KR20230113764A - Edge detection method of optical film - Google Patents

Abstract

A method for detecting an edge portion of an optical film capable of reliably detecting an edge portion of an optical film bonded to a rectangular panel is provided. The detection method includes a conveying step for conveying a rectangular panel on which optical films are laminated, a photographing step for photographing a target region including an edge of the optical film on the rectangular panel, and a plurality of images obtained by photographing the target region at a plurality of positions. An optimum image selection step for selecting an optimum image for detecting an edge portion from the image, and an edge detection step for detecting an edge portion in the optimum image. In the photographing step, light is sequentially irradiated from a plurality of light sources disposed along the transport direction of the rectangular panel, and a target region is photographed at a plurality of positions from upstream to downstream in the transport direction by one imaging unit.

Description

Edge detection method of optical film

The present invention relates to a method for detecting an edge portion of an optical film used for inspection of an optical display panel, and more specifically, in inspecting a bonding discrepancy between a rectangular panel and an optical film bonded thereto, a plurality of captured images. A method for detecting the edge of an optical film, wherein an optimal image capable of most reliably detecting the edge of an optical film is selected from the image, and the edge of the optical film is detected using the optimal image.

In an optical display panel, a display function is realized by bonding various optical films having optical functions to a rectangular panel as necessary. In the manufacturing process of the optical display panel, after bonding the optical film to the surface of the rectangular panel, inspection of the bonding state of the rectangular panel and the optical film (so-called bonding discrepancy inspection) is performed in order to confirm the bonding accuracy of both. As a conventional joint misalignment inspection method, for example, methods described in Patent Literature 1 and Patent Literature 2 have been proposed.

Patent Literature 1 discloses capturing an image of a corner portion of an optical display panel to which a polarizing plate and a liquid crystal panel are bonded with an area camera or a line camera disposed so that imaging is possible from vertically above the corner portion. The shift amount of bonding is calculated using an image captured by a camera. Further, Patent Literature 2 discloses a method for inspecting a bonding discrepancy by enabling imaging of a corner portion of the panel using an area sensor camera while conveying an optical display panel in which an optical film piece is bonded to an optical cell. In this method, the distance between the end of the optical cell and the end of the optical film piece is calculated from the photographed image, and the bonding shift is determined based on the distance.

Japanese Unexamined Patent Publication No. 2011-197281 Japanese Unexamined Patent Publication No. 2016-118580 Japanese Patent No. 4377964

In the conventional bonding discrepancy inspection method including Patent Document 1 and Patent Document 2, a certain area (hereinafter referred to as a target area) including a corner portion of both a rectangular panel and an optical film in an optical display panel is an imaging area of a camera , and shooting is performed when the imaging point is reached. The imaging point is usually a position when the edge of the optical film on the optical display panel (usually the frontmost side of the moving direction of the optical film) reaches the vertically downward direction of the camera. In the captured image, the edge of the optical film appears as a glowing line (bright line) when light from a light source is reflected by the edge of the optical film, and the edge of the optical film in the image can be detected by recognizing this reflected light. . However, depending on the state of the edge of the optical film bonded to the rectangular panel, it may be difficult to detect the edge only from an image taken when the edge reaches the imaging point.

For example, when the end face of an optical film in a photographed image has a shape that makes it difficult to reflect light from a light source, or when the reflected light from the end face has an angle that makes it difficult to reach the camera, the optical film The edges of the film may be difficult to detect.

The present invention provides a method for detecting an edge portion of an optical film capable of reliably detecting an edge portion of an optical film bonded to a rectangular panel for use in an inspection method enabling accurate inspection of a bonding discrepancy between a rectangular panel and an optical film. intended to provide

The present invention relates to an image obtained by photographing the edge of an optical film by irradiating light from a light source arranged upstream in the transport direction of a rectangular panel, and photographing the edge portion by irradiating light from a light source disposed downstream in the conveyance direction. It was completed based on the knowledge that the irradiation direction from which an image with easy detection of the edge portion can be obtained by comparing the images at the time of use differs depending on the position in the transport direction of the optical film.

In the present invention, with respect to an optical display panel in which an optical film is laminated on a rectangular panel, a plurality of images of a target region including a corner portion of the rectangular panel and a corner portion of the optical film are acquired by light sequentially irradiated from a plurality of light sources. , an optimal image capable of detecting the edge of the optical film most reliably is selected from among these plural images, and the edge of the optical film is detected using the optimal image.

That is, the present invention provides an optical film edge detecting method for detecting an edge of an optical film laminated on a rectangular panel, a conveyance step for conveying the rectangular panel on which the optical film is laminated, and an edge of the optical film on the rectangular panel. A photographing step for photographing a target region including a region, an optimal image selection step for selecting an optimal image for detecting an edge from a plurality of images obtained by photographing the target region at a plurality of positions, and detecting an edge in the optimal image. It includes an edge detection step to do. In the photographing step, light is sequentially irradiated from a plurality of light sources disposed along the transport direction of the rectangular panel, and a target region is photographed at a plurality of positions from upstream to downstream in the transport direction by one imaging unit. An optimum image is selected based on the luminance of the edge of each image.

In one embodiment, it is preferable that the plurality of light sources include at least an upstream light source arranged on an upstream side in the transport direction and a downstream light source arranged on a downstream side with respect to the imaging means for photographing the target region. In the photographing step, when the edge is located upstream in the conveying direction from the imaging point, which is the position when the edge reaches vertically downward of the imaging means, light is irradiated from the upstream light source and photographed, downstream of the imaging point in the conveying direction It is preferable to photograph by irradiating light from a downstream light source when there is an edge portion.

In one embodiment, in the optimal image selection step, it is preferable to select an optimal image based on the luminance of a plurality of locations set along the edge. Further, in another embodiment, in the photographing step, it is preferable to photograph a plurality of images while stopping the rectangular panel for each photograph, and further use light from light sources arranged to face each other in the width direction of the rectangular panel to capture a plurality of images. It is desirable to take pictures.

According to the present invention, since an optimal image capable of reliably detecting bright lines at the edges of an optical film is selected from a plurality of images obtained by photographing a predetermined area including an end portion of an optical film bonded to a rectangular panel, the image It is possible to inspect the bonding shift of the optical film more easily and with high accuracy by using.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the structure of the edge part detection apparatus for detecting the edge part of the polarizing film bonded to the liquid crystal cell used in liquid crystal panel manufacture.
Fig. 2 is a flow showing the flow of processing for selecting an optimal image from a plurality of captured images in the method for detecting an edge portion of an optical film according to an embodiment of the present invention.
3 is a flow showing details of processing for scoring in a method according to an embodiment of the present invention.
4 is an image showing the process of scoring processing.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail, referring drawings.

In the following description, the case where a polarizing film is used as an optical film, a liquid crystal cell is used as a rectangular panel, and an optical display panel in which an optical film is bonded to a rectangular panel is a liquid crystal panel is described as an example, but it is not limited to these. , The present invention can be equally used in inspection of various optical display panels manufactured by bonding a film having an optical function to a rectangular panel.

[Overview of Liquid Crystal Panel Manufacturing Equipment and Polarizing Film Edge Detection Equipment]

The film edge detection method according to the present invention, for example, in an apparatus (RTP system apparatus) for manufacturing a liquid crystal panel by continuously bonding a polarizing film drawn out from a roll to a liquid crystal cell, for the manufactured liquid crystal panel, It can be used for the purpose of detecting the edge of a polarizing film in order to inspect that a polarizing film is bonded to the surface of a liquid crystal cell in a state where it is shifted from a predetermined bonding position (hereinafter referred to as bonding displacement). In the RTP method, in the manufacturing process of a liquid crystal panel, only a normal sheet-shaped polarizing film free of defects is obtained from a strip-shaped laminate in which a plurality of sheet-shaped polarizing films are supported on a strip-shaped release film through an adhesive layer. It is a system which manufactures a liquid crystal panel continuously by peeling one by one from a release film with an adhesive layer, and bonding together with a liquid crystal cell through an adhesive layer. A continuous manufacturing system realizing this method is called a "continuous bonding (RTP; roll-to-panel)" device to distinguish it from a device realizing a conventional individual bonding method in which pre-cut sheets of polarizing film are bonded to a liquid crystal cell. As the device of the RTP system, for example, the device described in Patent Literature 3 can be used.

1 : is a schematic diagram which shows an example of the structure of the polarizing film edge part detection apparatus for detecting the edge part of the polarizing film bonded to the liquid crystal cell. This device can be attached as a part of the device used for the inspection process in the process after bonding the liquid crystal cell polarizing film manufactured by the above-mentioned RTP method, for example.

The apparatus shown in FIG. 1 has a transport path 1 that transports a liquid crystal panel P manufactured by bonding a polarizing film F to a liquid crystal cell C, and lighting disposed above the transport path 1. (2) and a camera (3) disposed above the illumination (2). When the target region A of the liquid crystal panel P being conveyed by the conveyance path 1 is within the shooting range of the camera 3, from the upstream side to the downstream side of the conveyance direction D of the liquid crystal panel P Over the period, the illumination 2 is turned on a plurality of times, and a plurality of images Is of the target region A are photographed by the camera 3 . The target area A is an area for inspecting the bonding misalignment between the liquid crystal cell C and the polarizing film F, and usually includes the edge portion CE and the corner portion CC of the liquid crystal cell C. , and an area including the edge portion FE (this is the edge portion to be detected) and the corner portion FC of the polarizing film F bonded to the liquid crystal cell C, but is not limited thereto. . , a region including at least the edge portion CE and the edge portion FE. A plurality of images Is in which the target region A is photographed at a plurality of positions are transmitted to a general-purpose computer, and an optimal image for detecting the edge portion FE of the polarizing film F is selected in the computer, and the selected The edge portion FE is detected using the optimal image.

It is preferable to use a plurality of lights 2 disposed along the conveying direction D so that the light is irradiated from different directions with respect to the target area A. At a plurality of positions while the target area A moves from the upstream side to the downstream side in the conveying direction D, a plurality of lights 2 are sequentially lit. It is preferable that the plurality of lights 2 are respectively arranged on the upstream and downstream sides of the conveyance direction D of liquid crystal panel P (lights 21 and 22 in FIG. 1 ), but in addition to this, conveyance It is preferable to arrange also in the direction transverse to the direction D (the width direction of the liquid crystal panel P) (illumination 23, 24 of FIG. 1). By arranging the illumination 2 also in the width direction of the liquid crystal panel P, since the edge FS of the polarizing film F in the width direction can also be detected more reliably, a more precise bonding discrepancy test can be performed. can do Further, as the lighting 2, a plurality of light sources may be arranged in an annular shape, and one ring light capable of individually and sequentially lighting the plurality of light sources may be used, for example. In the case of using such ring illumination, light can be radiated to the target area A from a plurality of different directions by individually turning on the light sources at a plurality of locations in the circumferential direction.

As the camera 3 used in the present invention, a line camera, an area camera, or the like can be used depending on the purpose. For example, when photographing the target area A while moving the liquid crystal panel P, it is preferable to use a line camera. In the case of using a line camera, the target region A may be photographed while the line camera is moved in a state where the liquid crystal panel P is stopped. As a method of photographing the target region A while moving the liquid crystal panel P, an area camera may be used and the photographing may be performed with the shutter speed sufficiently higher than the moving speed of the liquid crystal panel P. The area camera can also be used when the liquid crystal panel P is stopped when photographing the target area A.

In this embodiment below, one illumination 21, 22 is disposed on each of the upstream and downstream sides of the conveyance direction D of the liquid crystal panel P with respect to the target region A, and the liquid crystal panel A plurality of images Is are photographed with one camera 3 using a configuration in which one light 23, 24 is disposed in each of the width directions of (P), and a liquid crystal film F is formed from those images Is. An optimal image Ib for detecting the edge portion FE of is selected. In the following, the light from the four illuminations 21-24 arrange|positioned along the conveyance direction D of liquid crystal panel P so that the height from the conveyance surface of liquid crystal panel P is constant and the irradiation direction differs is used. And, while the edge part FE moves from the upstream side to the downstream side in the conveyance direction D, the present invention is described by taking a method of photographing by sequentially turning on lighting as an embodiment.

[Detection of Polarizing Film Edge]

(Conveyance and shooting of the liquid crystal panel)

In the device shown in FIG. 1 , the target region includes both the edge portion CE and the corner portion CC of the liquid crystal cell C and the edge portion FE and corner portion FC of the polarizing film F. For (A), a plurality of images Is are photographed. The camera 3 arranged so as to be able to photograph the target area A matches the lighting timing of the plurality of lights 21 and 22, until the target area A enters the shooting range of the camera 3 and then comes out. A plurality of images Is are acquired during Specifically, during the period from when the target region A enters the shooting range of the camera 3 to when it leaves, a plurality of images Is are obtained by stopping conveyance and shooting of the liquid crystal panel P at a plurality of predetermined positions. Acquire The predetermined position is when the edge portion FE of the polarizing film F is on the upstream side in the transport direction D with respect to the imaging point, when it is at or in the vicinity of the imaging point, or on the downstream side in the transport direction D with respect to the imaging point. You can do it when you are in . Shooting is, for example, when the edge FE is on the upstream side of the conveyance direction D with respect to the imaging point, the upstream lighting 21 is turned on, and when there is an imaging point, the upstream lighting 21 and the downstream This is performed by sequentially lighting the lighting 22 on the side and lighting the lighting 22 on the downstream side when it is on the downstream side of the transport direction D with respect to the imaging point. The number of acquired images Is is not limited, and the accuracy necessary for detecting the edge FE of the polarizing film F and the speed of processing for selecting the optimum image for detecting the edge FE are taken into consideration. So, you can decide.

Shooting of the plurality of images Is is preferably performed by stopping the liquid crystal panel P moving from the upstream side to the downstream side for each shooting as described above, but it is not limited to this, and is performed from the upstream side to the downstream side of the shooting range. You may make it perform sequentially, moving liquid crystal panel P across. In the case of photographing while moving the liquid crystal panel P, a plurality of images Is are each of the lighting timings of the lighting 21 and the lighting 22 from when the target area A enters the field of view of the camera 3 until it comes out. It can be acquired by opening the shutter of the camera 3 and photographing an image in accordance with . Alternatively, the plurality of images Is are photographed continuously by opening the shutter of the camera 3 until the target region A enters the field of view of the camera 3 and then comes out, and during that time, the illumination 21 and the illumination ( 22) may be acquired by sequentially lighting each. A plurality of acquired images Is are transmitted from the camera 3 to, for example, a general-purpose computer (not shown) via wire or wireless, and are stored in a storage unit such as a hard disk.

(Selection of optimal image)

A plurality of acquired images Is are retrieved from the storage unit, and an optimum image Ib is selected from the images Is. Optimum image Ib is an image which can most reliably detect edge part FE of polarizing film F bonded to liquid crystal cell C among several image Is. Selection of the optimal image measures the luminance of the edge portion FE of the polarizing film F for each of a plurality of images Is photographed, obtains an evaluation point based on the luminance, and calculates the obtained evaluation point between images Comparison is made, and the image with the highest evaluation point is selected as the optimum image Ib in which the edge portion FE can be most reliably detected.

2 is a flow 200 showing the flow of the entire process of selecting the optimal image Ib from a plurality of images Is. 3 is a flow showing an example of specific processing of a scoring process for obtaining evaluation points for evaluating a plurality of images Is, and FIG. 4 is an image showing an example of processing in the scoring process. Hereinafter, the method for selecting the optimum image Ib will be described in detail with reference to FIGS. 2 to 4 . In addition, the content of the optimal image selection processing shown in Figs. 2 to 4 is only an example, and other processing may be employed depending on the type of optical display panel.

First, in s201 of the flow 200, a plurality of images Is are obtained while liquid crystal panel P is conveyed from the upstream side to the downstream side in the conveying direction D. Next, in s202, the luminance of the edge portion of the film is measured for each of the plurality of images Is, and an evaluation point for each image Is is obtained based on the luminance. Next, in s203, evaluation points are compared among a plurality of images Is, and an image having the highest evaluation point is selected as the optimum image Ib in which the edge FE can be most reliably detected.

Next, each process in the flow 200 will be described in detail.

Acquisition of the image described in s201 of flow 200 is the same as described above in the item of imaging of the liquid crystal panel. Next, as shown in s202 of the flow 200, an evaluation point for evaluating the possibility of reliably detecting the edge portion FE of the polarizing film F is obtained for each of the obtained plurality of images Is. Specifically, for each of the plurality of images Is, the luminance is measured at a plurality of locations including the edge portion FE, the luminance at the plurality of locations is scored, and, for example, the total value, average value, maximum value, etc. are obtained. , these values are used as evaluation points. Among the plurality of images Is, the image with the highest evaluation point becomes the optimum image Ib capable of most reliably detecting the edge portion FE.

Fig. 3 shows an example of a process of obtaining an evaluation point for each of a plurality of images Is, selecting an optimal image, and determining the position of the edge FE of the polarizing film F in each of the images Is. It is flow 300 showing details. First, in s301, a plurality of small regions (squares SR1 shown in Fig. 4(a)) including a position where the edge of the polarizing film is assumed to exist and its periphery are set along the longitudinal direction of the edge of the polarizing film do. The plurality of small regions reads the alignment mark formed on the liquid crystal cell C, and calculates the position when the polarizing film F is bonded to the liquid crystal panel C as prescribed without shifting based on the position of the alignment mark. and is thus set to the calculated position. The size of the small region is not limited, but the length of the small region in the direction crossing the edge of the polarizing film is within the small region even if the polarizing film F is shifted and bonded to the liquid crystal panel C. It is desirable to set the entry length. In addition, the length of the small region along the longitudinal direction of the edge of the polarizing film is preferably set appropriately in consideration of the detection accuracy and processing speed of the edge. The number of small regions is not limited, and is preferably set in consideration of the detection accuracy and processing speed of the edge portion. In a plurality of small regions, luminance is measured and graphed. As shown in Fig. 4(b), the graph can be expressed as a relationship between the distance and luminance in the direction from the end of the small region toward the inside of the liquid crystal panel P.

Subsequently, in s302, for each graph generated for each of the plurality of small regions, the intersection of the line represented by the graph and the predetermined threshold value TH for determining the presence or absence of the edge portion FE of the polarizing film F is are explored It is assumed that the luminance employed as the threshold value TH is higher than the maximum luminance OBmax of other bright lines indicating edges other than the edge FE and that the edge FE in the image can be reliably detected if the luminance is equal to or greater than the luminance. can be done with a numerical value. Since the bright line of the edge portion FE shown in the image has a width, there are normally two intersections between the graph and the threshold value TH. Among the two intersections, the position CP1 of the intersection corresponding to the inner direction of liquid crystal panel P is the position of the inner edge of the bright line representing the edge FE. When the position of the inner edge of each recognized small region is connected in this way, the connected straight line is the inner edge of the bright line representing the edge portion FE (s303), and this position is the edge portion of the polarizing film F ( FE) becomes the position of the bright line.

On the other hand, in s304, for each of the plurality of small regions, the maximum luminance Bmax of the bright line representing the edge FE in the small region is scored. Scoring can be expressed as a relative luminance when 100 is the luminance corresponding to the maximum amount of incident energy that the light receiving element of the camera 3 can accept, for example. Alternatively, the measured maximum luminance (Bmax) itself may be used as the score of the small region. By scoring the luminance, the score of the small area is expressed as, for example, 82 points, 85 points, 90 points... and the like. After scores are calculated for each of the plurality of small regions, in S305, for example, the scores of all the small regions are summed, and the total value is used as the evaluation point of the image. In addition, the evaluation point of an image is not limited to the total value of the score of a small area, as long as it can judge the detection certainty of the edge part FE in between images. For example, the evaluation point of the image may be an average score of a plurality of small areas, or the number of small areas with a score equal to or higher than a certain specific score. Evaluation points are obtained in this way for each of a plurality of images Is, and the image with the highest evaluation point is set as the optimum image Ib.

As a specific example, 10 small areas are set along the edge FE for two images A and B taken, for example, and the luminance of each small area is measured. When the sum of the points of each small region of image A is 800 points and the sum of the points of each small region of image B is 700 points, the image A with the high evaluation score is more reliably the edge of the polarizing film. It is determined to be the optimum image Ib in which negative detection is possible. In addition, the inner edge of the edge part FE of the polarizing film F in this image A is the straight line which connected the inner edges in 10 small areas.

The data generated in the process for obtaining the evaluation point and the polarizing film edge position (s202 in the process flow 200 and s301 to 305 in the process flow 300) is, for example, via a communication line, a hard disk (not shown) ), etc., stored in the storage unit. The stored data is read out from the storage unit as needed, and can be used in a later process, for example, a process for determining the amount of joint misalignment.

In the above way, the optimal image Ib which can more accurately detect the edge part FE of the polarizing film F bonded to the liquid crystal cell C is selected from several image Is image|photographed. The edge FE is detected using the selected optimal image Ib, and is known to those skilled in the art from the relationship between the position of the edge FE detected and the position of the edge CE of the liquid crystal cell C, for example. The bonding shift amount of polarizing film FE can be calculated|required using the method.

As the edge portion FE and its position in the selected optimum image Ib, the edge portion and its position detected in the process of selecting the optimum image Ib in the image selected as the optimum image Ib can be used as they are. As another method, to the selected optimum image Ib, the same processing as the detection processing of the inner edge position performed for each of the plurality of images Is (s301 to s303 in flow 300) is performed again to select the optimum image Ib; The finally detected edge portion FE and its position can be used as the edge portion and its position for determining the bonding displacement amount.

Example

Hereinafter, embodiments of the present invention will be described.

In the present embodiment, a liquid crystal panel is provided by using one camera (CA-035C, manufactured by Keyence, Inc.) and two lights (CA-DBR8, manufactured by Keyence, Inc.) disposed above the transport path of the liquid crystal panel. Two images including the edge of the front end of the polarizing film included in were acquired. As a liquid crystal panel, what bonded the polarizing film of thickness 0.1mm to the 32-inch liquid crystal cell of thickness 1.6mm was used. Two illuminations were respectively arranged on the upstream and downstream sides of the liquid crystal panel transport direction with respect to the position of the camera, and both were adjusted so that light was irradiated toward the vertically downward imaging point of the camera. The vertical distance between the position of the camera and the position of the liquid crystal panel was 91 mm, and the vertical distance between the position of the light and the position of the liquid crystal panel was 8 mm. Using the luminance measured by an image processing apparatus (Keyence Corporation, XG-5000), two images captured were evaluated.

Table 1 shows the evaluation results. In Table 1, "polarizing film edge position" is a position at which the liquid crystal panel is stopped to take two images (image 1 and image 2), "upstream side", "imaging point" and "downstream side" ” means when the edge of the polarizing film is on the upstream side of the imaging point, when the edge is on the imaging point, and when the edge is on the downstream side of the imaging point, respectively. "Irradiation direction" is the position and direction of illumination for irradiating light toward the edge of the polarizing film when the liquid crystal panel is stopped for photographing, and "from the upstream side" and "from the downstream side" are respectively upstream of the camera. This means that light is irradiated toward the edge from the illumination placed on the side, and that light is irradiated toward the edge from illumination arranged on the downstream side of the camera. Each "polarizing film edge part position" and "irradiation direction" of Example 1 - Example 5 are as Table 1 shows. In this embodiment, luminance is used as an evaluation point for selecting an optimal image. Three small regions (see Fig. 4) including the position where the polarizing film edge portion exists and its surroundings are selected, Bmax is measured in each of the three small regions, and the average luminance of the three Bmax thus obtained is evaluated. made in points

In Example 1, image 1 taken with light irradiated from the upstream side when the edge portion of the polarizing film was upstream was compared with image 2 taken with light irradiated from the downstream side when the edge portion of the polarizing film was upstream, The optimal image was selected. Since the evaluation point 165 of the image 1 is higher than the evaluation point 120 of the image 2, the image 1 was selected as an optimum image capable of reliably detecting bright lines at the edges of the polarizing film.

In Example 2, image 1 captured in the same way as in Example 1 was compared with image 2 captured by light irradiated from downstream when the edge of the polarizing film was an imaging point, and an optimal image was selected. Further, in Example 3, image 1 captured in the same way as in Example 1 was compared with image 2 captured by light irradiated from the downstream side when the edge portion of the polarizing film was downstream, and an optimum image was selected. In both Example 2 and Example 3, Image 1 was selected.

In Example 4, image 1 photographed with light irradiated from the upstream side when the edge portion of the polarizing film was an imaging point was compared with image 2 photographed with light irradiated from the downstream side when the edge portion of the polarizing film was downstream, , selected the optimal image. In this example, since the evaluation point 150 of image 2 is higher than the evaluation point 135 of image 1, image 2 was selected as the optimum image capable of reliably detecting bright lines at the edges of the polarizing film. Further, in Example 5, image 1 photographed with light irradiated from the upstream side when the edge portion of the polarizing film was downstream was compared with image 2 photographed with light irradiated from the downstream side when the edge portion of the polarizing film was downstream. , selected the optimal image. Also in this example, image 2 was selected.

In Comparative Example 1, when the edge of the polarizing film was at the imaging point, an image was acquired using a ring light (CA-DRR8, manufactured by Keyence Co., Ltd.) arranged coaxially with the camera (manufactured by Keyence Corporation, CA-035C). This is the result. In any case from Example 1 to Example 5, the evaluation point of the image selected as the optimal image was higher than the evaluation point (127) of Comparative Example 1. Therefore, by using the optimum image selected by the present invention, it is possible to more reliably detect bright lines at the edges of the optical film compared to images taken by the prior art.

Claims (5)

An optical film edge detection method for detecting an edge of an optical film laminated on a rectangular panel, comprising:
A conveyance step for conveying the rectangular panel on which the optical film is laminated;
A target area including an edge of the optical film on the rectangular panel is sequentially irradiated with light from a plurality of light sources disposed along the transport direction of the rectangular panel, and a single imaging means is used to irradiate light from an upstream side to a downstream side in the transport direction of the rectangular panel. A photographing staff to photograph at a plurality of positions across the side;
an optimum image selection step of selecting an optimal image for detecting the edge portion, based on the luminance of the edge portion in each image, from a plurality of images obtained by photographing the target region at a plurality of positions;
and an edge detection step of detecting the edge in the optimum image. According to claim 1,
the plurality of light sources include at least an upstream light source arranged on an upstream side in the conveying direction and a downstream light source arranged on a downstream side with respect to the one imaging means;
In the photographing step, when the edge is located upstream in the conveying direction from an imaging point, which is a position when the edge reaches vertically downward of the imaging means, light is irradiated from the upstream light source to photograph, and the image pickup A method for detecting an edge portion of an optical film, comprising: radiating light from the downstream light source and photographing the edge portion when the edge portion is located downstream of a point in the conveyance direction. According to claim 1 or 2,
wherein the optimum image selection step includes selecting the optimum image based on luminance of a plurality of locations set along the edge portion. According to any one of claims 1 to 3,
wherein the photographing step includes photographing the plurality of images while stopping the rectangular panel for each photographing. According to any one of claims 1 to 4,
The optical film edge detection method according to claim 1 , wherein the photographing step includes photographing the plurality of images by additionally using light from light sources arranged to face each other in a width direction of the rectangular panel.