X-ray inspection device and X-ray inspection method

Abstract

An X-ray inspection device according to the present invention comprises: an X-ray emission device for emitting X-rays toward a measurement object; a scintillator for converting, into visible light, X-rays emitted from the X-ray emission device and incident through the object to be measured; and the shooting device is provided with an optical component for condensing the visible light irradiated by the scintillator, and the shooting device is used for receiving the visible light. The X-ray radiation device and the scintillator are set so that the following formula (1) is 30 [mu] m or less, where L1 [mm] is the distance from the radiation position of the X-ray radiation device to the installation position or conveyance position of the object to be measured, L2 [mm] is the distance from the radiation position to the scintillator, and R [mu] m is the focal diameter of the X-ray radiation device. Formula (1): (L2-L1*R / L1

Description

Technical Field

[0001] The present invention relates to an X-ray inspection device and an X-ray inspection method. Background Art

[0002] X-ray inspection is generally used as an inspection method using radiation and is applied to a wide range of fields such as medicine, food, and industry. In the industrial field, X-rays are irradiated to products, etc., and the X-rays that pass through the products are imaged to visualize the surface and inside of the products, thereby inspecting foreign matter or defective parts.

[0003] In recent years, for example, in the battery industry, there has been a strong demand to prevent metallic foreign matter from entering products, and metal inspection using X-rays has become increasingly common. Figure 8 The following describes conventional X-ray inspection. Figure 8 Schematic diagram of an example of a conventional X-ray inspection device. The X-ray inspection device 1 generally includes an X-ray radiating device 2 and an imaging device 3, and checks whether there is no metal foreign matter or the like mixed in the measurement object 10. The X-ray radiating device 2 radiates X-rays to the measurement object 10, and the imaging device 3 receives the X-rays transmitted through the measurement object 10. At this time, if a metal foreign matter 11 is mixed in the measurement object 10, the X-rays are absorbed in the said part and become a shadow, and the X-rays do not enter the corresponding part of the imaging device 3. The imaging device 3 includes: a scintillator 31, which generates fluorescence light based on the amount of incident X-rays and emits visible light; and a sensor 32, which receives the visible light emitted by the scintillator 31. The scintillator 31 in the part where the X-rays are incident generates fluorescence light and emits visible light, and the sensor 32 receives the visible light. Since the part where the metal foreign matter 11 is a shadow does not cause the scintillator 31 to generate fluorescence light, as a result, a dark signal is formed in the sensor 32. Based on the signal, it is determined whether there is a metal foreign matter 11 mixed in the measurement object 10.

[0004] In the past, the size of metal foreign matter to be inspected was large, but due to the increasing safety requirements for battery applications, the size of the inspection object, which was originally around 200μm, has gradually been reduced to less than 50μm. Fig. 9 The following describes how to deal with tiny metal foreign matter during conventional X-ray inspections. Fig. 9 This is a schematic diagram showing the use of conventional X-ray inspection equipment to inspect tiny metal foreign matter. Fig. 9 As shown in FIG. 1 , the distance from the measuring object 10 to the imaging device 3 is increased, and the shadow formed by the tiny metal foreign matter 11a in the measuring object 10 is geometrically enlarged. As a result, the corresponding part in the imaging device 3 is enlarged, and the detection in the sensor 32 is stabilized. However, it is known that the above method has low detection sensitivity for tiny metal foreign matter. Fig.10 Let's explain this. Fig.10This is an illustration of blur (penumbra) in X-ray inspection. X-rays are emitted from the X-ray radiating device 2, but the radiation area has a limited width (focal diameter). Especially when the metal foreign body to be inspected becomes smaller, it becomes impossible to ignore it. Fig.10 As shown, X-rays enter the area that should be the shadow of the metal foreign matter 11a, and generate blur (penumbra) 12. In the area corresponding to the blur 12, the dark signal intensity of the sensor 32 is weakened, so the metal foreign matter 11a cannot be detected with high accuracy.

[0005] As a means to solve the above problem, there is, for example, Patent Document 1. In Patent Document 1, in order to eliminate the blur 12, the scintillator 31 is brought close to the measurement object 10. The blur 12 is reduced by bringing it close. In addition, the image resolution on the scintillator is improved by using a visible light camera (and lens) as the sensor 32. These measures make it possible to detect tiny metal foreign matter.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2019-215205 Summary of the invention

[0009] Problems to be solved by the invention

[0010] However, in reality, it is difficult to make the interval between the measured object and the scintillator approximately zero as in Patent Document 1, and a certain distance must be ensured. In particular, when the measured object is being transported, a certain degree of distance must be ensured. Moreover, when, for example, a telecentric lens is used, the degree of freedom in adjusting the resolution for shooting becomes higher. If it is adjusted too small, such as below 4 μm, the range that can be shot becomes narrower, and in order to achieve the required inspection format, multiple shooting devices are required. Furthermore, if the shooting resolution is too small, it may sometimes become impossible to perform a stable inspection due to unevenness in the amount of X-rays emitted from the X-ray radiation device 2 or deviations in the fluorescent light emission of the scintillator 31.

[0011] The present invention provides an X-ray inspection device and an X-ray inspection method, which can naturally be applied to stationary measurement objects and can also be applied to measurement objects being transported. It can reduce the blurring effect caused by the limited width of the focal point diameter of the X-ray radiation device, thereby inspecting tiny metal foreign matter.

[0012] Technical means of solving problems

[0013] [1] The X-ray inspection device of the present invention for solving the above-mentioned problem comprises: an X-ray radiating device for radiating X-rays toward a measurement object; a scintillator for converting X-rays radiated from the X-ray radiating device and incident through the measurement object into visible light; and a photographing device having an optical component for focusing the visible light irradiated by the scintillator, the photographing device being used to receive the visible light, and assuming that the distance from the radiating position of the X-ray radiating device to the setting position or the conveying position of the measurement object is L1 [mm], the distance from the radiating position to the scintillator is L2 [mm], and the focal diameter of the X-ray radiating device is R [μm], and the X-ray radiating device and the scintillator are arranged so that the following formula (1) becomes less than 30 μm.

[0014] Formula (1): (L2-L1)×R / L1.

[0015] The X-ray inspection apparatus of the present invention is preferably any one of the following [2] to [8].

[0016] [2] According to the X-ray inspection device of [1], the imaging device has an imaging resolution of 60 μm or less when imaging the scintillator.

[0017] [3] The X-ray inspection device according to [1] or [2], wherein the imaging device is configured to image a surface of the scintillator that faces the measurement object.

[0018] [4] According to the X-ray inspection device of [3], a light-transmitting object is set as the measurement object, and the imaging device is configured to image the surface of the scintillator facing the measurement object through the measurement object.

[0019] [5] An X-ray inspection device according to [1] or [2], wherein the imaging device is configured to image a surface of the scintillator that is opposite to a surface facing the measurement object.

[0020] [6] An X-ray inspection device according to any one of [1] to [5], wherein the imaging device is a line sensor camera or a time-delay integration camera.

[0021] [7] According to the X-ray inspection device of [3] or [4], wherein the imaging device is a line sensor camera or a time-delayed integration camera, a component is provided between the setting position or conveying position of the measurement object and the scintillator to shield the X-rays incident on the scintillator except for at least the imaging area of ​​the scintillator photographed by the imaging device.

[0022] [8] According to the X-ray inspection device of [5], wherein the imaging device is a line sensor camera or a time-delayed integration camera, a component is provided between the setting position or conveying position of the measuring object and the scintillator for shielding the X-rays incident on the scintillator except for at least the following area, wherein the area is an area within the surface of the scintillator facing the measuring object and is an area on the opposite side of the imaging area of ​​the scintillator that is separated from the scintillator by the imaging device.

[0023] [9] The X-ray inspection method of the present invention for solving the above-mentioned problem radiates X-rays toward a measurement object, causes the radiated X-rays to enter a scintillator via the measurement object, converts the radiated X-rays into visible light by the scintillator, and focuses and photographs the visible light irradiated by the scintillator by an optical component, wherein, with respect to the radiation position of the X-rays and the position of the scintillator, the distance from the radiation position of the X-rays to the measurement object is L1 [mm], the distance from the radiation position to the scintillator is L2 [mm], and the focal diameter of the X-rays at the radiation position of the X-rays is R [μm], so that the following formula (1) becomes less than one sixth of the minimum diameter of the defect to be detected specified for each of the measurement objects.

[0024] Formula (1): (L2-L1)×R / L1.

[0025] The X-ray inspection method of the present invention is preferably any one of the following

[10] to

[16] .

[0026]

[10] An X-ray inspection method according to [9], wherein the imaging resolution of the scintillator is less than one third of the minimum diameter of a defect to be detected specified for each of the measuring objects.

[0027]

[11] An X-ray inspection method according to [9] or

[10] , wherein the surface of the scintillator facing the measurement object is photographed.

[0028]

[12] According to the X-ray inspection method of

[11] , the measurement object is light-transmissive, and the surface of the scintillator facing the measurement object is photographed through the measurement object.

[0029]

[13] An X-ray inspection method according to [9] or

[10] , wherein the surface of the scintillator opposite to the surface facing the measurement object is photographed.

[0030]

[14] An X-ray inspection method according to any one of [9] to

[13] , wherein the scintillator is photographed in a linear form.

[0031]

[15] An X-ray inspection method according to

[11] or

[12] , wherein the scintillator is photographed in a linear manner, and X-rays incident on the scintillator are shielded except for at least the area where the scintillator is photographed.

[0032]

[16] According to the X-ray inspection method of

[13] , the scintillator is photographed in a linear manner, and the X-rays incident on the scintillator are shielded except for at least the following area, which is an area within the surface of the scintillator facing the measurement object and is an area on the opposite side of the area where the scintillator is photographed, separated by the scintillator.

[0033] Effects of the Invention

[0034] According to the X-ray inspection device and the X-ray inspection method of the present invention, the blurring effect caused by the limited width of the focal spot diameter of the X-ray irradiation device can be reduced, thereby inspecting tiny metal foreign matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] [ Figure 1 ] is a schematic diagram of an embodiment of the X-ray inspection device of the present invention.

[0036] [ Figure 2 ] is an example of a schematic diagram showing the relationship between the X-ray radiation device, the measurement object, the position of the scintillator, the focal point diameter of the X-ray radiation device, and the blur width.

[0037] [ Figure 3 ] is a schematic diagram of an example of a scintillator.

[0038] [ Figure 4 ] is another embodiment of the X-ray inspection device of the present invention, and is a schematic diagram of an embodiment in which the surface of the scintillator facing the measurement object is photographed.

[0039] [ Figure 5 ] is a schematic diagram of an example of limiting the X-ray incident area on the scintillator.

[0040] [ Figure 6 ] is another embodiment of the X-ray inspection device of the present invention, and is a schematic diagram of an embodiment in which a component for shielding X-rays is provided.

[0041] [ Figure 7 ] is another embodiment of the X-ray inspection device of the present invention, and is a schematic diagram of an embodiment of imaging a scintillator through a measurement object.

[0042] [ Figure 8 ] is a schematic diagram of an example of a conventional X-ray inspection device.

[0043] [ Fig. 9 ] is a schematic diagram of using a conventional X-ray inspection device to inspect tiny metal foreign matter.

[0044] [ Fig.10 ] is an illustration of blur (penumbra) in X-ray inspection. DETAILED DESCRIPTION

[0045] Hereinafter, embodiments of the X-ray inspection apparatus and the X-ray inspection method of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiments described above.

[0046] Reference Figure 1 The X-ray inspection apparatus according to this embodiment will be described. Figure 1 It is a schematic diagram of an embodiment of the X-ray inspection device of the present invention. The X-ray inspection device 1 has an X-ray radiating device 2, a scintillator 31, and a photographing device 3. The X-ray radiating device 2 radiates X-rays to the measuring object 10, and the scintillator 31 is used to receive the X-rays that have passed through the measuring object 10. At this time, if a metal foreign matter 11 is mixed into the measuring object 10, the X-rays will be absorbed at the said part and become a shadow, and the X-rays will not be incident on the corresponding part of the scintillator 31. The part of the scintillator 31 that receives the X-rays produces fluorescence and irradiates visible light. That is, the part where no X-rays are incident because the metal foreign matter 11 becomes a shadow will not produce fluorescence and will not irradiate visible light. The photographing device 3 is used to receive the irradiated visible light, and the metal foreign matter (abnormal part) located in the measuring object 10 is inspected based on the light reception amount of each part.

[0047] The object 10 to be measured can be any material that does not shield X-rays, such as fiber, paper, film, resin, integrated circuit, or large-scale integrated circuit. The object 10 to be measured can be in any shape, such as an elongated shape, a long sheet, a single piece, or any other shape. Furthermore, the object 10 to be measured can be in a stationary state, in a state of being transported, or in a state of intermittent transport in which the object is repeatedly stationary and transported.

[0048] The X-ray irradiation device 2 may be a closed type or an open type, and may be a millimeter-level focusing type or a micrometer-level focusing type. As described later, in order to reduce the influence of blur, a micrometer-level focusing type is preferred. The settable voltage range is selected according to the type of the measurement object 10. If the measurement object 10 being transported is to be inspected, a voltage range that can output a large current is more preferred.

[0049] The scintillator 31 converts the incident X-rays into visible light, and preferably has a high conversion efficiency and a large amount of visible light irradiation. Moreover, it can be either a particle type or a single crystal type, and preferably has less light scattering inside the scintillator 31. Moreover, if the measurement object 10 is being transported, a scintillator with a short afterglow time is preferably used.

[0050] The imaging device 3 may be a line sensor camera, an area sensor camera, or a time-delay integration camera. For example, when the measuring object 10 is stationary, an area sensor camera is preferably used, while when the measuring object 10 is being transported, a line sensor camera or a time-delay integration camera is preferably used. The lens used may be a single focus type, a zoom type, or a telecentric lens.

[0051] use Figure 2 To illustrate the conditions for reducing blur (penumbra). Figure 2 This is an example of a schematic diagram showing the relationship between the respective installation positions of the X-ray radiating device 2, the measurement object 10, and the scintillator 31, the focal point diameter R [μm] of the X-ray radiating device 2, and the blur width r [μm].

[0052] The focal spot diameter R of the X-ray radiating device 2 may use the nominal value of the X-ray radiating device 2 or may be calculated from the light emission state of the scintillator by placing the scintillator just below the radiating position of the X-ray radiating device 2 .

[0053] The distance from the radiation position of the X-ray radiation device 2 to the measurement object 10 is L1 [mm]. Here, the so-called "distance to the measurement object" refers to the distance to the surface of the measurement object 10 ( Figure 2 In fact, to calculate the accurate blur width r, the distance to the position where the metal foreign matter 11 is located must be measured, but since the thickness of the measuring object 10 is negligible relative to the length L1, there is no problem even if it is set to the surface of the measuring object 10. In addition, since the thickness of the measuring object 10 is negligible relative to the length L1, when determining the position of setting the measuring object 10 in the X-ray inspection device 1 or the position of transporting the measuring object 10 in the design, the distance from the radiation position to the setting position or transport position can also be set to L1.

[0054] The distance from the radiation position of the X-ray radiation device 2 to the scintillator 31 is L2 [mm]. Here, the so-called "distance to the scintillator" refers to the distance to the surface ( Figure 2 However, since the thickness of the scintillator 31 is negligible relative to the length L2, there is no problem in measuring the distance to any position of the thickness of the scintillator 31.

[0055] The blur width r can be calculated using the following formula (1).

[0056] Formula (1): =(L2-L1)×R / L1.

[0057] Figure 2In the illustrated condition, blurring occurs at both ends of the metal foreign matter 11. Therefore, the shadow of the metal foreign matter 11 on the surface of the scintillator 31 is smaller than the ideal state without blurring (2×r). The inventors have conducted intensive research and found that in order to stably detect the metal foreign matter 11, the blur width r must be set to less than one-sixth of the width of the shadow of the metal foreign matter 11 in the ideal state without blurring. For example, when the focal diameter R is 40μm, L1 is 50mm, and the size of the metal foreign matter 11 is 50μm, L2 must be shorter than about 60mm.

[0058] Conventional X-ray inspection devices such as Fig. 9 As shown in the figure, the distance from the measuring object 10 to the scintillator 31 is increased, and the shadow formed by the tiny metal foreign matter 11a on the surface of the scintillator 31 is geometrically enlarged. However, in the X-ray inspection device of the present invention, in order to reduce the blur width r, the difference between the distance L1 and the distance L2 is reduced, that is, the measuring object 10 and the scintillator 31 are brought closer. Therefore, the size of the metal foreign matter 11 becomes approximately the same as the size of the shadow formed by the metal foreign matter 11 on the surface of the scintillator 31 in the ideal state without blur. Therefore, in order to stably detect the metal foreign matter 11, the blur width r must be set to less than one-sixth of the width of the minimum size of the metal foreign matter 11 that must be detected for each measuring object (the minimum diameter of the defect to be detected for each measuring object).

[0059] The size of the metal foreign matter 11 required to be detected in the X-ray inspection is gradually becoming smaller, but if the size required to be detected is considered to be less than 200μm, the blur width r is preferably set to less than 30μm, and the X-ray inspection device is preferably designed in such a way that the blur width r is achieved. Of course, the smaller the blur width r, the better, but especially when the object to be measured is being transported, the current output of the X-ray irradiation device 2 must be increased to increase the X-ray radiation amount to increase the irradiation amount of visible light in the scintillator 31. If so, the focal point diameter R will become larger, so there is a limit to the reduction of the blur width r. Even considering the size of the metal foreign matter to be inspected in the future, it is more preferable to design the X-ray inspection device in such a way that the blur width r is about 2μm to 10μm.

[0060] Furthermore, in general, in order to stably inspect the object to be detected, it is required to shoot with a shooting resolution of one-third or less of the size of the object. That is, it is preferred that the shooting resolution of the scintillator 31 be set to one-third or less relative to the width of the minimum size of the metal foreign matter 11 that must be detected for each measured object (the minimum diameter of the defect to be detected for each measured object). Therefore, if the size of the metal foreign matter 11 to be detected is considered to be less than 200 μm, the shooting resolution of the scintillator 31 is preferably less than 60 μm.

[0061] Furthermore, the fluorescence emission in the scintillator 31 is stronger the closer to the surface on which the X-rays are incident, and weaker the closer to the opposite surface. This phenomenon is particularly prominent in particle-type scintillators. Figure 3 While explaining. Figure 3 It is a schematic diagram of an example of a scintillator 31. In a particle-type scintillator, tiny fluorescent particles are distributed in a roughly uniform manner. Fluorescence is the emission of light corresponding to the amount of X-rays incident on the fluorescent particles. Therefore, near the surface on which the X-rays are incident, fluorescence corresponding to the amount of X-rays themselves is emitted, and the fluorescence is strong. However, if it is inside the scintillator 31, that is, if it is far away from the surface on which the X-rays are incident, the X-rays are reduced (attenuated) by the fluorescent particles that exist there, and the amount of X-rays incident on the fluorescent particles located far away is small, so the fluorescence becomes weaker. Therefore, for example, when the measurement object 10 is being transported, the exposure time of the imaging device 3 must be shortened from the perspective of imaging resolution. At this time, it is preferable to capture the surface of the scintillator 31 on which the X-rays are incident, that is, the surface facing the measurement object 10. While referring to Figure 4 , while explaining the example at this time. Figure 4 Schematic diagram of an example of an X-ray inspection device that images the surface of the scintillator 31 that faces the measurement object 10. Figure 4 As shown, the scintillator 31 is tilted, and the portion satisfying the formula (1) is photographed by the photographing device 3 in the surface of the scintillator 31 facing the measurement object 10. If it is difficult to directly photograph by the photographing device 3 in the space where the device is installed, it can also be photographed through a partition. Figure 7 As shown in the figure, if the measuring object 10 is light-transmissive, the surface of the scintillator 31 facing the measuring object 10 can be photographed through the measuring object 10. That is, the imaging device 3 can be set on the opposite side of the scintillator 31 with the measuring object 10 sandwiched therebetween. In this way, there can be an allowable range in the installation space of the imaging device 3.

[0062] Furthermore, it is preferable that X-rays incident on the scintillator 31 are shielded outside the imaging region of the scintillator 31 that is imaged by the imaging device 3. Figure 5 , while explaining this situation. Figure 5 This is a schematic diagram of an example of limiting the X-ray incident area on the scintillator. Figure 5In the embodiment, the measuring object 10 is assumed to be in a state of being conveyed, and the imaging device 3 uses, for example, a line sensor camera. In addition, there is a member 4 (hereinafter referred to as an X-ray shielding member) for shielding X-rays between the measuring object 10 and the scintillator 31. When X-rays pass through the measuring object 10 and enter the scintillator 31, the fluorescent particles inside the scintillator 31 emit light, but the light emitted by the fluorescent particles is radiated in all directions. Therefore, the fluorescent light emitted from the fluorescent particles outside the area where the luminescence information is to be obtained using the imaging device 3 will also enter the imaging device 3. It is noise and is preferably excluded. Therefore, in the scintillator 31, it is preferable to shield the X-rays incident outside the area where the luminescence information is to be obtained, and it is preferable to set an X-ray shielding member 4 between the measuring object 10 and the scintillator 31 to achieve this situation. By shielding the incident unnecessary X-rays using the X-ray shielding member 4, the influence caused by unnecessary light scattering inside the scintillator 31 can be reduced. Preferably, the shielding is performed regardless of which surface of the scintillator 31 corresponding to the measuring object 10 or the opposite surface thereof is photographed.

[0063] Example

[0064] Next, use Figure 6 , Figure 7 and Figure 8 To illustrate an embodiment of the present invention. Figure 6 and Figure 7 This is a schematic diagram of an embodiment of the X-ray inspection apparatus of the present invention. The present invention is not limited to the following embodiments.

[0065] [Example 1]

[0066] use Figure 6The X-ray inspection is performed by the illustrated X-ray inspection device 1. As the measurement object 10, a film with a thickness of about 30 μm is transported at 30 m / min. As the X-ray radiation device 2, a closed type is used, and the voltage and current conditions are set based on the measurement object 10. An example of the process of setting these conditions is shown. First, a film with a metal foreign body of about φ40 μm to be inspected is aligned with the transport position and is transported at an extremely low speed (for example, 0.1 m / min). This is used for transporting the metal foreign body part using a line sensor camera as the imaging device 3 as described later. The voltage is gradually reduced from a large value (for example, 80 keV) and is set to a voltage in which the ratio of the decrease in the signal value caused by the metal foreign body part relative to the signal value of the film texture in the signal value output by the imaging device 3 is the largest. In this embodiment, it is 40 keV. Next, at the voltage, the current is set to the maximum value that can be set (for example, 800 μA). In this state, it is confirmed that the signal value output by the imaging device 3 under the thin film texture is not saturated when the exposure time (24 microseconds) is set to achieve an imaging resolution of 12 μm at a speed of 30 m / min. If saturation is assumed, the setting value of the current is reduced to a level that is not saturated. In this embodiment, it is 800 μA.

[0067] Between the measuring object 10 and the scintillator 31, an X-ray shielding member 4 is provided to shield the X-rays incident on the scintillator 31. The X-ray shielding member 4 is a metal plate formed with a slit of about 0.1 mm in width, and is provided in such a manner that the long side direction of the slit is approximately orthogonal to the conveying direction of the measuring object. The scintillator 31 is a particle type with a thickness of about 0.1 mm. The imaging device 3 uses a line sensor camera, and the long side direction for imaging is set to be approximately orthogonal to the conveying direction of the measuring object 10. The lower surface (the surface facing the imaging device 3) of the scintillator 31 is photographed with a resolution of 12 μm in both the long side direction and the conveying direction by the imaging device 3. The imaging device 3 and the scintillator 31 are set such that the distance L1 is 50 mm and the distance L2 is 55 mm. The focal diameter R is 50 μm, so the blur width r is 5 μm. Under these conditions, X-ray inspection is performed on metal foreign matter of about φ40 μm. The blur width r is less than one sixth of the diameter of the metal foreign body. In the captured image, the binarization threshold is set to 3σ of the brightness deviation of the normal part of the measurement object 10, and the number of pixels detected as dark signals is 7, which is sufficient for inspection.

[0068] [Example 2]

[0069] use Figure 7The X-ray inspection is performed by the X-ray inspection device 1 shown in the figure. As the measuring object 10, a transparent film with a thickness of about 20μm is transported at 40m / min. As the X-ray irradiation device 2, a sealed type is used, and the voltage and current conditions are set to be the same as those in Example 1 (voltage: 40keV, current: 800μA). The scintillator 31 is a particle type with a thickness of about 0.1mm. The imaging device 3 uses a line sensor camera, and the long side direction for imaging is set to be approximately orthogonal to the transport direction of the measuring object 10. Using the imaging device 3, the upper surface of the scintillator 31 (the surface facing the measuring object 10) is photographed with a resolution of 15μm in both the long side direction and the transport direction through the measuring object 10. The imaging device 3 and the scintillator 31 are set at a distance L1 of 50mm and a distance L2 of 55mm. The focal diameter R is 50μm, so the blur width r is 5μm. Under this condition, X-ray inspection is performed on a metal foreign body of about φ50μm. The blur width r is less than one sixth of the diameter of the metal foreign matter. In the captured image, the binarization threshold is set to 3σ of the brightness deviation of the normal part of the measurement object 10, and the number of pixels detected as dark signals is 8, which is sufficient for inspection.

[0070] [Example 3]

[0071] use Figure 6 The X-ray inspection is performed using the illustrated X-ray inspection device 1. As the measurement object 10, a thin film with a thickness of about 30 μm is transported at a speed of 5 m / min. As the X-ray radiation device 2, a sealed type is used, and the voltage and current conditions are set to be the same as those in Example 1 (voltage: 40 keV, current: 800 μA). The scintillator 31 is a particle type with a thickness of about 0.1 mm. The imaging device 3 uses a line sensor camera, and the long side direction for imaging is set to be approximately orthogonal to the transport direction of the measurement object 10. Using the imaging device 3, the lower surface of the scintillator 31 (the surface facing the imaging device 3) is photographed with a resolution of 12 μm in both the long side direction and the transport direction. The imaging device 3 and the scintillator 31 are set so that the distance L1 is 50 mm and the distance L2 is 55 mm. The focal diameter R is 50 μm, so the blur width r is 5 μm. Under these conditions, X-ray inspection is performed on metal foreign matter of about φ30 μm. The blur width r is less than one sixth of the diameter of the metal foreign matter. In the captured image, the binarization threshold is set to 3σ of the brightness deviation of the normal part of the measurement object 10, and the number of pixels detected as dark signals is 6, which is sufficient for inspection.

[0072] [Comparative Example 1]

[0073] use Figure 8The X-ray inspection is performed using the X-ray inspection device 1 shown in the figure. The measurement object 10, the metal foreign matter of about φ40μm to be inspected, and the X-ray radiation device 2 are the same as those in Example 1, and the conveying speed of the measurement object 10 is also set to 30m / min as in Example 1. The distance from the X-ray radiation device 2 to the measurement object 10 is set to 50mm, the voltage of the X-ray radiation device 2 is set to 40keV, and the current is set to 800μA. As the imaging device 3, a commercially available X-ray camera is used, and the X-ray camera has a single crystal scintillator 31 and a sensor 32 composed of cells of about 50μm size. In order to set the resolution (12μm) to be the same as that in Example 1, the distance from the X-ray radiation device 2 to the imaging device 3 is set to about 200mm. Under the present conditions, the binarization threshold is set to 3σ of the brightness deviation of the normal part of the measurement object 10, but the metal foreign matter cannot be detected.

[0074] [Comparative Example 2]

[0075] In Comparative Example 1, it is considered that the metal foreign matter cannot be detected due to the influence of blur (penumbra), and the conditions of Comparative Example 1 are changed to set the distance from the X-ray radiation device 2 to the imaging device 3 to 55 mm. In addition, the current value is set to 550μA so that in this state, the signal value output by the imaging device 3 is not saturated under the thin film texture. Other conditions are set to be the same as those of Comparative Example 1. Under this condition, the binarization threshold is set to 3σ of the brightness deviation of the normal part of the measurement object 10, and the metal foreign matter is detected with 1 pixel or 2 pixels. However, a large amount of noise is superimposed on the image based on the signal output by the imaging device 3. If the inspection condition is set to detect more than 1 pixel or 2 pixels, the number of false detections will increase.

[0076] [Comparative Example 3]

[0077] In view of the results of Comparative Examples 1 and 2, the current of the X-ray radiation device 2 was adjusted within the range of 700μA to 800μA, and the distance from the X-ray radiation device 2 to the imaging device 3 was adjusted within the range of 100mm to 180mm. Other conditions were set to be the same as those of Comparative Example 1. The reason why the distance from the X-ray radiation device 2 to the imaging device 3 was set starting from 100mm was to set the imaging resolution in the measurement object 10 to be less than about 25μm, thereby stably detecting metal foreign matter by setting the vertical and horizontal resolution of the captured image to more than 2 pixels. Moreover, the current of the X-ray radiation device 2 was adjusted at each distance so that the signal value output by the imaging device 3 was not saturated under the thin film texture. However, no conditions were found under which metal foreign matter could be stably detected with more than 4 pixels (2 pixels vertically × 2 pixels horizontally).

[0078] Industrial Applicability

[0079] According to the X-ray inspection apparatus and the X-ray inspection method of the present invention, it is possible to inspect minute metal foreign matter while reducing the influence of blurring caused by the limited width of the focal spot diameter of the X-ray irradiation apparatus.

[0080] Explanation of symbols

[0081] 1: X-ray inspection device

[0082] 2: X-ray radiation device

[0083] 3: Shooting device

[0084] 4: X-ray shielding components

[0085] 10: Measurement object

[0086] 11: Metal foreign matter

[0087] 11a: Metallic foreign matter

[0088] 12: Blur

[0089] 31: Scintillator

[0090] 32: Sensor

Claims

1. An X-ray inspection device, comprising: An X-ray radiating device for radiating X-rays toward a measurement object; A scintillator for converting X-rays emitted from the X-ray radiating device and incident via the measurement object into visible light; and A photographing device having an optical component for focusing the visible light irradiated by the scintillator, the photographing device is used to receive the visible light, and in the X-ray inspection device, Assuming that the distance from the radiation position of the X-ray radiation device to the setting position or conveying position of the measurement object is L1 [mm], the distance from the radiation position to the scintillator is L2 [mm], and the focal diameter of the X-ray radiation device is R [μm], the X-ray radiation device and the scintillator are arranged so that the following formula (1) becomes less than 30 μm. Formula (1): (L2-L1)×R / L1 2 . The X-ray inspection apparatus according to claim 1 , wherein the imaging device has an imaging resolution of 60 μm or less when imaging the scintillator. 3 . The X-ray inspection apparatus according to claim 1 , wherein the imaging device is configured to image a surface of the scintillator that faces the measurement object.

4. The X-ray inspection apparatus according to claim 3, wherein a light-transmitting object is set as the measurement object, The imaging device is configured to capture an image of a surface of the scintillator that faces the measurement object via the measurement object. 5 . The X-ray inspection apparatus according to claim 1 , wherein the imaging device is configured to image a surface of the scintillator that is opposite to a surface facing the measurement object. 6 . The X-ray inspection apparatus according to claim 1 , wherein the imaging device is a line sensor camera or a time-delay integration camera.

7. The X-ray inspection device according to claim 3 or 4, wherein the photographing device is a line sensor camera or a time-delay integration camera, A member for shielding X-rays incident on the scintillator is provided between the installation position or the conveyance position of the measurement object and the scintillator, excluding at least an imaging region of the scintillator imaged by the imaging device.

8. The X-ray inspection device according to claim 5, wherein the photographing device is a line sensor camera or a time-delay integration camera, Between the setting position or conveying position of the measuring object and the scintillator, there is provided a component for shielding X-rays incident on the scintillator except for at least the following area, wherein the area is an area within the surface of the scintillator facing the measuring object and is an area on the opposite side of the scintillator and the photographing area of ​​the scintillator photographed by the photographing device.

9. An X-ray inspection method, X-rays are emitted toward the object being measured. The radiated X-rays are made incident on a scintillator via the measurement object, and the radiated X-rays are converted into visible light by the scintillator. The visible light irradiated by the scintillator is focused and photographed by an optical component. In the X-ray inspection method, With respect to the radiation position of the X-ray and the position of the scintillator, assuming that the distance from the radiation position of the X-ray to the measurement object is L1 [mm], the distance from the radiation position to the scintillator is L2 [mm], and the focal diameter of the X-ray at the radiation position of the X-ray is R [μm], the following formula (1) becomes less than one sixth of the minimum diameter of the defect to be detected specified for each of the measurement objects. Formula (1): (L2-L1)×R / L1 10 . The X-ray inspection method according to claim 9 , wherein an imaging resolution of the scintillator is equal to or less than one third of a minimum diameter of a defect to be detected that is specified for each of the measurement objects. 11 . The X-ray inspection method according to claim 9 , wherein an image of a surface of the scintillator facing the measurement object is imaged.

12. The X-ray inspection method according to claim 11, wherein the object to be measured has light transmissivity, The surface of the scintillator facing the measurement object is imaged via the measurement object. 13 . The X-ray inspection method according to claim 9 , wherein an image is taken of a surface of the scintillator that is opposite to a surface facing the measurement object.

14. The X-ray inspection method according to claim 9, wherein the scintillator is imaged in a linear form.

15. The X-ray inspection method according to claim 11 or 12, wherein photographing the scintillator in a linear form, X-rays incident on the scintillator are shielded except for at least a region where the scintillator is imaged.

16. The X-ray inspection method according to claim 13, wherein photographing the scintillator in a linear form, X-rays incident on the scintillator are shielded except for at least a region within a surface of the scintillator facing the measurement object and on the opposite side of a region where the scintillator is imaged via the scintillator.

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