JP2006329921A - Method for inspecting optical sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a striated defect occurring in an optical sheet to be detected automatically with high sensitivity in a production line of the optical sheet. <P>SOLUTION: A method for inspecting the optical sheet is provided, in which the optical sheet (lenticular lens sheet 1) is illuminated, and its reflection light is received by a striated region imaging means 11, and reception light intensity of the reflection light is measured from an image signal acquired by the striated region imaging means 11, and the striated defect 7 is detected. In the method, an imaging visual field 12 of the striated region imaging means 11 is brought to traverse the surface of the optical sheet while keeping the orientation of the imaging visual field 12 constant to the optical sheet, and in this period, the striated region imaging means 11 receives the reflection light sequentially or simultaneously under such a plurality of conditions that angles (incidence angles α) between illumination light 21a, 21b and the reflection light received by the striated region imaging means are different from each other, and the striated defect is detected from abnormal intensity in the reception light intensity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for inspecting the presence or absence of streak defects in an optical sheet such as a lenticular lens sheet.

  The lenticular lens sheet 1 used for the transmission type projection screen is made of a transparent resin such as methacryl styrene resin (MS resin), acrylic resin, polycarbonate resin, etc. As shown in FIG. A plurality of cylindrical lenses 2 and 3 are arranged at equal intervals on the incident side and the light emission side, respectively. Further, on the light exit side of the lenticular lens sheet 1, a black stripe 4 is provided at a non-condensing portion by the light incident side cylindrical lens 2 in order to increase the contrast in the bright room and sharpen the image. .

  The black stripe 4 is obtained by forming the light absorption layer 6 on the surface of the convex portion 5. As a method for producing the lenticular lens sheet 1 having the black stripe 4, methacryl styrene resin (MS resin), acrylic resin is generally used. By producing a lens sheet having cylindrical lenses 2 and 3 and a convex portion 5 by extruding a transparent resin such as polycarbonate resin, and subsequently printing a light-shielding paint on the convex portion 5 with an application roll. The light absorption layer 6 is formed.

  In the process of forming the light absorption layer 6, streaky uneven scratches and gloss abnormalities are formed extending in the longitudinal direction of the black stripes 4, for example, by agglomerating light-shielding paint aggregates between the coating roll and the lens sheet. There is a case. These are referred to as streak defects 7, and when the lenticular lens sheet 1 is used for a screen, it causes a reduction in image contrast and sharpness. For this reason, the lenticular lens sheet 1 on which the streak defect 7 is formed must be selected and removed, and the location where the streak defect 7 is formed needs to be specified.

  Conventionally, as a method for inspecting a defect of a black stripe, a visual inspection by human eyes has been performed. However, it is required to automate the inspection in response to an increase in quality and mass production of a lenticular lens sheet. Therefore, a CCD line sensor is arranged at a right angle to the black stripe, and a method for detecting defects by imaging with reflected dark field light from substantially directly above the lenticular lens sheet, or a CCD line sensor with an imaging field of view. A method has been proposed in which defects are detected by arranging the black stripes at a specific angle of about 60 ° or less and imaging with reflected dark field light (Patent Document 1).

Japanese Patent No. 3507171

  However, the conventional defect inspection method using a CCD line sensor is effective in detecting a so-called white defect in which a black stripe is partially missing or destroyed, but it cannot detect a streak defect. was there.

  The reason for this is that white defects can be detected by observing reflected dark field light scattered or diffracted at the defect portion using imaging means with reflected dark field illumination, whereas streak defects have long white defects. This is because the deformation of the black stripe is detected by observing it as a luminance change of the regular reflection light.

  Here, the dark field illumination means that the direction of the light from the illumination light is deviated from the image pickup means, and light does not enter the image pickup means in a place where there is no defect, and from a defective part in a place where there is a defect. The scattered light or diffracted light is incident on the imaging means.

  In contrast to the conventional inspection methods as described above, the present invention eliminates streak defects that occur in various optical sheets such as prism lenses, diffraction grating sheets, and diffusion sheets, as well as streak defects that occur in black stripes of lenticular lens sheets. An object of the present invention is to provide an optical sheet inspection method and inspection apparatus that can automatically detect with high sensitivity in an optical sheet production line.

  The present inventor arranges linear area imaging means such as a CCD line sensor and an area sensor so that the imaging field of view is parallel to the generation direction of streak defects expected from the manufacturing method of the optical sheet, etc. When imaging from the surface normal of the imaging field of view (that is, from directly above the imaging field of view), the amount of reflected light from the streak defect received by the linear region imaging means depending on the incident angle of the illumination light that illuminates the imaging field of view If the illumination means and the linear area imaging means are arranged on a straight line and illuminated at an incident angle of 0 °, the reflected light received by the individual imaging elements constituting the linear area imaging means The amount of light varies greatly depending on the angle between the illumination light and the reflected light received by the individual imaging elements, and therefore the illumination light and the individual imaging elements constituting the linear area imaging means or the linear area imaging means. Measure the intensity of the reflected light received by the linear area imaging device under multiple conditions where the angle between the reflected light and the light received by the sensor is different. It was found that it could be detected. In addition, when the imaging field of view is traversed on the optical sheet while measuring the received light intensity of the reflected light in this way, streak defects can be automatically detected with high sensitivity, and as a device for detecting streak defects in this way. Have found that various modes can be adopted by differentiating the angle between the illumination light and the reflected light received by the linear region imaging means.

That is, the present invention illuminates the optical sheet,
The reflected light is received by the linear region imaging means,
An optical sheet inspection method for measuring the received light intensity of reflected light from an image signal obtained by a linear region imaging means and detecting streak defects,
While keeping the direction of the imaging field of view of the linear region imaging means in a fixed direction with respect to the optical sheet, while traversing the imaging field on the optical sheet,
The reflected light is received by the linear area imaging means sequentially or simultaneously under a plurality of conditions where the angle between the illumination light and the reflected light received by the linear area imaging means is different.
An optical sheet inspection method for detecting streak defects based on an abnormal intensity generated in received light intensity is provided.

Moreover, this invention is as a 1st aspect of the inspection apparatus which implements the above-mentioned inspection method,
Illumination means for illuminating the optical sheet;
Linear area imaging means for receiving the reflected light,
From the image signal obtained by the imaging field moving means for traversing the imaging field on the optical sheet and the image signal obtained by the linear area imaging means while maintaining the direction of the imaging field of the linear area imaging unit in a certain direction with respect to the optical sheet An optical sheet inspection apparatus provided with an image processing means for measuring the received light intensity of reflected light,
While traversing the imaging field on the optical sheet, the illumination means is moved to change the incident angle of the illumination light to move the illumination means,
Provided is an optical sheet inspection apparatus in which a linear region imaging means receives reflected light at 0 ° with respect to a surface normal in an imaging visual field.

As a second aspect of the inspection apparatus,
Illumination means for illuminating the optical sheet;
Linear area imaging means for receiving the reflected light,
From the image signal obtained by the imaging field moving means for traversing the imaging field on the optical sheet while maintaining the direction of the imaging field of the linear area imaging unit in a certain direction with respect to the optical sheet, and the image signal obtained by the linear area imaging unit An optical sheet inspection apparatus provided with an image processing means for measuring the received light intensity of reflected light,
The illumination means includes a plurality of light sources having different incident angles with respect to the imaging field,
While traversing the imaging field of view on the optical sheet, it is equipped with illumination switching means for changing the incident angle of illumination light by sequentially switching the lighting of the light source,
Provided is an optical sheet inspection apparatus in which a linear region imaging means receives reflected light at 0 ° with respect to a surface normal in an imaging visual field.

As a third aspect of the inspection apparatus,
Illumination means for illuminating the optical sheet;
Linear area imaging means for receiving the reflected light,
From the image signal obtained by the imaging field moving means for traversing the imaging field on the optical sheet and the image signal obtained by the linear area imaging means while maintaining the direction of the imaging field of the linear area imaging unit in a certain direction with respect to the optical sheet An optical sheet inspection apparatus provided with an image processing means for measuring the received light intensity of reflected light,
A plurality of sets of illumination means having different incident angles of illumination light with respect to the imaging field and linear area imaging means for receiving reflected light at 0 ° with respect to the surface normal in the imaging field, and optically imaging each set of imaging fields An optical sheet inspection apparatus for simultaneously traversing on a sheet is provided.

Furthermore, as a fourth aspect of the inspection apparatus,
Illumination means for illuminating the optical sheet;
Linear area imaging means for receiving the reflected light,
From the image signal obtained by the imaging field moving means for traversing the imaging field on the optical sheet and the image signal obtained by the linear area imaging means while maintaining the direction of the imaging field of the linear area imaging unit in a certain direction with respect to the optical sheet An optical sheet inspection apparatus provided with an image processing means for measuring the received light intensity of reflected light,
Provided is an optical sheet inspection apparatus in which an illumination unit and a linear region imaging unit are arranged on a straight line, and an incident angle of illumination light is 0 °.

  According to the optical sheet inspection method of the present invention, it is possible to detect a streak defect of an optical sheet with high sensitivity.

  Furthermore, when the optical sheet inspection method of the present invention is performed on an optical sheet production line, it becomes possible to automatically detect streak defects in the optical sheet production line, and to detect streak defects during operation of the production line. In such a case, the manufacturing conditions can be adjusted so that no streak defect occurs immediately.

  Further, according to the optical sheet inspection apparatus of the present invention, the optical sheet inspection method of the present invention can be reliably implemented.

  Hereinafter, the present invention will be described in detail with reference to the drawings. In each figure, the same numerals indicate the same or equivalent components.

  FIG. 1 is an aspect of an inspection apparatus for carrying out the optical sheet inspection method of the present invention, and shows an inspection apparatus 10A for detecting streak defects 7 occurring in a black stripe 4 in a production line of a lenticular lens sheet 1. It is a typical block diagram, (a) is a top view, (b) is a side view seen from the X direction, and (c) is a side view seen from the Y direction.

  This inspection apparatus 10A includes a linear area imaging means 11 such as a CCD line sensor or an element sensor on the light emitting side surface of the lenticular lens sheet 1 (that is, the sheet surface on which the black stripe 4 is formed), and an LED. Illumination means 20 including illuminations 21a and 21b is provided to obliquely illuminate the imaging field 12, and linear area imaging is performed from the surface normal in the imaging field 12 of the lenticular lens sheet 1 (that is, from directly above the imaging field 12). More specifically, the longitudinal direction of the imaging field of view 12 is taken so that the longitudinal direction of the imaging field of view 12 is parallel to the direction of occurrence of streak defects expected in the black stripe 4. The inspection apparatus 10A and the lenticular lens sheet 1 are arranged so that the longitudinal direction of the black stripe 4 is parallel to the longitudinal direction. Here, as LED lighting 21a, 21b, it is preferable to use what was equipped with the lens system so that illumination light may become parallel light.

  The linear region imaging means 11 and the LED illuminations 21 a and 21 b are attached to a support base 31 provided on the arm 30 on the lenticular lens sheet 1. The support 31 traverses the lenticular lens sheet 1 as indicated by an arrow A. On the other hand, the lenticular lens sheet 1 is conveyed in the longitudinal direction of the black stripe 4 as indicated by an arrow B. Therefore, the imaging field of view moving means is constituted by the support base 31 and the conveying system of the lenticular lens sheet 1, and the imaging field of view 12 is held on the lenticular lens sheet 1 while its longitudinal direction is held in the longitudinal direction of the black stripe 4. As shown in FIG. 2, the traverse that crosses the lenticular lens sheet 1 diagonally is repeated. Even if the imaging field of view 12 does not scan the entire surface of the lenticular lens sheet 1 as described above, a black stripe streak defect generally continues over a length of several meters or more once it occurs, so By appropriately adjusting the travel distance L1 of the lenticular lens sheet 1 per traverse, it can be detected without any problem.

  In this inspection apparatus 10A, as shown in FIG. 1B, LED illuminations 21a and 21b are provided on both sides of the linear region imaging means 11, and the incident angle α of the illumination light with respect to the imaging field 12 is within ± 60 °. An illumination moving device 23 is provided so as to take a desired value. More specifically, the illumination moving device 23 sets the incident angle α of the illumination light from one LED illumination 21a in the range of −60 ° to 0 ° and the incident angle α of the illumination light from the other LED illumination 21b to 0 °. It consists of a step motor and its control mechanism that change sequentially in a range of ˜60 °. The means for changing the incident angle α of each LED illumination is not limited to the step motor.

  The illumination moving device 23 changes the incident angle α for each traverse of the imaging field of view 12 on the lenticular lens sheet 1, and images the incident angle α from −60 ° to + 60 ° by a plurality of traverses. It is preferable.

  An image processing means 40 for processing the image signal is connected to the linear area imaging means 11 and measures the intensity of reflected light received by the linear area imaging means 11. The measurement of the received light intensity can be performed by installing image signal processing software known in the personal computer or image signal processing software attached to the linear area imaging means 11. Further, the image processing means 40 receives information on the positions of the LED lights 21a and 21b (that is, the incident angle α) from the control mechanism of the illumination moving device 23, and the received light intensity of the linear region imaging means 11 is defined as the incident angle α. The relationship between the incident angle α and the received light intensity can be displayed on the display 41.

  FIG. 3 is a typical example of a relationship diagram between the incident angle α displayed on the display 41 and the received light intensity (luminance). When there are streak defects in the black stripe, as shown in the figure, the received light intensity protrudes and a higher peak appears than when there are no streak defects. The magnitude of the incident angle α at which such an abnormal intensity appears and the value of the intensity vary depending on the individual stripe defect that can be formed in the black stripe, but usually the incident angle α is in the range of ± 30 °, particularly in the range of ± 20 °. In addition, a deviation from the baseline based on the case where there is no defect appears as a difference in intensity of 50% or more. Therefore, in this inspection apparatus 10A, when an abnormal intensity appears in the received light intensity at any incident angle α during traversing of the imaging visual field 12, specifically, the received light at the time of the defect with respect to the normal received light intensity of the defective portion. When the intensity difference becomes 50% or more, it is determined that a streak defect has been detected, and a warning is issued to the user of the inspection apparatus 10A by an arbitrary method such as an alarm sound or an alarm lamp.

  If there is a streak defect, the reason why such an abnormal intensity is observed in the received light intensity of the reflected light is that the surface shape of the part where the streak defect exists is slightly smaller than the surface shape of the part where the streak defect is not present. It is thought that it is different. Therefore, according to this inspection method, not only the portion where the black stripe becomes white and the surface shape becomes abnormal, but also the printing unevenness of the light-shielding paint forming the black stripe and the convexity of the underlying lens sheet are detected. It is also possible to detect a streak defect in which the surface of the black stripe is not smoothly formed due to a defective formation of the shape portion.

  4A and 4B are schematic configuration diagrams of an inspection apparatus 10B according to the present invention that is different from the above-described inspection apparatus 10A. FIG. 4A is a top view, and FIG. 4B is a side view as viewed from the (X) direction. This inspection apparatus 10B differs from the above-described inspection apparatus 10A in the generation method of illumination light having a different incident angle α, but the linear region imaging means 11 and its imaging field 12 are placed on the lenticular lens sheet 1. The imaging field-of-view moving means for scanning and the image processing means 40 for measuring the received light intensity of the reflected light from the image signal obtained by the linear area imaging means 11 are similarly configured.

  That is, in this inspection apparatus 10B, the illumination unit 20 includes a plurality of LED illuminations 21a, 21b, 21c, 21d, 21e, 21f, 21g, 21h, 21i, and 21j arranged in a circular arc around the linear region imaging unit 11. , 21k, and −40 °, −30 °, −20 °, −10 °, −5 °, 0 °, + 5 °, + 10 ° with respect to the imaging field of view 12 of the linear region imaging means 11, respectively. Illumination light is emitted so that the incident angles are + 20 °, + 30 °, and + 40 °.

  The plurality of LED illuminations 21a to 21k are sequentially switched on by the illumination switching unit 24 while the imaging visual field 12 is traversed on the lenticular lens sheet 1, and the image processing unit 40 includes the LED illuminations 21a to 21k. , The incident angle α of the illumination light when receiving the reflected light is associated. Therefore, this inspection apparatus 10B can also form a relationship diagram between the incident angle α and the received light intensity as shown in FIG. 3, and when an abnormal intensity appears in the received light intensity at any incident angle α, the streak is detected. It can be determined that a defect has been detected.

  FIG. 5 is also a schematic configuration diagram of an inspection apparatus 10C according to the present invention that is different from the above-described inspection apparatus 10A. This inspection apparatus 10C differs from the above-described inspection apparatus 10A in that a plurality of methods of creating illumination light having different incident angles are different and that a plurality of linear region imaging means 11 are provided. However, the imaging field moving means for scanning the imaging field 12 on the lenticular lens sheet and the image processing means 40 for measuring the received light intensity of the reflected light from the image signal obtained by the linear region imaging means 11 are configured in the same manner. ing.

  That is, in this inspection apparatus 10C, the LED illumination 21 having a different incident angle α of the illumination light with respect to the imaging field 12 and the linear area imaging unit 11 that receives the reflected light at 0 ° with respect to the surface normal in the imaging field 12. A plurality of sets are provided in a range where the incident angle α is ± 60 °, and each set is attached to the support base 31. Therefore, by traversing the support base 31 on the lenticular lens sheet 1, reflected light corresponding to different incident angles α is simultaneously received by the respective linear area imaging means 11, and the image processing means 40 is configured to change the incident angle for each set. Associate α with the received light intensity. Therefore, this inspection apparatus 10C can also form a relationship diagram between the incident angle α and the received light intensity as shown in FIG. 3, and when an abnormal intensity appears in the received light intensity at any incident angle α, the streak is detected. It can be determined that a defect has been detected.

  6A and 6B are schematic configuration diagrams of still another inspection apparatus 10D, in which FIG. 6A is a top view and FIG. 6B is a side view as viewed from the (X) direction.

  In this inspection apparatus 10D, the linear area imaging means 11 and the LED illumination 21 are arranged on a straight line on the lenticular lens sheet 1, and the imaging visual field 12 of the linear area imaging means 11 has the longitudinal direction of the black stripe 4 as its longitudinal direction. It is perpendicular to the direction. The LED illumination 21 illuminates the lenticular lens sheet 1 with an incident angle of 0 °.

  The image processing means 40 recognizes the angle β sandwiched between the illumination light and the reflected light received by the image pickup element 11a for each image pickup element 11a constituting the linear area image pickup means 11, and each image pickup element 11a. The intensity of the reflected light received at 1 can be stored in correspondence with the angle β, and the relationship between the angle β and the received light intensity can be displayed on the display 41.

  In addition, the detection device 10D has a function of traversing the support base 31 to which the linear region imaging means 11 and the LED illumination 21 are attached on the lenticular lens sheet 1 in the same manner as the detection device 10A described above.

  Therefore, according to this detection apparatus 10D, the relationship between the angle β sandwiched between the illumination light and the reflected light received by the individual image sensors 11a and the received light intensity received by the individual image sensors 11a is shown in FIG. It can be determined that a streak defect has been detected when an abnormal intensity appears in the received light intensity.

  In addition, the present invention can take various forms. For example, the streak of the lenticular lens sheet 1 that has been cut to a predetermined length is used without using the detection device 10A as a device that continuously detects streak defects while the lenticular lens sheet 1 is conveyed on the production line. When inspecting for the presence or absence of defects in a sheet format, it is preferable to move the arm 30 in the longitudinal direction of the black stripe 4 and scan the imaging field 12 on the lenticular lens sheet 1 as in FIG.

  In the present invention, the detection target of the streak defect is not limited to the lenticular lens sheet, and various optical sheets such as a prism lens, a diffraction grating sheet, and a diffusion sheet can be detected.

  The present invention is useful for detecting streak defects in various optical sheets.

It is a typical block diagram of test | inspection apparatus 10A which detects the black stripe of a lenticular lens sheet. It is explanatory drawing of the scanning line of the imaging visual field in a lenticular lens sheet. It is an example of the relationship figure of an incident angle and received light intensity. It is a typical block diagram of the test | inspection apparatus 10B which detects the black stripe of a lenticular lens sheet. It is a typical block diagram of test | inspection apparatus 10C which detects the black stripe of a lenticular lens sheet. It is a typical block diagram of test | inspection apparatus 10D which detects the black stripe of a lenticular lens sheet. It is explanatory drawing of the stripe defect which arises in the black stripe of a lenticular lens sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lenticular lens sheet 2 Light incident side cylindrical lens 3 Light output side cylindrical lens 4 Black stripe 5 Convex part 6 Light absorption layer 7 Stripe defect (streak defect or gloss abnormality)
10A, 10B, 10C, 10D Inspection device 11 Linear region imaging means 12 Imaging field of view 20 Illumination means 21, 21a, 21b, 21c, 21d, 21e, 21f, 21g, 21h, 21i, 21j, 21k LED illumination 23 Illumination moving device 24 Illumination switching means 30 Arm 31 Support base 40 Image processing means 41 Display A Movement direction of support base α Incident angle of illumination light β Angle sandwiched between illumination light and reflected light received by each image sensor

Claims (7)

Illuminate the optical sheet,
The reflected light is received by the linear region imaging means,
An optical sheet inspection method for measuring the received light intensity of reflected light from an image signal obtained by a linear region imaging means and detecting streak defects,
While keeping the direction of the imaging field of view of the linear region imaging means in a fixed direction with respect to the optical sheet, while traversing the imaging field on the optical sheet,
The reflected light is received by the linear area imaging means sequentially or simultaneously under a plurality of conditions where the angle between the illumination light and the reflected light received by the linear area imaging means is different.
An optical sheet inspection method for detecting streak defects based on an abnormal intensity generated in received light intensity.   The inspection method according to claim 1, wherein the optical sheet is a lenticular lens sheet, and a black stripe stripe defect is detected.   The linear area imaging means is arranged so that the imaging field of view is parallel to the longitudinal direction of the black stripe, and the lenticular lens sheet is conveyed parallel to the direction of the imaging field of view while traversing the imaging field across the black stripe. The inspection method according to claim 2. Illumination means for illuminating the optical sheet;
Linear area imaging means for receiving the reflected light,
From the image signal obtained by the imaging field moving means for traversing the imaging field on the optical sheet and the image signal obtained by the linear area imaging means while maintaining the direction of the imaging field of the linear area imaging unit in a certain direction with respect to the optical sheet An optical sheet inspection apparatus provided with an image processing means for measuring the received light intensity of reflected light,
While traversing the imaging field of view on the optical sheet, it comprises illumination moving means for moving the illumination means to change the incident angle of the illumination light,
An inspection apparatus for an optical sheet, in which the linear region imaging means receives reflected light at 0 ° with respect to the surface normal in the imaging visual field. Illumination means for illuminating the optical sheet;
Linear area imaging means for receiving the reflected light,
From the image signal obtained by the imaging field moving means for traversing the imaging field on the optical sheet and the image signal obtained by the linear area imaging means while maintaining the direction of the imaging field of the linear area imaging unit in a certain direction with respect to the optical sheet An optical sheet inspection apparatus provided with an image processing means for measuring the received light intensity of reflected light,
The illumination unit has a plurality of light sources having different incident angles with respect to the imaging field,
While traversing the imaging field of view on the optical sheet, it is equipped with illumination switching means for changing the incident angle of illumination light by sequentially switching the lighting of the light source,
An inspection apparatus for an optical sheet, in which the linear region imaging means receives reflected light at 0 ° with respect to the surface normal in the imaging visual field. Illumination means for illuminating the optical sheet;
Linear area imaging means for receiving the reflected light,
From the image signal obtained by the imaging field moving means for traversing the imaging field on the optical sheet while maintaining the direction of the imaging field of the linear area imaging unit in a certain direction with respect to the optical sheet, and the image signal obtained by the linear area imaging unit An optical sheet inspection apparatus provided with an image processing means for measuring the received light intensity of reflected light,
A plurality of sets of illumination means having different incident angles of illumination light with respect to the imaging field and linear area imaging means for receiving reflected light at 0 ° with respect to the surface normal in the imaging field, and optically imaging each set of imaging fields Optical sheet inspection device that simultaneously traverses on a sheet. Illumination means for illuminating the optical sheet;
Linear area imaging means for receiving the reflected light,
From the image signal obtained by the imaging field moving means for traversing the imaging field on the optical sheet and the image signal obtained by the linear area imaging means while maintaining the direction of the imaging field of the linear area imaging unit in a certain direction with respect to the optical sheet An optical sheet inspection apparatus provided with an image processing means for measuring the received light intensity of reflected light,
An optical sheet inspection apparatus in which an illumination unit and a linear region imaging unit are arranged on a straight line, and an incident angle of illumination light is 0 °.

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