JP2008298557A - Method and apparatus for inspecting optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily determine whether defects which have occurred in optical films are defects (optical defects) which cause defects in bright spots or not. <P>SOLUTION: As illuminating with illumination light 7 via a polarizing plate 3 arranged on one surface side of an optical film 1, images are acquired via a polarizing plate 2 arranged on the other surface side of the optical film 1. The presence or absence of optical defects is determined on the basis of imaging results. The polarizing plate 2 and the polarizing plate 3 are arranged at positions of cross nicols. Single-wavelength light within the wavelength band from blue to green is used as the illumination light 7 to optimize exposure time by the illumination light 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inspection method and apparatus for inspecting defects in an optical film such as a retardation film.

  For defect inspection of long optical films such as retardation films used in liquid crystal displays and other flat panel displays, pixels are arranged in a direction substantially perpendicular to the feeding direction while the optical film is fed from a roll. This is done by scanning the film surface with a line sensor and detecting the presence and position of the defect based on this because the luminance value changes in the defective part compared to the remaining normal part. Yes. Such a defect may cause a point that looks shining in a state where the liquid crystal display is energized to display black (a volatile defect), which may cause a reduction in display quality.

  Defects that occur in the production of optical films can be broadly classified into kneading systems, transfer systems, crack systems, scratch systems, etc., depending on the cause of the defects. Examples of the kneading system include fish eyes generated from an unmelted gel of a film material (resin), burnt foreign materials formed by burning part of the materials, and black foreign materials mixed with foreign materials from the environment. As the transfer system, there are defects caused by transferring foreign matter attached to the roll in the semi-molten state, scratches on the roll, and dents and holes in the solidified state. Examples of the crack system include film tearing and tearing. As the scratch system, there are scratches associated with film transport and the like.

  All of these defects do not give rise to the volatile defects, and some defects do not need to be rejected in the quality inspection if they do not affect the display quality. However, conventionally, even those that do not need to be rejected as defects are rejected, resulting in poor yield and low manufacturing efficiency. Also, many defects that occur in the film, such as fish eyes, are generally elliptical with a major axis in the film feed direction. Conventionally, scanning is performed by feeding the film to a fixed line sensor. Since imaging is performed, defects are inevitably detected in the minor axis direction, and detection is performed with a small number of pixels among the imaging pixels in which the line sensors are arranged, and thus the defect detection reliability is not high. There was also.

  This invention is made | formed in view of such a point, The place made into the objective is whether the defect which has arisen in the film is a defect (optical defect) which produces a volatile defect, or it is not so. It is to make it easy to determine.

  According to a first aspect of the present invention, there is provided a method for inspecting an optical film, wherein a pre-imaging step of taking an image while illuminating the optical film, and an imaging result of the optical film based on an imaging result in the pre-imaging step An imaging step of illuminating with illumination light through the first polarizing plate arranged on one surface side and imaging through the second polarizing plate arranged on the other surface side of the optical film, and the imaging step And, by identifying the defective portion and the normal portion of the optical film based on the imaging result in the preliminary imaging step, and obtaining the difference in luminance value of the defective portion obtained in the imaging step And an optical film inspection method comprising a determination step of determining the presence or absence of an optical defect.

  When two polarizing plates are arranged, for example, in crossed Nicols, the illumination light cannot pass through these two polarizing plates, and the brightness value does not change in the imaging result. However, when the defect occurring in the optical film interposed between these two polarizing plates is an optical defect that causes a volatile defect, that is, the refractive index of the defective part is changed with respect to the remaining normal part. In that case, the light of that portion passes and is reflected in the imaging result. By determining the presence or absence of the passage of light (hereinafter also referred to as light omission) associated with the change in the refractive index of the defect portion, it is possible to easily determine whether the defect causes a volatile defect or not. .

  According to a second aspect of the present invention, there is provided an inspection apparatus for an optical film, the first imaging apparatus including at least one line sensor having a plurality of one-dimensionally arrayed pixels for imaging the optical film, and the optical A first illuminating device that illuminates the optical film from the opposite side of the first imaging device with respect to the film; a second imaging device that includes an area sensor having a plurality of two-dimensionally arranged pixels that image the optical film; A second illumination device that illuminates the optical film from the opposite side to the second imaging device with respect to the optical film, a first polarizing plate provided between the optical film and the second imaging device, A second polarizing plate provided between the optical film and the second illumination device; and a moving device for moving the optical film, the first imaging device and the second imaging device. Any inspection apparatus of the optical film so as to selectively switch whether to perform imaging by is provided.

  According to the present invention, there is an effect that it is possible to easily determine whether a defect occurring in a film is a defect (optical defect) causing a volatile defect or not.

[First Embodiment]
Hereinafter, 1st Embodiment which concerns on the inspection method of the optical film of this invention is described in detail.

  The optical film inspection method according to the present embodiment basically includes a pre-imaging step of imaging while illuminating the optical film, and one surface of the optical film based on an imaging result in the pre-imaging step. An imaging step of illuminating with illumination light through the first polarizing plate arranged on the side and imaging through the second polarizing plate arranged on the other surface side of the optical film; the imaging step; Based on the imaging result in the pre-article imaging process, after identifying the defective part and the normal part of the optical film, the difference in luminance value of the defective part obtained in the imaging process is obtained, thereby obtaining an optical defect. And a determination step for determining whether or not there is any. Here, an optical defect means the optical defect which has arisen in the said optical film which has a high possibility of appearing as a volatile defect when the said optical film is used for a liquid crystal display etc .. Further, the volatile defect means a point that appears to shine when the liquid crystal display is energized and displaying black.

(Imaging process)
FIG. 1 is a diagram showing a schematic configuration of an inspection apparatus used in the imaging process. In the figure, reference numeral 1 denotes an optical film as a film to be inspected, and examples thereof include a thermoplastic resin film and a stretched film obtained by stretching this monoaxially or biaxially using a tenter stretching apparatus or the like. Here, the optical film 1 is a retardation film used for a liquid crystal panel. Polarizing plates 2 and 3 are disposed on the upper and lower sides with the optical film 1 interposed therebetween. A camera (imaging device) 5 having a lens system 4 is disposed on the opposite side (upper side) of the polarizing plate 2 from the optical film 1.

  Here, an area camera is used as the camera 5. On the opposite side (lower side) of the polarizing film 3 from the optical film 1, a transmission illumination device 6 for performing transmission illumination is disposed. As the transmissive illumination device 6, an illumination light source having a light source that emits light in a blue to green wavelength band (wavelength 430 nm to 570 nm) is used. As the light source, a single wavelength oscillation semiconductor laser or a light emitting diode can be used. Illumination light 7 emitted from the transmission illumination device 6 is incident on the camera 5 through the polarizing plate 3, the optical film 1, the polarizing plate 2, and the lens system 4.

  As shown in FIG. 2, the polarizing plate 2 and the polarizing plate 3 are crossed Nicols, that is, the transmission axis 2a of the polarizing plate 2 and the transmission axis 3a of the polarizing plate 3 are substantially 90 degrees. The polarizing plate 2 and the polarizing plate 3 are disposed so as to obtain a dark field when observed by the camera 5 in relation to the optical axis of the optical film 1. In principle, a defect (abnormal part) 8 present on the optical film 1 causes light leakage at the defect part 8 when the defect 8 is an optical defect, as shown in FIG. Even if the image 8a is observed on the image 9 picked up in FIG. 5 and the defect (abnormal portion) 8 is present on the optical film 1, if the defect is not an optical defect, FIG. As shown, the image is not observed on the image 9 captured by the camera 5.

(Pre-imaging process)
Prior to the imaging step, the pre-imaging step scans the surface of the optical film 1 using another inspection apparatus in which the polarizing plate 2 and 3 in FIG. 1 is removed and the camera 5 is a line sensor camera. This is a step of performing imaging and extracting in advance a normal portion and a defective portion (abnormal portion) on the optical film 1 based on the imaging result. Since there are variations in the imaging results of the line sensor camera regardless of the presence or absence of defects, a threshold value is set in advance in relation to this variation, and a portion within the threshold range is a normal portion. A portion outside the threshold range is determined and extracted as a defective portion. Then, based on the result of this pre-imaging process, imaging by the camera 5 via the polarizing plates 2 and 3 (imaging process) is performed, and the normal part and the defective part extracted in the pre-imaging process of the imaging result by this imaging process The part corresponding to is determined by the luminance difference described later. In addition, as illumination in another inspection apparatus using the line sensor, either transmitted illumination or reflected illumination may be used.

(Judgment process)
The determination step is performed as follows. FIG. 5 and FIG. 6 are diagrams showing an example of the imaging result captured by the camera 5 as a graph. The output from the camera 5 is a set of two luminance values (two-dimensional image data) in a plurality of imaging pixels arranged two-dimensionally. In FIG. Data). In FIG. 5, the horizontal axis represents the position in the direction orthogonal to the integration direction, and the vertical axis represents the integrated value (or average value) of the luminance values.

  First, after performing the above-described pre-imaging process and specifying the defective portion by the above-described determination process, the above-described imaging process is performed. Next, a difference (luminance difference) between the average value of the luminance values of the normal portion and the maximum value of the luminance values of the defective portion is obtained from the result obtained in the imaging process. The brightness difference is compared with a predetermined threshold value for determining whether or not it is an optical defect, and when it is within the range of the threshold value, it is determined that it is not an optical defect, If it is outside the threshold range, it is determined that the optical defect is present. In the case of FIG. 5, since the luminance difference is equal to or greater than the threshold value, it is determined as an optical defect. In FIG. 6, since the luminance difference is less than the threshold value, it is not determined as an optical defect. .

  By making such a determination, even if it is a defect, it does not give rise to a volatile defect and does not affect the display quality can be passed, whether it is an optical defect or not. Compared with the prior art that has been rejected uniformly, the yield can be improved and the production efficiency can be increased.

(Optimization of light source color and exposure time)
FIG. 7 to FIG. 9 are graphs showing results obtained by experimentally determining the relationship between the exposure time and the luminance difference. FIG. 7 shows a light source that emits blue (wavelength: 430 nm to 460 nm) single wavelength light. FIG. 8 shows a case where green (wavelength 500 nm to 570 nm) single wavelength light is emitted as the light source, and FIG. 9 shows a case where a red (wavelength 610 nm to 780 nm) single wavelength light is used as the light source. Yes. These figures are actually measured by using the above-described inspection apparatus using an optical film having a defect (fish eye) as a film to be inspected. 7 to 9, the horizontal axis indicates the exposure time (s), the vertical axis indicates the luminance or the luminance difference, the dotted line indicates the luminance change of the normal portion, the alternate long and short dash line indicates the luminance change of the defective portion, and the solid line. Indicates a change in luminance difference between the normal part and the defective part.

  As shown in FIGS. 7 to 9, the brightness of the normal part and the defective part is large in the exposure time in any of the colors of blue (FIG. 7), green (FIG. 8), and red (FIG. 9). It grows as it becomes. However, regarding the luminance difference, red (FIG. 9) hardly changes even when the exposure time is increased, and since the luminance difference is small compared to blue and green, red is not suitable as a light source color. I understand that. Therefore, it can be said that it is desirable to use blue to green as the light source color. In comparison between blue (FIG. 7) and green (FIG. 8), when the exposure time is sufficiently long, green has a larger luminance difference than blue, so green is more appropriate. It can be said that there is. However, when the exposure time is short (in the case of 0.5 s or less), since the luminance difference in blue is larger, it can be said that blue is more appropriate in this case.

  From the viewpoint of creating a dark field state, in the case of a blue light source color, the optical axis of the optical film 1 must be aligned with the transmission axis of the polarizing plates 2 and 3 with extremely strict accuracy. However, in the case of a green light source color, the tolerance of angle alignment is large in the case of a green light source color, and from this point of view, the green light source color is more appropriate. I can say that.

  With regard to the exposure time, the luminance difference increases as the exposure time increases. However, in the case of FIG. 7, the luminance difference enlargement rate does not increase so much after 1.0 s, and in the case of FIG. It is in a state. Since the exposure time is preferably as short as possible from the viewpoint of inspection speed and inspection efficiency, from this viewpoint, the exposure time is set to about 1.0 s for a blue light source color and about 1.5 s for a green light source color. Is optimal.

  As described above, the use of single-wavelength light having a short wavelength of blue to green as the illumination light increases the phase difference of the defective portion as compared with the case of white light which has been mainly used conventionally. In addition, by optimizing the exposure time according to the wavelength, the luminance difference can be expanded and the false detection rate can be reduced.

[Second Embodiment]
Next, a second embodiment of the optical film inspection apparatus of the present invention will be described in detail with reference to the drawings.

(Overall configuration of inspection equipment)
FIG. 10 is a side view showing a schematic configuration of an optical film inspection apparatus according to the second embodiment of the present invention, and FIG. 11 is a front view of the same. In the following description, an XYZ orthogonal coordinate system is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system shown in FIG. 10 is set so that the X axis and the Z axis are parallel to the paper surface, and the Y axis is set to a direction perpendicular to the paper surface. The XYZ orthogonal coordinate system shown in FIG. 11 is set so that the Y axis and the Z axis are parallel to the paper surface, and the X axis is set in a direction perpendicular to the paper surface. In the XYZ orthogonal coordinate system, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z axis is set to the vertically upward direction.

  The inspection apparatus 10 is configured by arranging a film moving device 12, a camera unit 13, an illumination unit 14, and the like on a gantry 11. A control device (control panel) 16, a power supply device 17, and the like that comprehensively control the entire inspection device are installed inside or outside the gantry 11. The film moving device 12 is configured to include an installation table 21, an X-direction drive shaft 22, and a Y-direction drive shaft 23 on which an optical film 15 as a film to be inspected is cut into a single sheet.

  The shaft 22 is installed on the gantry 11 along the X direction and the shaft 23 along the Y direction, and the film installation table 21 is installed so as to be orthogonal to the shafts 22 and 23. The shafts 22 and 23 are driven by a drive motor (not shown), and the optical film 15 installed on the film installation table 21 is moved in the X and Y directions.

  Although illustration is omitted, the film mounting base 21 is provided with an opening or transparent glass, and this portion serves as an inspection portion. In this inspection part, the presence or absence of a defect in the optical film 15 and the position of the defect are detected. The shaft 22 can stop the feeding of the optical film 15 in the general −X direction at an arbitrary position.

  The camera unit 13 includes three cameras 31, 32, and 33 and a camera support bar 34 that fixes these to the mount 11.

  The cameras 31 and 32 are line cameras each including a line sensor and an imaging lens unit (both not shown) including a one-dimensional image sensor in which imaging pixels are arranged along the X direction. An area camera including an area sensor composed of a two-dimensional image sensor and an imaging lens unit (both not shown) arranged in the direction and the Y direction.

  The line cameras 31 and 32 are provided along the X direction so that a part of each other slightly overlaps on the object plane (on the test surface of the optical film 15) of the imaging lens system provided therein, and in the Y direction. They are slightly offset. The offset in the Y direction is to avoid physical interference between the cameras 31 and 32, and when such interference does not occur, they may be arranged in a line along the Y direction.

  The illumination unit 14 includes three illumination devices 41, 42, 43 and an illumination fixing base 44 that fixes them to the gantry 11. Three illumination devices 41, 42, 43 are arranged on the illumination fixing base 44 so as to be directed upward.

  The illumination device 41 is a transmission illumination device that supplies illumination light to the line camera 31, and is provided corresponding to the line camera 31. The illumination device 42 is a transmission illumination device that supplies illumination light to the line camera 32, and is provided corresponding to the line camera 32. The illumination device 43 is a transmission illumination device that supplies illumination light to the area camera 33, and is provided corresponding to the area camera 33. The illuminating devices 41 and 42 include, for example, lamps that emit white light as light sources, and the illuminating device 43 includes, for example, a blue LED that emits blue single-wavelength light as light sources.

  On the optical path connecting the area camera 33 and the illumination device 43, a pair of polarizing plates 19 and 20 are provided so as to face each other in the vertical direction. The upper polarizing plate 19 is integrally supported by a support rod 34 via a support member (not shown), and the lower polarizing plate 20 is integrally supported by a fixed base 44 via a support member (not shown). . The polarizing plates 19 and 20 are arranged in crossed Nicols, that is, so that the respective transmission axes are substantially perpendicular to each other, and are arranged so as to be a dark field with respect to the optical axis of the optical film 15.

  The line camera 31 images the surface of the optical film 15 with the illumination light of the transmission illumination device 41, and the line camera 32 images the surface of the optical film 15 with the illumination light of the transmission illumination device 42. The surface of the optical film 15 is scanned and imaged by the line cameras 31 and 32 by being continuously moved in the Y direction by the shaft 23.

  Further, the area camera 33 images the surface of the optical film 15 through the polarizing plates 19 and 20 by illumination by the transmission illumination device 43. The polarizing plates 19 and 20 are arranged in crossed Nicols and are arranged at a predetermined angular relationship with the optical axis of the optical film 15, so that it is possible to take an image in the dark field, thereby separating optical defects from other defects. Imaging with possible polarization modes can be performed.

(Control processing)
The operation of each part of the inspection device 10 is controlled by the control device 16. Hereinafter, the control by this control apparatus will be described with reference to the flowcharts shown in FIGS.

  As shown in FIG. 10, the inspection is started with the optical film 15 set on the installation base 21 of the film moving device 12. When the inspection is started, first, each part is initialized, and the optical film 15 is moved by the film moving device 12 to a predetermined initial position (in FIGS. 10 and 11, the side edge on the −Y side of the optical film 15 is (Position corresponding to the line cameras 31 and 32) (S100).

  From this state, the film moving device 12 is operated, and the conveyance (positioning movement in the X direction) of the optical film 15 is started (S110).

  If it is determined in S120 that the film has been conveyed (positioned) to the predetermined start position (in the case of Y), the film movement by the film moving device 12 is stopped (S130).

  The processing in the transmission mode (transmission mode inspection) is shown in FIG. When the transmission mode (S140) is started, first, illumination by the transmission illumination devices 41 and 42 is started (S141), and then the motor of the shaft 23 (in order to move the optical film 15 in the + Y direction for imaging) ( (Not shown) is driven, the film mounting table 21 is moved, and the surface (test surface) of the optical film 15 is scanned and imaged in the + Y direction (S142).

  Next, it is determined whether or not imaging of the entire width of the film 15 (width in the Y direction) has been completed, that is, a predetermined folding position (corresponding to the side edge on the + Y side of the optical film 15 in FIGS. 10 and 11). It is determined whether or not the film setting table 21 has been moved to (position) (S143). In S143, when imaging of the full width has not been completed (in the case of N), the process returns to S142, and when imaging of the full width has been completed (in the case of Y), the movement of the film setting table 21 is stopped ( In addition, the emission of illumination light by the transmission illumination devices 41 and 42 is stopped (S145). As a result, the imaging processing in the transmission mode ends, and the process proceeds to S150 in FIG.

  In the description of the imaging process in the transmission mode described above, the film setting table 21 has been described as moving and scanning in one direction from the start position to the turn-back position, but this is the case of the film setting table 21 at the start of the mode process. When the current position is at or near the start position, and conversely, when the current position of the film mounting table 21 is at or near the turn-back position, it is moved and scanned from the turn-back position toward the start position. Good.

  Next, in S150 of FIG. 12, the presence or absence of a defect is determined based on the imaging result in the transmission mode (S140), and when it is determined that there is no defect (in the case of N), the process returns to S110 and there is a defect. If it is determined (in the case of Y), the position of the defective part and the position of a representative part (also referred to as a normal part) of the normal part are recorded (S160). The detection of the position of the defective portion is performed by using the luminance value detected from each of the imaging pixels arranged in the X direction of the line sensors 31 and 32 at each position in the Y direction, which is the scanning direction of the line sensors 31 and 32, and Integration is performed in the X direction to obtain a one-dimensional signal (one-dimensional data), and a portion that is greater than or equal to a predetermined threshold value for a defect is determined as a defect, and the positions in the X and Y directions are obtained. Similarly, the detection of the position of the normal part is performed by determining the position in the X direction and the Y direction by setting a part that is less than a predetermined threshold value for the normal part as a normal part. Note that the normal portion (representative portion) is a portion that is sufficiently less affected by the defective portion, and may be selected from portions close to the defective portion.

  If the positions of the defective part and the normal part are obtained and recorded, then imaging processing (polarization mode inspection) in the polarization mode is performed (S170). The imaging process in the polarization mode is an imaging process using the area camera 33, the transmission illumination device 43, and the polarizing plates 19 and 20. The processing by this polarization mode is shown in FIG.

  When the polarization mode (S170) is started, first, the film mounting base 21 is positioned and moved so that the defective part and the normal part (representative part) recorded in S160 are within the imaging field of view of the area camera 33. (S171) Next, the transmission illumination device 43 performs exposure for a predetermined time (S172). Here, since the illuminating device 43 emits blue single-wavelength light, the predetermined exposure time is set to 1.0 s as the optimum exposure time as described with reference to FIG. 7 in the first embodiment described above. Has been. When the illumination device 43 emits green single wavelength light, 1.5 s is set as the optimum exposure time as described with reference to FIG. 8 in the first embodiment described above. Is done.

  Next, based on the imaging result of the area camera 33, a luminance difference that is a difference in luminance value between the defective portion and the normal portion is calculated (S173). The calculation of the luminance difference is performed as follows, for example. First, the imaging results (two-dimensional image data) of the area camera 33 are integrated in the X direction and the Y direction, respectively, and a one-dimensional signal in the Y direction (one-dimensional data) and a one-dimensional signal in the X direction (one-dimensional data) are obtained. Ask. Next, the average value of the luminance values of the portions corresponding to the normal portion recorded in S160 of these one-dimensional signals is obtained, and the luminance values of the portions corresponding to the defective portions recorded in S160 of these one-dimensional signals are determined. A maximum value is obtained, and a luminance difference is obtained by subtracting the average value from the maximum value.

  If the luminance difference between the defective portion and the normal portion is obtained, then the luminance difference is compared with the predetermined threshold with respect to the luminance difference (S174), and the luminance difference is equal to or greater than the threshold. Is determined (in the case of Y), the defect is recorded as an optical defect (S175), and the process proceeds to S176. When it is determined in S174 that the luminance difference is less than the threshold value (in the case of N), since it is not an optical defect, S175 is skipped and the process proceeds to S176.

  In S176, it is determined whether or not the detection by the polarization mode is completed for all defects in the range scanned by the line sensors 31 and 32. If not completed (in the case of N), the process returns to S171 and ends. If yes (Y), the process proceeds to S180 in FIG. In S180, it is determined whether or not the inspection has been completed for the entire length of the optical film 15 (the entire range in the X direction). If it has not been completed (in the case of N), the process returns to S110 and the film 15 is moved in the X direction. (S110 to S130), the above-described series of processing (S140 to S170) is repeated for the next surface to be tested, and when the processing is finished (in the case of Y), this processing is finished.

  According to the second embodiment described above, the imaging mode (transmission mode) using the line cameras 31 and 32 and the transmission illumination devices 41 and 42, and the imaging using the area camera 33, the pair of polarizing plates 19 and 20 and the transmission illumination device 43 are used. There are two imaging modes of mode (polarization mode).

  In the second embodiment described above, inspection in the transmission mode using the line cameras 31 and 32 is performed, and when it is determined that there is a defect, the inspection in the polarization mode using the area camera 33 is performed. Therefore, the accuracy of defect detection of the optical film 15 can be improved. However, instead of such a two-stage inspection, only one transmission mode or polarization mode may be selectively performed, or all transmission modes and polarization modes may be performed in series.

  Furthermore, according to the second embodiment described above, the surface of the optical film 15 is scanned and imaged in the transmission mode using the line sensors 31 and 32, the presence or absence of the defect is determined based on the imaging result, and the defect is detected. If it is determined that there is an image, the surface of the optical film 15 is further imaged in the polarization mode using the area camera 33 to determine whether or not the defect is an optical defect. Therefore, even if it is a defect, it does not give rise to an optical defect, and a defect that does not affect the display quality when used in a liquid crystal panel or the like can be accepted and whether it is an optical defect or not. However, the yield can be improved and the manufacturing efficiency can be increased as compared with the conventional technique which has been rejected uniformly.

  In the second embodiment described above, the transmission mode inspection using the line cameras 31 and 32 is performed, and when it is determined that there is a defect, the area camera 33 is directly positioned on the defect portion and the polarization mode is set. Therefore, even if an area camera 33 having a relatively small field of view is used, the area camera 33 can perform the inspection with high efficiency. Compared with the case where the entire area of the optical film 15 is imaged, the inspection speed can be increased.

  By the way, although the defect which arises in an optical film also depends on the cause, since the film is sent with tension applied in the flow direction at the time of manufacture, the shape of the defect becomes longer in the flow direction (for example, the major axis is directed in the flow direction). Tend to be oval). In the second embodiment described above, in the imaging by the line cameras 31 and 32, the line sensor is arranged along the X direction, and is scanned and imaged in the Y direction. Therefore, by placing the optical film on the installation table so that the flow direction thereof coincides with the X direction, an elliptical defect having a long diameter in the flow direction is detected by a sensor in which pixels are arranged in the long diameter direction. The number of pixels involved in detection of the defect is large. Since each pixel of the sensor has variations in detection accuracy, it is advantageous from the viewpoint of increasing detection accuracy that the same defect can be detected by many pixels. Conventionally, since the line sensor is arranged so that the imaging pixels thereof are aligned in the width direction and scanned in the flow direction to pick up an image, for example, an elliptical defect having a long diameter in the flow direction is reduced. The sensor in which the pixels are arranged in the direction scans in the major axis direction, and the number of pixels involved in the detection of the defect is small. Therefore, the inspection apparatus of the second embodiment described above is more advantageous than this. It is understood that

  The first and second embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

It is a figure which shows schematic structure of the test | inspection apparatus used for the test | inspection method of the optical film which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the principle of the light omission in the inspection method of the optical film which concerns on 1st Embodiment of this invention. It is a figure which shows the picked-up image in case there exists light omission in the inspection method of the optical film which concerns on 1st Embodiment of this invention. It is a figure which shows the captured image in case there is no light omission in the inspection method of the optical film which concerns on 1st Embodiment of this invention. It is the figure which displayed and graphed an example (when it is determined with the light omission) in the inspection method of the optical film which concerns on 1st Embodiment of this invention. It is the figure which graphed and displayed other examples (when it is judged with no light omission) in the inspection method of the optical film concerning a 1st embodiment of the present invention. It is a figure which shows the relationship between the exposure time in case the light source color of 1st Embodiment of this invention is blue, and a brightness | luminance or a brightness difference. It is a figure which shows the relationship between the exposure time in case the light source color of 1st Embodiment of this invention is green, and a brightness | luminance or a brightness difference. It is a figure which shows the relationship between the exposure time in case the light source color of 1st Embodiment of this invention is red, and a brightness | luminance or a brightness difference. It is a side view which shows schematic structure of the inspection apparatus of the optical film which concerns on 2nd Embodiment of this invention. It is a front view which shows schematic structure of the inspection apparatus of the optical film which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the control processing of the inspection apparatus of the optical film which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the imaging process by the transmission mode of the inspection apparatus of the optical film which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the imaging process by the polarization mode of the inspection apparatus of the optical film which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical film 2, 3 ... Polarizing plate 5 ... Camera 6 ... Illuminating device 7 ... Illuminating light 8 ... Defect 8a ... Optical defect (light omission)
DESCRIPTION OF SYMBOLS 10 ... Inspection apparatus 11 ... Stand 12 ... Film moving apparatus 13 ... Camera unit 14 ... Illumination unit 15 ... Optical film 16 ... Control apparatus 19, 20 ... Polarizing plate 21 ... Film installation base 22 ... X direction drive shaft 23 ... Y direction drive Axes 31, 32 ... line camera 33 ... area camera 34 ... camera support rods 41, 42, 43 ... transmission illumination device

Claims (7)

An inspection method for an optical film,
A pre-imaging step of imaging while illuminating the optical film;
Based on the imaging result in the preliminary imaging step, after identifying a defective portion of the optical film, while illuminating with illumination light through a first polarizing plate disposed on one surface side of the optical film An imaging step of imaging through the second polarizing plate disposed on the other surface side of the optical film;
Based on the imaging result in the imaging step and the imaging result in the preliminary imaging step, after identifying the defective portion and the normal portion of the optical film, the difference in luminance value of the defective portion obtained in the imaging step An optical film inspection method comprising: a determination step for determining the presence or absence of an optical defect.   The method for inspecting an optical film according to claim 1, wherein the first polarizing plate and the second polarizing plate are arranged in crossed Nicols.   In the determination step, a difference in luminance value with respect to a normal portion of a defective portion related to an imaging result in the imaging step is compared with a predetermined threshold value, and the difference in luminance value is equal to or greater than the threshold value. The defect portion is determined as the optical defect in a case, and the defect portion is not determined as the optical result when the difference in luminance value is less than the threshold value. Optical film inspection method.   The exposure time of the optical film by the illumination light in the imaging step is optimized based on the relationship between the exposure time and the difference between the luminance values. The inspection method of the optical film as described.   The optical film inspection method according to any one of claims 1 to 4, wherein the illumination light in the imaging step is light having a wavelength of the illumination light in a wavelength band from blue to green. . An optical film inspection device,
A first imaging device including at least one line sensor having a plurality of one-dimensionally arranged pixels for imaging the optical film;
A first illumination device that illuminates the optical film from the opposite side of the first imaging device with respect to the optical film;
A second imaging device including an area sensor having a plurality of pixels arranged two-dimensionally to image the optical film;
A second illumination device that illuminates the optical film from the opposite side of the second imaging device with respect to the optical film;
A first polarizing plate provided between the optical film and the second imaging device;
A second polarizing plate provided between the optical film and the second lighting device;
A moving device for moving the optical film,
An inspection apparatus for an optical film, wherein one of the first imaging device and the second imaging device is selectively switched. The first imaging device includes at least one line sensor having a plurality of pixels arranged one-dimensionally,
The second imaging device includes an area sensor having a plurality of pixels arranged two-dimensionally,
During the forward operation of the reciprocating operation of the moving device, illumination by the first illuminating device is performed, scanning imaging is performed by the first imaging device, and a defective portion and normal are determined based on an imaging result by the first imaging device. A portion is specified, and the moving device is controlled so that the defective portion falls within the imaging field of view of the second imaging device at the time of reverse operation, and the second imaging device takes an image under illumination by the second illumination device. The optical film inspection apparatus according to claim 6, wherein the inspection apparatus is an optical film inspection apparatus.

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