Pinhole detection device

Abstract

To provide a pinhole detection device capable of improving pinhole detection precision.SOLUTION: In a pinhole detection device 10, a detector 24 which detects a pinhole 110 formed in an object 100 to be inspected comprises a plurality of optical fibers 30 which propagate light transmitted through the object 100 to be detected. The plurality of optical fibers 30 are arranged side by side opposite a light source 20. Representing a maximum detectable angle to the optical axis of the light source 20 at which the pinhole 110 can be detected as θ, a maximum incidence angle of light that the optical fibers 30 can propagate to the optical axis of the light source 20 is set to θ+0° to θ+5°.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pinhole detection device. [Background technology]

[0002] Patent Document 1 discloses a method for accurately detecting through defects that are inclined with respect to the thickness direction of an object to be inspected. The purpose of the present invention is to provide a surface defect inspection device capable of detecting defects on a surface. (Line 13) In order to achieve this purpose, the surface defect inspection device of Patent Document 1 inspects the object to be inspected. The object to be inspected and the light are incident on a light source that irradiates the surface with light, and a detector that detects the amount of transmitted light from the irradiated light. An optical lens is disposed between the source and the detector to focus the light onto the detector (column 3, lines 15 to 20). , Figure 1).

[0003] Patent Document 2 discloses a method for forming a pinhole-like hole extending obliquely relative to the surface of a sheet-like object. The purpose of the present invention is to provide a pinhole detection device for sheet-like objects that can also detect abnormal parts (see Column 2). (Line 19 to column 3, line 2). In order to achieve this purpose, the abnormality of the sheet-like object in Patent Document 2 The part detection device includes a laser light source and a dispersed beam detector. a lens that converts the dispersed beam into a sheet that is positioned so that the dispersed beam is incident from one side and a sheet-like object on the other side of the sheet-like object, the sheet-like object being sensitive to transmitted light of the dispersed beam. The light-sensitive means is a fiber optic It has a photoconductor FO such as a glass and a photoelectric conversion element PH (column 4, lines 12 to 14, Figure surface).

[0004] Patent Document 3 aims to provide a pinhole detection device for sheet materials with high detection accuracy. (Page 4, lines 7-8). In order to achieve this purpose, Patent Document 3 describes Light is irradiated from one side of the sheet material, and the light that passes through the pinholes in the sheet material is shone on the other side. The light is received at the end of the optical fiber arranged perpendicular to the direction of travel of the material, and transmitted through the optical fiber. In a pinhole detection device for a sheet material that guides light to a detection element, the light receiving end of the optical transmission fiber is They are arranged in multiple rows in a bale-like stack (Claim 1, Figures 4 to 6). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 61-025042 [Patent Document 2] Japanese Patent Application Publication No. 50-034586 [Patent Document 3] Japanese Utility Model Application Publication No. 55-116256 Summary of the Invention [Problem to be solved by the invention]

[0006] Although Patent Document 1 explains that the detector (3) detects the amount of transmitted light of the irradiated light, (Column 3, lines 16-17, etc.), the specific configuration of the detector (3) is not explained. Furthermore, in Patent Document 2, a photoconductive element such as fiber optics is used as the photosensitive element. The body FO and the photoelectric conversion element PH are explained (column 4, lines 12 to 14, drawing). No specific consideration has been given to the specifications of the conductor FO (optical fiber).

[0007] Furthermore, Patent Document 3 discloses the cross-sectional shape and arrangement of the optical transmission fiber 7 (optical fiber). Although there are some (page 3, lines 16 to 20, Figures 4 to 6, etc.), other optical transmission fibers 7 Therefore, there is no need to improve the pinhole detection accuracy. There is room for improvement.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to improve the pinhole detection accuracy. The object of the present invention is to provide a pinhole detection device that can detect pinholes. [Means for solving the problem]

[0009] The pinhole detection device according to the present invention comprises: a light source that irradiates the object to be inspected with light; an optical lens disposed between the light source and the object to be inspected; The light that is converged by the optical lens and transmitted through the pinhole of the object to be inspected is detected. detector and and The detector includes an optical fiber that propagates light that has passed through a pinhole in the object to be inspected. , When the maximum detectable angle at which the pinhole can be detected with respect to the optical axis of the light source is θ, The maximum incident angle of light that can be propagated through the optical fiber relative to the optical axis of the light source is θ+0° to θ+5°. is in the range of ° It is characterized by:

[0010] According to the present invention, it is possible to reliably detect pinholes as a detection target while preventing disturbance light from reaching the optical fiber. As a result, the signal / noise of the transmitted light and the ambient light is reduced. This increases the signal-to-noise ratio (S / N ratio) and improves pinhole detection accuracy. According to the method, it can be suitably used when the object to be inspected is, for example, strip-shaped. , the object to be inspected is stretched in the conveying direction (for example, steel plate, opaque film, paper In the present invention, pinholes inclined in the conveying direction are easily generated. This makes it easier to detect the rule.

[0011] In the present invention, the light source is a linear light source that irradiates the object to be inspected with light in a linear shape. The optical lens is configured to reflect light irradiated from the light source and spread in a direction away from the optical axis of the light source. is converged in a direction approaching the optical axis of the light source, and the detector is When the optical fibers are arranged side by side and the maximum polarization angle of the optical lens is θ1, The large polarization angle θ1 may be set to be equal to or greater than the maximum detectable angle θ.

[0012] In the present invention, when the maximum polarization angle of the optical lens is θ1, the optical fiber can propagate The maximum incident angle of the light with respect to the optical axis of the light source is within the range of θ1+0° to θ1+5°. It may also be configured as follows.

[0013] In the present invention, the direction perpendicular to the longitudinal direction of the light source and perpendicular to the optical axis of the light source. a conveying device for moving the object to be inspected in a direction perpendicular to the optical axis; The end face of the optical fiber is placed at the focal point of the optical lens or The inspection device may be configured so that the inspection device is disposed closer to the object to be inspected than the inspection device.

[0014] According to the present invention, even when the object to be inspected is moved relative to the pinhole detection device, In other words, when the end face of the optical fiber is brought to the focal position of the optical lens, it becomes easier to detect pinholes. When placed in this position, the detector detects the light transmitted through the pinhole with a very sharp rise. On the other hand, the time to detect the rising edge is relatively short. When the object is located closer to the object than the focal point of the optical lens, the pinhole detected by the detector The rise due to the transmitted light of the coil is smaller than that of the former, but the time to detect the rise is Therefore, depending on the moving speed of the object to be inspected, the former arrangement (optical lens) Even if the pinhole cannot be detected in the latter arrangement (at the focal position of the lens), Therefore, in the latter arrangement, it may be possible to detect the Therefore, it is possible to increase the moving speed of the object to be inspected.

[0015] In either case, criteria for determining whether pinholes exist or not must be established. The criteria for the former and the latter may be different. The criteria include, for example, the signal strength of the detector and the number of data points used to calculate the moving average. .

[0016] In the present invention, a light source is provided between the light source and the detector, and the light source is provided along the longitudinal direction of the light source. a first linear Fresnel lens on the light source side, and a second linear Fresnel lens on the light source side along the longitudinal direction of the light source; a second linear Fresnel lens disposed closer to the detector than the Fresnel lens; The first linear Fresnel lens converts the light emitted from the light source into parallel light. The second linear Fresnel lens refracts the light beam when viewed in the longitudinal direction of the light source. The maximum polarization angle of the light refracted by the linear Fresnel lens is the maximum polarization angle of the light refracted by the linear Fresnel lens relative to the end face of the optical fiber. The parallel light is refracted so that the angle of incidence is equal to or smaller than the maximum angle of incidence. According to the present invention, the first linear Fresnel lens and the second linear Fresnel lens may be Since the light between them is parallel, it is easy to adjust the distance between the two Fresnel lenses. [Effects of the Invention]

[0017] According to the present invention, it is possible to improve the detection accuracy of pinholes.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a perspective view schematically showing the configuration of a pinhole detection device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram for explaining the optical characteristics of the optical lens and the optical fiber in the above embodiment.

Embodiments for Carrying Out the Invention

[0019] <A. One Embodiment> [A-1. Configuration] (A-1-1. Overall Configuration) FIG. 1 is a perspective view schematically showing the configuration of a pinhole detection device 10 according to an embodiment of the present invention. FIG. The pinhole detection device 10 detects a pinhole 110 generated in the inspection object 100. The pinhole detection device 10 includes a light source 20, optical lenses 22a and​​​​​​​​​​​​​​​​​​​​​​​​ At this time, the optical lenses 22 a and 22 b reflect the light 50 from the light source 20 in the longitudinal direction of the light source 20 . That is, the optical lenses 22a and 22b converge the light emitted from the light source 20 in the vertical direction. The light that spreads in a direction away from the optical axis of the light source 20 is converged in a direction approaching the optical axis of the light source 20. To make.

[0022] The optical lens 22a is a first linear frame that is disposed closer to the light source 20 than the optical lens 22b. (hereinafter referred to as "first linear Fresnel lens 22a" or "first lens 22a") The first lens 22a is disposed along the longitudinal direction of the light source 20. The first lens 22 refracts the light 50 emitted from the first lens 22 so that it becomes parallel light. a refracts the light emitted from the light source 20 and spreading in a direction away from the optical axis of the light source 20, Parallel to the axis.

[0023] The optical lens 22b is a second linear lens arranged closer to the detector 24 than the first optical lens 22a. The second linear Fresnel lens 22b is a Fresnel lens (hereinafter referred to as "second lens 22b" or "second lens 22b"). The second lens 22b is arranged along the longitudinal direction of the light source 20. When viewed in the direction from the light source 20 toward the detector 24 (downward in FIG. 1), the first level The parallel light from the lens 22a is converged in a direction perpendicular to the longitudinal direction of the light source 20. The second lens 22b converges the light parallel to the optical axis in a direction approaching the optical axis of the light source 20. .

[0024] FIG. 2 illustrates the optical properties of the optical lens 22b and the optical fiber 30 in this embodiment. In FIG. 2, θ1 is the maximum polarization angle of the light 50 refracted by the second lens 22b. θ2 is the maximum angle that the light 50 that can propagate through the optical fiber 30 makes with respect to the optical axis 60 of the light source 20. The angle of incidence is large. θ2' is an angle of θ2+5°. The second lens 22b is The maximum polarization angle θ1 of the light 50 refracted by the refractor 22b is the maximum incident angle θ1 of the light 50 to the end face of the optical fiber 30. Alternatively, the second lens 22b refracts the parallel light to be equal to the angle θ2. The parallel light may be refracted so that the angle θ1 is smaller than the maximum angle of incidence θ2.

[0025] (A-1-4. Detector 24) The detector 24 is focused by the optical lenses 22a and 22b and detects the pins of the object 100 to be inspected. The light 50 transmitted through the hole 110 is detected. Since the light 50 is converged by the do.

[0026] As shown in FIG. 1, the detector 24 includes a plurality of optical fibers 30 (optical fibers) and at least Each optical fiber 30 has one detecting element 32 and a pinhole determining unit (not shown). The light 50 transmitted through the inspection object 100 propagates to the detection element 32 (however, the maximum incident angle is less than θ2). Light 50 with a larger angle of incidence than this is not propagated by the optical fiber 30.

[0027] As shown in enlarged portion 34 of FIG. 1, the optical fiber 30 is oriented in a straight line along the length of the light source 20. The end face of the optical fiber 30 on the side of the inspection object 100 is connected to the optical lens 22. a, 22b are arranged parallel to the inspection object 100. In this case, the end face of the optical fiber 30 facing the object 100 to be inspected (the upper end face in FIG. 1) is , is placed at the focal position of the optical lens 22b.

[0028] The detecting element 32 is an element that converts the light propagating through the optical fiber 30 into an electrical signal, for example. The pinhole determination unit can be a detection element 3. The pinhole determination unit determines whether or not a pinhole 110 exists based on the output of the pinhole determination unit 2. The criteria for determining the pinhole 110 (signal strength, movement) are set according to the type of object 100, the transport speed, etc. The number of data used to calculate the moving average may be configured to be switchable.

[0029] (A-1-5. Conveyor device 26) The conveying device 26 is arranged in a direction perpendicular to the longitudinal direction of the light source 20 and perpendicular to the optical axis of the light source 20. The transport device 26 moves the inspection object 100 in the direction of the arrow. It has a rotating roll or the like and conveys the object to be inspected 100. When viewed in this direction, the conveying device 26 is oriented in a direction perpendicular to the longitudinal direction of the light source 20 (see FIG. 1). In this embodiment, the object 100 to be inspected is moved in the direction of the arrow 120. The object under test 100 moves, but the light source 20, the optical lenses 22a, 22b, and the detector 24 It is fixed.

[0030] (A-1-6. Inspection object 100) The object 100 to be inspected is a strip-shaped object, such as a steel plate, a light-opaque film, or paper. The inspection object 100 is stretched in the conveying direction (the direction of the arrow 120). When the inspection object 100 is a steel plate, the width (direction perpendicular to the traveling direction) The length in the direction can be, for example, 50 cm to 1 m.

[0031] [A-2. Manufacturing method (design method)] Next, a manufacturing method (design method) for the pinhole detection device 10 of this embodiment will be described. In this embodiment, the specifications of each part of the pinhole detection device 10 are detailed to improve the detection accuracy. An example of a manufacturing method (design method) is as follows:

[0032] The manufacturer (designer) determines the thickness (design value or actual measurement value) and pinhole The maximum detectable angle of the pinhole 110 based on the hole diameter of 110 (estimated value or past actual measurement value) The maximum detectable angle θ is determined by the angle θ of the object to be detected when viewed in the longitudinal direction of the light source 20. The maximum angle that the pinhole 110 makes with respect to the optical axis 60 (FIG. 2) of the light source 20. The thicker the object 100 is and the smaller the diameter of the pinhole 110 is, the more the oblique angle Therefore, the maximum detectable angle θ is reduced.

[0033] Next, the manufacturer (designer) determines whether the light 50 that can be propagated through the optical fiber 30 is aligned with the optical axis 60 of the light source 20. The maximum incident angle θ2 (FIG. 2) is determined. The maximum incident angle θ2 is, for example, the maximum detection angle. The maximum incident angle θ2 is determined as follows: The specifications of the optical fiber 30 that realize the angle θ2 are selected. The maximum incident angle θ2 is determined by the numerical aperture (NA) and They are essentially synonymous and vary depending on the material of the optical fiber 30, the refractive index of the core and clad, and the like. Therefore, the manufacturer (designer) selects an optical fiber 30 that achieves the maximum incident angle θ2.

[0034] Next, the manufacturer (designer) sets the specifications for the light source 20 and the lenses 22a and 22b. For example, when the maximum polarization angle of the optical lens 22b is θ1 (FIG. 2), the manufacturer (designer) The maximum polarization angle θ1 is set so that the maximum incident angle θ2 is within the range of θ1+0° to θ1+5°. Determine.

[0035] [A-3. Effects of this embodiment] According to this embodiment, when viewed in the longitudinal direction of the light source 20 (line light source), If the maximum detectable angle that the pinhole 110 makes with respect to the optical axis 60 of the light source 20 is θ, then The maximum incident angle θ2 of the light 50 that can propagate through the optical fiber 30 relative to the optical axis 60 is θ+0° to θ +5°. That is, the pinhole 110 relative to the optical axis 60 of the light source 20 is detected. If the maximum detectable angle is θ, the angle of the optical fiber 30 relative to the optical axis 60 of the light source 20 is The maximum incident angle of the light 50 that can be scattered is in the range of θ+0° to θ+5°. While ensuring the detection of the target pinhole 110, the optical fiber 30 is prevented from receiving ambient light (or leaked light). As a result, the signal-to-noise ratio (S / N ratio) of the transmitted light and the ambient light is This makes it possible to improve the detection accuracy of the pinhole 110.

[0036] In this embodiment, the light source 20 is a linear light source that irradiates the inspection object 100 with light in a linear shape. The optical lenses 22a and 22b are arranged to guide the light irradiated from the light source 20 along the optical axis 6 of the light source 20. 0 is converged in a direction approaching the optical axis 60 of the light source 20. The detector 24 has a plurality of optical fibers 30 arranged side by side facing the light source 20, and an optical lens. When the maximum polarization angle of the lens 22b is θ1, the maximum polarization angle θ1 is set to be equal to or larger than the maximum detectable angle θ. This makes it easier to ensure the amount of light required to detect the pinhole 110.

[0037] In this embodiment, the end face of the optical fiber 30 facing the inspection object 100 is an optical lens. 22b (FIG. 1). On the other hand, the optical fiber facing the object 100 to be inspected The end face of the optical lens 22b is located closer to the object 100 than the focal position of the optical lens 22b. This allows the inspection object 100 to be moved relative to the pinhole detection device 10. In other words, even if the end face of the optical fiber 30 is When placed at the focal point of the optical lens 22b, the detector 24 detects the light transmitted through the pinhole 110. The light is detected with a very sharp rise, but the time it takes to detect this rise On the other hand, the end face of the optical fiber 30 is positioned closer to the focal point of the optical lens 22b than the focal point of the optical lens 22b. When the detector 24 is placed on the side of the object 100 to be inspected, the light transmitted through the pinhole 110 is Although the rise caused by the former is smaller than that of the latter, the time to detect the rise is relatively long. Therefore, depending on the moving speed of the inspection object 100, the former arrangement (optical lens 22b Even if the pinhole 110 cannot be detected in the latter arrangement (the arrangement at the focal position of the In the latter case, the detection may be possible. In this arrangement, it is possible to increase the moving speed of the inspection object 100.

[0038] In this embodiment, the conveying device 26 is arranged in a direction perpendicular to the longitudinal direction of the light source 20 and The object 100 to be inspected is moved in a direction (indicated by an arrow 120) perpendicular to the optical axis 60 of the light source 20. This makes it suitable for use when the object 100 to be inspected is, for example, strip-shaped. In particular, when the object 100 to be inspected is stretched in the conveying direction (for example, a steel plate In the case of a material that is opaque (film, paper, etc.), tilted pinholes are likely to occur. In this form, it becomes easy to detect the pinhole 110 inclined in the conveyance direction.

[0039] In this embodiment, between the light source 20 and the detector 24, a first linear Fresnel lens 22a on the light source 20 side arranged along the longitudinal direction of the light source 20, and along the longitudinal direction of the light source 20 A second linear Fresnel lens 22b arranged on the detector 24 side with respect to the first linear Fresnel lens 22a is provided (FIG. 1). The first linear Fresnel lens 22a refracts the light 50 emitted from the light source 20 so as to become parallel light (FIG. 1). The second linear Fresnel lens 22b refracts the parallel light so that the maximum polarization angle θ1 of the light refracted by the optical lens 22b is equal to or smaller than the maximum incident angle θ2 with respect to the end face of the optical fiber 30 (FIGS. 1 and 2). Thereby, since the space between the first linear Fresnel lens 22a and the second linear Fresnel lens 22b becomes parallel light, it becomes easy to adjust the distance between both Fresnel lenses 22a and 22b.

[0040] <B. Modification Example> The present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the description in this specification. For example, the following configurations can be adopted.

[0041] [B-1. Light Source] In the above embodiment, the light source 20 is a linear light source (FIG. 1), but it may be other than a linear light source. In the above embodiment, one linear light source is used (FIG. 1), but for example, as shown in FIG. 5 of Patent Document 1 a plurality of light sources 20 may be used. In the above embodiment, the light source 20 is on the upper side and the detector 24 is on the lower side, but the reverse may be true.

[0042] [B-2. Optical Lens]​​​​​​​​​​ In the above embodiment, the first linear Fresnel lens 22a and the second linear Fresnel lens 2 2b was used (Fig. 1). However, other lenses can also be used.

[0043] [B-3. Detector] In the above embodiment, the optical fibers 30 are arranged linearly (FIG. 1). , the pinhole is formed over the entire width of the object 100 to be inspected (the length in the longitudinal direction of the light source 20). From the viewpoint of detecting 110, this is not limiting. The optical fiber 30 may be arranged in other ways, They may be offset from one another in the longitudinal direction of the light source 20 .

[0044] In the above embodiment, the end face of the optical fiber 30 facing the object 100 to be inspected is optically illuminated by the optical lens 2. 2b is positioned closer to the object 100 under inspection (FIG. 1). Depending on the transport speed of the object 100, the end face of the optical fiber 30 may be moved toward the focal point of the optical lens 22b. It may be placed in a position.

[0045] [B-4.Transportation Device] In the above embodiment, the transport device 26 is used to move the inspection object 100. 1), if attention is paid to the detection of the pinhole 110, it is possible to omit the transport device 26. do. [Explanation of symbols]

[0046] 10 pinhole detection device, 20 light source (linear light source), 22a optical lens (first linear Fresnel lens), 22b optical lens (second linear Fresnel lens), 24 detector , 26 conveying device, 30 optical fiber, 32 detecting element, 50 light, 60 optical axis, 100 Inspected object, 110 Pinhole, θ Maximum detectable angle, θ1 Maximum polarization angle, θ2 Maximum angle of incidence

Claims

1. A light source that irradiates a strip-shaped object to be inspected with light; an optical lens disposed between the light source and the object to be inspected, for converging the light emitted from the light source toward the object to be inspected; a detector that detects the light that has been converged by the optical lens toward the object to be inspected and then transmitted through a pinhole in the object to be inspected; A pinhole detection device having: the detector includes an optical fiber that propagates the light that has passed through the pinhole in the object to be inspected, When the maximum detectable angle at which the pinhole can be detected relative to the optical axis of the light source is θ, the maximum incident angle of light that can be propagated through the optical fiber relative to the optical axis of the light source is in the range of θ+0° to θ+5°, The optical lens refracts the light so that the maximum polarization angle of the light refracted by the optical lens when viewed in the longitudinal direction of the light source is equal to or smaller than the maximum incident angle with respect to the end face of the optical fiber. A pinhole detection device characterized by:

2. the light source is a linear light source that irradiates the inspection object with light in a linear shape, the optical lens converges light emitted from the light source and spreading in a direction away from the optical axis of the light source in a direction approaching the optical axis of the light source; the detector is arranged with a plurality of the optical fibers aligned opposite the light source, When the maximum polarization angle of the optical lens is θ1, the maximum polarization angle θ1 is set to be equal to or larger than the maximum detectable angle θ.

2. The pinhole detection device according to claim 1.

3. The maximum incident angle of the light that can propagate through the optical fiber and the optical axis of the light source is within the range of θ1+0° to θ1+5°.

3. The pinhole detection device according to claim 2.

4. a conveying device that moves the object to be inspected in a direction perpendicular to the longitudinal direction of the light source and in a direction orthogonal to the optical axis of the light source; The end face of the optical fiber facing the object to be inspected is positioned at the focal position of the optical lens, or is positioned closer to the object to be inspected than the focal position of the optical lens.

4. The pinhole detection device according to claim 1, wherein the pinhole detection device is a pinhole detection device.

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