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 detecting through defects with high accuracy even when the through defects are inclined with respect to the thickness direction of the 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. In order to achieve this purpose, the surface defect inspection device of Patent Document 1 inspects the object to be inspected. The inspection object and the light are detected by a light source that irradiates a surface with light and a detector that detects the amount of transmitted light of the irradiated light. An optical lens is disposed between the source and the detector to focus the light on the detector (column 3, lines 15 to 20) , Figure 1).

[0003] Patent Document 2 discloses a method for detecting pinholes that extend obliquely with respect to the surface of a sheet-like object. The purpose of the present invention is to provide a pinhole detection device for a sheet-like object 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 of Patent Document 2 The part detection device includes a laser light source and a dispersed beam detector that disperses a laser beam from the laser light source. and a sheet arranged so that the dispersed beam is incident on one side. a sheet-like object and a light-transmitting device on the other side of the sheet-like object that is sensitive to the transmitted light of the dispersed beam. The optical sensing means is a fiber optic. The photoconductor FO and the photoelectric conversion element PH are arranged in a shape similar to that of a glass substrate (see columns 4, 12 to 14, Fig. surface).

[0004] Patent Document 3 aims to provide a pinhole detection device for sheet materials with high detection accuracy. (Page 4, lines 7 to 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 penetrates the pinholes in the sheet material is captured on the other side. The light is received at the end of the optical transmission fibers arranged perpendicular to the direction of travel of the material, and the light is transmitted through the optical transmission fibers. 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 shape (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 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] In Patent Document 1, it is explained 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. In addition, in Patent Document 2, a photoconductive material such as fiber optics is used as the light-sensitive means. 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 differences (page 3, lines 16 to 20, Figures 4 to 6, etc.), the other optical transmission fibers 7 The specifications for the pinhole detection have not been considered. There is room for more.

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

[0009] The pinhole detection device according to the present invention comprises: A light source that irradiates light onto an object to be inspected; an optical lens disposed between the light source and the object to be inspected; Detecting light that is converged by the optical lens and passes through a pinhole in the object to be inspected. The detector and and The detector includes an optical fiber that transmits light transmitted through a pinhole in the object to be inspected. , If 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°. 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 entering an optical fiber. As a result, the signal / noise of the transmitted light and the ambient light is reduced. This makes it possible to improve the signal-to-noise ratio (S / N ratio) and improve the pinhole detection accuracy. According to the present invention, it is possible to suitably use the inspection object when the object is, for example, strip-shaped. The object to be inspected is stretched in the conveying direction (e.g. steel plate, light-opaque film, paper In the present invention, the 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 light linearly onto the object to be inspected. The optical lens is configured to receive light irradiated from the light source and diverge 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 angle of incidence of the light with respect to the optical axis of the light source is within the range of θ1+0° to θ1+5°. The configuration may be such that:

[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 conveying the object to be inspected in a direction parallel to the optical axis; The end face of the optical fiber is disposed at the focal position of the optical lens or is located at the focal position of the optical lens. The inspection object may be located closer to the inspection object 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 lens is placed closer to the object being inspected than the focal point of the optical lens, the pinhole detected by the detector is The rise in the light transmitted through the filter is smaller than that of the former, but the time required to detect the rise is longer. 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), In the latter case, the detection is possible. Therefore, it is possible to increase the moving speed of the object to be inspected.

[0015] In either case, criteria for determining the presence or absence of pinholes shall 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 detector is disposed between the light source and the detector along the longitudinal direction of the light source. A first linear Fresnel lens on the light source side, and a first linear Fresnel lens arranged along the longitudinal direction of the light source. and a second linear Fresnel lens disposed on the detector side relative to the a 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 a longitudinal direction of the light source. The maximum polarization angle of the light refracted by the linear Fresnel lens is the maximum 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 Since the light between them is parallel, it is easy to adjust the distance between the two Fresnel lenses. Effect 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. [Diagram 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 object 100 to be inspected. The pinhole detection device 10 includes a light source 20, optical lenses 22a and 22b, a detector 24, and a transport device 26. The detector 24 includes a plurality of optical fibers 30 and at least one detection element 32. The object 100 to be inspected is transported in the direction of the arrow 120 in FIG. 1 by the transport device 26.

[0020] (A-1-2. Light Source 20) The light source 20 irradiates the object 100 to be inspected with light 50. The light source 20 is, for example, a linear light source in which a plurality of lamps (not shown) are arranged linearly to irradiate the object 100 to be inspected with linear light.

[0021] (A-1-3. Optical Lenses 22a, 22b) As shown in FIG. 1, the optical lenses 22a and 22b are arranged between the light source 20 and the object 100 to be inspected. When viewed in the direction from the light source 20 toward the detector 24 (the downward direction in FIG. 1), At this time, the optical lenses 22a and 22b 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 a 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 arranged closer to the light source 20 than the optical lens 22b. The first linear Fresnel lens 22a is a 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 20 so as to become parallel light. a is a light refracting unit that refracts light emitted from the light source 20 and spreads 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 an aFresnel lens (hereinafter referred to as "second lens 22b" or "second lens 22b"). The second lens 22b is disposed along the longitudinal direction of the light source 20. When viewed in a 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 refracting beam 22b is the maximum incidence angle θ1 of the light 50 on the end face of the optical fiber 30. The second lens 22b refracts the parallel light to be equal to the angle θ2. 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. In this embodiment, the optical lenses 22a and 22b Since the light 50 is converged by the pinhole 110, the light 50 also passes through the pinhole 110. do.

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

[0027] As shown in the enlarged portion 34 of FIG. 1, the optical fibers 30 are aligned 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 so as to be 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 disposed at the focal position of optical lens 22b.

[0028] The detection 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 is present based on the output of the pinhole determination unit 2. The criteria for determining the pinhole 110 (signal strength, movement, etc.) are set according to the type of object 100, the transport speed, etc. The number of data items used to calculate the moving average may be configured to be switchable.

[0029] (A-1-5. Transport 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 is driven by an electric motor (not shown). The object 100 to be inspected is conveyed by a rotating roll or the like. When viewed in this direction, the conveying device 26 is arranged 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 inspection 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 to be inspected 100 is strip-shaped, and may be, for example, 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). In the case where the object 100 to be inspected is a steel plate, the width (the 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 in order 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 the maximum angle θ of the light source 20 that is the detection target 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 inclination Since the light 50 for detecting the target object is less likely to transmit, 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 possible angle is in the range of θ+0° to θ+5°. When the maximum incident angle θ2 is determined, Select the specifications of the optical fiber 30 that realizes the angle θ2. The maximum incident angle θ2 is determined by the numerical aperture (NA) and They are essentially the same 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 the optical fiber 30 that realizes the maximum incident angle θ2.

[0034] The manufacturer (designer) then sets the specifications for the light source 20 and the lenses 22a, 22b. For example, when the maximum polarization angle of the optical lens 22b is θ1 (FIG. 2), The maximum polarization angle θ1 is set so that the maximum incident angle θ2 is in 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 with respect to the optical axis 60 is θ+0° to θ +5°. In other words, the pinhole 110 relative to the optical axis 60 of the light source 20 is detected. If the maximum detectable angle is θ, the optical fiber 30 with respect 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 reliably detecting the pinhole 110 to be detected, the optical fiber 30 is prevented from receiving disturbance light (or leakage light). As a result, the signal-to-noise ratio (S / N ratio) of the transmitted light and the ambient light is It is possible to improve the detection accuracy of the pinhole 110 by increasing the light intensity.

[0036] In this embodiment, the light source 20 is a laser that irradiates the inspection object 100 with light in a linear manner. 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 object to be inspected 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 disposed closer to the object 100 than the focal position of the optical lens 22b. In this way, the inspection object 100 may be moved relative to the pinhole detection device 10. In other words, even if the end face of the optical fiber 30 is When the detector 24 is placed at the focal position of the optical lens 22b, the light transmitted through the pinhole 110 is The light is detected with a very sharp onset, but the time it takes to detect the onset On the other hand, the end face of the optical fiber 30 is located closer to the focal position of the optical lens 22b than the focal position of the optical lens 22b. When the detector 24 is placed on the side of the object to be inspected 100, the light transmitted through the pinhole 110 is Although the rise caused by the first is smaller than that of the second, 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 (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 perpendicular to the optical axis 60 of the light source 20 (in the direction of the arrow 120). This makes it possible to suitably use the test object 100 when it is, for example, strip-shaped. In particular, when the object 100 to be inspected is elongated in the conveying direction (e.g., a steel plate In the case of a material that does not transmit light (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 a second linear Fresnel lens 22b arranged on the detector 24 side with respect to the first linear Fresnel lens 22a are provided along the longitudinal direction of the light source 20 (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 light 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. 置された光源20側の第1リニアフレネルレンズ22aと、光源20の長手方向に沿って 、第1リニアフレネルレンズ22aよりも検出器24側に配置された第2リニアフレネル レンズ22bとが設けられる(図1)。第1リニアフレネルレンズ22aは、光源20か ら出射された光50を平行光になるように屈折させる(図1)。第2リニアフレネルレン ズ22bは、光学レンズ22bにより屈折した光の最大偏光角θ1が、光学繊維30の端 面に対する最大入射角θ2と同等になる又は最大入射角θ2よりも小さくなるように平行 光を屈折させる(図1及び図2)。これにより、第1リニアフレネルレンズ22aと第2 リニアフレネルレンズ22bの間は平行光となるため、両フレネルレンズ22a、22b 間の距離調整が容易となる。

[0040] <B. Modification Example> Note that the present invention is not limited to the above embodiment, and various configurations can of course be adopted based on the description in this specification. For example, the following configurations can be adopted. 採り得ることはもちろんである。例えば、以下の構成を採用することができる。

[0041] [B-1. Light Source] In the above embodiment, the light source 20 was a linear light source (FIG. 1), but it may be other than a linear light source. In the above embodiment, one linear light source was used (FIG. 1), but for example, a plurality of light sources 20 may be used as shown in FIG. 5 of Patent Document 1. In the above embodiment, the light source 20 was on the upper side and the detector 24 was on the lower side, but the reverse may be true. てもよい。上記実施形態では、1つのリニア光源を用いたが(図1)、例えば特許文献1 の第5図のように複数の光源20を用いてもよい。上記実施形態では、光源20が上側、 検出器24が下側であったが、逆であってもよい。

[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 (Figure 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 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 limited to this. The optical fiber 30 may be arranged in other ways. They may be offset from one another along the length 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. The focal position of the target object 100 is closer to the target object 100 than the focal position of the target object 2b (FIG. 1). Depending on the transport speed of the object 100, the end face of the optical fiber 30 may be brought into contact with the focal point of the optical lens 22b. It may be placed in the position.

[0045] [B-4.Transportation device] In the above embodiment, the transport device 26 is used to move the inspection object 100. In FIG. 1, if attention is paid to the detection of the pinhole 110, it is possible not to provide the conveying device 26. do. [Explanation of symbols]

[0046] 10 pinhole detection device, 20 light source (linear light source), 22a optical lens (first linear a 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 incident angle

Claims

1. A light source that irradiates light onto an object to be inspected; an optical lens disposed between the light source and the object to be inspected; Detecting light that is converged by the optical lens and passes through a pinhole in the object to be inspected. The detector and A pinhole detection device having The detector includes an optical fiber that transmits light transmitted through a pinhole in the object to be inspected. 、 If 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 A pinhole detection device comprising:

2. the light source is a linear light source that irradiates the object to be inspected with light in a linear shape, The optical lens divides the light emitted from the light source and spreading in a direction away from the optical axis of the light source into Converging in a direction approaching the optical axis of the light source; The detector has a plurality of the optical fibers arranged side by side facing the light source, When the maximum polarization angle of the optical lens is θ1, the maximum polarization angle θ1 is the maximum detectable Set the angle to θ or more.

2. The pinhole detection device according to claim 1.

3. The maximum incident angle of the light that can be propagated through the optical fiber with respect to the optical axis of the light source is θ1+0° to Included in the range of θ1+5° 3. The pinhole detection device according to claim 2.

4. The light source is arranged in a 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 inspection object is provided. The end face of the optical fiber facing the object to be inspected is disposed at the focal position of the optical lens. or is disposed 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 is a hole that is formed in the pinhole.

5. Between the light source and the detector: a first linear Fresnel lens disposed on the light source side along a longitudinal direction of the light source; Along the longitudinal direction of the light source, the first linear Fresnel lens is closer to the detector. a second linear Fresnel lens disposed; was established, The first linear Fresnel lens bends the light emitted from the light source to form parallel light. Fold it, The second linear Fresnel lens has a second linear fresnel lens when viewed in a longitudinal direction of the light source. The maximum polarization angle of the light refracted by the Lens is the maximum incident angle with respect to the end face of the optical fiber. or to be smaller than the maximum incidence angle.

5. The pinhole detection device according to claim 1, wherein the pinhole is a hole that is formed in the pinhole.

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