JP2007212939A - Misalignment inspection method, program, and misalignment inspection apparatus - Google Patents

Abstract

An error of a bonding position of a polarizing plate attached to a TFT array substrate or a color filter substrate is inspected.
An alignment mark AM formed on a TFT array substrate 10 is recognized, an X axis and a Y axis are set in the field of view of a camera 50, and the alignment mark AM is recognized. Then, using the recognized alignment mark AM as a reference, a predetermined X direction search area XSA in the X axis direction, which is predicted to have an edge line, and a predetermined Y direction search area YSA in the Y axis direction are set. . The X direction search area XSA and the Y direction search area YSA are scanned from the inside to the outside, and an edge line is detected based on the change in the light amount. Then, the amount of error from the alignment mark AM is output with the intersection of the edge lines as the vertex of the polarizing plate 20.
[Selection] Figure 3

Description

  The present invention relates to a misalignment inspection method, a program, and a misalignment inspection apparatus for inspecting misalignment of a polarizing plate attached to a TFT array substrate and a color filter substrate constituting a liquid crystal display.

  A liquid crystal display consists of a TFT (Thin Film Transistor) array substrate (with a TFT circuit formed on a glass substrate) and a color filter substrate (with a color filter formed on a glass substrate). It consists of a liquid crystal panel with substrates attached. The TFT array substrate is a substrate for driving each pixel of the liquid crystal display, and the color filter substrate is a substrate for displaying a color image. A polarizing plate for controlling the polarization direction is attached to the TFT array substrate and the color filter substrate, respectively.

  Here, the polarizing plate needs to be attached to a predetermined reference position of the TFT array substrate and the color filter substrate. For this reason, it is inspected whether or not the polarizing plate attached to the TFT array substrate and the color filter substrate is displaced from the reference position. As a result of the inspection, if the polarizing plate is affixed at an appropriate position, it is determined as a non-defective product, and if it is applied at an inappropriate position, it is determined as a defective product. A device that performs such an inspection is disclosed in Patent Document 1.

In Patent Document 1, in order to inspect the attachment position of the polarizing plate, an L-shaped bar illumination that illuminates red light directly from the liquid crystal panel, and an infrared transmission illumination that illuminates infrared light directly below the liquid crystal panel; A camera, which is an imaging means, is provided directly above the liquid crystal panel. And the edge line of a polarizing plate and the vertex coordinate of a polarizing plate are calculated | required with the 1st image acquired by irradiating the red light illuminated from bar illumination. Further, the outline of the black matrix pattern is extracted from the second image acquired by irradiating infrared light illuminated from the infrared transmission illumination, and the vertex coordinates of the black matrix pattern are obtained as the intersection of the vertical and horizontal lines of the outline. Then, the inclination of the edge line and the outline of the black matrix pattern is calculated, it is determined whether it is within the allowable range, the positional deviation between the vertex coordinates of the polarizing plate and the vertex coordinates of the black matrix pattern is detected, and the polarizing plate It is determined whether or not is pasted at an appropriate position.
JP 2005-165097 A

  By the way, when inspecting the error of the attaching position of the polarizing plate using image recognition, an image in the vicinity of the corner including the apex of the polarizing plate is obtained, and this image is image-processed to determine the attaching position of the polarizing plate. Check for errors. At this time, in order to perform image processing, the polarizing plate is irradiated with illumination light to reflect the edge line and the apex of the polarizing plate, and the position of the apex of the polarizing plate is detected using the reflected light as the outer shape of the polarizing plate. Here, since the TFT array substrate and the color filter substrate are made of a transparent glass substrate, reflected light such as a sealant and a TFT circuit pattern is also detected as disturbance light through the glass substrate. Further, since the color filter substrate is formed by forming a color filter on a glass substrate, the reflected light of the edge line of the color filter is also detected as disturbance light.

  For this reason, when the entire area of the field of view imaged by the camera is scanned, it is necessary to distinguish between the reflected light of the edge line of the polarizing plate and the vertex of the polarizing plate and the disturbing light in order to detect the disturbing light described above. May be erroneously detected as the edge line of the polarizing plate. In this case, an accurate position of the polarizing plate cannot be inspected. In addition, as in Patent Document 1, there is a method that does not detect disturbance light by irradiating infrared light directly from the polarizing plate. However, when the entire region of the field of view captured by the camera is scanned, scanning time and image processing are performed. There is also a problem that time required for the time becomes long. Furthermore, in the color filter substrate, not only the edge line of the polarizing plate but also the edge line of the color filter and the glass substrate are detected. At this time, any edge line among the detected plurality of edge lines is detected. There is a problem that it is necessary to determine whether it is a polarizing plate. On the other hand, if an extremely narrow area only near the top of the polarizing plate is imaged, the above-mentioned problems are eliminated, but before performing the inspection, the polarizing plate and the camera are aligned with a very high accuracy in advance, There is a problem that the apex of the polarizing plate must be within the field of view of the camera.

  Therefore, an object of the present invention is to inspect the displacement of the polarizing plate with high accuracy and in a short time.

  The misalignment inspection method of the present invention is a misalignment inspection method for inspecting misalignment of a polarizing plate affixed on a substrate, wherein alignment marks formed at corners of the substrate are recognized by a camera. X-axis and Y-axis are set in the visual field of the camera that has recognized the alignment mark and the alignment mark is recognized, and the edge line of the polarizing plate predicted from the alignment mark is included with reference to the alignment mark. A line detection region setting step for setting an X direction search area in a predetermined range in the axial direction and a Y direction search area in a predetermined range in the Y axis direction; and the X direction search area and the Y direction search area on the substrate. Scanning from the inside to the outside, the X-direction edge line of the polarizing plate is scanned based on the light amount change in the X-direction search area. An edge line detection step of detecting a Y-direction edge line of the polarizing plate based on a change in light amount in the Y-direction search area, and an intersection of the X-direction edge line and the Y-direction edge line as the polarizing plate A deviation amount calculating step of calculating a positional deviation amount between the polarizing plate and the substrate by comparing the coordinates of the vertex of the polarizing plate with the coordinates of the alignment mark. And

  The program of the present invention causes a computer to execute each step described in the above-described misregistration inspection method.

  The misalignment inspection apparatus of the present invention is a misalignment inspection apparatus for inspecting misalignment of a polarizing plate attached on a substrate, and a camera for observing alignment marks formed at corners of the substrate, A mark detection light source for irradiating the alignment mark, an edge detection light source for detecting an edge of the polarizing plate, and an image processing device for inspecting a positional deviation of the polarizing plate based on an image observed by the camera; The image processing apparatus has an X axis and a Y axis set in the field of view of the camera, and is formed at a corner of the substrate recognized by the camera by illumination light from the mark detection light source. With reference to the alignment mark, an X-direction search area in a predetermined range in the X-axis direction including an edge line of the polarizing plate predicted from the alignment mark, and a predetermined range in the Y-axis direction The X direction search area is set, and the X direction search area and the Y direction search area are scanned from the inside to the outside of the substrate by the illumination light from the edge detection light source, and the amount of light in the X direction search area is changed. The X direction edge line of the polarizing plate is detected based on the light amount, the Y direction edge line of the polarizing plate is detected based on the light amount change in the Y direction search area, and the X direction edge line and the Y direction edge line are detected. Is calculated as an apex of the polarizing plate, and the positional deviation amount between the polarizing plate and the substrate is calculated by comparing the coordinates of the apex of the polarizing plate with the coordinates of the alignment mark. .

  The liquid crystal panel manufacturing method of the present invention is characterized by using the above-described misalignment inspection method or the above-described misalignment inspection apparatus.

  The present invention can inspect misalignment of a polarizing plate with high accuracy and in a short time.

  Hereinafter, embodiments of the present invention will be described. FIG. 1 shows a side view of a misregistration inspection apparatus of the present invention applied to a liquid crystal panel 1, and FIG. 2 shows a plan view of a TFT array substrate 10. The misalignment inspection apparatus of the present invention is an apparatus used for inspecting misalignment of polarizing plates formed on the TFT array substrate 10 and the color filter substrate 80 constituting the liquid crystal panel 1. In FIG. 1, the misalignment inspection of the polarizing plate 20 formed on the TFT array substrate 10 is performed. However, after the misalignment inspection of the polarizing plate 20 is completed, the polarizing plate formed on the color filter substrate 80. 81 misalignment inspection is performed. The TFT array substrate 10 has a TFT circuit pattern formed on a transparent glass substrate, and the color filter substrate 80 has a color filter formed on a transparent glass substrate. The TFT array substrate 10 and the color filter substrate 80 are bonded together, and liquid crystal is sealed between them. Then, polarizing plates 20 and 81 for controlling the polarization direction are attached to the TFT array substrate 10 and the color filter substrate 80, respectively. The TFT array substrate 10 is formed with an alignment mark AM used for misalignment inspection. Since the alignment marks AM are formed at the corners of the TFT array substrate 10, they are usually formed at the four corners of the TFT array substrate 10. However, even if it is not formed in all four corners of the TFT array substrate 10, it may be formed in at least two places. What will be described below is to inspect the displacement of the polarizing plate 20 formed on the TFT array substrate 10.

  The mark detection light source 30 is an illumination light source for irradiating the alignment mark AM formed on the TFT array substrate 10. The mark detection light source 30 is disposed above the TFT array substrate 10 and emits illumination light for illuminating the alignment mark AM from above. Therefore, the mark detection light source 30 is provided corresponding to the number of alignment marks AM. In this embodiment, in order to inspect the positional deviation of the polarizing plate 20 at the four corners of the TFT array substrate 10, the alignment marks AM are formed at a total of four locations at each corner of the TFT array substrate 10, Units for detecting the alignment marks AM and inspecting are also provided at a total of four corners. Accordingly, the mark detection light sources 30 are also arranged in a total of four locations. However, as shown in FIG. 1, the mark detection light source 30 may be provided as a separate and independent light source, but illumination for irradiating illumination light corresponding to the number of alignment marks AM from one large light source device. A light source may be provided. Further, here, a description will be given of units arranged for inspection at four places. However, as with the alignment mark AM, inspection can be carried out as long as they are arranged at at least two places.

  The edge detection light source 40 is a light source for irradiating the polarizing plate 20 to detect the edge of the polarizing plate 20. In order to make the edge line of the polarizing plate 20 stand out, the edge detection light source 40 is disposed on the side or oblique side of the TFT array substrate 10 and irradiates the polarizing plate 20 with illumination light from the side or oblique direction. . That is, when the illumination light is irradiated to the TFT array substrate 10 at a shallow angle, disturbance light such as a sealant or a TFT circuit pattern is not detected, and the edge line of the polarizing plate 20 is clearly detected. In FIG. 1, the edge detection light source 40 is disposed obliquely below the TFT array substrate 10. Here, since FIG. 1 is a side view, two edge detection light sources 40 are shown. However, since the edge lines of the polarizing plate 20 irradiate illumination light from two directions orthogonal to each other, the edge detection light sources 40 40 is arranged in two other places (two places are arranged in a direction perpendicular to the paper surface).

  The camera 50 is an image recognition means for detecting an alignment mark AM formed on the TFT array substrate 10 and an edge line near the apex of the polarizing plate 20. In FIG. 1, cameras 50 are arranged at a total of four locations for recognizing the respective corners of the TFT array substrate 10 (FIG. 1 is a side view, so only two cameras are shown). ing). In FIG. 2, an image in an image area AR that is an area captured by the camera 50 is output to an image processing device 60 connected to the camera 50. The image processing device 60 is a processing device for performing image recognition based on a positional deviation inspection method for the polarizing plate 20 described later. Then, the amount of positional deviation of the polarizing plate 20 is calculated and output to an output device (not shown). Thereby, the amount of displacement of the polarizing plate 20 can be obtained.

  The transport means 70 is a transport means such as a roller shaft for transporting the TFT array substrate 10. Since the displacement inspection of the attaching position of the polarizing plate 20 is performed as one stage in the manufacturing process of the liquid crystal display, the TFT array substrate 10 is carried into the displacement inspection stage, and after the inspection is completed, the next stage is performed. The TFT array substrate 10 is unloaded. Then, the next uninspected TFT array substrate 10 is carried into the misalignment inspection stage. For this reason, a transfer means 70 for transferring the TFT array substrate 10 is provided.

  Next, the positional deviation inspection method of the present invention will be described. FIG. 3 is a flowchart showing the flow of processing, and FIG. 4 shows images recognized by the four cameras 50 that photograph each corner of the TFT array substrate 10. In FIG. 4, the camera 50 captures an image area AR in a predetermined range including the alignment mark AM formed on the TFT array substrate 10 and the vertex C of the polarizing plate 20. Therefore, in order to project the alignment mark AM in the field of view of the camera 50, it is necessary to align the camera 50 and the TFT array substrate 10 in advance. However, the alignment mark AM is roughly positioned to the extent that it is displayed in any one of the entire area of the field of view of the camera 50.

  First, the coordinates of the alignment mark AM, which is a feature point, are recognized from the image area AR (step S1). Various images are imaged in the image area AR. For example, a method called gray search can be applied as a method for determining the alignment mark AM from the image area AR. Gray search is a method of extracting a pattern that approximates a registered grayscale image pattern. Therefore, the pattern of the grayscale image of the alignment mark AM is registered in the image processing apparatus 60 in advance, and a pattern that approximates the registered pattern of the alignment mark AM is detected from the image area AR. Of course, other methods may be used, but in any case, the alignment mark AM is recognized from the image area AR.

  At this time, the X axis and the Y axis are set in the image area AR, and the coordinates (AMX, AMY) of the recognized alignment mark AM are obtained. Here, the X axis and the Y axis are fixedly set within the field of view of the camera 50 with the alignment mark AM as a reference.

  Next, the image processing device 60 sets two search areas (X direction search area XSA and Y direction search area YSA) with the recognized alignment mark AM as a reference (step S2). Here, the search area is an area in a range where the two edge lines of the polarizing plate 20 are scanned from the acquired image. When the search area is set, the search area is fixed, Only scanning is performed. For this reason, the area | region for scanning becomes a one part area | region among all the imaged area | regions. The two search areas are set based on the alignment mark AM. The X direction search area XSA is set as a predetermined region that is predicted to include the X direction edge line LX of the polarizing plate 20 with the alignment mark AM as a reference, and the Y direction search area YSA is set with the alignment mark AM as a reference. The Y-direction edge run LY of the polarizing plate 20 is set as a predetermined region that is predicted to be included.

  In other words, using the alignment mark AM as a reference, the positions of two edge lines that are approximately orthogonal to each other of the polarizing plate 20 can be predicted. This is because the relative positional relationship between the alignment mark AM and the two edge lines is known in advance. The predicted range includes an edge line, and is set with a target narrowed down to a region where the edge line is predicted so that the edge line of the TFT array substrate 10 is not erroneously detected. At this time, since the coarse positioning is performed in advance and a constant search area with the best conditions can be set with reference to the alignment mark AM, erroneous detection of disturbance light can be prevented even if the TFT array substrate 10 moves slightly. Thus, the edge line of the polarizing plate 20 can be detected. In FIG. 4, the search area has a rectangular shape, but an arbitrary shape may be adopted. However, as a range of the search area, if a wide range is set, the time required for scanning becomes long. If a narrow range is set, the edge line may be out of the search area and the edge line cannot be detected. Accordingly, an appropriate range is set as the search area range in consideration of the balance between the two.

  The polarizing plate 20 is bonded with the alignment mark AM as a reference. Therefore, the polarizing plate 20 and the alignment mark AM are close to each other. Therefore, if the X-direction search area XSA and the Y-direction search area YSA having the predetermined range as described above are set with the alignment mark AM as a reference, the X-direction edge lines LX and Y near the vertex C of the polarizing plate 20 are set. The direction edge line LY is predicted to be displayed in two search areas. If the edge line is not projected in one of the X direction search area XSA and the Y direction search area YSA, or the edge line is in two search areas of the X direction search area XSA and the Y direction search area YSA. Is not projected, it is obvious that the polarizing plate 20 is pasted with a large displacement.

  Then, the X direction search area XSA and the Y direction search area YSA are scanned (step S3). Here, the scanning of the edge line of the polarizing plate 20 is performed by detecting the reflected light at the edge line by the illumination light from the edge detection light source 40 of FIG. As described above, the edge detection light source 40 for detecting the X direction edge line LX and the edge detection light source 40 for detecting the Y direction edge line LY are provided separately and independently. Since the edge detection light source 40 irradiates illumination light obliquely from below, the reflected light of the edge line becomes clear and other disturbance light is prevented from being detected. For this reason, as a scanning method of the X direction search area XSA and the Y direction search area YSA, a light amount change point where the light amount changes greatly is detected, and a straight line connecting the light amount change points can be recognized as an edge line. In order to detect the light quantity change point, for example, scanning for detecting the intensity of the reflected light is performed, and the point where the differential value becomes large can be detected as the light quantity change point.

  Incidentally, the X direction search area XSA and the Y direction search area YSA are set with the X direction edge line LX and the Y direction edge line LY as targets, but depending on the setting method, not only the edge line of the polarizing plate 20 The edge line of the TFT array substrate 10 may also be detected. Further, for example, when inspecting the positional deviation of the polarizing plate 81 attached to the color filter substrate instead of the TFT array substrate 10, the edge line of the color filter may be detected in the search area. For this reason, depending on the setting range of the search area, a plurality of edge lines may be detected in the X direction search area XSA and the Y direction search area YSA. Considering such a case, scanning of the X direction search area XSA and the Y direction search area YSA is performed from the inside to the outside of the TFT array substrate 10.

  That is, it is known in advance that the polarizing plate 20 is smaller in shape than the TFT array substrate 10 and smaller in shape than the color filter substrate. Therefore, even if a plurality of edge lines are detected in the X direction search area XSA and the Y direction search area YSA, the innermost edge line is the edge line of the polarizing plate 20. For this reason, scanning is performed from the inner side to the outer side of the TFT array substrate 10, and when the first light quantity change point is detected, the scan is stopped (step S4), and the straight line connecting the light quantity change points is defined as the X-direction edge line LX and It is recognized as a Y direction edge line LY (step S5).

  Then, after recognizing the X-direction edge line LX and the Y-direction edge line LY, the coordinates of the intersection of the X-direction edge line LX and the Y-direction edge line LY can be the apex of the polarizing plate 20, so that this is polarized. Calculated as the apex of the plate 20 (step S6). Then, a difference between the coordinates of the alignment mark AM calculated in step S1 and the coordinates of the vertex of the polarizing plate 20 calculated in step S6 is calculated (step S7), and this is output as the amount of positional deviation of the polarizing plate 20. (Step S8). Thereby, the shift | offset | difference amount of the sticking position of the polarizing plate 20 can be obtained.

  Next, it is determined whether or not the deviation amount obtained in step S8 is equal to or less than a preset threshold value (allowable range) (step S9). If it is above, it will discriminate | determine that it is inferior goods (step S11). The threshold value can be set to an arbitrary value according to the positional accuracy required for the polarizing plate 20.

  As described above, the shift amount of the polarizing plate 20 can be inspected. In the present invention, a characteristic alignment mark AM is detected in advance, and an X-direction search of a certain region where the X-direction edge line LX and the Y-direction edge line LY of the polarizing plate 20 are predicted based on the alignment mark AM. The vertex of the polarizing plate 20 is calculated by setting the area XSA and the Y-direction search area YSA, scanning the search area, and detecting the X-direction edge line LX and the Y-direction edge line LY. At this time, the X direction search area XSA and the Y direction search area YSA are not the entire image area AR picked up by the camera 50, but the X direction search area XSA and the Y direction search area YSA including the edge line are targeted. Scan with narrowing down. For this reason, the X-direction edge line LX and the Y-direction edge line LY can be detected without erroneously detecting other disturbance light. Even when an edge line other than the polarizing plate 20 is detected, the edge line of the polarizing plate 20 can be specified by scanning from the inside to the outside. In addition, since only a limited part of the image area AR is the target of scanning, image recognition can be performed at high speed.

  Furthermore, in the present invention, a stable misalignment inspection can be performed without performing high-precision alignment of a substrate such as the TFT array substrate 10 or the color filter substrate on which the polarizing plate 20 is formed in advance. That is, the X direction search area XSA and the Y direction search area YSA for scanning the edge line are set with the alignment mark AM as a reference. Therefore, no matter where the alignment mark AM is projected in the field of view of the camera 50, the alignment mark AM is automatically set with reference to the alignment mark AM. For example, even if the substrate such as the TFT array substrate 10 is largely inclined within the field of view of the camera 50, if the alignment mark AM is projected, the X-direction search area that always has a fixed relative positional relationship based on this. XSA and Y direction search area YSA can be set. Therefore, by always scanning the search area at the same position as viewed from the alignment mark AM, it is possible to ensure the stability of the misalignment inspection, and to omit the work of previously aligning the substrate with high accuracy. Play.

  By the way, an orientation flat (orientation flat) for confirming directionality and front and back may be formed in the corner of the polarizing plate 20. That is, since the polarizing plate 20 generates linearly polarized light that vibrates in one direction from light having a random polarization direction, the polarization direction of the light transmitted through the polarizing plate 20 may be controlled to a predetermined direction. In this case, it is necessary to attach the polarizing plate 20 to the TFT array substrate 10 in a predetermined direction. In order to confirm the attaching direction of the polarizing plate 20 at this time, an orientation flat with chamfered corners of the polarizing plate 20 is formed. The orientation flat is also used to confirm the front and back of the polarizing plate 20.

  Here, when the orientation flat having the chamfered corners of the polarizing plate 20 is formed, the apex portion of the polarizing plate 20 disappears. Therefore, it is impossible to inspect the positional deviation of the polarizing plate 20 by comparing the positions of the apex portion of the polarizing plate 20 and the alignment mark AM. However, in the present invention, the error in the attaching position of the polarizing plate 20 is inspected based on the position where the apex of the polarizing plate 20 is predicted from the X direction search area XSA and the Y direction search area YSA not including the apex portion. Therefore, it can be calculated as a virtual vertex of the polarizing plate 20, and an error can be inspected even when an orientation flat is formed at the corner of the polarizing plate 20.

It is a side view of the position shift inspection apparatus of the present invention. It is a top view of a TFT array substrate and a polarizing plate. It is a flowchart which shows the flow of a process of this invention. It is explanatory drawing for demonstrating the process when setting an X direction search area and a Y direction search area, and performing a scan.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 TFT array substrate 20 Polarizing plate 30 Mark detection light source 40 Edge detection light source 50 Camera 60 Image processing apparatus 70 Conveyance means AR Image area C Vertex LX X direction edge line LY Y direction edge line XSA X direction search area YSA Y direction search area

Claims (8)

A misalignment inspection method for inspecting misalignment of a polarizing plate attached on a substrate,
An alignment mark recognition step for recognizing an alignment mark formed at a corner of the substrate by a camera;
A predetermined range in the X-axis direction in which the X axis and the Y axis are set with reference to the alignment mark and the edge line of the polarizing plate predicted from the alignment mark is included in the field of view of the camera that has recognized the alignment mark An edge line detection area setting step for setting the X direction search area and a predetermined range of the Y direction search area in the Y axis direction;
The X direction search area and the Y direction search area are scanned from the inside to the outside of the substrate, and the X direction edge line of the polarizing plate is detected based on the light amount change in the X direction search area. An edge line detection step of detecting a Y-direction edge line of the polarizing plate based on a light amount change in a direction search area;
The intersection of the X-direction edge line and the Y-direction edge line is calculated as the vertex of the polarizing plate, and the coordinates of the virtual vertex of the polarizing plate and the coordinates of the alignment mark are compared. And a displacement amount calculating step for calculating a displacement amount with respect to the substrate.   The positional deviation detection method determines whether or not the polarizing plate is properly attached to the substrate based on whether or not the deviation amount calculated in the deviation amount calculation step exceeds an allowable range. The misregistration inspection method according to claim 1, further comprising a determination step.   2. The positional deviation detection method according to claim 1, wherein an orientation flat is formed at one corner of the polarizing plate, and a virtual vertex of the corner is detected.   The alignment mark illumination light for irradiating the alignment mark of the substrate and the edge line illumination light for detecting the X-direction edge line and the Y-direction edge line of the polarizing plate are irradiated from different illumination light sources, The position shift detection method according to claim 1, wherein the edge line illumination light illuminates the polarizing plate from a side or an oblique direction.   The program for making a computer perform each step described in any one of Claims 1 thru | or 4. A misalignment inspection device for inspecting misalignment of a polarizing plate attached on a substrate,
A camera for observing alignment marks formed at corners of the substrate, a mark detection light source for irradiating the alignment mark, an edge detection light source for detecting the edge of the polarizing plate, and the camera observing An image processing device for inspecting the positional deviation of the polarizing plate based on the image obtained,
The image processing apparatus includes:
The X axis and the Y axis are set in the field of view of the camera, and the alignment mark is formed on the basis of the alignment mark formed at the corner of the substrate recognized by the camera by illumination light from the mark detection light source. A predetermined X-direction search area in the X-axis direction including the predicted polarizing plate edge line and a predetermined search area in the Y-axis direction are set;
The X direction search area and the Y direction search area are scanned from the inner side to the outer side of the substrate by illumination light from the edge detection light source, and X of the polarizing plate is determined based on a change in light amount of the X direction search area. Detecting a direction edge line, detecting a Y direction edge line of the polarizing plate based on a light amount change in the Y direction search area,
The intersection of the X direction edge line and the Y direction edge line is calculated as a virtual vertex of the polarizing plate, the coordinates of the virtual vertex of the polarizing plate and the coordinates of the alignment mark are compared, A misregistration inspection apparatus for calculating a misregistration amount between a polarizing plate and the substrate.   The misalignment inspection apparatus according to claim 6, wherein the edge detection light source irradiates the polarizing plate with illumination light from a side or an oblique direction. A method for manufacturing a liquid crystal panel using the positional deviation inspection method according to claim 1 or the positional deviation inspection apparatus according to claim 6.

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