JP2016130672A - Sheet inspection device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet inspection device and method capable of detecting a defect in a sheet having a conductive pattern formed on a substrate at a practical processing speed.SOLUTION: There is provided an inspection device 10 for a sheet 40 having a conductive pattern with periodicity formed on a substrate, the sheet inspection device comprising at least: a conveying part that conveys the sheet; an illumination part 22 that illuminates the sheet; an imaging part 23 that receives transmitted light or reflection light from the sheet to create a gray image; and first image processing means that performs high-definition binarization of the gray image, recognizes the position of a feature point having periodicity of the conductive pattern, and detects a defect in the sheet.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an appearance inspection apparatus and method for a sheet on which a conductive pattern used for a touch panel or the like is formed.

  In recent years, touch panels have been increasingly incorporated into large screens for personal computer displays and digital signage installed on the streets. When ITO (indium tin oxide) is used for the sensor of such a large touch panel, there is a problem that the response speed becomes slow because the resistance value of the ITO film is high. In particular, when a resin film is used as the substrate, this problem is more serious because it is difficult to form a film at a high temperature and it is difficult to lower the resistance value of the ITO film.

  Therefore, as an alternative to ITO, it has been studied to form a wiring pattern with silver or copper fine wires. For example, Patent Document 1 describes a conductive sheet for a projected capacitive touch panel in which a conductive pattern of a sensor unit is formed with a thin metal wire. Patent Document 2 describes a touch panel using mesh-shaped metal wiring.

JP2013-152559A JP 2010-277392 A

  However, there has been no practical inspection method for such a conductive sheet using fine metal wires. Since the conductive sheet is disposed on the front surface of the screen display unit, the thin metal wire is formed in a mesh shape or a parallel pattern by reducing the line width. Therefore, it is difficult to detect even a minute defect in a part of the thin line by an electrical inspection method such as resistivity measurement.

  On the other hand, in the field of printed circuit boards, a method is known in which an image of a circuit is optically acquired and checked for the presence or absence of wiring defects and foreign matter by collating with a non-defective image. However, in the conductive sheet for touch panels and the like, the width of the fine metal wire is narrower and smaller than the optical resolution of a practical optical device, so that there is a problem that accurate inspection cannot be performed depending on image collation. Further, even if image collation is performed using advanced image processing, there is a problem that it is difficult to perform inspection at a practical processing speed because the size of image data to be processed is large.

  The present invention has been made in view of the above, and an object of the present invention is to provide a sheet inspection apparatus and method capable of detecting a defect of a sheet having a conductive pattern formed on a substrate at a practical processing speed. .

  In view of the above problems, the present invention pays attention to the fact that the conductive pattern of a sheet for a touch panel or the like has periodicity, and performs inspection using the periodicity.

  The sheet inspection apparatus of the present invention is an inspection apparatus for a sheet in which a conductive pattern having periodicity is formed on a substrate, and includes a conveyance unit that conveys the sheet, an illumination unit that illuminates the sheet, and the sheet An imaging unit that receives transmitted light or reflected light from the image and generates a grayscale image, binarizes the grayscale image, recognizes the position of the feature point having the periodicity of the conductive pattern, and First image processing means for detecting a defect.

  With this configuration, the sheet defect can be detected at a practical processing speed.

  Preferably, the sheet inspection apparatus further includes a second image processing unit that detects the omission of the conductive pattern having the periodicity by binarizing the grayscale image.

  Preferably, the base material is transparent, and the imaging unit is disposed to face the illumination unit with the sheet interposed therebetween, and receives a transmitted light from the sheet to generate a grayscale image.

  Preferably, the conductive pattern having the periodicity is mesh-shaped, and the feature point is the mesh-shaped intersection. Preferably, the base material is a synthetic resin film. Preferably, the sheet is a touch panel material. Preferably, the conductive pattern having the periodicity is formed by printing.

  Preferably, the sheet further includes an aperiodic wiring including an electrode connected to an end portion of the conductive pattern having the periodicity and a lead wiring, and the sheet inspection apparatus displays the grayscale image in high definition. The image processing apparatus further includes third image processing means for detecting a defect in the non-periodic wiring by digitizing and collating with a reference image.

  The sheet inspection method of the present invention is an inspection method for a sheet in which a conductive pattern having periodicity is formed on a substrate, and images the image by irradiating the sheet with light while conveying the sheet. Step S1 for receiving transmitted light or reflected light from the sheet by the unit to generate a grayscale image, Step S2 for converting the grayscale image into a high-definition binary image, and the high-definition binary image, It has step S3 which recognizes the position of the feature point which has the periodicity of a conductive pattern, and step S4 which detects the defect of the sheet.

  Preferably, the step S4 is a step of detecting a defect of the sheet based on the high-definition binary image and the position of the feature point.

  ADVANTAGE OF THE INVENTION According to this invention, it can test | inspect with a practical process speed with respect to the sheet | seat in which the conductive pattern which has periodicity was formed on the base material.

It is a perspective view of the sheet inspection apparatus which is one Embodiment of this invention. It is a side view of the sheet inspection apparatus which is one embodiment of the present invention. It is a functional block diagram of the sheet inspection apparatus which is one embodiment of the present invention. It is a flowchart of the sheet inspection method which is one Embodiment of this invention. It is an example of the sheet | seat which the apparatus and method of this invention make a test object. It is a figure for demonstrating the relationship between the optical resolution of a grayscale image, and a metal fine wire.

  An embodiment of the present invention will be described with reference to the drawings. The present embodiment relates to inspection of a conductive sheet for a touch panel using a transparent synthetic resin film as a base material. In this specification, a sheet on which a conductive pattern is formed is simply referred to as a “conductive sheet”.

  First, the conductive sheet targeted by the inspection apparatus and method of the present embodiment will be described with reference to FIG.

  In FIG. 5, in the conductive sheet 40, a mesh-shaped pattern 43 having periodicity is formed on a transparent base material 41 by thin metal wires 42. In the pattern 43, there are intersecting portions 44 of fine metal wires and are scattered with periodicity corresponding to the periodicity of the pattern 43. This intersection is used for inspection as a feature of a thin metal wire. Further, the pattern 43 includes a broken portion 45 of a fine metal wire.

  The electrode 46 and the lead-out wiring 47 are electrically connected to the left and right ends of the mesh pattern 43 to form a non-periodic metal wiring 48 having no periodicity. Thereby, between the corresponding left and right electrodes 46, 46 can be energized by the mesh pattern 43, and as a whole, conductive bands crossing the figure left and right are formed in parallel in the vertical direction. When this conductive sheet 40 is used as a touch panel, a panel is formed by overlapping with a conductive sheet having a conductive band formed in a direction orthogonal to the conductive sheet and a surface protective layer. When the finger touches the panel surface, the capacitance between the conductive bands of the two conductive sheets changes, and the position of the fingertip can be determined by detecting this change with an IC circuit.

  Although the kind of transparent base material 41 is not specifically limited, It is preferable that it is a synthetic resin film. When a synthetic resin film is used as the base material, inspection becomes difficult due to vibration during transportation, etc., so that the merit of using the present invention is great. In addition, as a base material of the conductive sheet for touch panels, a PET film is often used.

  The width of the conductive sheet 40 is not particularly limited. However, if the sheet width is too small, the merit of using the inspection apparatus and method of the present embodiment is small, so the sheet width is preferably 100 mm or more, and more preferably 300 mm or more. When the sheet width is large, the imaging units can be provided in parallel as will be described later. However, if the sheet width is too large, vibration during conveyance becomes excessive, so the sheet width is preferably 2000 mm or less. Also, the length of the conductive sheet is not particularly limited, and it may be a single sheet or a long sheet that can be wound into a roll.

  The material of the fine metal wire 42 is not particularly limited, but silver and copper are often used. In addition, as a method for forming a thin metal wire, a method of printing an ink containing metal nanowires or nanoparticles, a method using a silver salt photographic technique, a method of etching a metal film formed on the entire surface, or the like is used.

  The width of the fine metal wire 42 is often 10 μm or less. Usually, the line width of the fine metal wire 42 (conductive pattern) is preferably 3 times or more of the optical resolution, but in the present invention, the metal fine wire 42 (conductive pattern) is conductive even if the width of the fine metal wire 42 (conductive pattern) is less than the optical resolution. Pattern inspection is possible. From the viewpoint that the effects of the present embodiment can be remarkably obtained, the width of the fine metal wire is preferably 15 μm or less, more preferably 10 μm or less, and particularly preferably 8 μm or less. Further, if the fine metal wire is too thin, the inspection is difficult even with this embodiment. Therefore, the width of the fine metal wire is preferably 1 μm or more, more preferably 3 μm or more. Although the space | interval (mesh pitch) of a metal fine wire is not specifically limited, A thing of 100-400 micrometers is used abundantly for touch panels.

  Next, the structure of the inspection apparatus of this embodiment is demonstrated based on FIGS.

  1 and 2, the inspection apparatus 10 includes a conveyance unit that conveys a conductive sheet 40 to be inspected, a linear illumination 22, and a line sensor camera 23 as an imaging unit. In the figure, the frame of the apparatus is omitted, and the transport unit shows only two rollers 21 which are a part thereof.

  The linear illumination 22 is arranged below the conductive sheet so that the longitudinal direction thereof is orthogonal to the conveying direction of the conductive sheet 40 and irradiates the light L toward the conductive sheet. The kind of linear illumination is not specifically limited, For example, what uses an LED element as a light source can be used. The width of the light emitting surface of the linear illumination is preferably narrow in order to obtain a clearer transmission image. The length of the light emitting surface of the linear illumination is preferably larger than the width of the conductive sheet to be inspected.

  The line sensor camera 23 is disposed above the conductive sheet 40 so as to face the linear illumination 22 with the conductive sheet interposed therebetween. The line sensor camera collects the transmitted light from the conductive sheet with a lens and receives the light with an internal linear imaging device. A linear imaging device is an imaging device in which cells that sense light are arranged in a line. The fact that the line sensor camera is arranged to face the linear illumination means that the linear imaging device is arranged in parallel to the linear illumination and facing each other. As the linear imaging device, a device constituted by a CCD or a CMOS can be used. Analog image signals from the linear imaging device are also quantized into a multi-tone digital image, that is, a grayscale image (also referred to as a multi-value image) by an A / D converter inside the line sensor camera.

  The optical resolution d of the grayscale image may be equal to or greater than the width of the fine metal wire 42 because high-definition binarization processing is performed later. However, if the optical resolution d is too coarse with respect to the width of the fine metal wire, accurate inspection becomes difficult. Therefore, the optical resolution is preferably not more than 8 times the width of the fine metal wire, and more preferably not more than 4 times. It is particularly preferable that it is 2 times or less. On the other hand, the optical resolution d may be finer than the width of the thin metal wire. However, if the optical resolution d is too fine, the size of the image data to be processed becomes large. Therefore, the optical resolution is preferably 0.5 times or more the width of the metal thin line. The optical resolution d depends on the lens specifications of the line sensor camera 23 and the number of cells of the linear imaging device. In addition, the substantial resolution of the obtained image depends on the vibration when the conductive sheet is conveyed, the width of the light emitting surface of the linear illumination, and the like.

The grayscale image has an information amount equal to the number of gradations m per pixel. In order to obtain a clear image later by high-definition binarization processing, it is preferable that the number of gradations m is large. Gradation number m is the width w and the optical resolution d of the metal thin wires, m> is preferably (d / ^{w) 2,} m> and more preferably a (2d / ^{w) 2.} On the other hand, the size of the image data to be processed and the number of gradations m is too large increases, the number of gradations m is preferably 2 ³² or less, more preferably 2 ¹⁶ or less. The number of gradations m depends on the cell area of the linear image sensor of the line sensor camera, the specifications of the A-D converter, and the like.

The line sensor camera 23, the number of cells of about 16,000 linear image sensor, the number of gradations those ^{2 10} are commercially available. By combining this with an appropriate lens, a grayscale image having a width of about 160 mm can be generated with an optical resolution of about 10 μm. When the width of the conductive sheet 40 is larger than this, a plurality of licensor cameras may be arranged in the width direction. For example, in FIG. 1 and FIG. 2, three line sensor cameras are juxtaposed.

  In FIG. 3, the conductive sheet inspection apparatus 10 includes a conveyance unit 20, a linear illumination 22, a line sensor camera 23, a processing unit 26, a control unit 30, and a storage unit 31.

Each line sensor camera 23 has a linear imaging device 24 and an A-D converter 25 therein. Each line sensor camera is in the camera holds grayscale image of gray scale level 2 ^10, when outputting outside the camera, in order to reduce the transmission load, and outputs the gradation lowering the gray image of the 2 ⁸ Also good.

  A processing unit 26 is connected to each line sensor camera 23. Inside the processing unit 26, a first image processing unit 27, a second image processing unit 28, and a third image processing unit 29 are configured. The first image processing unit 27 binarizes at least the area of the mesh pattern (43 in FIG. 5) in the grayscale image transferred from the line sensor camera, recognizes the position of the feature point of the fine metal line, Detect defects in the same area. The second image processing means 28 detects at least the mesh pattern pattern by low-definition binarizing at least the area of the mesh pattern (43 in FIG. 5) in the grayscale image transferred from the line sensor camera. The third image processing means 29 binarizes at least the area of the non-periodic metal wiring (48 in FIG. 5) in the grayscale image transferred from the line sensor camera, and compares it with the reference image in the same area. , Detecting defects in the same region. As the processing unit 26, a computer such as a personal computer (PC) or a workstation (WS) can be used. The first to third image processing means 27 to 29 may be implemented as software that operates on the processing unit 26, or may be implemented as an image processing circuit in the processing unit 26.

  The storage unit 31 stores information on the periodicity of the feature points of the fine metal wires, a reference image of the non-periodic metal wiring, a threshold value for binarization processing, and the like. As the storage unit, various storage devices such as a hard disk device can be used. The control unit 30 controls the entire inspection apparatus 10. A computer such as a PC or WS can be used as the control unit.

  Note that the configuration of the inspection apparatus 10 is not limited to the configuration of FIG. For example, in FIG. 3, the processing unit 26 is connected to each of the line sensor cameras 23. However, if processing can be performed at a practical speed, the grayscale image data from a plurality of line sensor cameras can be combined into 1 You may process with two computers. Alternatively, the first to third image processing means 27 to 29 may be constituted by physically separate computers or the like. Furthermore, among the first to third image processing means, some image processing means may be constituted by a plurality of computers or the like to perform parallel processing. In FIG. 3, one storage unit 31 is connected to the control unit 30, but each processing unit 26 may be provided with a storage unit.

  Next, the inspection method of this embodiment is demonstrated along FIG. 1 to 3 and FIG. 5 are used as reference numerals for members and the like.

  The conductive sheet 40 is irradiated with light by the linear illumination 22 while being transported by the transport unit 20. The light transmitted through the conductive sheet is received by the line sensor camera 23, and a grayscale image is generated by the line sensor camera (step S1 above). As described above, the internal operation of the line sensor camera is such that the transmitted light from the conductive sheet is collected by the lens and received by the linear imaging device 24, and the analog image signal from the linear imaging device is shaded by the A / D converter 25. Quantized to digital image. At this time, since the metal line on the transparent substrate 41 is opaque, the pixel corresponding to the part where the metal line exists is dark, and the pixel corresponding to the part where the metal line does not exist becomes bright. Since the number of bright pixels increases in the area of the mesh pattern 43, the A / D converter may increase the contrast by performing nonlinear quantization or the like. By step S1, if the optical resolution is 10 μm for one line in the width direction of the conductive sheet, an image for one line having a width of 10 μm is generated. By repeating step S1, an image of the entire conductive sheet is generated.

  The grayscale image data generated by the line sensor camera 23 is transferred to the first to third image processing means 27 to 29 in parallel while repeating Step S1.

  In the first image processing means 27 that has received the grayscale image data, the mesh pattern 43 region is inspected.

The first image processing means 27 converts at least the area of the mesh pattern 43 in the grayscale image into a high-definition binary image (step S2). In the high-definition binarization process, each pixel of the grayscale image is further finely divided while being interpolated (interpolated), and converted into two gradations of white and black by comparison with a predetermined threshold value. The interpolation can be performed by various known methods such as bilinear interpolation or higher order interpolation using grayscale image data for a plurality of continuous lines. If the metal thin line 42 is thin, the entire width may be included in one pixel of the grayscale image, and the outline may not be clearly obtained in the high-definition binary image. However, if there is a crossing portion 44 of fine metal lines in the mesh pattern, the gray image of that portion is slightly darker than the straight line or curved portion of the fine metal line, and appears slightly larger in the high-definition binary image. This can be determined, for example, by the size of the connected component that is a collection of black pixels connected to each other. In our experiments, the optical resolution 10 [mu] m, high definition binary to 4 × 4 times the gray-scale image obtained by gradation lowering the image data of two ¹⁰ gradations obtained from the imaging element 2 ⁸ gradations (16-fold) In the converted image, it was possible to clearly confirm the intersection of the thin metal wires having a width of about 10 μm.

  Note that the feature point means a point that has a predetermined periodicity and can appear darker than a straight line or a curved portion of a thin metal wire in a grayscale image. FIG. 6 shows an example when the width w of the fine metal wire 42 is 0.6 times the optical resolution d of the grayscale image. One pixel 50 of the grayscale image is represented by a square with one side d. Compared with the straight line portion (FIG. 6A), the area ratio of the thin metal wire that can be included in one pixel is at the intersection 44 (FIG. 6B) and the corner 51 (FIG. 6C) sharpened in a V shape by bending the thin metal wire. growing. As described above, the intersections of the fine metal wires and the corners sharpened in the V shape by bending the fine metal wires are characteristic points.

  Next, the first image processing means 27 recognizes the position of the feature point 44 of the fine metal wire 42 on the high-definition binary image (step S3). Since the feature points have periodicity corresponding to the mesh pattern, the first image processing unit 27 acquires information on the periodicity of the feature points set in advance from the storage unit 31 (for example, the pitch of the intersection). By referencing, it is possible to recognize which position on the high-definition binary image corresponds to the feature point. Note that the information regarding the periodicity of feature points can be automatically calculated by extracting a plurality of feature point candidates from a high-definition binary image.

  Next, the first image processing means 27 detects various defects based on the position of the high-definition binary image and the feature point 44 (step S4). Specifically, the quality of the feature point is determined from the size of the feature point on the high-definition binary image, for example, from the size of the connected component at the position corresponding to the feature point on the high-definition binary image. Can do. The crossing portion 44 of the fine metal wires has an important influence on the electrical characteristics, but manufacturing defects are likely to occur. Therefore, the merit of determining whether or not the crossing portion is normally formed is great. Moreover, when a big point (for example, big connected component) exists in the part which is not an intersection part, it can be judged that it is a foreign material, dirt, etc.

  As described above, the first image processing unit 27 can detect defects in the conductive sheet such as defective feature points and foreign matters in the pattern having periodicity.

  In the second image processing means 28 that has received the grayscale image data, the mesh pattern 43 area is inspected.

  The second image processing means 28 converts at least the area of the mesh pattern 43 in the grayscale image into a low-definition binary image (step S5). In the low-definition binarization processing, the pixels of the grayscale image data are integrated by taking the average of the grayscale levels for several adjacent pixels, and are converted into two gradations of white and black by comparison with a certain threshold value. At this time, the entire normal portion of the mesh pattern can be blackened by setting an appropriate threshold value. In the above-described low-definition binarization processing, the image is compressed (the number of pixels of the image is reduced), and there is an effect that the subsequent image processing can be speeded up. As another method, the entire image may be smoothed and then binarized, but in this case, the number of pixels is the same as the original grayscale image.

  Next, the second image processing means 28 detects a missing mesh pattern from the low-definition binary image (step S6). Here, the missing pattern means that a part of the fine metal wire constituting the pattern does not exist. If there is a portion in the mesh pattern 43 that has a certain extent and does not have the thin metal wire 42, only the pixel corresponding to the portion remains white in the low-definition binary image, and this can be detected. For example, a case where at least one or more minimum elements constituting a repetitive pattern does not exist may be detected as a missing pattern. Specifically, in the mesh pattern 43 of FIG. 5, when there is no fine metal wire 42 constituting at least one quadrangle, this can be detected as a missing pattern. Further, when the thin metal wire 42 has a thin line width or a thin line portion with a certain extent or more, it can be similarly detected as a missing pattern.

  As described above, the second image processing unit 28 can detect missing patterns having periodicity. With this method, it is possible to detect only omissions with a certain extent, but such omissions occur frequently due to substrate contamination during pattern formation, printing defects, etc., and they can be detected by simple image processing. There is an advantage in that it can be detected. In particular, there is a great merit when the inspection by the first image processing means 27 is supplemented by the inspection by the second image processing means.

  In the third image processing means 29 that has received the grayscale image data, the non-periodic metal wiring 48 including the electrodes and the lead wiring is inspected.

  The third image processing means 29 converts at least the region of the non-periodic metal wiring 48 in the grayscale image into a high-definition binary image (step S7). Unlike the metal thin line 42 that forms the mesh pattern 43, the non-periodic metal wiring 48 has a line width of about 30 to 100 μm at the minimum, so if the optical resolution of the grayscale image is sufficiently small, it is in one pixel of the grayscale image. Does not include the entire line width. Therefore, an image with a clear outline can be obtained by the high-definition binarization processing.

Next, the third image processing means 29 collates the high-definition binary image with the reference image of the non-periodic metal wiring 48 to detect a defect (step S8). The third image processing unit 29 acquires a reference image of the aperiodic metal wiring stored in the storage unit 31. The reference image may be a design image generated from CAD software or the like, or may be an image acquired in advance from a non-defective conductive sheet by the inspection apparatus of the present embodiment. If there is a difference between the obtained high-definition binary image and the reference image, it can be determined that a defect exists in that portion. In our experiments, the optical resolution 10 [mu] m, high definition binary to 10 × 10 times the density image gradation lowering in 2 ⁸ gradation image data of two ¹⁰ gradations obtained from the image sensor (100-fold) In the converted image, it was possible to inspect the appearance of the metal wiring with the minimum line width / interval of 30 μm by image matching.

  As described above, the third image processing unit 29 can detect a defect in the non-periodic metal wiring 48. Since the comparison with the reference image is performed, almost all defects such as missing wiring, short-circuiting, and foreign matter can be detected. The mesh pattern 43, which is difficult to inspect by image collation, is inspected by the first image processing means 27 and / or the second image processing means 28, and combined with the inspection of the non-periodic metal wiring by the third image processing means. The entire sheet 40 can be inspected.

  The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the technical idea.

  For example, the conductive sheet is not limited to that for the touch panel, but may be for an electromagnetic shielding plate provided on the front surface of the screen. The present invention is applicable to various conductive sheets in which a pattern having periodicity and a feature point having periodicity are formed.

  For example, although the mesh lattice shown in FIG. 5 is substantially square, the mesh shape is not limited to this, and may be a rhombus, a rectangle, or various polygons. Moreover, the pattern which has the periodicity of an electroconductive sheet is not restricted to a mesh form, You may be such that a broken line etc. are arranged side by side.

DESCRIPTION OF SYMBOLS 10 Conductive sheet inspection apparatus 20 Conveyance part 21 Roller 22 Linear illumination (illumination part)
23 Line sensor camera (imaging part)
24 linear imaging device 25 A-D converter 26 processing unit 27 first image processing unit 28 second image processing unit 29 third image processing unit 30 control unit 31 storage unit 40 conductive sheet 41 transparent substrate 42 metal fine wire 43 mesh shape Pattern (pattern with periodicity)
44 Intersection of metal thin wires (characteristic points)
45 Disconnection of fine metal wire 46 Electrode 47 Lead wire 48 Non-periodic metal wire 50 One pixel of grayscale image 51 Corner of metal fine wire (feature point)
L ray d Optical resolution of gray image m Number of gray levels of gray image w Metal thin line width

Claims (10)

A sheet inspection apparatus in which a conductive pattern having periodicity is formed on a substrate,
A transport unit for transporting the sheet;
An illumination unit that illuminates the sheet;
An imaging unit that receives transmitted light or reflected light from the sheet and generates a grayscale image;
First image processing means for binarizing the grayscale image, recognizing positions of feature points having periodicity of the conductive pattern, and detecting defects on the sheet;
A sheet inspection apparatus including at least. A second image processing means for detecting the omission of the conductive pattern having the periodicity by binarizing the grayscale image;
The sheet inspection apparatus according to claim 1. The substrate is transparent, and the imaging unit is disposed to face the illumination unit with the sheet interposed therebetween, and receives a transmitted light from the sheet to generate a grayscale image;
The sheet inspection apparatus according to claim 1 or 2. The conductive pattern having the periodicity is mesh-shaped, and the feature point is the mesh-shaped intersection.
The sheet inspection apparatus according to any one of claims 1 to 3. The substrate is a synthetic resin film;
The sheet inspection apparatus according to any one of claims 1 to 4. The sheet is a touch panel material,
The sheet inspection apparatus according to any one of claims 1 to 5. The conductive pattern having the periodicity is formed by printing,
The sheet inspection apparatus according to any one of claims 1 to 6. The sheet further includes an aperiodic wiring including an electrode and an extraction wiring connected to an end of the conductive pattern having the periodicity,
The sheet inspection apparatus further includes a third image processing unit that binarizes the gray image and detects a defect of the non-periodic wiring by collating with a reference image.
The sheet inspection apparatus according to any one of claims 1 to 7. A method for inspecting a sheet in which a conductive pattern having periodicity is formed on a substrate,
Step S1 of irradiating the sheet with light while conveying the sheet and generating a grayscale image by receiving transmitted light or reflected light from the sheet with the imaging unit;
Converting the gray image into a high-definition binary image;
Recognizing the position of the feature point having the periodicity of the conductive pattern on the high-definition binary image;
Detecting a defect of the sheet S4;
Method for inspecting a sheet having The step S4 is a step of detecting a defect of the sheet based on the position of the high-definition binary image and the feature point.
The sheet inspection method according to claim 9.

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