curved portion of the sheet-like material illuminated with dark field illumination.

6. In paragraph 3, A defect detection device characterized in that the first image acquisition unit generates a one-dimensional projection image displayed with brightness intensity at a predetermined point in time for a tangent portion of a portion where the sheet-like material is curved.

7. In paragraph 6, A defect detection device characterized in that it further includes an image processing unit configured to image process light received by at least one of the first image acquisition unit and the second image acquisition unit.

8. In paragraph 7, A defect detection device characterized in that the image processing unit performs a step of generating a two-dimensional array image in time sequence from one-dimensional projection images generated at a plurality of predetermined points in time.

9. In paragraph 8, A defect detection device characterized in that the image processing unit additionally performs a differentiation processing step of extracting only images having a predetermined change in brightness compared to the surroundings from the two-dimensionally arranged images according to the time sequence.

10. In paragraph 9, A defect detection device characterized in that the image processing unit additionally performs a BLOB step (Binary Large Object step) for identifying an object judged to be one object in the extracted image.

11. In paragraph 10, A defect detection device characterized in that the image processing unit additionally performs a step of obtaining location and size information for individual objects and generating an information map.

12. In a defect detection assembly having a plurality of defect detection devices of the first clause, The plurality of defect detection devices are a plurality of defect detection devices in a first row arranged in parallel along the width direction of the sheet-like material; and A defect detection assembly characterized by comprising a plurality of defect detection devices of a second row arranged opposite to the plurality of defect detection devices of the first row in the longitudinal direction of the sheet-like material.

13. In paragraph 12, A defect detection assembly characterized in that the individual defect detection devices of the plurality of defect detection devices of the first row and the individual defect detection devices of the plurality of defect detection devices of the second row are arranged alternately in the width direction of the sheet-like material.

14. In paragraph 12, Including a second image acquisition unit extending in the width direction of the above sheet-like material, A defect detection assembly characterized in that the second image acquisition unit is arranged between the plurality of defect detection devices of the first row and the plurality of defect detection devices of the second row.

15. In paragraph 14, A defect detection assembly characterized in that the second image acquisition unit is positioned on the upper side of the surface of the sheet-like material and detects a defect on the surface of the sheet-like material by line scanning light reflected from the surface of the sheet-like material or light transmitted from the lower side.

16. In paragraph 15, The above second image acquisition unit, a second camera unit extending in the width direction of the sheet-like material; and A second rod lens array that focuses light acquired by the second camera unit; The second image acquisition unit further includes a pair of upper light irradiation units arranged on each side of the second camera unit, A pair of the upper light irradiating portions obliquely illuminate the surface of the sheet-like material, A defect detection assembly characterized in that the second image acquisition unit generates a one-dimensional reflection image displayed as a brightness intensity at a predetermined point in time for the surface of the sheet-like material illuminated with dark field illumination.

17. In paragraph 16, The second image acquisition unit further includes a lower light irradiation unit positioned on the opposite side of the second camera unit with respect to the sheet-like material, The lower light irradiation unit illuminates the surface of the sheet-like material from below, A defect detection assembly characterized in that the second image acquisition unit generates a one-dimensional transmission image displayed as a brightness intensity at a predetermined point in time for the surface of the sheet-like material irradiated by the lower light irradiation unit (246).

18. In paragraph 12, A defect detection assembly, characterized in that each of the plurality of defect detection devices of the first row and the plurality of defect detection devices of the second row each includes an optical path control element that controls an optical path.

19. In paragraph 15, A defect detection assembly characterized in that it further includes an image processing unit configured to process an image generated from at least one of the first image acquisition unit and the second image acquisition unit.

Images