Inspection equipment

Abstract

An inspection device (1) detects a flaw in a sheet-like or plate-like light-transmissive target (9). A profile acquisition unit of a flaw detection unit acquires, from a captured image, a plurality of brightness profiles in a plurality of inspection regions, which linearly extend in a second direction at a plurality of inspection positions in a first direction. A periodic flaw identification unit detects a periodic change in brightness for each of the plurality of brightness profiles. The periodic flaw identification unit determines that there is a first periodic flaw if there is a common periodic change in brightness in the plurality of brightness profiles in the same period, and determines that there is a second periodic flaw if a periodic change in brightness that is the same as the periodic change in brightness present in one brightness profile among the plurality of brightness profiles is not present in the other brightness profiles. As a result, a flaw can be detected while automatically identifying the type thereof.

Description

Technical Field

[0001] The present invention relates to an inspection apparatus for detecting defects in a sheet-shaped or plate-shaped object having translucency. [Citation of Related Applications] This application claims the benefit of priority from Japanese Patent Application JP2021-072442 filed on April 22, 2021, and the entire disclosure of the said application is incorporated herein.

Background Art

[0002] Conventionally, techniques for continuously manufacturing sheet-shaped or plate-shaped members have been known. For example, in the roll forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2010-46798 (Document 1), molten resin extruded from a die is continuously conveyed while being sandwiched between rolls, and a sheet-shaped member is continuously formed.

[0003] On the other hand, various techniques for inspecting continuously manufactured sheet-shaped members have also been proposed. For example, in the inspection method disclosed in Japanese Patent Application Laid-Open No. 2007-211092 (Document 2), a sheet-shaped film is disposed obliquely with respect to a screen between a light source and the screen, and an image projected onto the screen is photographed by a camera disposed on the side of the film, whereby unevenness in the thickness of the film caused by gentle wavy irregularities on the film surface is inspected. Further, in the measurement method disclosed in Japanese Patent Application Laid-Open No. 2019-191112 (Document 3), a plurality of images used for inspecting an object are acquired by repeating image acquisition while changing the inclination angle of a sheet-shaped object disposed obliquely with respect to a screen. In the inspection apparatus disclosed in Japanese Patent Application Laid-Open No. 2003-172707 (Document 4), light is irradiated from directly above a polarizing film provided with an antireflection film, and an image projected onto a screen disposed directly below the polarizing film is imaged by a camera disposed directly below the screen, whereby defects in the antireflection film are detected.

[0004] Incidentally, in the inspection method described in reference 2, the camera is positioned at an angle so that its optical axis is tilted relative to the normal direction of the screen, in order to avoid the camera being reflected on the screen. As a result, the distance to the camera varies depending on the position on the screen, causing distortion in the image captured by the camera, making it difficult to accurately detect thickness variations. In the measurement method described in reference 3, the camera is also positioned at an angle relative to the normal direction of the screen.

[0005] On the other hand, in reference 4, unlike references 2 and 3, the polarizing film and the screen are arranged parallel to each other, and there is no mechanism for tilting the polarizing film. Furthermore, even if the polarizing film were tilted relative to the screen, the distance to the screen would differ depending on the position on the polarizing film, causing distortion in the image projected onto the screen, making it difficult to accurately detect scratches.

[0006] Furthermore, in recent years, the sheet-like materials described above have also been used for optical applications such as surface substrates for liquid crystal displays. For sheet-like materials used in optical applications, particularly, reducing defects during manufacturing is crucial. Therefore, high-precision adjustments are necessary in the sheet-like material manufacturing equipment to reduce defects. However, during the manufacturing of sheet-like materials, various types of defects can occur, not just the thickness variations and scratches mentioned above. The adjustment points and methods in the sheet-like material manufacturing equipment differ depending on the type of defect. Therefore, in order to efficiently adjust the sheet-like material manufacturing equipment, it is necessary to identify the type of defect in the sheet-like material. [Overview of the project]

[0007] The present invention is directed to an inspection device for detecting defects in sheet-like or plate-like translucent objects, and aims to automatically determine and detect the type of defect.

[0008] An inspection apparatus according to one preferred embodiment of the present invention comprises: an object holding unit for holding an object; an auxiliary member holding unit for holding a sheet-like or plate-like imaging auxiliary member parallel to the object; an illumination unit for irradiating the object with observation light; an imaging unit positioned on the opposite side of the object from the object, with the imaging auxiliary member in between, having an optical axis parallel to the normal direction of the object, and acquiring an image by capturing an image formed on the imaging auxiliary member by the observation light transmitted through the object; and a defect detection unit for detecting defects in the object based on the image. Defects detectable by the defect detection unit include first periodic defects which are a plurality of streaks that extend linearly along a first direction on the object and are periodically arranged in a second direction perpendicular to the first direction, and second periodic defects which are non-streaky and periodically arranged in the second direction on the object. The defect detection unit includes a profile acquisition unit that sets a plurality of inspection areas in the captured image that extend linearly parallel to the second direction at a plurality of inspection positions in the first direction, and acquires a plurality of luminance profiles which are luminance changes in the second direction in each of the plurality of inspection areas; and a periodic defect determination unit that detects periodic luminance fluctuations for each of the plurality of luminance profiles, determines that a first periodic defect exists if periodic luminance fluctuations with the same period exist in all of the plurality of luminance profiles, and determines that a second periodic defect exists if periodic luminance fluctuations with the same period as those present in one of the plurality of luminance profiles do not exist in any of the other luminance profiles.

[0009] This inspection device can automatically determine and detect the type of defect.

[0010] Preferably, the defects detectable by the defect detection unit further include aperiodic defects such as scratches or deposits on the surface of the object, or contaminants mixed into the interior of the object. The defect detection unit further includes an aperiodic defect determination unit that detects aperiodic luminance fluctuations in at least one of the plurality of luminance profiles and determines that the aperiodic luminance fluctuations are aperiodic defects.

[0011] Preferably, the inspection apparatus further comprises a rotation mechanism that rotates the object, the imaging assist member, and the imaging unit relative to the optical axis of the illumination unit about a rotation axis perpendicular to the optical axis of the illumination unit, while maintaining the distance between the object and the imaging assist member in the optical axis direction of the illumination unit, and the distance between the imaging assist member and the imaging unit in the optical axis direction of the imaging unit, thereby changing the measurement angle, which is the angle between the optical axis of the illumination unit and the normal direction of the object; and a control unit that controls the imaging unit and the rotation mechanism to acquire the image with the measurement angle set to a predetermined first measurement angle for defect detection by the periodic defect discrimination unit, and to acquire the image with the measurement angle set to a predetermined second measurement angle different from the first measurement angle for defect detection by the non-periodic defect discrimination unit.

[0012] Preferably, the inspection apparatus further includes a movement mechanism that changes the projection distance, which is the distance between the imaging support member and the object in the optical axis direction of the illumination unit, while maintaining the distance between the imaging support member and the imaging unit in the optical axis direction of the imaging unit, and moves the imaging support member and the imaging unit relative to the object in the optical axis direction of the illumination unit; and a control unit that controls the imaging unit and the movement mechanism to acquire a plurality of imaging images with different projection distances. The aperiodic defect includes a first aperiodic defect, which is a scratch or deposit on the surface of the object, and a second aperiodic defect, which is a contaminant mixed inside the object. The profile acquisition unit sets an inspection area in each of the plurality of imaging images that extends linearly parallel to the second direction at a predetermined inspection position in the first direction, and acquires a brightness profile, which is the brightness change in the second direction in the inspection area. The defect detection unit further includes an evaluation value calculation unit that detects aperiodic brightness fluctuations in the brightness profile of one of the plurality of imaging images and calculates an evaluation value of the aperiodic brightness fluctuations in each of the plurality of imaging images. The nonperiodic defect discrimination unit determines that the nonperiodic brightness fluctuation is a first nonperiodic defect if the evaluation value fluctuation index, which indicates the degree of fluctuation of the evaluation value in the plurality of captured images, is less than or equal to a predetermined threshold, and determines that it is a second nonperiodic defect if the evaluation value fluctuation index is greater than the threshold.

[0013] Preferably, the inspection apparatus further includes a rotation mechanism that rotates the object, the imaging support member, and the imaging unit relative to the optical axis of the illumination unit about a rotation axis perpendicular to the optical axis of the illumination unit, while maintaining the distance between the object and the imaging support member in the optical axis direction of the illumination unit, and the distance between the imaging support member and the imaging unit in the optical axis direction of the imaging unit, thereby changing the measurement angle, which is the angle between the optical axis of the illumination unit and the normal direction of the object. The control unit controls the imaging unit, the movement mechanism, and the rotation mechanism, and acquires multiple image captures with different projection distances for each of the multiple measurement angles. The profile acquisition unit acquires multiple luminance profiles from the multiple image captures for each of the multiple measurement angles. The evaluation value calculation unit obtains multiple evaluation values ​​of the aperiodic luminance fluctuations from the multiple image captures for each of the multiple measurement angles. The evaluation value fluctuation index is also determined based on the fluctuations of the multiple evaluation values ​​for each of the multiple measurement angles.

[0014] Preferably, the aperiodic defect includes a first aperiodic defect which is a scratch or deposit on the surface of the object, and a second aperiodic defect which is a contaminant that has entered the interior of the object. The aperiodic luminance fluctuation includes a lower peak which is a downward peak, and a first upper peak and a second upper peak which are upward peaks adjacent to both sides of the lower peak. Let a1 and a2 be the upward and downward uniaxial amplitudes of the luminance fluctuation in the at least one luminance profile, b be the luminance difference between the first upper peak and the background luminance a0, and c be the luminance difference between the second upper peak and the background luminance a0. The nonperiodic defect discrimination unit determines that the nonperiodic defect corresponding to the nonperiodic brightness variation is the first nonperiodic defect if b and c in the nonperiodic brightness variation are less than or equal to Max(a1,a2), which is the larger of a1 and a2, and determines that the nonperiodic defect corresponding to the nonperiodic brightness variation is the second nonperiodic defect if at least one of b and c is greater than Max(a1,a2).

[0019] Preferably, the illumination unit includes a light source unit and a lens that converts the light from the light source unit into the observation light that is parallel light and irradiates the object. The distance between the lens and the imaging auxiliary member in the optical axis direction of the illumination unit is not less than half of the focal length of the lens.

[0020] The above object and other objects, features, aspects and advantages will be clarified by the following detailed description of the present invention made with reference to the attached drawings.

Brief Description of the Drawings

[0021] [Figure 1] It is a front view of an inspection apparatus according to an embodiment. [Figure 2] It is a plan view of an image acquisition device. [Figure 3] It is a plan view of an image acquisition device. [Figure 4] It is a plan view of an image acquisition device. [Figure 5] It is a diagram showing the configuration of a computer. [Figure 6] It is a block diagram showing functions realized by a computer. [Figure 7] It is a diagram showing a manufacturing device. [Figure 8] It is a diagram showing an object. [Figure 9] It is an image of an object. [Figure 10] It is an image of an object. [Figure 11] It is an image of an object. [Figure 12] It is a diagram showing the flow of defect detection. [Figure 13] It is a diagram showing a captured image and an inspection area. [Figure 14] It is a diagram showing a luminance profile. [Figure 15] It is a diagram showing a luminance profile. [Figure 16] It is a diagram showing the flow of defect detection. [Figure 17] It is a diagram showing a luminance profile. [Figure 18] It is a diagram showing an evaluation value. [Figure 19A] It is a diagram showing a luminance profile. [Figure 19B] It is a diagram showing a luminance profile. [Figure 20] It is a front view of another inspection device.

Embodiments for Carrying Out the Invention

[0022] FIG. 1 is a front view showing an inspection device 1 according to one embodiment of the present invention. The inspection device 1 includes an image acquisition device 11 and a computer 12. FIG. 2 is a plan view of the image acquisition device 11. In FIGS. 1 and 2, for convenience of explanation, the X direction, Y direction, and Z direction are shown. The X direction, Y direction, and Z direction are perpendicular to each other. In the example shown in FIGS. 1 and 2, the X direction and Y direction are horizontal directions, and the Z direction is a vertical direction, but it is not limited thereto.

[0023] The object 9 to be inspected is a sheet-like or plate-like translucent member that is manufactured while being continuously conveyed in a predetermined conveyance direction. The object 9 is formed of, for example, a thermoplastic resin. The object 9 can be used, for example, as an optical film such as a surface substrate of a liquid crystal screen or a 5G-compatible component of a smartphone, or as a substitute for an automobile window glass. The material and use of the object 9 may be variously changed. In the present embodiment, the object 9 is a substantially transparent member, but may be a translucent member as long as it has translucency. The object 9 is, for example, substantially rectangular when viewed from a direction perpendicular to the main surface. Both main surfaces of the object 9 are substantially parallel and substantially flat surfaces. The main surface of the object 9 is the largest surface that the object 9 has.

[0024] As shown in FIGS. 1 and 2, the image acquisition device 11 includes an object holding portion 21, a lighting portion 22, an imaging auxiliary member 23, an imaging portion 24, an auxiliary member holding portion 26, a rotation mechanism 27, and a movement mechanism 28.

[0025] The object holding section 21 holds the object 9. In the examples shown in Figures 1 and 2, the object holding section 21 is a substantially cylindrical member extending substantially parallel to the Z direction. The object 9 is held from below by the object holding section 21 such that its main surface is perpendicular to the XY plane. In other words, the normal direction of the object 9 (i.e., the direction perpendicular to the main surface of the object 9) is parallel to the XY plane. The XY plane is a predetermined, hypothetical plane parallel to the X and Y directions. In the object 9 held by the object holding section 21, the direction corresponding to the transport direction during the manufacturing of the object 9, which will be described later, is parallel to the XY plane.

[0026] The illumination unit 22 comprises a light source 221, a light emission unit 222, and a lens 223. In Figure 2, the light source 221 is not shown. In the example shown in Figure 1, the optical axis J1 of the illumination unit 22 is parallel to the X direction (i.e., perpendicular to the YZ plane). In the example shown in Figure 1, the optical axis J1 of the illumination unit 22 passes through approximately the center of the main surface of the object 9. The light source 221 is, for example, an LED. A light source other than an LED may be used as the light source 221. The light generated by the light source 221 is guided to the light emission unit 222 via an optical fiber. The light emission unit 222 emits light from a pinhole. That is, the light emission unit 222 is a point light source. The light source 221 and the light emission unit 222 may be a single unit. In the following description, the light source 221 and the light emission unit 222 will be collectively referred to as the "light source unit 220". Light emitted from the light-emitting unit 222 is converted into parallel light by the lens 223 and irradiated onto the object 9. In the following description, the light irradiated onto the object 9 from the illumination unit 22 is also referred to as "observation light 71". In the example shown in Figure 1, the light-emitting unit 222, the lens 223, and the object-holding unit 21 are attached to a single frame 31 and are relatively fixed. The lens 223 is a plano-convex lens, with one lens surface being flat and the other being convex. The lens 223 is positioned on the optical axis J1 with the flat lens surface facing the light source unit 220 and the convex lens surface facing the object 9. The shape and arrangement of the lens 223 can be changed in various ways.

[0027] The imaging support member 23 is a sheet-like or plate-like translucent member. The imaging support member 23 is, for example, a diffusion film. Other materials may be used as the imaging support member 23. The imaging support member 23 is, for example, a roughly rectangular shape that is roughly the same size as the object 9 when viewed from a direction perpendicular to the main surface. The imaging support member 23 may be larger or smaller than the object 9. The shape of the imaging support member 23 can be changed in various ways. The two main surfaces of the imaging support member 23 are roughly parallel to each other and are roughly planar. The main surface of the imaging support member 23 is the largest surface that the imaging support member 23 has.

[0028] The auxiliary member holder 26 holds the imaging auxiliary member 23. In the examples shown in Figures 1 and 2, the auxiliary member holder 26 is a substantially cylindrical member extending substantially parallel to the Z direction. The imaging auxiliary member 23 is held from below by the auxiliary member holder 26 such that its main surface is perpendicular to the XY plane. The auxiliary member holder 26 holds the imaging auxiliary member 23 parallel to the object 9. In other words, the imaging auxiliary member 23 is held by the auxiliary member holder 26 such that its main surface is parallel to the main surface of the object 9. In the examples shown in Figures 1 and 2, the imaging auxiliary member 23 is positioned substantially at the same location as the object 9 in the Z direction and overlaps substantially with the entire object 9 when viewed along the normal direction of the object 9.

[0029] The imaging unit 24 is positioned on the opposite side of the object 9 from the imaging auxiliary member 23. In the example shown in Figure 1, the object 9, the imaging auxiliary member 23, and the imaging unit 24 are arranged in this order from the (-X) side to the (+X) direction. The illumination unit 22 is positioned on the (-X) side of the object 9. The optical axis J2 of the imaging unit 24 is parallel to the XY plane and parallel to the normal direction of the object 9. In the example shown in Figure 1, the optical axis J2 of the imaging unit 24 passes through approximately the center of the main surface of the imaging auxiliary member 23 and approximately the center of the main surface of the object 9. The imaging unit 24 is, for example, an industrial digital camera equipped with a CMOS or CCD. The imaging unit 24 is, for example, an area camera capable of acquiring two-dimensional images. The imaging unit 24 may be other types of cameras.

[0030] In the image acquisition device 11, the illumination unit 22 illuminates the object 9 with observation light 71 from the (-X) side. The observation light 71 that has passed through the object 9 is guided to the imaging auxiliary member 23 and projected onto the imaging auxiliary member 23. The imaging unit 24 captures the image formed on the imaging auxiliary member 23 from the (+X) side of the imaging auxiliary member 23 to acquire an image. In other words, the imaging unit 24 acquires the transmitted image of the object 9 that has passed through the imaging auxiliary member 23 as an image. More precisely, the imaging unit 24 acquires data representing the image of the object 9 projected onto the imaging auxiliary member 23.

[0031] In the example shown in Figure 1, the imaging unit 24 and the auxiliary member holder 26 are mounted on a single frame 32, and the relative position of the imaging unit 24 with respect to the auxiliary member holder 26 and the imaging auxiliary member 23 is fixed. Therefore, the distance L2 between the imaging auxiliary member 23 and the imaging unit 24 in the direction in which the optical axis J2 of the imaging unit 24 extends (hereinafter also referred to as the "optical axis direction of the imaging unit 24") is maintained constant.

[0032] The rotation mechanism 27 rotates the object 9 together with the object holder 21 around a rotation axis J3 extending in the Z direction. The object holder 21 rotates on the frame 31, while the frame 31 does not rotate. Figure 3 is a plan view showing the object 9 rotated by a predetermined angle by the rotation mechanism 27. In the example shown in Figure 3, the object 9 has been rotated approximately 30° counterclockwise from the state shown in Figure 2. The rotation axis J3 passes approximately through the center of the object holder 21 in a plan view. The rotation axis J3 passes approximately through the center of the main surface of the object 9 when viewed along the normal direction of the object 9. The rotation axis J3 also intersects perpendicularly with the optical axis J1 of the illumination unit 22 on the object 9. In the following description, the angle θ between the optical axis J1 of the illumination unit 22 and the normal direction of the object 9 in a plan view (i.e., viewed along the rotation axis J3) will also be called the "measurement angle θ". The rotation mechanism 27 is a mechanism for changing the measurement angle θ.

[0033] The rotation mechanism 27 also rotates the frame 32 around a rotation axis J4 extending in the Z direction, thereby integrally rotating the imaging auxiliary member 23, the auxiliary member holder 26, and the imaging unit 24. The rotation axis J4 passes approximately through the center of the auxiliary member holder 26 in a plan view. The rotation axis J3 and the rotation axis J4 are parallel to each other. When viewed along the normal direction of the imaging auxiliary member 23, the rotation axis J4 passes approximately through the center of the main surface of the imaging auxiliary member 23. Furthermore, the rotation axis J4 intersects perpendicularly with the optical axis J1 of the illumination unit 22 and the optical axis J2 of the imaging unit 24 on the imaging auxiliary member 23.

[0034] In the image acquisition device 11, the rotation direction and rotation angle of the object 9 and the imaging support member 23 by the rotation mechanism 27 are the same. Therefore, the object 9 and the imaging support member 23 are parallel to each other regardless of the magnitude of the measurement angle θ mentioned above. Also, the angle between the normal direction of the imaging support member 23 and the optical axis J1 of the illumination unit 22 in a plan view (i.e., viewed along the rotation axis J4) is equal to the measurement angle θ.

[0035] As described above, the imaging unit 24 is fixed relative to the auxiliary member holder 26. Therefore, when the imaging auxiliary member 23 and the auxiliary member holder 26 are rotated by the rotation mechanism 27, the imaging unit 24 also rotates together. The optical axis J2 of the imaging unit 24 intersects the optical axis J1 of the illumination unit 22 on the rotation axis J4, regardless of the magnitude of the measurement angle θ. In a plan view (i.e., viewed along the rotation axis J4), the angle between the optical axis J2 of the imaging unit 24 and the optical axis J1 of the illumination unit 22 is equal to the measurement angle θ. Also, regardless of the magnitude of the measurement angle θ, the distance L2 between the imaging auxiliary member 23 and the imaging unit 24 in the optical axis direction of the imaging unit 24 is constant.

[0036] In the example shown in Figure 1, the rotation mechanism 27 comprises a motor 271 and a belt 272. The motor 271 is a rotary motor mounted below the object holding section 21. The belt 272 is an annular member that contacts the sides of the object holding section 21 and the auxiliary member holding section 26. When the motor 271 rotates, the object holding section 21 connected to the motor 271 rotates. Also, due to the frictional force acting between the object holding section 21 and the belt 272, the belt 272 rotates as well, and the rotation of the object holding section 21 is transmitted to the auxiliary member holding section 26, causing the auxiliary member holding section 26 to rotate by the same angle as the object holding section 21.

[0037] The moving mechanism 28 moves the imaging auxiliary member 23 and the imaging unit 24 in the X direction (i.e., in the direction of the optical axis of the illumination unit 22). Figure 4 is a plan view showing the state in which the imaging auxiliary member 23 and the imaging unit 24 have been moved in the (+X) direction from the position shown in Figure 3 by the moving mechanism 28. In the example shown in Figure 4, the moving mechanism 28 moves the imaging auxiliary member 23, the auxiliary member holder 26, and the imaging unit 24, which is fixed to the auxiliary member holder 26 via the frame 32, as a whole by moving the auxiliary member holder 26 in the X direction. This changes the distance L1 (hereinafter also referred to as "projection distance L1") between the object 9 and the imaging auxiliary member 23 in the X direction. The projection distance L1 is the distance in the X direction between the rotation axis J3 and the rotation axis J4. The moving mechanism 28 includes, for example, a linear motor or an air cylinder.

[0038] As described above, in the image acquisition device 11, the auxiliary member holder 26 and the imaging unit 24 are moved integrally by the moving mechanism 28, and this movement is performed while maintaining a constant distance L2 (see Figure 3) between the imaging auxiliary member 23 and the imaging unit 24 in the optical axis direction of the imaging unit 24. When the auxiliary member holder 26 is moved in the X direction by the moving mechanism 28, for example, the belt 272 of the rotation mechanism 27 expands and contracts, so that the imaging auxiliary member 23 and the auxiliary member holder 26 rotate by the same angle in synchronization with the rotation of the object 9 and the object holder 21. Furthermore, the rotation of the object 9, the imaging auxiliary member 23 and the imaging unit 24 by the rotation mechanism 27 is performed while maintaining a constant distance (i.e., projection distance L1) between the object 9 and the imaging auxiliary member 23 in the X direction, and a constant distance L2 between the imaging auxiliary member 23 and the imaging unit 24 in the optical axis direction of the imaging unit 24. The structures of the rotating mechanism 27 and the moving mechanism 28 are not limited to the above example and may be modified in various ways.

[0039] In the image acquisition device 11, if the distance between the lens 223 and the imaging support member 23 in the X direction (i.e., the optical axis direction of the illumination unit 22) is L3 (see Figures 1 and 2), it is preferable that the distance L3 is at least half the focal length of the lens 223. This suppresses the projection of a secondary real image of the light source 221 onto the imaging support member 23 by the lens 223, and suppresses the inclusion of such secondary real image in the captured image acquired by the imaging unit 24. The secondary real image is formed when observation light 71 emitted from the illumination unit 22 is reflected by the object 9, re-enters the lens 223, is reflected by the lens surface of the lens 223 on the light source unit 220 side, and is imaged on the (+X) side of the lens 223. In this embodiment, since the light reflected by the object 9 and re-entered by the lens 223 is approximately parallel light, the secondary real image is imaged on the (+X) side of the lens 223 at a position approximately half the focal length of the lens 223. In detail, the distance L3 mentioned above is the distance between the point on the optical axis J1 that serves as the reference point for the focal length of the lens 223 and the position of the imaging assist member 23 on the optical axis J1 (the rotation axis J4 in the above example).

[0040] Figure 5 shows the configuration of computer 12. Computer 12 is a typical computer system comprising a processor 101, memory 102, input / output unit 103, and bus 104. Bus 104 is a signal circuit connecting the processor 101, memory 102, and input / output unit 103. Memory 102 stores programs and various information. The processor 101 performs various processes (for example, numerical calculations and image processing) using memory 102, etc., according to the programs etc. stored in memory 102. The input / output unit 103 includes a keyboard 105 and mouse 106 that accept input from the operator, and a display 107 that displays output from the processor 101 etc.

[0041] Figure 6 is a block diagram showing the functions implemented by the computer 12. In the example shown in Figure 6, the computer 12 implements a storage unit 41, a control unit 42, and a defect detection unit 43. The defect detection unit 43 includes a profile acquisition unit 44, a periodic defect discrimination unit 45, a non-periodic defect discrimination unit 46, and an evaluation value calculation unit 47. The storage unit 41 is mainly implemented by the memory 102 and stores captured images acquired by the imaging unit 24. The control unit 42 is mainly implemented by the processor 101 and controls the imaging unit 24, the rotation mechanism 27, and the movement mechanism 28. By controlling the imaging unit 24, the rotation mechanism 27, and / or the movement mechanism 28 by the control unit 42, multiple captured images with different measurement angles θ and / or projection distances L1 are acquired. The defect detection unit 43 is mainly implemented by the processor 101 and detects defects in the object 9 based on the captured images acquired by the imaging unit 24, as will be described later.

[0042] Figure 7 shows a manufacturing apparatus 8 for producing the object 9. The manufacturing apparatus 8 is a so-called extrusion molding apparatus. The manufacturing apparatus 8 comprises a hopper 81, an extruder 82, a gear pump 83, a die 84, and molding rolls 85a to 85c. The outer diameters of the molding rolls 85a to 85c are, for example, 200 mm to 500 mm.

[0043] In the manufacturing apparatus 8, resin pellets or resin powder (i.e., the material for the object 9) supplied from the hopper 81 are melted in the extruder 82, and the molten resin is sent to the die 84 by the gear pump 83. Then, from the lower end of the die 84, it is supplied as a film falling between the rotating molding rolls 85a and 85b. The molten resin supplied from the die 84 is cooled while being compressed between the molding rolls 85a and 85b, and is formed into a sheet member 90 of a predetermined thickness (i.e., a continuous object 9) and wrapped around the surface of the molding roll 85b. The sheet member 90 is pulled out by passing between the molding rolls 85b and 85c. In the manufacturing apparatus 8, the direction along the area of ​​the outer surface of the molding rolls 85b and 85c that is in contact with the sheet member 90, and the direction in which the sheet member 90 is transported when separated from the molding roll 85c, are the transport directions of the sheet member 90 (i.e., the transport directions of the object 9 described above). In Figure 7, the transport direction is indicated by an arrow labeled 91. The object 9 described above is a part cut out of the sheet member 90.

[0044] Figure 8 shows the object 9. In Figure 8, the arrow indicating the direction corresponding to the transport direction 91 in Figure 7 is denoted with the symbol 91. In the following explanation, the direction on the object 9 corresponding to the transport direction 91 will also be referred to as the "transport direction 91". The direction parallel to the main surface of the object 9 and perpendicular to the transport direction 91 will also be referred to as the width direction 92. In Figures 1 and 2, the width direction 92 is perpendicular to the XY plane.

[0045] Defects in object 9 mainly occur during the manufacturing process in the manufacturing apparatus 8. Defects in object 9 can be classified into periodic defects, which appear periodically in the aforementioned transport direction 91, and non-periodic defects, which do not exhibit periodicity.

[0046] Periodic defects include striped first periodic defects, which are multiple streaks that are periodically aligned in the transport direction 91 on the object 9. Figure 9 is an image of multiple streaks on the object 9 captured by the imaging unit 24. The multiple streaks extend substantially linearly along the width direction 92 on the object 9. Each streak can also be considered as a substantially band-like shape, with a length in the width direction 92 being longer than its width in the transport direction 91. Each streak extends substantially continuously along the width direction 92 without interruption. In the example shown in Figure 9, each streak traverses the image along the width direction 92. The period of the multiple streaks (i.e., the distance in the transport direction 91 between two adjacent streaks) is small compared to the circumference of the outer surface of the forming roll 85b. For example, the period of the multiple streaks is 0.1% to 5% of the circumference of the outer surface of the forming roll 85b. These multiple streaks are caused, for example, by deviations from the appropriate range in the rotational speeds of the forming rolls 85a to 85c.

[0047] Multiple streaks may extend parallel to the width direction 92, or they may extend in a direction that is inclined to some extent with respect to the width direction. The angle between the direction in which the multiple streaks extend and the width direction 92 is, for example, 0° to 10°. Multiple streaks may extend in a strictly straight line, or they may extend in a substantially straight line with some curvature. Multiple streaks may appear at exactly the same period in the conveying direction 91, or they may appear at substantially the same period with some deviation. If the above-mentioned width direction 92 and conveying direction 91 are called the "first direction" and the "second direction," respectively, then the multiple streaks extend substantially in a straight line along the first direction on the object 9, and are periodically aligned in the second direction perpendicular to the first direction.

[0048] The periodic defects described above further include non-streaky second periodic defects, which are different from the multiple streaks that constitute the first periodic defects. The second periodic defects are arranged periodically in the transport direction 91 on the object 9, much like the first periodic defects. The period of the second periodic defects in the transport direction 91 is generally larger than the period of the first periodic defects in the transport direction 91, but it may be smaller than or approximately the same as the period of the first periodic defects. The period of the second periodic defects in the transport direction 91 is, for example, 0.5% to 100% of the circumference of the outer surface of the forming roll 85b. The term "non-streaky" above means a shape that does not extend long along the width direction 92 (for example, long enough to cross the image vertically) and is substantially non-linear. Each defect included in the second periodic defects is, for example, approximately elliptical or approximately rectangular in shape. The second periodic defect includes, for example, defects (hereinafter also referred to as "transfer defects") that result from the transfer of unintended irregular shapes (e.g., scratches or foreign matter) present on the outer surface of the forming roll 85b to the main surface of the sheet member 90. For example, if there is only one such irregular shape on the outer surface of the forming roll 85b, the period of the transfer defect is approximately the same as the circumference of the outer surface of the forming roll 85b.

[0049] The second periodic defect also includes defects (hereinafter also called "peeling marks") that occur when the sheet member 90 is peeled off from the outer surface of the forming roll 85b, etc., and a portion of the outer surface of the forming roll 85b, etc. is not properly peeled off. The second periodic defect also includes defects caused by insufficient cooling of the sheet member 90. These defects due to insufficient cooling include so-called "uneven cooling" and "uneven thickness." Uneven cooling is a cosmetic defect that may occur when a relatively thick sheet member 90 is cooled, due to the difference in cooling rate between the vicinity of the surface and the interior of the sheet member 90. Specifically, if the vicinity of the surface of the sheet member 90 has cooled and solidified, but the interior of the sheet member 90 is still molten, uneven cooling may occur due to this difference in state. Also, uneven thickness is a defect in which the heat inside the molten sheet member 90 causes the vicinity of the surface, which has once solidified, to remelt, resulting in an uneven thickness of the sheet member 90. Figure 10 is an image of the uneven cooling on the object 9 captured by the imaging unit 24.

[0050] The second periodic defect also includes defects that occur when molten resin is supplied to a position shifted from the desired drop position and improper pressing occurs due to disturbances such as wind or the accumulation of molten resin on the molding rolls 85a and 85b as the molten resin falls from the die 84 between the molding rolls 85a and 85b (hereinafter also referred to as "drop misalignment defects"). The second periodic defect also includes defects caused by periodic pulsation of the molten resin due to the meshing of the gears of the gear pump 83 (hereinafter also referred to as "pump marks"), and periodic fluctuations in the thickness of the sheet member 90 due to differences in the viscosity of the molten resin that occur during kneading by the screw in the extruder 82 (hereinafter also referred to as "flow marks").

[0051] The aforementioned aperiodic defects include a first aperiodic defect, which is a scratch formed on the surface of the object 9 or foreign matter (i.e., adhering matter) attached to the surface, and a second aperiodic defect, which is foreign matter (i.e., contamination) mixed into the interior of the object 9. The contamination may be entirely located inside the object 9, or a portion of it may be exposed from the surface of the object 9. Figure 11 is an image of a scratch (i.e., the first aperiodic defect) on the surface of the object 9 captured by the imaging unit 24. In Figure 11, the scratch is surrounded by a dashed circle. The first aperiodic defect occurs after the sheet member 90 is molded in the manufacturing apparatus 8, or during the transport of the sheet member 90 molded in the manufacturing apparatus 8, when the surface of the sheet member 90 comes into contact with something or when foreign matter in the air adheres to the surface. The second aperiodic defect occurs during the manufacturing of the sheet member 90 in the manufacturing apparatus 8 when foreign matter in the air is mixed into the molten resin.

[0052] Next, we will explain the process of detecting defects in the object 9 using the inspection device 1. Figure 12 shows an example of the defect detection process when detecting first periodic defects, second periodic defects, and aperiodic defects in the object 9.

[0053] In the inspection apparatus 1 shown in Figure 1, first, the rotation mechanism 27 and the movement mechanism 28 are controlled by the control unit 42 (see Figure 6) so that the imaging auxiliary member 23, the auxiliary member holding unit 26, and the imaging unit 24 are rotated and moved to a predetermined measurement angle θ and projection distance L1. Then, observation light 71 is irradiated onto the object 9 from the illumination unit 22, and an image is acquired by the imaging unit 24 (step S11). The acquired image is sent from the imaging unit 24 to the computer 12 and stored in the storage unit 41 (see Figure 6).

[0054] Next, as shown in Figure 13, in the captured image 95, multiple inspection areas 96 are set by the profile acquisition unit 44 (see Figure 6) at multiple inspection positions in the direction corresponding to the width direction 92 of the object 9 (hereinafter also simply referred to as "width direction 92"). In Figure 13, the contour of the captured image 95 and the inspection areas 96 are shown, but the illustration of defects etc. contained in the captured image 95 is omitted. Each inspection area 96 is a rectangular strip-shaped area that extends linearly in the direction corresponding to the transport direction 91 of the object 9 (hereinafter also simply referred to as "transport direction 91"). Preferably, each inspection area 96 is provided over the entire length of the transport direction 91 of the captured image 95. The width in the width direction 92 of each inspection area 96 is smaller than the length of the transport direction 91, for example, 0.003% to 0.1% of the width in the width direction 92 of the captured image 95. Multiple inspection areas 96 are arranged spaced apart from each other in the width direction 92. In the example shown in Figure 13, three inspection areas 96 are arranged at both ends and the center of the width direction 92 of the captured image 95. Preferably, these three inspection areas 96 are arranged at approximately equal intervals in the width direction 92. The number of inspection areas 96 can be varied in a range of two or more. The width in the width direction 92 of each inspection area 96 may be less than 0.003% of the width in the width direction 92 of the captured image 95, or it may be greater than 0.1%. The multiple inspection areas 96 do not necessarily have to be spaced apart from each other and may be arranged continuously in the width direction 92.

[0055] Next, the profile acquisition unit 44 acquires a luminance profile for each of the multiple inspection areas 96 (step S12). The luminance profile is the change in luminance in the transport direction 91 in each inspection area 96. Figure 14 schematically shows the luminance profiles of three inspection areas 96 side by side for an image 95 in which multiple streaks exist, as shown in Figure 9. In Figure 14, the horizontal axis indicates the position in the transport direction 91, and the vertical axis indicates luminance. Figure 14 shows a portion of the luminance profile for each inspection area 96. The same applies to similar drawings described later.

[0056] In the defect detection unit 43, the periodic defect discrimination unit 45 (see Figure 6) detects periodic brightness fluctuations from the brightness profile of each inspection area 96 (step S13). Periodic brightness fluctuations refer to a state in which brightness peaks 97 appear periodically in the transport direction 91, as shown in Figure 14. Periodic brightness fluctuations are detected by performing frequency analysis such as Fourier transform on the brightness profile. Detection of periodic brightness fluctuations may also be performed by other methods. In step S13, if there are no relatively large brightness fluctuations in the brightness profile of each inspection area 96 (for example, peaks that are more than a predetermined good product threshold away from the average brightness of the brightness profile), the object 9 is judged to be a good product.

[0057] When periodic luminance fluctuations are detected in step S13, the period of the periodic luminance fluctuations in each inspection area 96 (i.e., the distance between adjacent peaks 97 on the maximum or minimum value side) is determined. This period is also calculated using the frequency analysis or other methods described above. As shown in Figure 14, if periodic luminance fluctuations with the same period are common to multiple luminance profiles, the periodic defect discrimination unit 45 determines that a first periodic defect (i.e., multiple streaks) exists in the object 9 (steps S14, S15). The state in which the periods of periodic luminance fluctuations are the same means that the periods of the periodic luminance fluctuations detected from multiple luminance profiles fall within an error range of 15% or less.

[0058] On the other hand, as shown in Figure 15, if the luminance profiles of the multiple inspection areas 96 do not contain periodic luminance fluctuations with the same period as those present in one luminance profile (i.e., if the multiple luminance profiles do not share periodic luminance fluctuations with the same period), the periodic defect discrimination unit 45 determines that a second periodic defect exists in the object 9 (steps S14, S16).

[0059] Furthermore, in the defect detection unit 43, if the period of the periodic brightness fluctuation determined in step S13 is relatively large (for example, larger than 5% of the circumference of the outer surface of the molding roll 85b), the periodic defect discrimination unit 45 may determine that a second periodic defect exists instead of a first periodic defect, regardless of the result of step S14.

[0060] Once the detection of periodic defects is complete, the defect detection unit 43 performs detection of non-periodic defects. Specifically, in each brightness profile of the captured image 95 described above, the non-periodic defect discrimination unit 46 (see Figure 6) detects non-periodic brightness fluctuations from among the relatively large brightness fluctuations (for example, peaks that are more than a predetermined threshold away from the average brightness of the brightness profile) that have been excluded from the periodic brightness fluctuations (step S17). Then, the non-periodic defect discrimination unit 46 determines that these non-periodic brightness fluctuations are non-periodic defects (step S18). Note that in steps S17 to S18, it is not necessarily required that all brightness profiles in the multiple inspection areas 96 of the captured image 95 be used; at least one brightness profile may be used, and non-periodic defects may be detected from that one brightness profile. Alternatively, an inspection area 96 other than the multiple inspection areas 96 described above may be set in the captured image 95, and non-periodic defects may be detected using the brightness profile of that other inspection area 96.

[0061] In the above description, the captured image 95 used for detecting periodic defects in steps S13 to S16 and the captured image 95 used for detecting non-periodic defects in steps S17 to S18 are the same, but they may be different.

[0062] For example, in step S11, an image 95 for detecting periodic defects and an image 95 for detecting non-periodic defects may be acquired separately, and in step S12, the brightness profile of the inspection area 96 of each image 95 may be acquired. Preferably, the imaging unit 24 and the rotation mechanism 27 are controlled by the control unit 42 so that the image 95 for detecting periodic defects is acquired with a measurement angle θ set to a predetermined first measurement angle, and the image 95 for detecting non-periodic defects is acquired with a measurement angle θ set to a predetermined second measurement angle. The second measurement angle is a different angle from the first measurement angle. Preferably, the first measurement angle is larger than the second measurement angle. By increasing the first measurement angle, the difference in density between multiple streaks and areas other than the streaks in the image 95 becomes larger, so that multiple streaks can be detected with high accuracy. For example, the first measurement angle is 30° to 80°, and the second measurement angle is 0° to 60°.

[0063] Figure 16 shows an example of the defect detection flow when detecting a first non-periodic defect and a second non-periodic defect in an object 9. In the inspection apparatus 1 shown in Figure 1, the acquisition of an image 95 (see Figure 13) is performed in substantially the same manner as in step S11 described above. Then, the movement mechanism 28 is controlled by the control unit 42, and after the projection distance L1 is changed, the image acquisition unit 24 acquires an image 95. The change in projection distance L1 and the acquisition of the image 95 are repeated a predetermined number of times, thereby acquiring multiple images 95 with different projection distances L1 (step S21). These multiple images 95 are sent from the image acquisition unit 24 to the computer 12 and stored in the storage unit 41 (see Figure 6). In step S21, for example, images 95 are acquired when the projection distance L1 is 30 mm, 50 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, and 350 mm. The projection distance L1 may be changed in various ways, and the number of multiple captured images 95 may also be changed in various ways within a range of 2 or more.

[0064] Next, the profile acquisition unit 44 sets the inspection area 96 described above for each captured image 95. In the following description, it will be assumed that there is one inspection area 96 set for each captured image 95, but multiple inspection areas 96 may be set for each captured image 95. The profile acquisition unit 44 acquires the brightness profile for the inspection area 96 of each captured image 95 (step S22).

[0065] In the defect detection unit 43, the evaluation value calculation unit 47 (see Figure 6) detects aperiodic luminance fluctuations in the luminance profile of one captured image 95 (step S23). These aperiodic luminance fluctuations correspond to aperiodic defects on the object 9 (i.e., a first aperiodic defect or a second aperiodic defect). Detection of aperiodic luminance fluctuations is performed, for example, if the luminance profile contains the above-mentioned periodic luminance fluctuations, by removing the periodic luminance fluctuations from the luminance profile and then detecting relatively large luminance fluctuations (for example, peaks that are more than a predetermined threshold away from the average luminance of the luminance profile) from the remaining luminance fluctuations. Figure 17 is a schematic diagram showing a luminance profile in which one aperiodic luminance fluctuation exists. Note that in step S23, if there are no relatively large luminance fluctuations in the luminance profile of the inspection area 96, the object 9 is determined to be a good product.

[0066] If the aperiodic defect corresponding to the aperiodic brightness fluctuation is a first aperiodic defect which is a scratch or deposit on the surface of the object 9, then the first aperiodic defect diffusely reflects the observation light 71, so almost no observation light 71 enters the region on the imaging support member 23 corresponding to the first aperiodic defect. Therefore, the aperiodic brightness fluctuation corresponding to the first aperiodic defect appears as a dark spot or line (i.e., a black spot or black line, hereinafter also referred to as "black spot, etc.") compared to the surrounding area. The aperiodic brightness fluctuation corresponding to the first aperiodic defect does not fluctuate much even if the projection distance L1 is changed.

[0067] On the other hand, if the aperiodic defect corresponding to the aperiodic brightness fluctuation is a second aperiodic defect which is an inclusion inside the object 9, the resin layer surrounding the second aperiodic defect specularly reflects the observation light 71, causing the specularly reflected light to reinforce each other around the region on the imaging support member 23 corresponding to the second aperiodic defect. Therefore, the aperiodic brightness fluctuation corresponding to the second aperiodic defect has a roughly annular region that is brighter than the surrounding region, between the aforementioned sunspot, etc. and the surrounding region. As the projection distance L1 increases, the specularly reflected light spreads out more widely, causing the sunspot, etc. to become larger, and the aforementioned roughly annular bright region also becomes larger.

[0068] The evaluation value calculation unit 47 calculates an evaluation value for the aperiodic luminance fluctuation described above. The evaluation value calculation unit 47 also detects aperiodic luminance fluctuations corresponding to the aperiodic luminance fluctuation in the luminance profiles of the captured images 95 other than the first captured image 95, and calculates an evaluation value for the detected aperiodic luminance fluctuation. In other words, the evaluation value calculation unit 47 obtains an evaluation value for the aperiodic luminance fluctuation in each of the multiple captured images 95 described above (step S24).

[0069] The evaluation value is calculated, for example, in Figure 17, by dividing the larger of A and B, which are the differences between the downward-pointing peak 971 corresponding to the black dots, and the upward-pointing peaks 972 and 973 adjacent to peak 971, by the distance W between peak 972 and peak 973. In other words, the evaluation value is calculated as Max(A,B) / W.

[0070] Furthermore, the evaluation value obtained in step S24 is not limited to that obtained by the above formula (Max(A,B) / W), and may be modified in various ways as long as it has at least one of the following characteristics. One characteristic of the evaluation value is that the evaluation value increases as Max(A,B), which is the difference between the downward peak 971 and the upward peaks 972 and 973, increases. Another characteristic of the evaluation value is that the evaluation value decreases as the distance W between peak 972 and peak 973 increases. For example, the evaluation value is (Max(A,B))2 / W 2 Alternatively, the evaluation value may be Max(A,B).

[0071] The non-periodic defect discrimination unit 46 (see Figure 6) determines an evaluation value variation index that indicates the degree of variation in evaluation values ​​in multiple captured images 95 (step S25). This evaluation value variation index is obtained, for example, by arranging the evaluation values ​​of non-periodic brightness variations in multiple captured images 95 with different projection distances L1 in ascending order of projection distance L1, as shown in Figure 18, and taking the arithmetic mean of the differences between each pair of adjacent evaluation values ​​(i.e., the absolute value of the difference between each pair of adjacent evaluation values). The evaluation value variation index obtained in step S25 can be changed in various ways, as long as it has the characteristic of increasing as the degree of variation in evaluation values ​​with respect to the variation in projection distance L1 increases, and decreasing as the degree of variation in evaluation values ​​with respect to the variation in projection distance L1 decreases.

[0072] As described above, if the aperiodic defect is a first aperiodic defect, which is a scratch or deposit on the surface of the object 9, the aperiodic luminance fluctuation in the luminance profile does not change much even when the projection distance L1 is changed. On the other hand, if the aperiodic defect is a second aperiodic defect, which is an inclusion inside the object 9, the aperiodic luminance fluctuation in the luminance profile changes relatively large when the projection distance L1 is changed. The aperiodic defect discrimination unit 46 determines that the aperiodic defect corresponding to the aperiodic luminance fluctuation is a first aperiodic defect if the evaluation value fluctuation index of the aperiodic luminance fluctuation in the luminance profile is below a predetermined threshold (steps S26, S27). Also, if the evaluation value fluctuation index of the aperiodic luminance fluctuation in the luminance profile is greater than the threshold, it determines that the aperiodic defect corresponding to the aperiodic luminance fluctuation is a second aperiodic defect (steps S26, S28). The threshold value is predetermined and stored in the storage unit 41 based on the captured image 95 of the object 9 in which the first aperiodic defect and the second aperiodic defect exist.

[0073] In step S21 described above, multiple images 95 corresponding to multiple projection distances L1 are acquired with the measurement angle θ fixed to one angle. However, the measurement angle θ may also be changed, and multiple images 95 corresponding to multiple measurement angles θ may also be acquired. If the aperiodic defect is a first aperiodic defect, which is a scratch or deposit on the surface of the object 9, the aperiodic brightness fluctuation corresponding to the aperiodic defect will fluctuate relatively large when the measurement angle θ is changed. On the other hand, if the aperiodic defect is a second aperiodic defect, which is an inclusion inside the object 9, the aperiodic brightness fluctuation corresponding to the aperiodic defect will not fluctuate very large even when the measurement angle θ is changed.

[0074] When acquiring captured images 95 by changing the measurement angle θ, for example, when the measurement angle θ is 0°, multiple captured images 95 are acquired by changing the projection distance L1, and after the measurement angle θ is changed to 30°, multiple captured images 95 are acquired by changing the projection distance L1. Furthermore, after the measurement angle θ is changed to 60°, multiple captured images 95 are acquired by changing the projection distance L1, and further after the measurement angle θ is changed to 80°, multiple captured images 95 are acquired by changing the projection distance L1. In other words, for each of the measurement angles θ = 0°, 30°, 60°, and 80°, multiple captured images 95 with different projection distances L1 are acquired. Note that the magnitude of the measurement angle θ may be changed in various ways within the range of 0° or more and less than 90°, and the number of multiple captured images 95 may be changed in various ways within the range of 2 or more.

[0075] In this case, in step S22, multiple luminance profiles are obtained from multiple captured images 95 with different projection distances L1 for each of the multiple measurement angles θ. Furthermore, in steps S23 to S24, multiple evaluation values ​​of aperiodic luminance fluctuations are obtained from multiple captured images 95 with different projection distances L1 for each of the multiple measurement angles θ.

[0076] In step S25, the evaluation value fluctuation index is determined based on the fluctuations of multiple evaluation values ​​at each measurement angle θ. Specifically, first, for each of the multiple measurement angles θ, the value obtained using the same method as the evaluation value fluctuation index described above is called the "provisional fluctuation index." Then, among the multiple provisional fluctuation indices corresponding to the multiple measurement angles θ, the value obtained by dividing the smallest provisional fluctuation index by the largest provisional fluctuation index is acquired as the evaluation value fluctuation index.

[0077] In steps S26 and S27, if the evaluation value fluctuation index is below a predetermined threshold (i.e., the change in aperiodic luminance fluctuation with respect to the change in measurement angle θ is relatively large), the aperiodic defect corresponding to the aperiodic luminance fluctuation is determined to be a first aperiodic defect. Also, if the evaluation value fluctuation index of the aperiodic luminance fluctuation in the luminance profile is greater than the threshold (i.e., the change in aperiodic luminance fluctuation with respect to the change in measurement angle θ is relatively small), the aperiodic defect corresponding to the aperiodic luminance fluctuation is determined to be a second aperiodic defect. The threshold when the projection distance L1 and measurement angle θ are changed in step S21 is different from the threshold when only the projection distance L1 is changed and the measurement angle θ is not changed in step S21.

[0078] In the inspection device 1, as described above, steps S11 to S18 (i.e., discrimination between first periodic defects and second periodic defects, and detection of non-periodic defects) may be performed, or only steps S11 to S16 (i.e., discrimination between first periodic defects and second periodic defects) may be performed. Also, in the inspection device 1, steps S21 to S27 (i.e., discrimination between first non-periodic defects and second non-periodic defects) may be performed instead of steps S17 to S18 (i.e., detection of non-periodic defects) of steps S11 to S18. In this case, steps S11 to S16 and steps S21 to S27 may be performed in any order.

[0079] As described above, the inspection device 1 detects defects in a sheet-like or plate-like translucent object 9. The inspection device 1 comprises an object holding unit 21, an auxiliary member holding unit 26, an illumination unit 22, an imaging unit 24, and a defect detection unit 43. The object holding unit 21 holds the object 9. The auxiliary member holding unit 26 holds a sheet-like or plate-like imaging auxiliary member 23 parallel to the object 9. The illumination unit 22 irradiates the object 9 with observation light 71. The imaging unit 24 is positioned on the opposite side of the object 9, with the imaging auxiliary member 23 in between. The imaging unit 24 has an optical axis J2 parallel to the normal direction of the object 9 and acquires an image 95 by capturing an image formed on the imaging auxiliary member 23 by the observation light 71 transmitted through the object 9. The defect detection unit 43 detects defects in the object 9 based on the image 95.

[0080] The defects detectable by the defect detection unit 43 include first periodic defects and second periodic defects. The first periodic defects are multiple streaks that extend linearly along a first direction (width direction 92 in the above example) on the object 9 and are periodically arranged in a second direction perpendicular to the first direction (conveying direction 91 in the above example). The second periodic defects are non-streaky defects that are periodically arranged in the second direction on the object 9.

[0081] The defect detection unit 43 includes a profile acquisition unit 44 and a periodic defect discrimination unit 45. The profile acquisition unit 44 sets multiple inspection regions 96 in the captured image 95, each extending linearly parallel to the second direction at multiple inspection positions in the first direction. The profile acquisition unit 44 acquires multiple luminance profiles, which are the luminance changes in the second direction at each of the multiple inspection regions 96. The periodic defect discrimination unit 45 detects periodic luminance fluctuations for each of the multiple luminance profiles. The periodic defect discrimination unit 45 then determines that a first periodic defect exists if periodic luminance fluctuations with the same period exist in multiple luminance profiles, and determines that a second periodic defect exists if periodic luminance fluctuations with the same period as those present in one of the multiple luminance profiles do not exist in the other luminance profiles.

[0082] The inspection device 1 can automatically determine and detect the type of periodic defect in the object 9. As a result, the manufacturing equipment 8 (see Figure 7) of the object 9 can be adjusted accurately and efficiently according to the type of periodic defect. For example, if a first periodic defect, consisting of multiple streaks, is detected as a defect in the object 9, the first periodic defect can be reduced or prevented by adjusting the difference in rotational speed of the molding rolls 85a to 85c in the manufacturing equipment 8.

[0083] As described above, it is preferable that the defects detectable by the defect detection unit 43 further include aperiodic defects, which are scratches or deposits on the surface of the object 9, or contaminants mixed into the interior of the object 9. It is preferable that the defect detection unit 43 further comprises an aperiodic defect discrimination unit 46 that detects aperiodic brightness fluctuations in at least one of the plurality of brightness profiles described above and determines that the aperiodic brightness fluctuations are aperiodic defects. This makes it possible to automatically detect aperiodic defects in the object 9 in addition to discriminating the first periodic defects and second periodic defects described above. As a result, defect inspection of the object 9 can be performed with greater accuracy.

[0084] As described above, it is preferable that the inspection device 1 further comprises a rotation mechanism 27 and a control unit 42. The rotation mechanism 27 rotates the object 9, the imaging support member 23, and the imaging unit 24 relative to the optical axis J1 of the illumination unit 22, around rotation axes J3 and J4 perpendicular to the optical axis J1 of the illumination unit 22, while maintaining the distance between the object 9 and the imaging support member 23 in the optical axis direction of the illumination unit 22 (i.e., projection distance L1), and the distance between the imaging support member 23 and the imaging unit 24 in the optical axis direction of the imaging unit 24, thereby changing the measurement angle θ, which is the angle between the optical axis J1 of the illumination unit 22 and the normal direction of the object 9. The control unit 42 controls the imaging unit 24 and the rotation mechanism 27 to acquire an image 95 with a measurement angle θ set to a predetermined first measurement angle for defect detection by the periodic defect discrimination unit 45, and to acquire an image 95 with a measurement angle θ set to a predetermined second measurement angle different from the first measurement angle for defect detection by the non-periodic defect discrimination unit 46.

[0085] In this way, by detecting periodic defects based on the image 95 acquired at a first measurement angle suited to the characteristics of periodic defects, and detecting non-periodic defects based on the image 95 acquired at a second measurement angle suited to the characteristics of non-periodic defects, both periodic and non-periodic defects can be detected with high accuracy.

[0086] In the inspection device 1, the control unit 42 may control the imaging unit 24 and the moving mechanism 28 to acquire an image 95 with a projection distance L1 set to a predetermined first projection distance for defect detection by the periodic defect discrimination unit 45, and to acquire an image 95 with a projection distance L1 set to a predetermined second projection distance different from the first projection distance for defect detection by the non-periodic defect discrimination unit 46. In this case as well, both periodic and non-periodic defects can be detected with high accuracy.

[0087] As described above, the inspection apparatus 1 preferably further comprises a moving mechanism 28 and a control unit 42. The moving mechanism 28 maintains the distance between the imaging auxiliary member 23 and the imaging unit 24 in the optical axis direction of the imaging unit 24, and moves the imaging auxiliary member 23 and the imaging unit 24 relative to the object 9 in the optical axis direction of the illumination unit 22, thereby changing the projection distance L1, which is the distance between the imaging auxiliary member 23 and the object 9 in the optical axis direction of the illumination unit 22. The control unit 42 controls the imaging unit 24 and the moving mechanism 28 to acquire a plurality of imaging images 95 with different projection distances L1. Non-periodic defects include a first non-periodic defect which is a scratch or deposit on the surface of the object 9, and a second non-periodic defect which is a contaminant that has entered the interior of the object 9.

[0088] The profile acquisition unit 44 preferably sets an inspection area 96 extending linearly parallel to a second direction at a predetermined inspection position in a first direction in each of the multiple captured images 95, and acquires a brightness profile which is the brightness change in the second direction in the inspection area 96. The defect detection unit 43 preferably further comprises an evaluation value calculation unit 47. The evaluation value calculation unit 47 detects aperiodic brightness fluctuations in the brightness profile of one of the multiple captured images 95, and calculates an evaluation value for the aperiodic brightness fluctuations in each of the multiple captured images 95. The aperiodic defect discrimination unit 46 preferably determines that a periodic brightness fluctuation is a first aperiodic defect if the evaluation value fluctuation index, which indicates the degree of fluctuation of the evaluation value in the multiple captured images 95, is below a predetermined threshold, and determines that a periodic defect is a second aperiodic defect if the evaluation value fluctuation index is greater than the threshold. This makes it possible to automatically determine and detect the type of aperiodic defect in the object 9.

[0089] More preferably, the inspection device 1 further comprises a rotation mechanism 27. The rotation mechanism 27 rotates the object 9, the imaging auxiliary member 23, and the imaging unit 24 relative to the optical axis J1 of the illumination unit 22 around rotation axes J3 and J4 perpendicular to the optical axis J1 of the illumination unit 22, while maintaining the distance between the object 9 and the imaging auxiliary member 23 in the optical axis direction of the illumination unit 22 (i.e., projection distance L1), and the distance between the imaging auxiliary member 23 and the imaging unit 24 in the optical axis direction of the imaging unit 24, thereby changing the measurement angle θ, which is the angle between the optical axis J1 of the illumination unit 22 and the normal direction of the object 9. Preferably, the imaging unit 24, the movement mechanism 28, and the rotation mechanism 27 are controlled by the control unit 42, and multiple image capture images 95 with different projection distances L1 are acquired for each of the multiple measurement angles θ. Then, the profile acquisition unit 44 acquires multiple luminance profiles from the multiple image capture images 95 for each of the multiple measurement angles θ. Furthermore, the evaluation value calculation unit 47 obtains multiple evaluation values ​​of aperiodic brightness fluctuations from the multiple captured images 95 for each of the multiple measurement angles θ. Preferably, the evaluation value fluctuation index is also determined based on the fluctuations of the multiple evaluation values ​​at each of the multiple measurement angles θ. This enables highly accurate automatic identification of the type of aperiodic defect.

[0090] In the inspection device 1, steps S11 to S18 described above (i.e., discrimination between the first periodic defect and the second periodic defect, and detection of aperiodic defects) do not necessarily need to be performed, and only steps S21 to S27 (i.e., discrimination between the first aperiodic defect and the second aperiodic defect) may be performed.

[0091] In this case, the inspection device 1 for detecting defects in a sheet-like or plate-like translucent object 9 comprises an object holding unit 21, an auxiliary member holding unit 26, an illumination unit 22, an imaging unit 24, a moving mechanism 28, a defect detection unit 43, and a control unit 42. The object holding unit 21 holds the object 9. The auxiliary member holding unit 26 holds a sheet-like or plate-like imaging auxiliary member 23 parallel to the object 9. The illumination unit 22 irradiates the object 9 with observation light 71. The imaging unit 24 is positioned on the opposite side of the object 9, with the imaging auxiliary member 23 in between. The imaging unit 24 has an optical axis J2 parallel to the normal direction of the object 9 and acquires an image 95 by capturing an image formed on the imaging auxiliary member 23 by the observation light 71 transmitted through the object 9. The moving mechanism 28 maintains the distance between the imaging assist member 23 and the imaging unit 24 in the optical axis direction of the imaging unit 24, and moves the imaging assist member 23 and the imaging unit 24 relative to the object 9 in the optical axis direction of the illumination unit 22, thereby changing the projection distance L1, which is the distance between the imaging assist member 23 and the object 9 in the optical axis direction of the illumination unit 22. The defect detection unit 43 detects defects in the object 9 based on the captured image 95. The control unit 42 controls the imaging unit 24 and the moving mechanism 28 to acquire multiple captured images 95 with different projection distances L1.

[0092] The defects detectable by the defect detection unit 43 include a first non-periodic defect, which is a scratch or deposit on the surface of the object 9, and a second non-periodic defect, which is a contaminant that has entered the interior of the object 9.

[0093] The defect detection unit 43 includes a profile acquisition unit 44, an evaluation value calculation unit 47, and a non-periodic defect discrimination unit 46. The profile acquisition unit 44 sets an inspection area 96 in each of the multiple captured images 95, at a predetermined inspection position in the first direction (width direction 92 in the above example), and extending linearly parallel to a second direction (transport direction 91 in the above example) perpendicular to the first direction. The profile acquisition unit 44 acquires a brightness profile, which is the brightness change in the second direction in the inspection area 96. The evaluation value calculation unit 47 detects non-periodic brightness fluctuations in the brightness profile of one of the multiple captured images 95, and calculates an evaluation value for the non-periodic brightness fluctuations in each of the multiple captured images 95. The non-periodic defect discrimination unit 46 determines that a non-periodic brightness fluctuation is a first non-periodic defect if the evaluation value fluctuation index, which indicates the degree of fluctuation of evaluation values ​​in multiple captured images 95, is below a predetermined threshold, and determines that it is a second non-periodic defect if the evaluation value fluctuation index is greater than the threshold. This makes it possible to automatically determine and detect the type of non-periodic defect in the object 9. As a result, it is possible to efficiently adjust the manufacturing equipment 8 (see Figure 7) of the object 9 and remove defective products of the object 9 according to the type of non-periodic defect.

[0094] As described above, it is preferable that the inspection device 1 further comprises a rotation mechanism 27. The rotation mechanism 27 rotates the object 9, the imaging auxiliary member 23, and the imaging unit 24 relative to the optical axis J1 of the illumination unit 22, around rotation axes J3 and J4 perpendicular to the optical axis J1 of the illumination unit 22, while maintaining the distance between the object 9 and the imaging auxiliary member 23 in the optical axis direction of the illumination unit 22 (i.e., projection distance L1), and the distance between the imaging auxiliary member 23 and the imaging unit 24 in the optical axis direction of the imaging unit 24, thereby changing the measurement angle θ, which is the angle between the optical axis J1 of the illumination unit 22 and the normal direction of the object 9. Preferably, the control unit 42 controls the imaging unit 24, the movement mechanism 28, and the rotation mechanism 27, and multiple image capture images 95 with different projection distances L1 are acquired for each of the multiple measurement angles θ. Then, the profile acquisition unit 44 acquires multiple luminance profiles from the multiple image capture images 95 for each of the multiple measurement angles θ. Furthermore, the evaluation value calculation unit 47 obtains multiple evaluation values ​​of aperiodic brightness fluctuations from the multiple captured images 95 for each of the multiple measurement angles θ. Preferably, the evaluation value fluctuation index is also determined based on the fluctuations of the multiple evaluation values ​​at each of the multiple measurement angles θ. This enables highly accurate automatic identification of the type of aperiodic defect.

[0095] Inspection device 1 may perform various defect inspections other than those described in steps S11 to S18 and steps S21 to S27 above. In this case, inspection device 1 for detecting defects in a sheet-like or plate-like translucent object 9 comprises an object holding unit 21, an auxiliary member holding unit 26, an illumination unit 22, an imaging unit 24, a rotation mechanism 27, and a defect detection unit 43. The object holding unit 21 holds the object 9. The auxiliary member holding unit 26 holds a sheet-like or plate-like imaging auxiliary member 23 parallel to the object 9. The illumination unit 22 irradiates the object 9 with observation light 71. The imaging unit 24 is positioned on the opposite side of the object 9, with the imaging auxiliary member 23 in between. The imaging unit 24 has an optical axis J2 parallel to the normal direction of the object 9 and acquires an image 95 by capturing an image formed on the imaging auxiliary member 23 by the observation light 71 transmitted through the object 9. The rotation mechanism 27 maintains the distance between the object 9 and the imaging support member 23 in the optical axis direction of the illumination unit 22 (i.e., projection distance L1), and the distance between the imaging support member 23 and the imaging unit 24 in the optical axis direction of the imaging unit 24. It rotates the object 9, the imaging support member 23, and the imaging unit 24 relative to the optical axis J1 of the illumination unit 22, around rotation axes J3 and J4 perpendicular to the optical axis J1 of the illumination unit 22, thereby changing the measurement angle θ, which is the angle between the optical axis J1 of the illumination unit 22 and the normal direction of the object 9. The defect detection unit 43 detects defects in the object 9 based on the captured image 95. This makes it possible to acquire the captured image 95 at a measurement angle θ suitable for various types of defects to be detected. As a result, various types of defects can be detected with high accuracy.

[0096] As described above, it is preferable that the inspection device 1 further includes a moving mechanism 28. The moving mechanism 28 maintains the distance between the imaging auxiliary member 23 and the imaging unit 24 in the optical axis direction of the imaging unit 24, and moves the imaging auxiliary member 23 and the imaging unit 24 relative to the object 9 in the optical axis direction of the illumination unit 22, thereby changing the projection distance L1, which is the distance between the imaging auxiliary member 23 and the object 9 in the optical axis direction of the illumination unit 22. This makes it possible to acquire an image 95 at a projection distance L1 suitable for each of the various types of defects to be detected. As a result, various types of defects can be detected with even greater accuracy.

[0097] The method for detecting the first and second aperiodic defects in object 9 is not limited to the examples shown in steps S21 to S27 above, and can be modified in various ways. Below, examples of other detection methods for determining whether the aperiodic brightness fluctuations in a brightness profile, as shown in Figures 19A and 19B, are first aperiodic defects or second aperiodic defects will be described.

[0098] In the luminance profiles shown in Figures 19A and 19B, the aperiodic luminance fluctuations include a downward peak 971, which corresponds to the aforementioned sunspots, and a first upward peak 972 and a second upward peak 973, which are upward peaks adjacent to both sides of the downward peak 971. In the inspection apparatus 1, the background luminance a0 is acquired by the aperiodic defect discrimination unit 46 (see Figure 6). The background luminance a0 in Figures 19A and 19B is the average of the luminance fluctuations in the luminance profiles exemplified in Figures 19A and 19B (i.e., the average luminance). The aperiodic defect discrimination unit 46 also acquires the upward and downward uniaxial amplitudes a1 and a2 of the luminance fluctuations in the luminance profile. The background luminance a0 is the average luminance in the entire region of the luminance profile excluding the aperiodic luminance fluctuations. The uniaxial amplitudes a1 and a2 are the averages of the upward and downward uniaxial amplitudes in the entire region of the luminance profile excluding the aperiodic luminance fluctuations. If the proportion of aperiodic luminance fluctuations in the luminance profile is relatively small, the background luminance a0 and the amplitudes a1 and a2 may be calculated as the average over the entire region of the luminance profile, including the aperiodic luminance fluctuations. Subsequently, the aperiodic defect discrimination unit 46 obtains the luminance difference b between the first upper peak 972 and the background luminance a0, and the luminance difference c between the second upper peak 973 and the background luminance a0. The luminance differences b and c are absolute values ​​(i.e., 0 or greater).

[0099] As described above, when the aperiodic defect is a second aperiodic defect, in the aperiodic brightness fluctuation, there is a roughly ring-shaped region that is brighter than the surrounding region between the sunspot, etc. and the surrounding region. On the other hand, when the aperiodic defect is a first aperiodic defect, the area around the sunspot, etc. does not become very bright. Based on this characteristic, as shown in Figure 19A, the aperiodic defect discrimination unit 46 determines that the aperiodic defect corresponding to the aperiodic brightness fluctuation is a first aperiodic defect if the brightness difference b and brightness difference c are less than or equal to Max(a1,a2), which is the larger of the two amplitudes a1 and a2. Also, as shown in Figure 19B, if at least one of the brightness difference b and brightness difference c is greater than Max(a1,a2), the aperiodic defect corresponding to the aperiodic brightness fluctuation is determined to be a second aperiodic defect. This makes it possible to automatically and accurately determine and detect the type of aperiodic defect in the object 9.

[0100] The peak brightness value of the lower peak 971 may be greater than or equal to the background brightness a0, but from the viewpoint of accurately distinguishing the type of aperiodic defect, it is preferable that it be less than the background brightness. That is, if the brightness difference between the lower peak 971 and the first upper peak 972 is B, and the brightness difference between the lower peak 971 and the second upper peak 973 is C, then it is preferable that at least one of (b / B) and (c / C) is less than 1, and it is even more preferable that both are less than 1.

[0101] Furthermore, the background brightness a0 described above may be the average brightness of the brightness profiles in the inspection area 96 corresponding to the brightness profile in which aperiodic brightness fluctuations exist, and in other inspection areas 96 adjacent to it. Alternatively, the average brightness of the brightness profiles in other inspection areas 96 where it has been confirmed that aperiodic brightness fluctuations do not exist may be used as the background brightness a0. Or, the average brightness of the brightness profiles of good quality objects 9 acquired in the past may be used as the background brightness a0.

[0102] As described above, in the inspection device 1, the illumination unit 22 comprises a light source unit 220 and a lens 223, and it is preferable that the lens 223 converts the light from the light source unit 220 into parallel light, which is observation light 71, and irradiates the object 9 with it. Furthermore, it is preferable that the distance L3 between the lens 223 and the imaging support member 23 in the optical axis direction of the illumination unit 22 (X direction in the above example) is half or more of the focal length of the lens 223. This makes it possible to suppress the projection of a secondary real image of the light source 221 onto the imaging support member 23 by the lens 223, and to suppress the inclusion of such secondary real image in the image acquired by the imaging unit 24. As a result, various types of defects can be detected with even greater accuracy. In addition, from the viewpoint of suppressing the projection of the secondary real image onto the imaging support member 23, it is also preferable that an anti-reflective coating be provided on the lens surface of the lens 223.

[0103] Various modifications are possible to the inspection device 1 described above.

[0104] For example, the structures of the rotating mechanism 27 and the moving mechanism 28 are not limited to those described above and may be modified in various ways.

[0105] The rotation axes J3 and J4 do not necessarily need to extend in the Z direction as long as they are perpendicular to the optical axis J1 of the illumination unit 22; for example, they may extend in the Y direction. The rotation mechanism 27 only needs to rotate the imaging support member 23 and the imaging unit 24 relative to the optical axis J1 of the illumination unit 22, for example, the illumination unit 22, the object 9 and the object holding unit 21 may be rotated while maintaining their relative positions to each other. The movement mechanism 28 only needs to move the imaging support member 23 and the imaging unit 24 relative to the object 9 in the optical axis direction of the illumination unit 22 (i.e., the X direction), for example, the illumination unit 22, the object 9 and the object holding unit 21 may be moved in the X direction while maintaining their relative positions to each other.

[0106] In the example described above, in step S13, if there are no relatively large luminance fluctuations in the luminance profile of the inspection area 96, the object 9 is judged to be a good product. However, the judgment of whether the object 9 is good or bad may be made by other methods. For example, first, an object that has been confirmed to be a good product in advance (hereinafter also referred to as the "reference object") is imaged at a predetermined measurement angle θ (for example, 30°, hereinafter also referred to as the "reference angle"), and the acquired image is stored in the storage unit 41 as a reference image. The luminance profile in the inspection area of ​​the reference image is also stored in the storage unit 41 as a reference profile. The reference image is assumed to have multiple streaks with density differences within an acceptable range. Next, the object 9 that is the target of the defect inspection is imaged at the same measurement angle θ (i.e., the reference angle) as above, and the luminance profile in the inspection area 96 of the acquired image 95 is determined. Next, the brightness profile of the captured image 95 is compared with the brightness profile of the reference image (i.e., the reference profile), and the acquisition of the captured image 95 and brightness profile is repeated while changing the measurement angle θ until the difference between the upward and downward peaks corresponding to the streaks in both brightness profiles (i.e., the difference in streak density) is approximately the same. Then, the measurement angle θ of the object 9 at which the difference in streak density between the brightness profile of the captured image 95 and the reference profile is approximately the same is determined. If this measurement angle θ is greater than or equal to the reference angle, it is judged to be a good product; if it is less than the reference angle, it is judged to have a first periodic defect (i.e., multiple streaks outside the acceptable range).

[0107] Alternatively, training data may be created using multiple images of objects that have been previously confirmed to be in good condition, a trained model may be generated using machine learning with this training data, and the detection of first periodic defects and other defects, as well as the identification of defect types, may be performed using this trained model.

[0108] The observation light 71 does not necessarily have to be parallel light; for example, it may be diffuse light. When diffuse light is used as the observation light 71, a change in projection distance L1 changes the size of the area on the object 9 acquired as the captured image 95, and the amount of light from the observation light 71 incident on the imaging unit 24 also changes. For this reason, before defect detection based on the captured image 95, the captured image 95 is corrected to match the change in the size of the area and the change in the amount of light. For example, when the projection distance L1 is increased, the captured image 95 is reduced in size and the contrast between light and dark in the captured image 95 is emphasized.

[0109] In the above description, the inspection device 1 was described as being a device independent of the manufacturing device 8, but it is not limited to this. For example, along the transport path of the sheet member 90 manufactured by the manufacturing device 8, each part of the continuous sheet member 90 may be treated as an object 9, and defect inspection of the object 9 may be performed on the object 9. In other words, the structure of the inspection device 1 may be used for in-line inspection in the manufacturing line of the sheet member 90.

[0110] Figure 20 is a front view showing an example of the configuration of an inspection device 1a used for inline inspection. In the inspection device 1a, the object holding unit 21a is a transport roller that holds the sheet member 90 and transports it in the transport direction 91. The illumination unit 22a is positioned above the sheet member 90 (i.e., on the (+Z) side), and the imaging auxiliary member 23a, auxiliary member holding unit 26a, and imaging unit 24a are positioned below the sheet member 90 (i.e., on the (-Z) side). The rotation mechanism 27a is positioned around a rotation axis J5 extending in the Y direction, and the illumination unit 22 a The components are rotated as shown by the dashed line. At this time, the imaging support member 23a, the support member holder 26a, and the imaging unit 24a are slid in the X direction as necessary so that they can receive the observation light 71 from the illumination unit 22a. The moving mechanism 28a moves the imaging support member 23a, the support member holder 26a, and the imaging unit 24a in the Z direction as shown by the dashed line. At this time as well, the imaging support member 23a, the support member holder 26a, and the imaging unit 24a are slid in the X direction as necessary so that they can receive the observation light 71 from the illumination unit 22a.

[0111] Similarly, inspection device 1a can automatically detect periodic and non-periodic defects in the object 9 (i.e., each part of the sheet member 90) while determining the type of defect. In inspection device 1a, adjustment information may be sent from computer 12a to manufacturing device 8 (see Figure 7) according to the type of defect detected, and the manufacturing device 8 may be automatically adjusted to reduce the defect. For example, if a first periodic defect is detected, the load on the molding rolls 85a to 85c is automatically adjusted according to the characteristics of the first periodic defect, such as its period. Also, if a peeling mark of a second periodic defect is detected, the temperature of the molding rolls 85a to 85c and the tension of the sheet member are automatically adjusted. If a drop slip defect (also called a "pre-impact defect") of a second periodic defect is detected, the distance between the die 84 and the molding rolls 85a and 85b is automatically adjusted.

[0112] The configurations in the above embodiments and each modified example may be combined as appropriate, as long as they do not contradict each other.

[0113] Although the invention has been described in detail, the above description is illustrative and not limiting. Therefore, it can be said that numerous modifications and embodiments are possible as long as they do not deviate from the scope of the present invention. [Explanation of symbols]

[0114] 1,1a Inspection device 9. Object 21,21a Object holding part 22,22a Lighting section 23,23a Imaging support member 24,24a Imaging Unit 26,26a Auxiliary member holding part 27,27a Rotation mechanism 28,28a Moving mechanism 42 Control Unit 43 Defect detection unit 44 Profile Acquisition Unit 45 Periodic defect discrimination unit 46 Non-periodic defect discrimination unit 47 Evaluation Value Calculation Unit 71 Observation light 91 Conveying direction 92 Width direction 95 Acquired Images 96 Examination Areas 220 Light source section 223 Lens J1 (Illumination section) Optical axis J2 (optical axis of the imaging unit) J3, J4, J5 Rotation axis L1 projection distance S11-S18, S21-S27 Step θ measurement angle

Claims

1. An inspection device for detecting defects in a sheet-like or plate-like translucent object, An object holding unit that holds the object, An auxiliary member holding section that holds a sheet-like or plate-like imaging auxiliary member parallel to the object, An illumination unit that irradiates the object with observation light, An imaging unit is positioned on the opposite side of the object from the imaging support member, has an optical axis parallel to the normal direction of the object, and captures an image formed on the imaging support member by the observation light transmitted through the object to acquire an image. A defect detection unit that detects defects in the object based on the captured image, Equipped with, The defects that can be detected by the defect detection unit are: A first periodic defect is a plurality of streaks on the object that extend linearly along a first direction and are periodically arranged in a second direction perpendicular to the first direction, Non-streaky second periodic defects arranged periodically in the second direction on the object, Includes, The defect detection unit is In the captured image, a profile acquisition unit sets a plurality of inspection areas that extend linearly parallel to the second direction at a plurality of inspection positions in the first direction, and acquires a plurality of luminance profiles which are the luminance changes in the second direction in each of the plurality of inspection areas. A periodic defect determination unit detects periodic luminance fluctuations for each of the multiple luminance profiles, determines that a first periodic defect exists if periodic luminance fluctuations with the same period exist in all of the multiple luminance profiles, and determines that a second periodic defect exists if periodic luminance fluctuations with the same period as those present in one of the multiple luminance profiles do not exist in any of the other luminance profiles. It is equipped with.

2. An inspection apparatus according to claim 1, The defects detectable by the defect detection unit further include non-periodic defects such as scratches or deposits on the surface of the object, or contaminants mixed into the interior of the object. The defect detection unit further includes an aperiodic defect determination unit that detects aperiodic luminance fluctuations in at least one of the plurality of luminance profiles and determines that the aperiodic luminance fluctuations are aperiodic defects.

3. The inspection apparatus according to claim 2, A rotation mechanism that, while maintaining the distance between the object and the imaging support member in the optical axis direction of the illumination unit, and the distance between the imaging support member and the imaging unit in the optical axis direction of the imaging unit, rotates the object, the imaging support member, and the imaging unit relative to the optical axis of the illumination unit about a rotation axis perpendicular to the optical axis of the illumination unit, thereby changing the measurement angle which is the angle between the optical axis of the illumination unit and the normal direction of the object, A control unit controls the imaging unit and the rotation mechanism to acquire the image when the measurement angle is a predetermined first measurement angle for defect detection by the periodic defect discrimination unit, and to acquire the image when the measurement angle is a predetermined second measurement angle different from the first measurement angle for defect detection by the non-periodic defect discrimination unit. To further prepare.

4. The inspection apparatus according to claim 2, A moving mechanism that maintains the distance between the imaging assist member and the imaging unit in the optical axis direction of the imaging unit, moves the imaging assist member and the imaging unit relative to the object in the optical axis direction of the illumination unit, and changes the projection distance, which is the distance between the imaging assist member and the object in the optical axis direction of the illumination unit, A control unit that controls the imaging unit and the movement mechanism to acquire multiple images with different projection distances, Furthermore, The aforementioned non-periodic defects are The first non-periodic defect is a scratch or deposit on the surface of the object, The second non-periodic defect is an inclusion that has become mixed into the interior of the aforementioned object, Includes, The profile acquisition unit sets an inspection area in each of the plurality of captured images that extends linearly parallel to the second direction at a predetermined inspection position in the first direction, and acquires a brightness profile which is the brightness change in the second direction within the inspection area. The defect detection unit further includes an evaluation value calculation unit that detects aperiodic brightness fluctuations in the brightness profile of one of the plurality of captured images and calculates an evaluation value for the aperiodic brightness fluctuations in each of the plurality of captured images. The nonperiodic defect discrimination unit determines that the nonperiodic brightness fluctuation is a first nonperiodic defect if the evaluation value fluctuation index, which indicates the degree of fluctuation of the evaluation value in the plurality of captured images, is less than or equal to a predetermined threshold, and determines that it is a second nonperiodic defect if the evaluation value fluctuation index is greater than the threshold.

5. The inspection apparatus according to claim 4, The system further includes a rotation mechanism that, while maintaining the distance between the object and the imaging assist member in the optical axis direction of the illumination unit, and the distance between the imaging assist member and the imaging unit in the optical axis direction of the imaging unit, rotates the object, the imaging assist member, and the imaging unit relative to the optical axis of the illumination unit about a rotation axis perpendicular to the optical axis of the illumination unit, thereby changing the measurement angle, which is the angle between the optical axis of the illumination unit and the normal direction of the object. The control unit controls the imaging unit, the moving mechanism, and the rotating mechanism, and multiple images with different projection distances are acquired for each of the multiple measurement angles. The profile acquisition unit acquires multiple luminance profiles from the multiple captured images for each of the multiple measurement angles. The evaluation value calculation unit obtains multiple evaluation values ​​of the non-periodic brightness fluctuations from the multiple captured images for each of the multiple measurement angles. The aforementioned evaluation value fluctuation index is also determined based on the fluctuations of the plurality of evaluation values ​​at each of the plurality of measurement angles.

6. The inspection apparatus according to claim 2, The aforementioned non-periodic defects are The first non-periodic defect is a scratch or deposit on the surface of the object, The second non-periodic defect is an inclusion that has become mixed into the interior of the aforementioned object, Includes, The aforementioned non-periodic luminance fluctuations are The lower peak is a downward-sloping peak, The first upper peak and the second upper peak are upward-pointing peaks adjacent to both sides of the aforementioned lower peak, Includes, Let a1 and a2 be the upward and downward amplitudes of the luminance variation in the at least one luminance profile, let b be the luminance difference between the first upper peak and the background luminance a0, and let c be the luminance difference between the second upper peak and the background luminance a0. The nonperiodic defect discrimination unit determines that the nonperiodic defect corresponding to the nonperiodic brightness variation is the first nonperiodic defect if b and c in the nonperiodic brightness variation are less than or equal to Max(a1, a2), which is the larger of a1 and a2, and determines that the nonperiodic defect corresponding to the nonperiodic brightness variation is the second nonperiodic defect if at least one of b and c is greater than Max(a1, a2).

7. An inspection apparatus according to any one of claims 1 to 6, The aforementioned lighting unit is Light source section, A lens that converts the light from the light source into parallel light, which is the observation light, and irradiates the object with it. Equipped with, The distance between the lens and the imaging assist member in the optical axis direction of the illumination unit is at least half the focal length of the lens.

Images