JP2017219343A - Defect inspection device, defect inspection method, film manufacturing device, and film manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defect inspection device with which it is possible to improve the capability of detecting a defect.SOLUTION: A defect inspection device 10 comprises: a light source 17 for transmitted light that emits transmitted light L1 toward an imaging area R that is set on a polarizing film 110; an area sensor 16 for obtaining a two-dimensional image of the imaging area R; an image analysis device 13 for performing an inspection process on a defect using the two-dimensional image; and a conveyance device 11 for conveying the polarizing film 110 in a conveyance direction Y relatively to the area sensor 16. The image analysis device 13 includes a pixel selection unit 22a for selecting a plurality of pixels P arranged along the width direction X of the polarizing film 110 from the two-dimensional image, and a shading correction unit 22c for performing shading correction on the plurality of pixels P using a prescribed luminance correction value.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a defect inspection apparatus, a defect inspection method, a film manufacturing apparatus, and a film manufacturing method for detecting a film defect.

  There is known a defect inspection apparatus for detecting defects such as optical films such as polarizing films and retardation films, and films used for battery separators. This type of defect inspection apparatus conveys a film by a conveying means, emits light to an imaging area of the film by a light emitting means, images an imaging area of the film by an imaging means, and performs defect inspection based on the captured image. Do. For example, Patent Document 1 describes a defect inspection apparatus that inspects defects of a sheet-like inspection object.

JP 2011-95171 A

  The image obtained by imaging the inspection object may include various noise components in addition to the components indicating defects. These noise components may hinder improvement in defect detection capability.

  Therefore, an object of the present invention is to provide a defect inspection apparatus, a defect inspection method, a film manufacturing apparatus, and a film manufacturing method that can improve the defect detection capability.

  One embodiment of the present invention is a defect inspection apparatus for defect inspection of a film, and includes a light emitting unit that emits light toward an imaging region set on the film, and imaging that obtains a two-dimensional image of the imaging region Means, image analysis means for inspecting defects using a two-dimensional image, and transport means for transporting the film relative to the imaging means in the transport direction. Means for selecting a plurality of pixels arranged along the width direction of the film from the image; and means for performing shading correction on the plurality of pixels using a predetermined brightness correction value.

  The light emitting means emits light toward the imaging area of the film. The imaging area irradiated with light is imaged by the imaging means. Using the two-dimensional image obtained by this imaging, the image analysis means performs defect inspection processing. Here, the image analysis means selects a plurality of pixels from the two-dimensional image, and performs shading correction on the selected pixels. According to this shading correction, image unevenness that hinders improvement in defect detection capability is reduced. According to the image in which the unevenness of the image, which is an example of the noise component, is reduced, the defect detection capability can be improved.

  The image analysis means further includes means for obtaining a predetermined brightness correction value, and the predetermined brightness correction value is a brightness value at a plurality of pixels in at least one pixel region set for the selected plurality of pixels. The means for performing the shading correction may perform the shading correction using a predetermined brightness correction value corresponding to each pixel in the pixel region among the plurality of selected pixels. According to this configuration, a luminance correction value is obtained using a plurality of selected pixels. Then, a luminance correction value is obtained each time a two-dimensional image is obtained by the imaging means. When shading correction is performed using the luminance correction value obtained for each two-dimensional image, unevenness of the image that changes with time is reduced. Therefore, the defect detection capability can be further improved.

  The defect inspection apparatus may further include a light blocking means disposed between the light emitting means and the film so as to block a part of the light emitted from the light emitting means. According to the light blocking means, in the imaging region, a portion that is directly exposed to light and a portion that is not directly exposed to light are generated. According to the portion where the light hits, an image of a defect based on direct light can be obtained. Moreover, according to the part which does not receive light, the image of the defect based on the light scattered in the part which receives light can be obtained. Accordingly, since a two-dimensional image including an image of a defect based on light of different modes is obtained, the defect detection capability can be further improved. Here, a boundary where the brightness changes abruptly exists between a portion where the light hits and a portion where the light does not hit. When an imaging region including a portion that is exposed to light, a portion that is not exposed to light, and a boundary is imaged, the position of the boundary in the two-dimensional image may be shifted for each image depending on the positional relationship between the film and the imaging unit. Since the defect inspection apparatus includes means for obtaining a predetermined brightness correction value, the brightness correction value can be obtained every time a two-dimensional image is obtained. Therefore, even when the boundary is shifted for each image, the unevenness of the image can be suitably reduced, so that the defect detection capability can be further improved.

  The film manufacturing apparatus which concerns on another form of this invention is equipped with said defect inspection apparatus. According to this film manufacturing apparatus, since the defect inspection apparatus is provided, the defect detection capability can be enhanced.

  Another aspect of the present invention is a defect inspection method for defect inspection of a film, the step of transporting the film relative to an imaging unit that obtains a two-dimensional image of an imaging region set on the film. And a two-dimensional obtained in a step of emitting light to the film by a light emitting unit that emits light toward the imaging region, a step of imaging the imaging region by the imaging unit, and a step of imaging the imaging region A step of performing defect inspection processing using an image, and the step of performing defect inspection processing is a step of selecting a plurality of pixels arranged along the width direction of the film from a two-dimensional image. And a step of performing shading correction on a plurality of pixels using a predetermined luminance correction value.

  The imaging region irradiated with light from the light emitting unit in the step of emitting light is imaged by the imaging unit in the step of imaging the imaging region. In the step of performing defect inspection processing, defect inspection processing is performed using a two-dimensional image obtained by imaging. Here, in the step of performing the defect inspection process, a plurality of pixels are selected from the two-dimensional image, and shading correction is performed on the selected pixels. According to this shading correction, image unevenness that hinders improvement in defect detection capability is reduced. According to the image in which the unevenness of the image, which is an example of the noise component, is reduced, the defect detection capability can be improved.

  The step of performing defect inspection processing further includes a step of obtaining a predetermined luminance correction value between the step of selecting a plurality of pixels and the step of performing shading correction, and the predetermined luminance correction value is selected. The average value of the luminance values in a plurality of pixels in at least one pixel region set for the plurality of pixels, and the step of performing shading correction includes selecting each pixel in the pixel region from among the plurality of selected pixels. The shading correction may be performed using a predetermined luminance correction value corresponding to. According to this process, the brightness correction value is obtained using the selected plurality of pixels. Then, a luminance correction value is obtained each time a two-dimensional image is obtained by the imaging means. When shading correction is performed using the luminance correction value obtained for each two-dimensional image, unevenness of the image that changes with time is reduced. Therefore, the defect detection capability can be further improved.

  The film manufacturing method which concerns on another form of this invention has said defect inspection method. According to this film manufacturing method, since the defect inspection method is provided, the defect detection capability can be enhanced.

  ADVANTAGE OF THE INVENTION According to this invention, the defect inspection apparatus, the defect inspection method, the film manufacturing apparatus, and film manufacturing method which can improve the detection capability of a defect are provided.

FIG. 1 is a diagram illustrating a polarizing film manufacturing apparatus to which a defect inspection apparatus according to an embodiment of the present invention is applied. FIG. 2 is a perspective view showing a defect inspection apparatus according to an embodiment of the present invention. FIG. 3 is a side view showing a defect inspection apparatus according to an embodiment of the present invention. FIG. 4 is a diagram illustrating an imaging region. FIG. 5 is a block diagram illustrating the image analysis apparatus. FIG. 6 is a diagram for explaining the image processing process. FIG. 7 is a diagram illustrating one process of the shading process. FIG. 8 is a diagram illustrating one process of the shading process.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  An apparatus and a method for manufacturing a film according to an embodiment of the present invention manufacture a polarizing film (optical film) having polarizing characteristics, a retardation film (optical film) having no polarizing characteristics, a battery separator film, and the like. To do. Although an example of the manufacturing apparatus and manufacturing method of the polarizing film which has a polarization characteristic is shown in FIG. 1, description of manufacturing apparatuses and manufacturing methods, such as a phase difference film which does not have a polarizing characteristic, and a battery separator film, is abbreviate | omitted.

  As shown in FIG. 1, the film manufacturing apparatus 100 includes two sets of defect inspection apparatuses 10, bonding rollers 104 and 105, and a conveyance roller 106. First, the film manufacturing apparatus 100 manufactures a polarizing film main body (optical film main body) 111 by attaching protective films to both sides of the main surface of the polarizer. The manufactured polarizing film main body 111 is inspected for defects by the defect inspection apparatus 10. Next, the film manufacturing apparatus 100 takes out the pressure-sensitive adhesive material 112 with a separate film in which a separate film (release film) is bonded to the pressure-sensitive adhesive material from the raw roll 101. And the adhesive material 112 with a separate film is bonded to the one main surface side of the polarizing film main-body part 111 with the bonding roller 104. FIG. Next, the film manufacturing apparatus 100 takes out the surface protection film 113 from the raw roll 102. Then, the surface protection film 113 is bonded to the other main surface side of the polarizing film main body 111 by the bonding roller 105. Through the above steps, the polarizing film 110 is manufactured. And the film manufacturing apparatus 100 conveys the polarizing film 110 with the conveyance roller 106. FIG. The polarizing film 110 is inspected for defects by the defect inspection apparatus 10. The inspected polarizing film 110 is wound up by the original fabric roll 103.

  Examples of the polarizer material in the polarizing film body 111 include PVA (Polyvinyl Alcohol). Examples of the material for the protective film in the polarizing film body 111 include TAC (Triacetylcellulose). Moreover, PET (Polyethylene Terephthalate) etc. are mentioned as a material of the separate film and the surface protection film 113 in the adhesive material 112 with a separate film. By peeling off the separate film, the polarizing film 110 is bonded to a liquid crystal panel, another optical film, or the like with an adhesive.

  Hereinafter, the defect inspection apparatus 10 according to the embodiment of the present invention will be described in detail. The defect inspection apparatus 10 for inspecting the polarizing film main body 111 and the defect inspection apparatus 10 for inspecting the polarizing film 110 have the same configuration. Therefore, the defect inspection apparatus 10 that performs the defect inspection of the polarizing film 110 will be described, and the description of the defect inspection apparatus 10 that performs the defect inspection of the polarizing film main body 111 will be omitted.

  As shown in FIGS. 2 and 3, the defect inspection apparatus 10 and the defect inspection method perform defect inspection of the polarizing film 110 having the above-described polarization characteristics. The defect inspection may include a process of creating a defect map, which will be described later, in addition to a process of detecting a defect that may occur during the manufacturing process and the transport process of the polarizing film 110. Examples of this defect include the entrapment of bubbles generated at the time of bonding, the mixing and adhesion of foreign matters generated at the time of bonding, flaw transfer due to the adhering foreign matters generated during conveyance, and the mixing and adhesion of bright spots that occur at the time of glue adhesion. and so on. The defect inspection apparatus 10 includes a conveyance device (conveyance means) 11, a defect inspection imaging device 12, an image analysis device (image analysis means) 13, and a marking device 14. 2 and 3 show XYZ orthogonal coordinates. The X direction indicates the width direction of the polarizing film 110, and the Y direction indicates the transport direction of the polarizing film 110. The Z direction indicates a direction orthogonal to each of the X direction and the Y direction.

  The transport device 11 transports the polarizing film 110 relative to the defect inspection imaging device 12 in the transport direction Y. As an example, the transport device 11 includes a transport roller 106 and an original fabric roll 103.

  The defect inspection imaging device 12 includes a plurality of area sensors (imaging means) 16 and a transmitted light source (light emitting means) 17.

  The plurality of area sensors 16 obtain an image used for defect inspection and output the image to the image analysis device 13. The area sensor 16 is a so-called optical system device and has a function of recognizing a defect that may be included in the polarizing film 110.

  The plurality of area sensors 16 are arranged apart from each other in the width direction X on the one main surface 110 a side of the polarizing film 110. Each area sensor 16 has a two-dimensional imaging region R. The imaging region R overlaps with a part of the imaging region R adjacent in the width direction X. Since the imaging region R of the area sensor 16 is two-dimensional, the field of view in the transport direction Y is wider than that of the line sensor. Here, the imaging region R is a region set on the polarizing film 110, but is not set at a specific position on the polarizing film 110. The imaging region R includes a transmissive region R1 for acquiring a transmitted light image. The transmissive region R1 is a portion through which light emitted from the transmitted light source 17 in the imaging region R is transmitted.

  As shown in FIG. 3, the transmitted light source 17 emits transmitted light L <b> 1 for obtaining a transmitted light image to the polarizing film 110. The transmitted light source 17 includes a light source unit 17 a that emits light that does not affect the composition and properties of the polarizing film 110. Examples of the light source unit 17a include a fluorescent lamp (particularly a high-frequency fluorescent lamp), a metal halide lamp, a halogen transmission light, and a light emitting diode (LED). The light emitted from the transmitted light source 17 is simply referred to as “transmitted light L1”. The “transmitted light L 1” means light that is emitted from the transmitted light source 17 and enters the area sensor 16. Therefore, the “transmitted light L1” includes both the light before passing through the polarizing film 110 and the light after passing through the polarizing film 110.

  The transmitted light source 17 is disposed on the other main surface 110 b side of the polarizing film 110. That is, the transmitted light source 17 is arranged on the opposite side of the area sensor 16 with respect to the polarizing film 110. The transmitted light source 17 is arranged at a predetermined distance from the main surface 110b. The transmitted light source 17 is disposed such that the incident angle α of the transmitted light L1 to the polarizing film 110 is a predetermined angle. As an example, the incident angle α is not less than 30 degrees and not more than 60 degrees. Thus, when the incident angle α of the transmitted light L1 to the polarizing film 110 is not 90 degrees, the optical path length of the transmitted light L1 in the polarizing film 110 is longer than when the incident angle α is 90 degrees. Become. If it does so, it will become easy to spread | diffuse when the transmitted light L1 passes a defect. Therefore, the detection capability of the defect detected by diffuse transmitted light is improved. The transmitted light L1 is light having a two-dimensional spread. The length of the transmitted light L <b> 1 in the width direction X is larger than the width of the polarizing film 110. In addition, the width direction of the transmitted light L1 does not need to exactly coincide with the width direction X of the polarizing film 110, and may be inclined with respect to the transport direction Y.

  A light shielding plate (light blocking means) 18 for obtaining a diffuse transmission image is disposed between the transmitted light source 17 and the polarizing film 110. The light shielding plate 18 is disposed between the light source for transmitted light 17 and the polarizing film 110 so as to block a part of the transmitted light L1. The light shielding plate 18 is arranged so that half of the transmission region R1 in the transport direction Y is hidden when viewed from the area sensor 16 (knife edge). The light shielding plate 18 is a polarizing filter, and may be disposed so as to form a crossed Nicols state with the polarizing film 110.

  Here, a transmitted light image based on the transmitted light L1 will be described. As shown in part (a) of FIG. 4, the image 50 obtained by the area sensor 16 includes a light / dark part 51. The light / dark part 51 includes a bright part 51a and a dark part 51b. A specularly transmitted light image 52a may appear in the bright part 51a. A transmitted scattered light image 52b may appear in the dark part 51b. The regular transmitted light image 52a is an image based on light emitted from the transmitted light source 17 and transmitted through the polarizing film 110 and then perpendicularly incident on the area sensor 16 (see part (b) of FIG. 4). The transmitted scattered light image 52b is an image based on the light emitted from the transmitted light source 17, scattered when passing through the polarizing film 110, and then incident on the area sensor 16 (see part (c) of FIG. 4). ).

  As shown in FIG. 5, the image analysis device 13 is connected to an area sensor 16 and a marking device 14. From the area sensor 16, data relating to a two-dimensional image is input. The image analysis device 13 performs defect detection processing using data related to the two-dimensional image. The result of the detection process is output to the marking device 14.

  The image analysis device 13 includes an image acquisition unit 21, an image correction unit 22, a line composition processing unit 23, and a defect detection processing unit 24. The image analysis device 13 is a so-called processing system device having these functional components. The image analysis device 13 is not particularly limited as long as it can execute image processing using a two-dimensional image. Examples of the image analysis device 13 include a personal computer in which image processing software is installed, an image processing board having an FPGA in which an image processing circuit is described, and a camera having a microprocessor capable of executing an image processing program. .

  The image acquisition unit 21 receives the two-dimensional image output from the area sensor 16 and outputs the two-dimensional image to the image correction unit 22. The image correction unit 22 performs shading correction on the two-dimensional image input from the image acquisition unit 21 and outputs the corrected two-dimensional image to the line composition processing unit 23. The image correction unit 22 includes a pixel selection unit (means for selecting a pixel) 22a, an average calculation unit (means for obtaining a luminance correction value) 22b, and a shading correction unit (means for performing shading correction) 22c. The pixel selection unit 22 a selects a plurality of pixels arranged along the width direction X of the polarizing film 110. The average calculation unit 22b extracts a luminance value from each of the selected plurality of pixels, and calculates an average of the luminance values. The shading correction unit 22c performs shading processing using the average of the luminance values. The line composition processing unit 23 performs line composition processing using the corrected two-dimensional image input from the image correction unit 22. The defect detection processing unit 24 performs defect detection processing using the result of the line synthesis processing, generates defect position information, and generates a defect map. And the defect detection process part 24 outputs defect position information and a defect map as a result of a defect detection process. For example, the defect detection processing unit 24 outputs a defect map to the marking device 14.

  The marking device 14 is a so-called control system device, and attaches a mark M (see FIG. 2) on the polarizing film 110 using a defect map. The marking device 14 includes, for example, an arm extending along the width direction X of the polarizing film 110 and a marker head having a pen or the like. When the marker head moves on the arm in the width direction X, the mark M is attached to an arbitrary position on the polarizing film 110.

  Next, the defect inspection method according to the embodiment of the present invention will be described. The defect inspection method includes a step of transporting the polarizing film 110, a step of emitting the transmitted light L1, a step of imaging the polarizing film 110, a step of detecting a defect, and a step of applying a mark M. In the period when the process of conveying the polarizing film 110 is continuously performed, the process of emitting the transmitted light L1 is continuously performed. And the process of imaging the polarizing film 110 based on the preset timing is implemented. Each time a step of imaging the polarizing film 110 is performed, a step of detecting a defect and a step of applying the mark M are performed.

  First, the transport device 11 transports the polarizing film 110 along the transport direction Y. This process is continuously performed during the manufacture of the polarizing film 110. The transmitted light L1 is emitted from the transmitted light source 17 to the polarizing film 110 being conveyed.

  The defect inspection imaging device 12 images the imaging region R of the polarizing film 110 being transported. Then, the defect inspection imaging device 12 transmits the two-dimensional image obtained by imaging to the image analysis device 13. The area sensor 16 images the imaging region R at predetermined time intervals. In this time interval, the length in the transport direction Y of the two-dimensional image captured by the area sensor 16 is such that the polarizing film 110 is transported during a period from when the area sensor 16 captures the next two-dimensional image. This time is at least twice as long as the transport distance. That is, the imaging time interval is a time interval at which the same region of the polarizing film 110 can be imaged twice or more. According to this time interval, the length of the transport direction Y of the two-dimensional image is made larger than the transport distance in the image capture section, and the number of images of the same part of the polarizing film 110 is increased, thereby causing a defect with high accuracy. Can be inspected.

  The area sensor 16 images the imaging region R at a predetermined frame rate. As a result, an image group (images G1, G2, G3, G4) as shown in part (a) of FIG. 6 is output to the image analysis device 13. In FIG. 6A, the imaging timing of the image G1 is time t1 (t), the imaging timing of the image G2 is time t2 (t + Δt), and the imaging timing of the image G3 is time t3 (t + 2 × Δt). Yes, the imaging timing of the image G4 is time t4 (t + 3 × Δt). Each of the images G1, G2, G3, and G4 includes a linear defect D. Since the polarizing film 110 moves in the transport direction Y, the defect D also appears to move in the transport direction Y. In this example, it is assumed that transmitted scattered light is not generated. Therefore, the defect D does not appear in the dark part 51b.

  The image analysis device 13 performs a defect detection process on the two-dimensional image. The defect detection process includes a shading process, a line synthesis process, and a process for detecting a defect from an image obtained by the line synthesis process.

  The shading process is performed on the input images G1, G2, G3, and G4 by the image correction unit 22. Hereinafter, a shading process for the image G1 will be described as an example. First, the pixel selection part 22a performs the process of selecting the some pixel arrange | positioned along the width direction X of the polarizing film 110 from the image G1. As shown in FIG. 7, the image G1 has a plurality of pixels P (m, n) arranged two-dimensionally. Here, P (m, n) indicates a pixel in the n-th column (Y-axis direction) in the m-th row (X-axis direction).

  The pixel selection unit 22a selects, for example, one of the columns of pixels extending in the width direction X (for example, P (m, 5)). Hereinafter, processing performed on a plurality of pixels P (m, 5) will be described as an example. The column of pixels is a column extending from one side G1b facing each other in the width direction X to the other side G1c in the image G1. Next, as illustrated in part (a) of FIG. 8, the pixel selection unit 22 a divides the column of the selected pixels into a plurality of pixel areas PA (k). In this example, the pixel selection unit 22a divides a plurality of pixels P (m, 5) into three pixel areas PA (1), PA (2), and PA (3). In each of the three pixel areas PA (1), PA (2), and PA (3), the luminance value in each pixel may be different. This difference in luminance value can cause unevenness in the image G1. The pixel selection unit 22a outputs pixel information belonging to each pixel area PA (1), PA (2), PA (3) to the average calculation unit 22b. According to the pixel information, for example, the pixel area PA (1) has pixels P (1,5), P (2,5), P (3,5), P (4,5), P (5, 5) belongs to.

Next, the average calculation unit 22b calculates an average value of luminance values (brightness correction value). Specifically, the average calculation unit 22b includes a plurality of pixels P (1, 5), P (2, 5), P (3, 5), P (4, 5), P ( 5, 5), luminance values L (1, 5), L (2, 5), L (3, 5), L (4, 5), and L (5, 5) are poured out. Next, the average calculator 22b calculates the average of the luminance values L (1,5), L (2,5), L (3,5), L (4,5), and L (5,5). . An average C (1) of luminance values of the pixel area PA (1) is expressed by the following formula (1). Here, m is a value representing the position of the pixel in the X-axis direction. For example, m = 1 indicates that it is the first pixel from the left. L (m, 5) indicates the luminance value of the pixel P (m, 5) indicated by m. Similarly, the average C (2) of the luminance values of the pixel area PA (2) is expressed by the following formula (2), and the average C (3) of the luminance values of the pixel area PA (3) is expressed by the following formula (3). Indicated. The averages C (1), C (2), and C (3) of these luminance values are luminance correction values.

  Next, the average calculation unit 22b generates luminance correction information in which the average C (k) of luminance values is associated with the pixel area PA (k). The average calculation unit 22b similarly performs the extraction of the luminance value, the calculation of the average, and the generation of the luminance correction information for the pixel areas PA (2) and PA (3). Then, the average calculation unit 22b outputs the luminance correction information to the shading correction unit 22c.

Next, the shading correction unit 22c performs shading correction using the luminance correction information. Specifically, the shading correction unit 22c specifies the pixel area PA (k) from the image G1 using the luminance correction information. Next, the shading correction unit 22c extracts a luminance value from the pixel P (m, 5) included in the pixel area PA (k), and average C of luminance values included in the luminance correction information from the extracted luminance value. Subtract (k). This process is shown by the following formula (4). SL (m, 5) _[k] is a luminance value after correction in the pixel P (m, n) in the pixel area PA (k). By these processes, unevenness is reduced for each pixel area PA (k) (see part (b) in FIG. 8).

  Through the above-described steps, the shading correction process for one pixel row (that is, P (m, 5)) selected by the pixel selection unit 22a is completed. Here, the shading correction processing for P (m, 5) as one pixel column has been described as an example, but the same applies to other pixel columns. The image correction unit 22 performs the above process on all the pixel columns arranged along the conveyance direction Y of the image G1. In other words, the image correction unit 22 performs shading correction for each pixel column extending in the width direction X. The image correction unit 22 outputs the image G1 subjected to the shading correction to the line composition processing unit 23.

  This shading process is similarly performed on the images G2, G3, and G4.

  The line composition processing unit 23 divides each image G1, G2, G3, G4 into four lines along the transport direction Y (see the part (b) in FIG. 6). Next, a line corresponding to the same position in the image group G (for example, see the lines G1a, G2a, G3a, and G4a) is selected. This selection can also be said to extract the same line in every unit time. Then, the selected lines G1a, G2a, G3a, and G4a are joined along the transport direction Y (see part (c) in FIG. 6). The composite image G5 is an image equivalent to an image captured by the line sensor that captures the first line, and the composite image G6 is an image equivalent to an image captured by the line sensor that captures the second line. Similarly, the composite image G7 is an image equivalent to the image captured by the line sensor that captures the third line, and the composite image G8 is an image equivalent to the image captured by the line sensor that captures the fourth line. It is. In this way, a process of selecting lines at the same position from a plurality of images in time series captured by the area sensor 16 and combining them is called a line synthesis process.

  Next, as illustrated in part (d) of FIG. 6, the image analysis device 13 performs a process of enhancing the defect D on the composite image. By this processing, processed images G5A, G6A, G7A, and G8A are obtained. For this process, a vertical differential filter method, a binarization method, or the like is used. For example, a threshold value fixed using a Laplacian histogram method is used for the binarization method.

  Next, as illustrated in part (e) of FIG. 6, the image analysis device 13 further superimposes the images in which the defect D is emphasized. The imaging ranges of the polarizing film 110 included in the processed images G5A, G6A, G7A, and G8A are different from each other even though a part thereof overlaps in the transport direction Y. The image analysis device 13 performs integration processing on the processed images G5A, G6A, G7A, and G8A using the overlapping portions, and generates one composite image G9. Moreover, according to this process, the images imaged under various optical conditions from the bright field to the dark field are integrated. Therefore, the foreign substance detection capability is further enhanced. Furthermore, it can be said that the processing described above is equivalent to the processing when a plurality of line sensors are used.

  Next, the defect detection processing unit 24 performs a process of detecting the defect D using the composite image G9. For this process, a detection method based on a feature amount is used. The image analysis device 13 has data in which the form of the defect D is associated with the characteristics when the defect D is captured as an image. This data is also called teacher data. First, the image analysis device 13 calculates a feature amount of the composite image G9. Subsequently, the image analysis apparatus 13 selects the most relevant teacher data by comparing the calculated feature amount with the teacher data. Then, the image analysis device 13 determines that the defect D included in the composite image is a defect in a form associated with the selected teacher data.

  There are various values that can be acquired from the entire image. For example, the various values include a luminance total value, luminance average, luminance median value, luminance dispersion, luminance gradient direction, and luminance gradient intensity. Various values that can be acquired from defects in the image can also be used as the feature amount. Values that can be acquired from the defect include a defect area, a defect perimeter, a defect circularity, a defect Ferre diameter, and a defect aspect ratio.

  The teacher data may be applied as necessary to newly acquired data with respect to previously recorded data. According to this data update, the degree of association between the feature amount and the defect mode increases. Further, the relationship between the feature amount and the defect mode can be obtained by using a technique such as a neural network or machine learning.

  Next, the image analysis device 13 creates defect inspection information using data regarding the detected defect. The defect inspection information includes information regarding the type of defect and the position of the defect. Further, the defect inspection information may include information indicating the presence or absence of defects for one lot. An example of the defect inspection information is a defect map of the entire area of the polarizing film 110.

  Next, the marking device 14 attaches a mark M indicating the presence of a defect to the polarizing film 110 using the defect inspection information. This mark M can be confirmed visually or by other means. The mark M indicating the defect position is used for, for example, a process of separating the sheet product into a normal product and a defective product after the polarizing film 110 is cut into a sheet product of a predetermined size.

  Hereinafter, the effects of the defect inspection apparatus 10, the film manufacturing apparatus 100, the defect inspection method, and the film manufacturing method according to the present embodiment will be described.

  The transmitted light source 17 emits transmitted light L1 toward the imaging region R of the polarizing film 110. The imaging region R irradiated with the transmitted light L1 is imaged by the area sensor 16. Using the two-dimensional image obtained by this imaging, the image analysis device 13 performs a defect inspection process. Here, the image analysis device 13 selects a plurality of pixels from the two-dimensional image, and performs shading correction on the selected pixels. According to this shading correction, image unevenness that hinders improvement in defect detection capability is reduced. According to the image in which the unevenness of the image, which is an example of the noise component, is reduced, the defect detection capability can be improved.

  According to the average calculation unit 22b, a luminance correction value is obtained using a plurality of selected pixels. Then, a luminance correction value is obtained every time a two-dimensional image is obtained by the area sensor 16. When shading correction is performed using the luminance correction value obtained for each two-dimensional image, unevenness of the image that changes with time is reduced. Therefore, the defect detection capability can be further improved.

  According to the light shielding plate 18, in the imaging region R, a bright part 51 a that is directly exposed to light and a dark part 51 b that is not directly exposed to light are generated. According to the bright part 51a, an image of a defect based on direct light can be obtained. Moreover, according to the dark part 51b, the image of the defect based on the light scattered in the part which light strikes can be obtained. Accordingly, since a two-dimensional image including an image of a defect based on light of different modes is obtained, the defect detection capability can be further improved.

  Here, a boundary where the brightness changes abruptly exists between the bright portion 51a and the light-dark portion 51b. When the imaging region R including the bright part 51a, the dark part 51b, and the boundary is imaged, the position of the boundary in the two-dimensional image may be shifted for each image depending on the positional relationship between the polarizing film 110 and the area sensor 16. Since the defect inspection apparatus 10 includes the average calculation unit 22b, a luminance correction value can be obtained every time a two-dimensional image is obtained. Therefore, even when the boundary is shifted for each image, the unevenness of the image can be suitably reduced, so that the defect detection capability can be further improved.

  The defect inspection apparatus, defect inspection method, film manufacturing apparatus, and film manufacturing method according to the present invention are not limited to the above embodiment.

  For example, the defect inspection apparatus 10 includes the transmitted light source 17 as a light source. The defect inspection apparatus 10 may use a light source as a reflected light source. The reflected light source emits reflected light for obtaining a reflected light image with respect to the polarizing film 110. The light source for reflected light is disposed on one main surface side of the polarizing film 110. That is, the reflected light source is arranged on the same side as the area sensor 16 with respect to the polarizing film 110.

  For example, a value acquired in advance may be used as the brightness correction value. The unevenness of the image may be based on the optical system of the area sensor 16. In this case, the unevenness of the image does not change with time. Therefore, the unevenness of the image can be suitably reduced by using the brightness correction value acquired in advance.

  For example, the shading process may be performed during the line synthesis process. Specifically, each of the images G1, G2, G3, and G4 is divided into four lines along the transport direction Y (see the part (b) in FIG. 6), and then the divided line images are subjected to the division. Shading processing may be performed.

DESCRIPTION OF SYMBOLS 10 ... Defect inspection apparatus, 11 ... Conveyance apparatus (conveyance means), 13 ... Image analysis apparatus (image analysis means), 14 ... Marking apparatus, 16 ... Area sensor (imaging means), 17 ... Light source for transmitted light (light emission means) ), 18..., Light shielding plate (light blocking means), 21... Image acquisition unit, 22... Image correction unit, 22 a... Pixel selection unit (means for selecting pixels), 22 b ... average calculation unit (means for obtaining luminance correction values) , 22c ... shading correction unit (means for performing shading correction), 23 ... line composition processing unit, 24 ... defect detection processing unit, 100 ... film manufacturing apparatus, 101, 102, 103 ... original fabric roll, 104, 105 ... bonding Roller 106, transport roller 110, polarizing film 110 a, one main surface 110 b, the other main surface, X width direction, Y transport direction.

Claims (7)

A defect inspection apparatus for film defect inspection,
A light emitting means for emitting light toward an imaging region set on the film;
Imaging means for obtaining a two-dimensional image of the imaging region;
Image analysis means for inspecting defects using the two-dimensional image;
Transporting means for transporting the film relative to the imaging means in the transporting direction,
The image analysis means includes
Means for selecting a plurality of pixels arranged along the width direction of the film from the two-dimensional image;
And a means for performing shading correction on the plurality of pixels using a predetermined luminance correction value. The image analysis means further includes means for obtaining the predetermined brightness correction value,
The predetermined luminance correction value is an average value of luminance values in a plurality of pixels in at least one pixel region set for the selected plurality of pixels,
The means for performing the shading correction performs the shading correction using the predetermined luminance correction value corresponding to each of the pixels in the pixel region among the plurality of selected pixels. Defect inspection equipment.   The defect inspection apparatus according to claim 2, further comprising a light blocking unit disposed between the light emitting unit and the film so as to block a part of the light emitted from the light emitting unit.   The film manufacturing apparatus provided with the defect inspection apparatus as described in any one of Claims 1-3. A defect inspection method for defect inspection of a film,
A step of relatively transporting the film with respect to an imaging unit that obtains a two-dimensional image of an imaging region set on the film;
A step of emitting light to the film by light emitting means for emitting light toward the imaging region;
Imaging the imaging area by the imaging means;
Using the two-dimensional image obtained in the step of imaging the imaging region, performing a defect inspection process,
The step of inspecting the defect includes
Selecting a plurality of pixels arranged along the width direction of the film from the two-dimensional image;
Performing a shading correction on the plurality of pixels using a predetermined luminance correction value. The step of performing the defect inspection process further includes a step of obtaining the predetermined luminance correction value between the step of selecting the plurality of pixels and the step of performing the shading correction.
The predetermined luminance correction value is an average value of luminance values in a plurality of pixels in at least one pixel region set for the selected plurality of pixels,
6. The shading correction is performed according to claim 5, wherein the shading correction is performed using the predetermined luminance correction value corresponding to each pixel in the pixel region among the plurality of selected pixels. Defect inspection method.   A film manufacturing method comprising the defect inspection method according to claim 5.

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