JP2007171137A - Pinhole detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pinhole detector capable of accurately detecting pinholes. <P>SOLUTION: An optical fiber bundle 3 comprises a fiber group 31 including optical fibers 3a-3f, a fiber group 32 including optical fibers 3g-3m, and a fiber group 33 including optical fibers 3n-3s. One end face sides of the fiber groups 31, 32, 33 are arrayed linearly, to be attached to a light-receiving member 2. The other end face sides of the fiber groups 31, 32, 33 are bundled to form a bundled state into a circle 34. The plurality of optical fibers included in the respective fiber groups 31, 32, 33 are bundled regularly to disperse positions of the plurality of optical fibers, without being one-sided intensively within the circle 34, in the other end face sides of the fiber groups 31, 32, 33, i.e. the attaching side of a Frensnel lens. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pinhole detection device that detects a pinhole of a sheet-like object.

  Conventionally, a pinhole detection device has been used to detect pinholes existing in a sheet-like object made of, for example, a metal foil, an iron plate, or a film (see, for example, Patent Document 1). A pinhole means a minute hole having a diameter of about 1000 μm or less.

This pinhole detection device includes a linear light source including a fluorescent lamp, a linear light guide, or a light emitting diode (LED) arranged in a linear form, and a pinhole of a sheet-like object emitted from the linear light source. And a photomultiplier tube that converges light from the line light guide and photoelectrically converts the light. And the presence or absence of a pinhole is determined from the output voltage of the photomultiplier tube.
Japanese Patent Laid-Open No. 2-107951 Japanese Patent Laid-Open No. 9-292550

The photomultiplier tube has an incident window for receiving light from the line light guide. In general, borosilicate glass, ultraviolet transmissive glass, synthetic quartz, magnesium fluoride (MgF ₂ ) crystal, or the like is used as the material of the entrance window.

  The photomultiplier tube is provided with a photocathode (cathode) that converts light from the incident window into electrons. As a material for the photocathode, a compound semiconductor (GaAs or the like) whose main component is an alkali metal having a low work function is used.

  However, the light receiving accuracy has been lowered due to the characteristics of the material of the photocathode as described above or the sensitivity unevenness of the photocathode. As a result, it may be difficult to accurately determine the presence or absence of pinholes.

  The objective of this invention is providing the pinhole detection apparatus which can detect a pinhole correctly.

  A pinhole detection apparatus according to the present invention is a pinhole detection apparatus that detects a pinhole of an inspection object, and is configured to face a linear light source that irradiates light to the inspection object and the linear light source through the inspection object. A light receiving means having one end face disposed on the other end face and a light receiving area opposite to the other end face of the light receiving means, a conversion means for converting light from the light receiving means into an electrical signal, and a conversion means. Determining means for determining the presence / absence of a pinhole in the inspection object based on a predetermined electrical value and a predetermined reference value, and the light receiving means includes a plurality of fiber groups each including a plurality of optical fibers. A plurality of optical fibers included in each of the plurality of fiber groups are arranged linearly on the end face, and the plurality of optical fibers are arranged in the other end face so as to be dispersed without being concentrated in a concentrated manner. It is those that are bundled in Thailand.

  In the pinhole detection device according to the present invention, light is irradiated onto the inspection object by the linear light source. One end surface of the light receiving means is disposed so as to face the linear light source through the inspection object. The converting means has a light receiving area facing the other end face of the light receiving means. The light from the light receiving means is converted into an electric signal by the converting means. Further, the presence or absence of a pinhole in the inspection object is determined by the determination unit based on the electric signal obtained by the conversion unit and a predetermined reference value. Further, the light receiving means includes a plurality of fiber groups each consisting of a plurality of optical fibers.

  In such a configuration, a plurality of optical fibers included in each of the plurality of fiber groups are linearly arranged on one end surface of the light receiving unit, and a plurality of optical fibers are concentrated on each fiber group on the other end surface of the light receiving unit. By being bundled in a state of being distributed and arranged without being biased, it is possible to obtain an electric signal having a constant property that does not affect the sensitivity unevenness of the light receiving region of the conversion means. Thus, not only the presence / absence of a pinhole but also a pinhole having a desired size can be accurately detected by predetermining a reference value based on the size (diameter) of the pinhole. .

  The pinhole detection device further includes a light collecting means provided between the other end face of the light receiving means and the converting means, and the light collecting means is an area smaller than the light receiving area of the converting means and excluding the outer peripheral portion in the light receiving area. The light from the light receiving means may be condensed.

  In this way, the light is condensed by the condensing means on the area smaller than the light receiving area of the converting means and excluding the outer peripheral portion in the light receiving area, thereby affecting the sensitivity unevenness of the outer peripheral portion of the light receiving area of the converting means. Can be removed. Thereby, an electric signal having a certain property can be obtained, and a pinhole having a desired size can be detected more accurately.

  The light collecting means may include a Fresnel lens. In this case, the light condensing property can be improved efficiently.

  The determination means may include setting means for setting an arbitrary reference value, and comparison means for comparing the electrical signal obtained by the conversion means with the reference value set by the setting means and outputting a comparison result. .

  In this case, an arbitrary reference value is set by the setting means. Then, the electrical signal obtained by the conversion means and the reference value set by the setting means are compared by the comparison means, and the comparison result is output by the comparison means. Therefore, a desired reference value can be set by the setting means, and a comparison result between the set desired reference value and the electric signal can be obtained.

  The conversion means may include a photomultiplier tube. In this case, the light from the light receiving means is accurately converted into an electric signal by the photomultiplier tube.

  According to the pinhole detection device of the present invention, it is possible to accurately detect a pinhole.

  Hereinafter, the pinhole detection apparatus according to the present embodiment will be described with reference to the drawings.

(1) Overall Configuration Including Pinhole Detection Device FIG. 1 is a block diagram showing a pinhole detection system including a pinhole detection device.

  As shown in FIG. 1, the pinhole detection system includes a pinhole detection device 100 including a linear light source 1, a light receiver 20 and a control unit 50, an inverter I, an input device 51, a display device 52, and a printing device 53. .

  The linear light source 1 is lit at a high frequency by the inverter I based on the control of the control unit 50. The light generated by the linear light source 1 is applied to the inspection object W.

  The light receiver 20 receives light transmitted through a pinhole (not shown) existing in the inspection object W, converts the received light into an electric signal, and outputs the electric signal to the control unit 50.

  The control unit 50 includes an amplifier, a comparator, an output circuit, a display unit, and the like. The control unit 50 controls each component, and outputs an electrical signal output from the light receiver 20 and a preset reference voltage (threshold value). The presence or absence of a pinhole is determined by comparison.

  The input device 51 includes a keyboard and a mouse, and is used for inputting various commands and data.

  The display device 52 includes a liquid crystal display panel, a CRT (cathode ray tube), or the like, and displays various information, images, and the like. The printing device 53 prints information related to pinholes.

  FIG. 2 is a schematic diagram showing the pinhole detection apparatus 100 according to the present embodiment.

  As shown in FIG. 2, the pinhole detection device 100 according to the present embodiment includes a linear light source 1 and a light receiving member 2 made of, for example, a fluorescent lamp, a linear light guide, a plurality of light emitting diodes (LEDs), or a sodium lamp. , Optical fiber bundle 3, Fresnel lens 4, and photomultiplier tube 5. The light receiving member 2, the optical fiber bundle 3, the Fresnel lens 4, and the photomultiplier tube 5 constitute the light receiver 20 of FIG. In FIG. 2, illustration of the control unit 50 constituting the pinhole detection device 100 is omitted.

  The light emitted from the linear light source 1 is applied to the inspection object W, which is a sheet-like opaque body made of, for example, a metal foil, an iron plate, or a film. The light receiving member 2 receives light transmitted through a pinhole (not shown) existing in the inspection object W. When the inspection object W has no pinhole, the light emitted from the linear light source 1 is blocked by the inspection object, so that the light does not reach the light receiving member 2.

  Here, the light receiving member 2 has a light receiving surface 2a constituted by one end face of an optical fiber bundle 3 composed of a plurality of optical fibers. That is, the light receiving member 2 is for forming a linear light receiving surface 2a by linearly arranging end faces of a plurality of optical fibers. Details of the configuration of the optical fiber bundle 3 in the present embodiment will be described later.

  In such a configuration, the light received by the light receiving surface 2 a of the light receiving member 2 is guided to the Fresnel lens 4 by the optical fiber bundle 3.

  The other end face of the optical fiber bundle 3 is attached so as to be in close contact with the Fresnel lens 4. Details of the Fresnel lens 4 will be described later.

  Further, a photomultiplier tube 5 as a light receiving element is attached to the Fresnel lens 4. Details of the configuration of the photomultiplier tube 5 will be described later.

  In such a configuration, the light guided by the optical fiber bundle 3 is collected by the Fresnel lens 4 and guided to the photomultiplier tube 5.

(2) Configuration of Fresnel Lens Next, the configuration of the Fresnel lens 4 will be described with reference to the drawings. The Fresnel lens 4 is for condensing light.

  FIG. 3 is a schematic diagram showing the configurations of the normal spherical lens 40 and the Fresnel lens 4.

  As shown in FIG. 3A, the spherical lens 40 as a condenser lens has a spherical surface 40a and a back surface 40b opposite to the spherical surface 40a.

  As shown in FIG. 3B, the Fresnel lens 4 is formed in a thin plate shape, and has a plurality of annular convex portions 4a and a back surface 4b facing these.

  In the spherical lens 40, the light incident on the spherical surface 40a is refracted by the spherical surface 40a. This refracted light travels straight through the spherical lens 40 and is refracted again at the back surface 40b when it is emitted out of the spherical lens 40.

  On the other hand, in the Fresnel lens 4, the light respectively incident on the plurality of convex portions 4a is refracted by the convex portions 4a and then emitted from the back surface 4b.

  As described above, in the Fresnel lens 4, the portion where the light goes straight through the inside is relatively small as compared with the spherical lens 40. As a result, the Fresnel lens 4 has a light condensing effect and has a shape similar to a flat lens, thereby realizing a reduction in weight and size.

  The Fresnel lens 4 is made of, for example, glass or plastic including acrylic resin, polycarbonate, and high density polyethylene. When the Fresnel lens 4 is made of plastic, the specific gravity of the plastic is 1/2 or less that of glass, so that the weight can be significantly reduced and the impact resistance and the like can be improved.

(3) Configuration of Photomultiplier Tube Next, the configuration of the photomultiplier tube 5 will be described with reference to the drawings.

  FIG. 4 is a schematic diagram showing the configuration of the photomultiplier tube 5.

  As shown in FIG. 4, the photomultiplier tube 5 includes an incident window 61, a photocathode (cathode) 62, a focusing electrode 63, an electron multiplier (dynode) 64, an anode 65, a stem pin 66, and a container having a tubular structure. K is included.

The container K houses a photocathode 62, a focusing electrode 63, an electron multiplier (dynode) 64, and an anode 65. Note that the inside of the container K is in a vacuum state of 10 ⁻⁴ Pa or less.

  An incident window 61 through which light enters is formed on one end surface of the container K, and a plurality of stem pins 66 are attached to the other end surface.

  Light incident from the incident window 61 is converted into photoelectrons by the photocathode 62 provided in the photomultiplier tube 5.

  Photoelectrons are emitted from the photocathode 62 into the vacuum in the container K. The emitted photoelectrons are guided to the electron multiplier 64 by the focusing electrode 63.

The photoelectrons guided to the electron multiplier 64 are multiplied by about 10 ⁴ to 10 ⁵ times by the electron multiplier 64. In other words, secondary electrons are emitted from the electron multiplying unit 64 to multiply photoelectrons.

  The multiplied photoelectrons are collected at the anode 65. Then, a current corresponding to the amount of photoelectrons is supplied from the anode 65 to the control unit 50.

  In the controller 50, the amplifier converts the current supplied from the photomultiplier tube 5 into a voltage, and the comparator compares the output voltage of the amplifier with a predetermined reference voltage (threshold). Determine the presence or absence of pinholes. The determination result is output from the output circuit of the control unit 50 as a binarized signal.

  Any one or a plurality of reference voltages can be set in the control unit 50 using the input device 51 of FIG.

  Thus, since photoelectron multiplication is performed by the emission of secondary electrons, the photomultiplier tube 5 is a light receiving element used for measurement of ultraviolet light, visible light, near infrared light, etc. It has outstanding sensitivity characteristics and low noise.

(4) Configuration of Optical Fiber Bundle Next, the configuration of the optical fiber bundle 3 of the pinhole detection device 100 according to the present embodiment will be described with reference to the drawings.

  FIG. 5 is a schematic diagram showing the configuration of the optical fiber bundle 3 of the pinhole detection device 100.

  As shown in FIG. 5, the optical fiber bundle 3 includes a fiber group 31 including optical fibers 3a to 3f, a fiber group 32 including optical fibers 3g to 3m, and a fiber group 33 including optical fibers 3n to 3s.

  One end surfaces of these fiber groups 31, 32, and 33 are linearly arranged and attached to the light receiving member 2.

  Further, the other end surfaces of the fiber groups 31, 32, and 33 are bundled so that the converged state is a circle 34. Thus, the light transmission efficiency is improved by setting the convergence form of the fiber groups 31, 32, and 33 to the circle 34 corresponding to the circular shape of the Fresnel lens 4.

  Here, in the present embodiment, the positions of the plurality of optical fibers included in each of the fiber groups 31, 32, 33 are on the other end face side of the fiber groups 31, 32, 33, that is, on the attachment side of the Fresnel lens 4. In the circle 34, a plurality of optical fibers are regularly bundled so as to be distributed without being concentrated in a concentrated manner.

  In FIG. 5, for example, the optical fibers 3 a to 3 f constituting the fiber group 31 are indicated by A to F for convenience, and the A to F are dispersed and arranged in a circle 34 on the attachment side of the Fresnel lens 4. I understand that.

  In the present embodiment, the optical fiber bundle 3 is arranged so that the Fresnel lens 4 collects the light emitted from the other end face of the optical fiber bundle 3 in a region excluding the outer peripheral portion in the photocathode 62 of the photomultiplier tube 5. A Fresnel lens 4 and a photomultiplier tube 5 are arranged. Thereby, it is possible to remove the influence of sensitivity unevenness on the outer peripheral portion of the photocathode 62 of the photomultiplier tube 5.

(5) Effects in the present embodiment In the present embodiment, the optical fibers included in the fiber groups 31, 32, 33 on the attachment side of the Fresnel lens 4 of the fiber groups 31, 32, 33 in the optical fiber bundle 3. Each optical fiber is regularly bundled so that the positions 3a to 3s are dispersedly arranged in the circle 34 without being intensively biased.

  Generally, the photosensitivity 62 of the photomultiplier tube 5 has uneven sensitivity of light reception. In particular, a significant decrease in sensitivity characteristics is confirmed at the outer peripheral portion (peripheral portion) of the photocathode 62.

  Even when such a photocathode 62 is used, by using the optical fiber bundle 3 as described above, it is possible to obtain an output voltage having a constant property that does not affect the sensitivity unevenness of the photocathode 62. As a result, not only the presence / absence of a pinhole is detected, but a reference voltage (threshold) is determined in advance based on the size (diameter) of the pinhole, so that a pinhole having a desired size can be accurately determined. Can be detected.

(6) Correspondence between each component of claim and each part of embodiment The following describes an example of a correspondence between each component of the claim and each part of the embodiment. It is not limited.

  In the present embodiment, the light receiving member 2 and the optical fiber bundle 3 correspond to light receiving means, the photomultiplier tube 5 corresponds to conversion means, the control unit 50 corresponds to determination means and comparison means, and the Fresnel lens 4 Corresponds to the light condensing means, the input device 51 corresponds to the setting means, and the incident window 61 and the photocathode 62 correspond to the light receiving area of the converting means.

(A) Example In the following example, the same pinhole detection apparatus 100 as that in the above embodiment was manufactured. And the sensitivity distribution of the output voltage by the pinhole which exists in the test | inspection object W was investigated using the produced pinhole detection apparatus 100. FIG.

  The inspection object W was previously provided with a plurality of pin holes having a diameter of 1000 μm at predetermined intervals in the length direction of the light receiving surface 2a.

  In this example, similarly to the above, a diameter of 800 μm, a diameter of 500 μm, a diameter of 400 μm, a diameter of 300 μm, and a diameter of 200 μm were previously provided.

  FIG. 6 is a graph showing the sensitivity distribution of pinholes by the pinhole detection device 100 of the example.

  The vertical axis in FIG. 6 indicates the output voltage (V), and the horizontal axis indicates the position on the inspection object W in the length direction of the light receiving surface 2a.

  In FIG. 6, the output voltage when a 1000 μm diameter pinhole is detected is indicated by a white circle (◯), the output voltage when an 800 μm diameter pinhole is detected is indicated by a white triangle (Δ), and the output voltage is 500 μm. The output voltage when a pinhole is detected is indicated by a white square (□), the output voltage when a pinhole with a diameter of 400 μm is detected is indicated with a black triangle (▲), and the output when a pinhole with a diameter of 300 μm is detected The voltage is indicated by a black square (■), and the output voltage when a pinhole having a diameter of 200 μm is detected is indicated by a black rhombus (♦).

  As shown in FIG. 6, the output voltage was almost constant in the pinholes having any diameter.

(B) Comparative Example The pinhole detection device of the comparative example is different from the pinhole detection device 100 of the above embodiment in that the configuration of the optical fiber bundle is different. Hereinafter, description will be given with reference to the drawings.

  FIG. 7 is a schematic diagram showing the configuration of the optical fiber bundle 30 in the pinhole detection device of the comparative example.

  As shown in FIG. 7, the optical fiber bundle 30 of the comparative example is similar to the optical fiber bundle 3 of the embodiment, the fiber group 31 including the optical fibers 3a to 3f, the fiber group 32 including the optical fibers 3g to 3m, and It consists of the fiber group 33 containing the optical fibers 3n-3s.

  One end surfaces of these fiber groups 31, 32, and 33 are linearly arranged and attached to the light receiving member 2. Further, the other end surfaces of the fiber groups 31, 32, and 33 are bundled so that the converged state is a circle 34.

  Here, in this comparative example, the positions of the plurality of optical fibers included in each of the fiber groups 31, 32, and 33 on the other end surface side of the fiber groups 31, 32, and 33, that is, on the attachment side of the Fresnel lens 4, are as follows. In the circle 34, a plurality of optical fibers are regularly bundled so as to be intensively arranged for each fiber group.

  In FIG. 7, for example, the optical fibers 3 a to 3 f constituting the fiber group 31 are indicated by A to F for convenience, and the A to F are concentrated on a predetermined region in the circle 34 on the attachment side of the Fresnel lens 4. It can be seen that they are arranged in a biased manner.

  Then, the pinhole detection apparatus of the comparative example was produced using said optical fiber bundle 30. FIG. Then, using the produced pinhole detection device, the sensitivity distribution of the output voltage due to the pinholes present in the inspection object W was investigated in the same manner as in the above example.

  The inspection object W was previously provided with a plurality of pin holes having a diameter of 1000 μm at predetermined intervals in the length direction of the light receiving surface 2a.

  In this example, similarly to the above, a diameter of 800 μm, a diameter of 500 μm, a diameter of 400 μm, a diameter of 300 μm, and a diameter of 200 μm were previously provided.

  FIG. 8 is a graph showing the sensitivity distribution of pinholes by the pinhole detection device of the comparative example.

  The vertical axis in FIG. 8 indicates the output voltage (V), and the horizontal axis indicates the position on the inspection object W in the length direction of the light receiving surface 2a.

  Similarly to FIG. 6, in FIG. 8, the output voltage when a pinhole having a diameter of 1000 μm is detected is indicated by a white circle (◯), and the output voltage when a pinhole having a diameter of 800 μm is detected is indicated by a white triangle (Δ ), The output voltage when a pinhole with a diameter of 500 μm is detected is indicated by a white square (□), the output voltage when a pinhole with a diameter of 400 μm is detected is indicated by a black triangle (▲), and a pin with a diameter of 300 μm The output voltage when a hole is detected is indicated by a black square (■), and the output voltage when a pinhole having a diameter of 200 μm is detected is indicated by a black diamond (♦).

  As shown in FIG. 8, as the diameter of the pinhole increases, the output voltage becomes inconsistent and disturbance occurs.

(C) Comprehensive evaluation (c-1) Evaluation of the embodiment A plurality of optical fibers included in each fiber group are arranged so that the positions of the plurality of optical fibers are distributed without being concentrated in the circle 34 of FIG. By using the optical fiber bundle 3 in which the optical fibers are regularly bundled, it was confirmed that the light was dispersed and guided to the photomultiplier tube 5. As a result, it was possible to obtain a constant output voltage for pinholes having the same diameter.

(C-2) Evaluation of Comparative Example Each optical fiber is bundled regularly so that the position of each optical fiber included in each fiber group is intensively arranged for each fiber group in the circle 34 of FIG. Due to the use of the optical fiber bundle 30, the sensitivity variation occurs on the photocathode 62 of the photomultiplier tube 5, resulting in variations in output voltage for pinholes having the same diameter.

  In FIG. 8, a drop in the output voltage was confirmed at a position of 200 mm on the inspection object W.

  This is because when the transmitted light that has passed through the pinhole located at the position of 200 mm is guided to one or a plurality of optical fibers in the optical fiber bundle 30 and then guided to the photomultiplier tube 5, the photocathode 62 This is because the one or more optical fibers are intensively arranged in a region where the sensitivity unevenness occurs.

(C-3) Summary It was found that by using the optical fiber bundle 3 of the example, an output voltage having a constant property that does not affect the sensitivity unevenness of the photocathode 62 can be obtained. As a result, not only the presence / absence of a pinhole, but also a pinhole having a desired size (diameter) can be accurately detected by arbitrarily setting a reference voltage (threshold). all right.

  The present invention can be used to determine the presence or absence of an object to be detected by light in addition to a pinhole detection device.

It is a block diagram which shows the pinhole detection system containing a pinhole detection apparatus. It is a schematic diagram which shows the pinhole detection apparatus which concerns on this Embodiment. It is a schematic diagram which shows the structure of a normal lens and a Fresnel lens, respectively. It is a schematic diagram which shows the structure of a photomultiplier tube. It is a schematic diagram which shows the structure of the optical fiber bundle of a pinhole detection apparatus. It is a graph which shows the sensitivity distribution of the pinhole by the pinhole detection apparatus of an Example. It is a schematic diagram which shows the structure of the optical fiber bundle in the pinhole detection apparatus of a comparative example. It is a graph which shows the sensitivity distribution of the pinhole by the pinhole detection apparatus of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Linear light source 2 Light receiving member 2a Light receiving surface 3 Optical fiber bundle 3a-3s Optical fiber 4 Fresnel lens 4a Convex part 5 Photomultiplier tube 20 Light receiver 31, 32, 33 Fiber group 50 Control part 51 Input apparatus 52 Display apparatus 53 Printing device 61 Entrance window 62 Photocathode (cathode)
64 Electron multiplier (dynode)
100 Pinhole detector W Inspection object

Claims (5)

A pinhole detection device for detecting a pinhole of an inspection object,
A linear light source that irradiates the inspection object with light;
A light receiving means having one end face arranged to face the linear light source via an inspection object and having the other end face;
A light-receiving region facing the other end surface of the light-receiving means, and conversion means for converting light from the light-receiving means into an electrical signal;
Determination means for determining the presence or absence of a pinhole in the inspection object based on an electrical signal obtained by the conversion means and a predetermined reference value;
The light receiving means includes a plurality of fiber groups each consisting of a plurality of optical fibers,
A plurality of optical fibers included in each of the plurality of fiber groups are linearly arranged on the one end face, and the plurality of optical fibers are dispersed and arranged in the other end face for each of the fiber groups without being intensively biased. Pinhole detection device, characterized in that it is bundled in a state where it is formed. A light collecting means provided between the other end face of the light receiving means and the converting means;
2. The pinhole detection device according to claim 1, wherein the condensing unit condenses light from the light receiving unit in a region smaller than the light receiving region of the converting unit and excluding the outer peripheral portion in the light receiving region. . The pinhole detection device according to claim 2, wherein the condensing unit includes a Fresnel lens. The determination means includes
Setting means for setting an arbitrary reference value;
4. The pin according to claim 1, further comprising a comparison unit that compares an electrical signal obtained by the conversion unit with a reference value set by the setting unit and outputs a comparison result. 5. Hall detection device. The pinhole detection device according to claim 1, wherein the conversion unit includes a photomultiplier tube.

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