JP2012163533A - Defect inspection apparatus and method for lenticular sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect even a minute defect of a lenticular sheet.SOLUTION: A light source unit 15 irradiates a lenticular sheet 11 with linearly polarized illumination light which has been made linear in parallel with a width direction of the lenticular sheet. Imaging apparatuses 21 and 22 image a region R irradiated with the illumination light from a direction tilted at a predetermined angle with respect to an irradiation direction of the illumination light through a second polarizer 23. A polarization direction of the second polarizer 23 is orthogonal with that of the illumination light. A defect is detected as a portion having a luminance higher than that of a normal portion.

Description

  The present invention relates to a defect inspection apparatus and method for inspecting the presence or absence of defects on a lenticular sheet on which a plurality of lenticular lenses are formed.

  A lenticular sheet in which a large number of lenticular lenses having a substantially semicircular cross section and extending linearly are arranged is known. The lenticular sheet is used for a projection screen, a 3D photograph capable of observing a stereoscopic image, and the like. The lenticular sheet is generally made of a transparent plastic resin.

  In the manufacturing process of the lenticular sheet, the lens is manufactured so as not to have defects such as lens formation defects, foreign matter mixing, adhesion, and scratches, but such defects are unavoidable. Since the desired optical characteristics of the lenticular sheet cannot be obtained in the defective portion, the lenticular sheet including the defective portion becomes a defective product. For this reason, the lenticular sheet is inspected for defects and the subsequent process is controlled so that the defective part is excluded from the product, or for defects that occur continuously, it is quickly manufactured so as not to continue to produce defective products. Must be interrupted and the cause removed.

  As a lenticular sheet defect inspection device, while conveying the lenticular sheet, it is illuminated with transmitted illumination or reflected dark field illumination so that only the normal incident light from the lenticular sheet is incident on the line sensor camera. A configuration in which a Fresnel lens or a convex lens is disposed between the lenticular sheet and the lenticular sheet is known (see Patent Document 1). Further, in Patent Document 1, in addition to the above-described line sensor camera, two line sensor cameras directly shoot a lenticular sheet from the left and right.

  There is known a defect inspection apparatus that detects a black defect whose transmittance is lowered due to contamination of foreign matters by illuminating a lenticular sheet with a line-shaped light source and photographing the transmitted light from three directions in the width direction. (See Patent Document 2). In the defect inspection apparatus of Patent Document 2, one line sensor camera takes an image from the front of the lenticular sheet, and two line sensor cameras are arranged on both sides in the width direction of the line sensor camera.

  On the other hand, it is not a lenticular sheet, but as a defect inspection device for a prism sheet in which a large number of prisms are arranged, linear illumination light is irradiated onto the prism sheet in a direction parallel to the prism arrangement direction, and the line is connected through a light collecting means. A sensor camera that receives light transmitted from a prism sheet is known (see Patent Document 3). In this patent document 3, by defining the relationship between the main refraction angle of the prism and the angle of view of the light collecting means, the light quantity distribution width of the light from the prism sheet received by the light receiving sheet is narrowed to a certain threshold. Defects can be detected using the values.

  Further, it is a flat optical sheet defect inspection device, in which a polarizer and an analyzer are arranged so as to sandwich the optical sheet, illumination light is irradiated to the optical sheet through the polarizer, and light transmitted through the optical sheet is transmitted. What receives light with a television camera via an analyzer is known (see Patent Document 4). In Patent Document 4, the polarization direction of the analyzer is shifted in a range of ± 5 degrees to ± 20 degrees from the state in which the polarization directions of the polarizer and the analyzer are orthogonal to each other, and internal foreign matter and surface-attached foreign matter are obtained by image processing. And are detected.

JP-A-8-159988 JP-A-7-159345 JP 2010-38715 A JP-A-9-189668

  By the way, when detecting a fine defect, it is necessary to photograph a lenticular sheet with high resolution. On the other hand, since a large number of lenses are arranged on the surface of the lenticular sheet, the amount of transmitted light or reflected light of the lenticular sheet changes in the lens arrangement direction. For this reason, when the resolution at the time of shooting is increased in the configuration in which transmitted light or reflected light is received as in Patent Documents 1 and 2, a signal change caused by the lens arrangement on the light reception signal of one line obtained by shooting is changed. As a result, it becomes difficult to distinguish between a small defect and a normal part, and as a result, only a large-sized defect can be detected. Further, in order to remove the signal change caused by the lens arrangement, complicated image processing is required. Similar problems also occur when imaging is performed with a lenticular sheet to be inspected arranged between a polarizer and an analyzer as in Patent Document 4. Further, since Patent Document 3 is a method using the refraction angle of the prism constituting the prism sheet, it cannot be applied to a lenticular sheet having a lenticular lens whose refraction angle is not constant.

  The present invention has been made in view of the above problems, and has been made to be able to inspect the presence or absence of fine defects by photographing a lenticular sheet with high resolution without being affected by the arrangement of lenses. It is an object of the present invention to provide a defect inspection apparatus and method for a lenticular sheet.

  In order to achieve the above object, in the defect inspection apparatus for a lenticular sheet of the present invention, a light source that irradiates the lenticular sheet with linear illumination light parallel to the width direction of the lenticular sheet, and a predetermined direction with respect to the illumination direction of the illumination light An observation means for observing the diffused light of the illumination light transmitted through the lenticular sheet, facing the irradiation area of the illumination light of the lenticular sheet from a direction tilted at an angle of between the lenticular sheet and the observation means. A polarizing unit comprising: a polarizer that polarizes illumination light in a specific direction; and an analyzer that is disposed between the lenticular sheet and the observation unit and whose polarization direction is perpendicular to the polarization direction of the polarizer. Are provided.

  In the defect inspection apparatus for a lenticular sheet according to claim 2, the polarization direction of the polarization unit is determined with respect to the lenticular sheet so that the amount of transmitted light incident on the observation means through the analyzer is minimized. It is what.

  In the defect inspection apparatus for a lenticular sheet according to claim 3, the polarization direction with respect to the lenticular sheet is within a range of 10 ° to 45 ° with respect to the longitudinal direction of the lenticular lens.

  In the defect inspection apparatus for a lenticular sheet according to claim 4, the polarization direction with respect to the lenticular sheet is in a range of 20 ° to 40 ° with respect to the longitudinal direction of the lenticular lens.

  6. The defect inspection apparatus for a lenticular sheet according to claim 5, wherein the observation means is arranged such that the photographing optical axis is inclined at the predetermined angle with respect to the illumination light irradiation direction, and diffused transmitted light is transmitted through the analyzer. An imaging unit that captures an illumination light irradiation region by receiving light is provided, and a determination unit that determines the presence / absence of a defect based on a photoelectric signal output from the imaging unit is provided.

  According to a defect inspection apparatus for a lenticular sheet according to a sixth aspect of the present invention, the imaging means are arranged apart from each other in the width direction of the lenticular sheet, and each is a first and second imaging apparatus for imaging an irradiation area.

  8. The defect inspection apparatus for a lenticular sheet according to claim 7, wherein the determination means has a defect when a signal component indicating a defect is included in a photoelectric signal from at least one of the first and second imaging apparatuses. Is determined.

  In the defect inspection apparatus for a lenticular sheet according to claim 8, the opening angle formed by the respective photographic optical axes of the first and second imaging apparatuses is set within a range of 5 ° to 15 °.

  In the defect inspection apparatus for a lenticular sheet according to claim 9, the determination means determines the presence or absence of a defect based on the level of a photoelectric signal with respect to a predetermined threshold value.

  The defect inspection apparatus for a lenticular sheet according to claim 10, further comprising a release unit that temporarily releases the crossed Nicols state of the polarization unit, and the determination unit is configured to release the crossed Nicols state by the release unit. In addition, a normal lenticular sheet is irradiated with illumination light from the light source, and a photoelectric signal for one line is obtained as a reference waveform in a state in which the amount of transmitted light incident on the photographing apparatus is temporarily increased. In order to determine the presence / absence of a defect based on the reference waveform, inspection sensitivity correction means is provided that relatively changes the relationship between the reference level and the photoelectric signal obtained at the time of inspection within one line.

  The defect inspection method for a lenticular sheet according to claim 11 irradiates the lenticular sheet with illumination light polarized in a specific direction in a line parallel to the width direction of the lenticular sheet, and is predetermined with respect to the illumination direction of the illumination light. Light that has passed through the analyzer out of the diffuse transmitted light from the lenticular sheet, facing the irradiation area of the illumination light of the lenticular sheet through the analyzer with the polarization direction orthogonal to the polarization direction of the illumination light from the direction inclined at the angle of The presence or absence of a sheet defect is determined based on the amount of light.

  In the defect inspection method for a lenticular sheet according to claim 12, the polarization direction of the illumination light with respect to the lenticular sheet is determined so that the amount of diffusely transmitted light passing through the analyzer is minimized.

  In the defect inspection method for a lenticular sheet according to claim 13, the polarization direction with respect to the lenticular sheet is within a range of 10 ° to 45 ° with respect to the longitudinal direction of the lenticular lens.

  In the defect inspection method for a lenticular sheet according to claim 14, the polarization direction with respect to the lenticular sheet is set within a range of 20 ° to 40 ° with respect to the longitudinal direction of the lenticular lens.

  16. The defect inspection method for a lenticular sheet according to claim 15, wherein the illumination light irradiation area is imaged by an imaging means arranged with the imaging optical axis inclined at the predetermined angle with respect to the illumination light irradiation direction. The presence / absence of a defect is determined based on the output photoelectric signal.

  In the defect inspection method for a lenticular sheet according to a sixteenth aspect, first and second imaging devices that are arranged apart from each other in the width direction of the lenticular sheet and each shoot an irradiation area are used as the imaging means.

  The defect inspection method for a lenticular sheet according to claim 17, wherein when there is a signal component indicating a defect in a photoelectric signal from at least one of the first and second imaging devices, it is determined that there is a defect. It is a thing.

  In the defect inspection method for a lenticular sheet according to claim 18, the opening angle formed by each imaging optical axis of the first and second imaging apparatuses is 30 °.

  In the defect inspection method for a lenticular sheet according to claim 19, the presence / absence of a defect is determined based on the level of a photoelectric signal with respect to a predetermined threshold value.

  21. The defect inspection method for a lenticular sheet according to claim 20, wherein the illumination light is applied to a normal lenticular sheet while the crossed Nicol state between the polarization direction of the illumination light and the polarization direction of the analyzer is temporarily released. In order to determine the presence or absence of a defect based on this reference waveform, a photoelectric signal for one line is obtained with the amount of transmitted light incident on the imaging device being temporarily increased. The inspection sensitivity in one line is corrected by relatively changing the relationship with the photoelectric signal sometimes obtained in one line.

  According to the present invention, the illumination light polarized in a specific direction is irradiated in a linear shape parallel to the width direction of the lenticular sheet, and illumination is performed from a direction inclined at a predetermined angle with respect to the illumination light irradiation direction. The irradiation area is observed through an analyzer having a polarization direction orthogonal to the polarization direction of light, and the presence or absence of defects in the lenticular sheet is determined based on the amount of light transmitted through the analyzer, so that it is not affected by the lenticular lens. Therefore, it is possible to accurately inspect the presence or absence of fine defects.

It is a perspective view which shows the structure of the defect inspection apparatus which implemented this invention. It is a perspective view which shows a lenticular sheet. It is explanatory drawing explaining the relationship between the irradiation direction of the illumination light by a light source part, and the imaging | photography direction of an imaging device. It is explanatory drawing explaining the irradiation area | region of illumination light, and the positional relationship of two imaging devices. It is explanatory drawing which shows the photoelectric signal for 1 line obtained from the irradiation area | region of the normal part of a lenticular sheet. It is explanatory drawing which shows the photoelectric signal for 1 line obtained from the irradiation area | region containing the defective part of a lenticular sheet. It is a graph which shows the relationship between angle (theta) which the polarization direction of the 1st polarizing plate makes with respect to the conveyance direction of a lens sheet, and contrast.

  A defect inspection apparatus for a lenticular sheet embodying the present invention is shown in FIG. The defect inspection apparatus 10 inspects defects inside or on the surface of the lenticular sheet 11 while continuously conveying the long lenticular sheet 11. The lenticular sheet 11 to be inspected is supplied from the manufacturing apparatus to the defect inspection apparatus 10. In addition, you may comprise so that the lenticular sheet 11 may be supplied to the defect inspection apparatus 10 from the roll which wound up the elongate lenticular sheet 11. FIG.

  As shown in FIG. 2, the lenticular sheet 11 has a large number of lenticular lenses (hereinafter simply referred to as lenses) 12 arranged on the front side and a flat surface on the back side. Each lens 12 has a substantially semicircular cross section and extends linearly, and has a photorefractive action in a direction orthogonal to the extending direction (arrow S direction). The lenticular sheet 11 is elongated in the longitudinal direction of the lens 12 (hereinafter referred to as the lens longitudinal direction), and the lens 12 is orthogonal to the lens longitudinal direction, that is, the width direction of the lenticular sheet 11 (hereinafter referred to as the sheet). Many are arranged in the width direction). The lens width of one lens 12 is about 0.25 mm, for example, and the arrangement pitch of the lenses 12 is also the same.

  The lenticular sheet 11 is made of a transparent plastic such as PET, and is produced, for example, by bonding a plastic film in which a large number of lenses 12 are molded to a flat plastic film. The lenticular sheet 11 has a birefringence characteristic due to molecular orientation accompanying stretching in the manufacturing process, and exhibits a polarizing action due to the birefringence characteristic. For convenience of explanation, the lens 12 is exaggerated in each drawing.

  In FIG. 1, the transport mechanism 14 includes a transport roller, a motor, and the like, and continuously transports the lenticular sheet 11 in the defect inspection apparatus 10. The conveyance direction (arrow S direction) of the lenticular sheet 11 by the conveyance mechanism 14 is parallel to the lens longitudinal direction. Therefore, the sheet width direction is a direction (arrow M direction) perpendicular to the conveyance direction. In this example, the lenticular sheet 11 is conveyed in the horizontal direction with the lens 12 side up, but the lens 12 side may be down or the conveyance direction may be vertical.

  A light source unit 15 is disposed below the conveyance path (back side) of the lenticular sheet 11. The light source unit 15 irradiates the lenticular sheet 11 with linear illumination light polarized in a specific direction, and includes a light source 16 (FIG. 3) such as an LED or a halogen lamp, and a housing 17 that houses the light source 16. The first polarizer 18 is used as a polarizer. The first polarizing plate 18 is of a linear polarization type that linearly polarizes illumination light.

  A pair of photographing devices 21 and 22 as observation means are arranged above the conveyance path (lens side) of the lenticular sheet 11. The photographing device 21 is a linear array camera configured with a photographing lens 21a and a line sensor 21b composed of a large number of pixels (light receiving elements) arranged in a line. The photographing device 21 photographs a line-shaped irradiation region R of the lenticular sheet 11 irradiated with illumination light as one line, and outputs a photoelectric signal.

  The imaging device 22 has a similar configuration, and is a linear array camera configured with an imaging lens 22a and a line sensor 22b. The imaging device 22 captures an irradiation region R as one line and outputs a photoelectric signal. The photographing devices 21 and 22 are controlled by a control device (not shown) so that the same irradiation region R is simultaneously photographed every time the lenticular sheet 11 is conveyed by one line.

  The conveyance of the lenticular sheet 11 is adjusted so that the conveyance direction is parallel to the longitudinal direction of the lens, but may be skewed due to various factors. Therefore, a detection device that detects the angle in the lens longitudinal direction with respect to the conveyance direction is arranged upstream of the defect inspection device 10, and the line-shaped illumination light is accurately detected in the sheet width direction based on the detection result of the detection device. The light source unit 15, the imaging devices 21 and 22, etc. may be rotated around a rotation axis perpendicular to the transport surface so as to be parallel to each other.

  As will be described later, the photographing devices 21 and 22 are arranged so as to be shifted from directly above the irradiation region R to the upstream side in the transport direction so that the illumination by the light source unit 15 is dark field illumination, and obliquely downward from the position. The photographing optical axes 21c and 22c are inclined with respect to the illumination light irradiation direction. The photographing devices 21 and 22 have a predetermined opening angle φ between the photographing optical axes 21c and 22c.

  A second polarizing plate 23 serving as an analyzer is disposed on the front surface of each of the photographing lenses 21 a and 22 a, and each of the photographing devices 21 and 22 photographs the irradiation region R through the corresponding second polarizing plate 23. The second polarizing plate 23 is of the linearly polarized light type like the first polarizing plate 18. Each second polarizing plate 23 is arranged so as to be perpendicular to the corresponding photographing optical axes 21c and 22c. The polarization direction of these second polarizing plates 23 is orthogonal to the polarization direction of the first polarizing plate 18 so as to be crossed Nicols with the first polarizing plate 18. That is, the polarization directions of the polarizing plates 18 and 23 are determined so that the illumination light linearly polarized by the first polarizing plate 18 does not pass through the second polarizing plate 2.

  The linearly polarized illumination light from the light source unit 15 passes through the lenticular sheet 11 having birefringence characteristics, and becomes elliptically polarized transmitted light according to the birefringence characteristics. A part of the diffuse transmitted light out of the elliptically polarized transmitted light is incident on the second polarizing plate 23. For this reason, the first polarizing plate 18 and the second polarizing plate 23 are in a crossed Nicols relationship, but coincide with the polarization direction of the second polarizing plate 23 in the diffused transmitted light incident on the second polarizing plate 23. The polarization component passes through the second polarizing plate 23 and is received by the photographing devices 21 and 22.

  The second polarizing plate 23 may be arranged in parallel with the first polarizing plate 18. Further, the position of the second polarizing plate 23 may not be the front surface of the photographing lenses 21a and 22a. For example, a single second polarizing plate 23 may be disposed so as to cover the irradiation region R in the vicinity of the lenticular sheet 11, and each of the imaging devices 21 and 22 may be configured to perform imaging through the second polarizing plate 23. Good.

  Each of the polarizing plates 18 and 23 is maintained from the normal portion to the second portion when the normal portion of the lenticular sheet 11 is irradiated with the illumination light polarized by the first polarizing plate 18 while maintaining the chronicol relationship as described above. The polarization direction with respect to the lenticular sheet 11 is adjusted according to the birefringence characteristics of the lenticular sheet 11 so that the amount of transmitted light that enters the polarizing plate 23 and passes through the second polarizing plate 23 is reduced. In this way, by reducing the amount of light transmitted through the second polarizing plate 23, it is possible to increase the contrast between the normal part and the defect part observed as a brighter part than the normal part.

  In order to maximize the contrast, it is preferable to adjust the amount of light transmitted through the second polarizing plate 23 to the minimum, and in this example as well. By passing through the lenticular sheet 11, one polarization direction of the first polarizing plate 18 or the second polarizing plate is set to the short axis direction of the elliptically polarized light and the other polarization direction is set long for the elliptically polarized illumination light. By making it be in the axial direction, the amount of transmitted light can be minimized. The minor axis direction and the major axis direction of the elliptically polarized light can be specified by measuring the birefringence characteristics of the lenticular sheet 11.

  The position detection unit 25 generates position information in the conveyance direction of the lenticular sheet 11 and sends this to the determination unit 26. The position detection unit 25 includes a roller that rotates following the conveyance of the lenticular sheet 11, an encoder that generates an encode pulse each time the roller rotates by a certain angle, a circuit that generates position information in the conveyance direction based on the encoder pulse, and the like. It is composed of

  The determination unit 26 determines the presence / absence of a defect, the size of the defect, and the like based on the photoelectric signals from the imaging devices 21 and 22. As this determination processing, for example, a threshold value is set for the luminance indicated by the photoelectric signal, and when the luminance signal brighter than the threshold value is included in the photoelectric signal in one line, the shot irradiation region R is detected. It shall be flawed. At this time, if each photoelectric signal from both of the photographing devices 21 and 22 includes a luminance portion exceeding the threshold value, it is determined that there is a relatively large scratch or internal foreign matter, and either one of the photographing devices is used. In the case where only the photoelectric signal includes a luminance portion exceeding the threshold value, it is determined that the scratch is on the back surface of the lenticular sheet 11.

  When the determination unit 26 detects a defect, the determination unit 26 generates and outputs defect information including position information from the position detection unit 25 indicating a position where the defect is detected and the type and size of the determined defect. This defect information is used as control information for preventing a defective portion of the lenticular sheet 11 from being used as a product.

  Note that only the presence / absence of a defect may be determined. In this case, if a photoelectric signal from both or one of the imaging devices includes a luminance portion exceeding a threshold, it may be determined that there is a defect. . Alternatively, the size of the defect may be determined by making the luminance distribution two-dimensional from the sequentially obtained photoelectric signals and calculating the number of pixels in the portion where the threshold value is exceeded.

  As shown in FIGS. 3 and 4, the casing 17 of the light source unit 15 is formed long in the sheet width direction, and the light source 16 is built therein. On the upper surface of the housing 17, an emission port 17a for emitting illumination light from the light source 16 is formed. The injection port 17a is narrowed in the conveyance direction and is formed long in the width direction of the lenticular sheet 11, thereby causing the line-shaped illumination light parallel to the sheet width direction to rise upward along the normal line L1 of the lenticular sheet 11. Irradiate. In this example, the illumination light irradiation direction is the normal direction of the lenticular sheet 11 in this way. The injection port 17a has a length equal to or longer than the width of the lenticular sheet 11, and irradiates the entire width of the lenticular sheet 11 with illumination light. 3 and 4, the illustration of the lens 12 is omitted.

  A first polarizing plate 18 is disposed above the housing 17 so as to cover the exit port 17a, and illumination light emitted from the exit port 17a is linearly polarized in a specific direction by the first polarizing plate 18. . In this example, the illumination light is polarized by arranging the first polarizing plate 18 between the lenticular sheet 11 and the light source 16 as described above. However, the illumination light polarized by another method is generated. The lenticular sheet 11 may be irradiated.

  As described above, the light source unit 15 emits illumination light upward along the normal line L1 of the lenticular sheet 11. Thereby, from the irradiation area | region R, the regular transmitted light of the transmitted light which permeate | transmits the lenticular sheet 11 is inject | emitted upwards along a normal line direction.

  The photographic optical axes 21c and 22c use the imaging optical axes 21c and 22c so that the imaging devices 21 and 22 capture the irradiation region R from a position separated from the position directly above the irradiation region R by a distance D1 (D1 ≠ 0) upstream of the conveyance path. It is tilted at an angle α with respect to the line L1, that is, the irradiation direction of the illumination light. By arranging the imaging devices 21 and 22 in this way, the light source unit 15 takes an image of diffused and transmitted light scattered in the irradiation region R without entering the regular transmitted light of the illumination light with respect to the imaging devices 21 and 22. The dark field illumination is designed to be incident on the devices 21 and 22. As described above, the angle α is an angle that is set so that the photographing devices 21 and 22 do not receive the regular transmitted light but only the diffuse transmitted light, and the photographing devices 21 and 22 with respect to the transport direction. It can be determined based on the width of the imaging range, the length of the irradiation region R, etc.

  The light source unit 15 and the imaging devices 21 and 22 are arranged such that the imaging optical axis is tilted with respect to the illumination light irradiation direction (transmission direction of the regular transmitted light) and the light source unit 15 is relative to the imaging devices 21 and 22. The dark field illumination is not limited to the above. For example, the photographing devices 21 and 22 may be arranged so as to be shifted to the downstream side of the conveyance path. Further, the light source unit 15 may irradiate the illumination light obliquely upward with respect to the lenticular sheet 11, and the photographing apparatus may shoot from right above the irradiation region R.

  As described above and as shown in FIG. 4, the lenticular sheet 11 is irradiated with linear illumination light in parallel with the sheet width direction. Since the lens 12 has a photorefractive action only in the direction orthogonal to the lens longitudinal direction, that is, in the sheet width direction, the linear illumination light parallel to the sheet width direction as described above is emitted from the lenticular sheet 11. In this case, it only spreads in the sheet width direction and does not spread in the longitudinal direction of the lens 14. For this reason, the state of dark field illumination can be secured.

  Further, the photographing devices 21 and 22 are arranged separated by a distance D2 (D2 ≠ 0) in the sheet width direction, and as shown in FIG. 1, the photographing optical axes 21c and 22c have an opening angle φ. They are open to each other. The photographing devices 21 and 22 are arranged at equal distances from the center of the lenticular sheet 11 in the sheet width direction, and the photographing optical axes 21 c and 22 c intersect with each other on the lenticular sheet 11.

  When scratches are present on the back surface of the lenticular sheet 11, the scratches may be enlarged or may not be recognized depending on the observation direction from the front side. When the image is printed on the back side of the cut sheet obtained by cutting the lenticular sheet 11 into an appropriate size and viewed from the front side, the left of the observer is observed from each position separated in the width direction of the cut sheet. Focusing on the observation with the eyes and the right eye, defects such as scratches are detected under optical conditions similar to this normal use mode.

In order to obtain an optical condition similar to that of a normal use mode, it is appropriate that the opening angle φ is 10 ° ± 5 °. When viewing the cut sheet from the normal direction of the cut sheet by a distance of 400 mm with both eyes, if the distance between both eyes (pupil distance) is 70 mm, the angle at which both eyes are viewed from the cut sheet is about 10 ° ( = 2 tan ^-1 (35/400)). This is because when the distance between the sheet and the viewer's eyes is assumed to vary within a range of about 270 mm to 800 mm, the angle at which the eyes are viewed from the cut sheet is about 5 ° to 15 °.

  FIG. 5 shows an example of a photoelectric signal for one line obtained from the imaging devices 21 and 22. As described above, the second polarizing plate 23 transmits the polarized light component that matches the polarization direction of the diffuse transmitted light incident from the lenticular sheet 11, and the polarized light component is received by the imaging devices 21 and 22. For this reason, the luminance indicated by the photoelectric signal in the photoelectric signal of one line in the normal portion is not “0”. However, since the polarization directions of the first and second polarizing plates 18 and 23 are adjusted so that the amount of light transmitted through the second polarizing plate 23 becomes the smallest as described above, the luminance becomes a small value.

  In addition, a plurality of lenses 12 are arranged on the lenticular sheet 11, and the refracting action of the lenses 12 causes the amount of light transmitted through the lenticular sheet 11 to be strong or weak in the sheet width direction. The luminance for one line changes according to the arrangement. However, in this configuration, since only the diffuse transmitted light is received, the luminance change for one line corresponding to the arrangement of the lenses 12 is minute. Thereby, it is possible to determine the presence or absence of a minute defect without being affected by the arrangement of the plurality of lenses 12.

  The threshold value used when determining the defect is set to a constant value Th higher than the photoelectric signal when the normal part of the lenticular sheet 11 is photographed. This value Th is determined by, for example, experimentally examining the photoelectric signal for many lines so that the photoelectric signal obtained when the normal portion is photographed is higher than the maximum value that can be taken.

  FIG. 6 shows an example of a photoelectric signal for one line including a defective portion. When the lenticular sheet 11 has a defect, the birefringence characteristic of the lenticular sheet 11 locally differs from the normal part in the defective part, and the polarization state of the diffuse transmitted light is different from that of the normal part. This change in the polarization state increases the polarization component transmitted through the second polarizing plate 23, so that the signal level corresponding to the defective portion in the photoelectric signal of one line becomes high. Thereby, the determination part 26 can determine with a defect because a photoelectric signal becomes higher than a threshold value.

  In this example, a constant threshold value is used. However, the photographing optical axes 21c and 22c of the photographing devices 21 and 22 are arranged to be inclined with respect to the irradiation direction with an opening angle φ. Since the photoelectric signal of one line is inclined in the width direction in principle, the threshold value may be changed in one line based on the change of the photoelectric signal. However, since the first and second polarizing plates 18 and 23 are crossed Nicols and adjusted so that the amount of transmitted light is minimized, and only diffused transmitted light is received, the photoelectric signal level on the normal surface It is difficult to accurately reflect the inclination in the width direction of the one-line photoelectric signal. Therefore, for example, by temporarily removing the first polarizing plate 18 and the second polarizing plate 23, the waveform of the photoelectric signal for one line obtained in a state where the crossed Nicols are canceled is obtained. By using a threshold generated by passing through a low-pass filter with a cut-off frequency to remove high-frequency geosynthesis and electrical noise, and extracting only the slope and large swell of the photoelectric signal for one line May be. At this time, the inclination or large undulation of the photoelectric signal is extracted as a threshold waveform for one line, and the signal level of the threshold waveform for one line is increased or decreased as a whole to detect a defect. Sensitivity can be adjusted.

  Alternatively, a so-called “shading correction” in which a photoelectric signal waveform for one line obtained in a state where crossed nicols are released is stored as a reference waveform, and a predetermined magnification based on the reference waveform is applied to the photoelectric signal waveform at the time of inspection. May be performed. Moreover, although the example which removes a polarizing plate was demonstrated as a means to cancel | release cross nicol, you may make it rotate one or both polarizing plates. In this way, by temporarily canceling crossed Nicols and increasing the amount of transmitted light, and determining and setting the threshold value using the photoelectric signal at that time, the detection sensitivity in the sheet width direction can be made uniform, and the brightness rises. Even a few smaller defects can be detected.

  Since the photoelectric signal of one line changes according to the lens 12 and the arrangement of the lenses 12, the threshold value may be changed in one line based on the change of the photoelectric signal. For example, by removing the first polarizing plate 18 and the second polarizing plate 23, the waveform of the photoelectric signal for one line obtained in a state where the crossed nicols are released is inverted, and the threshold value is as in the inverted waveform. May be moved up and down in one line. In this way, it is possible to detect even a smaller defect with a slight increase in luminance.

  The operation of the defect inspection apparatus will be described. The lenticular sheet 11 to be inspected is fed into the defect inspection apparatus 10 and continuously conveyed. During the conveyance, the lenticular sheet 11 is irradiated with linear illumination light from the light source unit 15 via the first polarizing plate 18.

  The illumination light converted into linearly polarized light by the first polarizing plate 18 becomes elliptically polarized light due to the birefringence characteristic of the lenticular sheet 11 and passes through the lenticular sheet 11. A part of the diffuse transmitted light out of the transmitted light that has become the elliptically polarized light is incident on each second polarizing plate 23. Furthermore, out of the diffusely transmitted light incident on the second polarizing plate 23, only the polarization component in the polarization direction of the second polarizing plate 23 is transmitted and incident on the photographing devices 21 and 22, and the incident light is equivalent to one line. Is taken. The photographing devices 21 and 22 capture one line each time the lenticular sheet 11 is fed for one line.

  Each time one line is imaged, each line of photoelectric signals from the imaging devices 21 and 22 is sequentially output, and each photoelectric signal is sent to the determination unit 26. The determination unit 26 compares each photoelectric signal with a threshold value, and determines the presence / absence, type, size, and the like of the defect. In this comparison, when there is no portion exceeding the threshold value in both photoelectric signals, it is determined that there is no defect in the photographed irradiation region R. On the other hand, if both photoelectric signals include a luminance part exceeding the threshold value, it is determined that the defect is a relatively large scratch or internal foreign matter, and only one of the photoelectric signals includes a luminance part exceeding the threshold value. If it is, it is determined that the flaw is a small scratch on the back surface of the lenticular sheet 11. Then, the defect information including the position information of the defect detected by the position detection unit is output together with the type and size of the defect.

  By the way, the transmitted light of the lenticular sheet 11 becomes elliptically polarized light due to the birefringence characteristic of the portion of the lenticular sheet 11 through which it passes, and part of the diffused transmitted light is incident on the second polarizing plate 23. The linearly polarized light component transmitted through the second polarizing plate 23 is received by the photographing devices 21 and 22. The light amount of the linearly polarized light component transmitted through the second polarizing plate 23 depends on the polarization state of the diffusely transmitted light. It will be a thing.

  Therefore, when the illumination light is irradiated on the normal portion having the desired birefringence characteristic of the lenticular sheet 11, a light amount corresponding to the desired birefringence characteristic is received. For this reason, if the irradiation region R is a normal part, each photoelectric signal for one line output from each of the imaging devices 21 and 22 does not become higher than the threshold value Th. It is determined that there are no defects.

  On the other hand, if there is a defect due to scratches on the front or back surface of the irradiation region R or the presence of foreign matter inside the lenticular sheet 11, the duplication of the lenticular sheet 11 locally occurs around the defective portion or its periphery. The refraction characteristics are different from the normal part. For this reason, the polarization state of the transmitted light is different from that transmitted through the normal part, and the polarization component transmitted through the second polarizing plate 23 increases. Thereby, the signal level (luminance) corresponding to the defective portion in the photoelectric signal of one line becomes higher than the threshold value, and as a result, it is determined that there is a defect. Even if the foreign matter in the lenticular sheet 11 is opaque or very fine, the birefringence characteristics around it are different from those of the normal part, and therefore can be detected in the same manner.

  Further, when there is a minute scratch on the back side of the lenticular sheet 11, the lens 12 may not be observed depending on the direction of observation due to the refractive action of the lens 12. However, since the photographing devices 21 and 22 are arranged with the opening angle φ as described above, at least one of the photographing devices 21 and 22 is to be observed with respect to a scratch that is observed in an actual use state. The scratch is detected from the photoelectric signal. Of course, it is needless to say that a flaw that is enlarged according to the observation direction can be detected.

  As described above, the determination is performed based on each photoelectric signal, and the change in signal level due to the arrangement of the large number of lenses 12 in the sheet width direction is minute in each photoelectric signal. Therefore, the change in the signal level is not affected by the presence or absence of defects.

[Example 1]
In Example 1, the defect detection apparatus 10 configured as described above was used to detect defects using the lenticular sheet 11 mainly composed of PET as an inspection target. The photographing devices 21 and 22 use 7000 pixel line sensors 21b and 22b, and the focal length of the photographing lens so that the resolution of the lens 12 on the surface of the lenticular sheet 11 is 0.05 mm, and Set the shooting distance. Further, the opening angle φ of the photographing optical axes 21c and 22c was set to be 10 °.

  In Example 1, a circular scratch having a diameter of about 0.2 mm (hereinafter referred to as a surface scratch) is formed as a defect on the surface of the lens 12, and the polarization direction of the first polarizing plate 18 with respect to the conveying direction of the lenticular sheet 11 is changed. The angle θ formed was changed to obtain the contrast for each angle θ. As shown in FIG. 6, the contrast is obtained by measuring the average luminance h1 of the normal part and the luminance h2 of the defective part in the photoelectric signals from the photographing devices 21 and 22, and setting the ratio (= h1 / h2) of the two as the contrast. . Table 1 shows the average luminance h1, luminance h2, and contrast at each angle θ. The results are shown as a graph in FIG. In the case of surface scratches in this example, there was no significant difference between the photoelectric signals of the two photographing devices 21 and 22.

  Considering the signal due to the variation in formation on the normal surface and noise, it is preferable that the contrast is 2 or more in order to stably extract the defect. From Table 1 and FIG. 10 ° ≦ θ ≦ 45 ° ”, and it can be seen that the detection of the surface flaw can be preferably performed within this range. Further, it can be seen that the contrast becomes higher in the range of 20 ° ≦ θ ≦ 40 °, and the surface flaw can be detected with high sensitivity.

[Example 2]
In the second embodiment, a plurality of circular scratch marks having a diameter of about 0.05 mm are formed on the back surface of the lenticular sheet 11, and the lenticular sheet 11 is photographed by the photographing devices 21 and 22. Each photoelectric signal from was examined. The conditions were the same as in Example 1 except that the opening angle φ was fixed at 10 °.

  In the second embodiment, the luminance h2 corresponding to the dent scratch obtained from the photographing device 21 or the photographing device 22 varies greatly depending on the position of the dent scar, but at least one of the photographing devices corresponds to the dent scratch. It was possible to obtain a luminance h2 sufficient for detection. From this result, even if the scratch is enlarged or reduced in the shooting direction of each photographing device depending on the positional relationship between the lens 12 and the scratch, the scratch is enlarged in any one of the photographing devices. It can be seen that the image can be photographed, but it is possible to detect a scratch on the back side that is relatively small but is magnified depending on the observation direction and in which actual damage is recognized.

  In the above embodiment, two photographing devices are used as photographing means, but one photographing device or three or more photographing devices may be used. The imaging device is not limited to a linear array camera, and may be a camera using an area sensor. In addition, the example using the imaging device as the observation unit has been described, but the observation unit is not limited to this, for example, so as to observe the lenticular sheet from the direction of each imaging device of the above example, It may be an optical system that defines the viewing direction with the naked eye.

DESCRIPTION OF SYMBOLS 10 Defect inspection apparatus 11 Lenticular sheet 12 Lenticular lens 15 Light source part 18 and 23 Polarizing plate 21 and 22 Imaging apparatus 26 Judgment part

Claims (20)

In the defect inspection apparatus for a lenticular sheet in which a plurality of lenticular lenses extending linearly are arranged in the width direction,
A light source that irradiates the lenticular sheet with linear illumination light parallel to the width direction of the lenticular sheet;
An observation means for observing the illumination light irradiation region of the lenticular sheet from a direction inclined at a predetermined angle with respect to the illumination light irradiation direction, and observing diffuse transmission light of the illumination light transmitted through the lenticular sheet;
A polarizer that is arranged between the lenticular sheet and the light source and polarizes illumination light in a specific direction, and a polarizer that is arranged between the lenticular sheet and the observation means, and the polarization direction is orthogonal to the polarization direction of the polarizer A defect inspection apparatus for a lenticular sheet, comprising: a polarization unit including the analyzer.   The defect of the lenticular sheet according to claim 1, wherein the polarization unit has a polarization direction determined with respect to the lenticular sheet so that the amount of transmitted light incident on the observation means via the analyzer is minimized. Inspection device.   3. The defect inspection apparatus for a lenticular sheet according to claim 2, wherein a polarization direction with respect to the lenticular sheet is in a range of 10 [deg.] To 45 [deg.] With respect to a longitudinal direction of the lenticular lens.   The defect inspection apparatus for a lenticular sheet according to claim 2, wherein a polarization direction with respect to the lenticular sheet is in a range of 20 ° to 40 ° with respect to a longitudinal direction of the lenticular lens. The observation means is arranged such that the photographing optical axis is inclined at the predetermined angle with respect to the illumination light irradiation direction, and the diffused light is received through the analyzer to photograph the illumination light irradiation region. Photographing means,
5. The lenticular sheet defect inspection apparatus according to claim 1, further comprising a determination unit that determines the presence or absence of a defect based on a photoelectric signal output from the imaging unit.   6. The defect inspection apparatus for a lenticular sheet according to claim 5, wherein the photographing means are first and second photographing apparatuses that are arranged apart from each other in the width direction of the lenticular sheet and that respectively photograph the irradiation area.   7. The determination unit according to claim 6, wherein the determination unit determines that there is a defect when a signal component indicating a defect is included in a photoelectric signal from at least one of the first and second imaging devices. Lenticular sheet defect inspection device.   The defect inspection apparatus for a lenticular sheet according to claim 6 or 7, wherein an opening angle formed by each imaging optical axis of the first and second imaging apparatuses is within a range of 5 ° to 15 °.   9. The defect inspection apparatus for a lenticular sheet according to claim 5, wherein the determination unit determines the presence or absence of a defect based on a level of a photoelectric signal with respect to a predetermined threshold value. A release means for temporarily releasing the crossed Nicols state of the polarization unit;
The determination unit irradiates a normal lenticular sheet with illumination light from the light source while temporarily canceling the crossed Nicols state by the release unit, and temporarily increases the amount of transmitted light incident on the photographing apparatus. In this state, a photoelectric signal for one line is obtained as a reference waveform, and based on this reference waveform, the relationship between the reference level and the photoelectric signal obtained at the time of inspection is determined relative to each other in order to determine the presence or absence of defects. 10. The defect inspection apparatus for a lenticular sheet according to any one of claims 5 to 9, further comprising inspection sensitivity correction means for changing the inspection sensitivity. In the defect inspection method of a lenticular sheet in which a plurality of lenticular lenses extending linearly are arranged in the width direction,
Illuminate the lenticular sheet with illumination light polarized in a specific direction in a line parallel to the width direction of the lenticular sheet,
From the direction tilted at a predetermined angle with respect to the illumination light irradiation direction, facing the illumination area of the lenticular sheet through the analyzer in the polarization direction orthogonal to the polarization direction of the illumination light, the diffuse transmitted light from the lenticular sheet A defect inspection method for a lenticular sheet, wherein the presence or absence of a sheet defect is determined based on the amount of light transmitted through the analyzer.   12. The defect inspection method for a lenticular sheet according to claim 11, wherein the polarization direction of the illumination light with respect to the lenticular lens is determined so that the amount of diffusely transmitted light transmitted through the analyzer is minimized.   13. The defect inspection method for a lenticular sheet according to claim 12, wherein a polarization direction with respect to the lenticular sheet is within a range of 10 [deg.] To 45 [deg.] With respect to a longitudinal direction of the lenticular lens.   The lenticular sheet defect inspection method according to claim 13, wherein a polarization direction with respect to the lenticular sheet is in a range of 20 ° to 40 ° with respect to a longitudinal direction of the lenticular lens. Photographing the illumination light irradiation area by the photographing means arranged to be inclined at the predetermined angle with respect to the illumination light irradiation direction,
15. The defect inspection method for a lenticular sheet according to claim 11, wherein the presence or absence of a defect is determined based on a photoelectric signal output from the photographing unit.   16. The defect inspection method for a lenticular sheet according to claim 15, wherein the first and second imaging devices that are arranged apart from each other in the width direction of the lenticular sheet and each shoot an irradiation area are used as the imaging unit.   17. The defect inspection of a lenticular sheet according to claim 16, wherein when there is a signal component indicating a defect in a photoelectric signal from at least one of the first and second imaging devices, it is determined that there is a defect. Method.   18. The lenticular sheet defect inspection method according to claim 16 or 17, wherein an opening angle formed by each imaging optical axis of the first and second imaging apparatuses is within a range of 5 to 15 degrees.   19. The defect inspection method for a lenticular sheet according to any one of claims 15 to 18, wherein the presence or absence of a defect is determined based on a level of a photoelectric signal with respect to a predetermined threshold value.   While temporarily canceling the crossed Nicols state between the polarization direction of the illumination light and the polarization direction of the analyzer, the illumination light is irradiated to a normal lenticular sheet, and the amount of transmitted light incident on the imaging device is temporarily In this state, the photoelectric signal for one line is obtained as a reference waveform, and the relationship between the reference level and the photoelectric signal obtained at the time of inspection is determined within one line in order to determine the presence / absence of a defect based on this reference waveform. 20. The lenticular sheet defect inspection method according to claim 15, wherein the inspection sensitivity in one line is corrected by relatively changing the lenticular sheet.

Images