JP2012142199A - X-ray tube and x-ray inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray tube capable of switching energy without changing the X-ray generating position, and to provide an X-ray inspection device using it.SOLUTION: A target 14 includes a first irradiated part being irradiated with a first characteristic X-ray by irradiating an electron beam 12, and a second irradiated part being irradiated with a second characteristic X-ray different from the first characteristic X-ray by irradiating an electron beam 12. An electron beam source 11 emits an electron beam 12, and is located so that the electron beam 12 thus emitted impinges on a predetermined position. A drive unit 16 displaces the target 14 so that a part of the target 14 irradiated with the electron beam 12 at the predetermined position is switched between the first and second irradiated parts.

Description

  The present invention relates to an X-ray tube and an X-ray inspection apparatus.

  In X-ray fluoroscopic inspection such as inspection of metallic foreign matter in plastic, an image having a sufficiently high contrast between plastic and metal can be easily obtained without specifying X-ray energy. However, there are some types of inspections that cannot easily ensure contrast. For example, in plastic recycling, when identifying a plastic containing brominated flame retardant from a large number of plastic pieces, the difference in contrast between the one containing brominated flame retardant and the one not containing brominated flame retardant is the case of the metal foreign matter inspection described above. Not as big as it is. Japanese Patent Laying-Open No. 2009-255049 (Patent Document 1) discloses a sorting apparatus that takes this problem into consideration. The apparatus includes an X-ray source for irradiating continuous X-rays, a first filter containing bromine, and a second element containing an element having an X-ray absorption edge on a higher energy side than the X-ray absorption edge of bromine. And a filter. Moreover, the 1st X-ray detector which detects the 1st X-ray which permeate | transmitted the 1st filter and the resin piece among the continuous X-rays irradiated from the X-ray source, and the 2nd filter and the resin piece A second X-ray detector that detects the transmitted second X-ray, and a control unit that sorts the resin piece based on the detection data of the first X-ray and the second X-ray. According to this apparatus, when determining the presence or absence of bromine in a resin piece that is an object to be selected, the determination result is suppressed from being influenced by the thickness of the resin piece, and the possibility of erroneous determination of the result is reduced. be able to.

  An X-ray tube is usually used as an X-ray source for X-ray inspection. Some X-ray tubes can switch the energy of generated X-rays. According to Japanese Patent Application Laid-Open No. 2007-323964 (Patent Document 2), an X-ray tube has an anti-cathode having a plurality of regions, and an electron whose posture can be switched between a first posture and a second posture by rotating. A gun assembly. By switching the attitude of the electron beam assembly, the X-ray energy can be switched by switching the region of the counter cathode that is irradiated with the electron beam.

JP 2009-255049 A JP 2007-323964 A

  The apparatus disclosed in Japanese Patent Application Laid-Open No. 2009-255049 has two detection systems in order to perform inspection using each of X-rays having different energies. This complicates the device. If the X-ray tube disclosed in Japanese Patent Application Laid-Open No. 2007-323964 is applied to this apparatus, it is possible to perform inspection using X-rays having different energies with one detection system. However, in this X-ray tube, when the energy is switched, the position where X-rays are generated changes, so the optical axis of the X-ray emitted from the X-ray tube also changes.

  The present invention has been made in view of the above problems, and an object thereof is an X-ray tube capable of switching energy without changing a position where X-rays are generated, and an X-ray inspection apparatus using the same. And to provide.

  The X-ray tube of the present invention has a target, an electron beam source, and a drive unit. The target includes a first irradiated portion that emits a first characteristic X-ray by irradiation with an electron beam, and a second irradiated portion that emits a second characteristic X-ray different from the first characteristic X-ray by irradiation with an electron beam. Including. The electron beam source emits an electron beam and is arranged so that the emitted electron beam enters a predetermined position. The drive unit is configured to displace the target so that a portion where the target is irradiated with the electron beam at a predetermined position is switched between the first and second irradiated portions.

  According to the X-ray tube, since the X-ray energy is switched by the displacement of the target, the position where X-rays are generated is maintained at a predetermined position.

It is sectional drawing which shows schematically the structure of the X-ray tube in Embodiment 1 of this invention. It is a schematic sectional drawing in alignment with line II-II of FIG. It is a schematic sectional drawing in alignment with line III-III of FIG. It is a partial cross section figure which shows schematically the structure of the X-ray tube in Embodiment 2 of this invention. It is a schematic diagram which shows the structure of the X-ray inspection apparatus in Embodiment 3 of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience of explanation, in some drawings, an orthogonal coordinate system having an x direction, a y direction, and a z direction is shown.

(Embodiment 1)
Referring to FIG. 1, an X-ray tube 51 of the present embodiment includes a filament 11 (electron beam source), an electromagnetic lens 13, a target disk 14 (target), a rotating shaft 15, and a motor 16 (driving unit). ), A filter disk 17, a case 18, and a rotating shaft adjusting portion 19a.

  The case 18 has an X-ray window 18W for transmitting the X-ray 54 used. In the case 18, the filament 11, the electromagnetic lens 13, the target disk 14, the rotating shaft 15, the motor 16, the filter disk 17, and the rotating shaft adjusting portion 19a are housed.

  The rotating shaft adjusting unit 19 a is fixed to the case 18 and supports the motor 16. The motor 16 rotates the rotary shaft 15 along the z-axis direction. Each of the target disk 14 and the filter disk 17 is attached to the rotating shaft 15. With this configuration, the target disk 14 and the filter disk 17 can be rotated as indicated by an arrow RT in the figure. That is, the motor 16 can rotationally displace both the target disk 14 and the filter disk 17. Thereby, the target disk 14 and the filter disk 17 can be easily interlocked.

  The target disk 14 and the filter disk 17 are arranged so as to be opposed to each other. Further, with respect to this pair, the filament 11 is positioned on the target disk 14 side (upper side in FIG. 1), and the X-ray window 18W is positioned on the filter disk 17 side (lower side in FIG. 1). Therefore, the X-ray tube 51 is a so-called transmission type.

  2 and 3, the target disk 14 emits X-rays 54 when irradiated with the electron beam 12. The target disk 14 includes an irradiated portion 14a (first irradiated portion) that emits first characteristic X-rays, and an irradiated portion 14b that emits second characteristic X-rays different from the first characteristic X-rays when irradiated with an electron beam. (Second irradiated portion). Further, the target disk 14 is positioned opposite to the first surface (upper surface in FIG. 1) on which the electron beam is incident and the second surface that emits the first and second characteristic X-rays. And a surface (the lower surface in FIG. 1). Accordingly, by reducing the dimension between the first and second surfaces, that is, by sufficiently reducing the thickness of the target disk 14, the thickness of the region where X-rays are generated can be reduced. . That is, the region where X-rays are generated can be made smaller.

  The filament 11 emits an electron beam 12, and the emitted electron beam 12 is in a predetermined position (a position where the electron beam 12 is converged in FIG. 1, and a position of the electron beam 12 indicated by a broken line in FIG. 2). ). The electromagnetic lens 13 converges the electron beam 12 to this predetermined position. The size of the predetermined position is, for example, about several μm. The motor 16 rotates and displaces the target disk 14 so as to switch the portion of the target disk 14 irradiated with the electron beam 12 between the irradiated portions 14a and 14b at the predetermined position.

  The irradiated portion 14 a further emits third characteristic X-rays different from the first characteristic X-rays upon incidence of the electron beam 12. The irradiated portion 14b further emits fourth characteristic X-rays different from the second characteristic X-rays upon incidence of the electron beam 12. These third and fourth characteristic X-rays are desirably removed as much as possible in order to reduce the monochromaticity of the X-rays 54. The filter disk 17 includes an absorption part 17a (first absorption part) for absorbing third characteristic X-rays and an absorption part 17b (second absorption part) for absorbing fourth characteristic X-rays. The filter disk 17 is displaced in conjunction with the target. Thereby, the intensity | strength of the X-ray which has energy other than desired energy can be suppressed.

  In the present embodiment, irradiated portions 14a and 14b are alternately arranged in each of the regions obtained by dividing the target disk 14 into four sectors. In this case, if the target disk 14 is rotated at 10 revolutions per second, X-rays 54 having two different energies can be alternately emitted every 25 ms. Therefore, in the inspection apparatus using the X-ray tube 51, if the inspection object is allowed to pass through the X-ray irradiation / detection system range in about 0.1 s, the energy differs for a certain inspection object 2. It becomes possible to confirm a fluoroscopic image by each type of X-ray twice. Therefore, the foreign object can be detected with sufficient accuracy by the processing of these fluoroscopic images. In addition, what is necessary is just to change the number of the area | region divided | segmented in the target disk 14 according to the objective. The same applies to the filter disk 17.

  The rotating shaft adjusting unit 19a is configured to be able to adjust the position of the rotating shaft 15 in the xy plane. Specifically, the rotation axis adjustment unit 19a is a support member of the motor 16 that can change the position on the xy plane while maintaining the posture of the motor 16. Thereby, as shown to the arrow AJ of FIG. 2, the place where the electron beam 12 is irradiated among the target disks 14 can be adjusted. Thereby, since the wider range of the target disk 14 can be utilized, the lifetime of the target disk 14 can be extended. Further, as indicated by an arrow AJ in FIG. 3, a place where the X-ray 54 is irradiated in the filter disk 17 can be adjusted. Thereby, since a wider range of the filter disk 17 can be used, the life of the filter disk 17 can be extended.

  According to the X-ray tube 51 of the present embodiment, since the energy of the X-ray 54 is switched by the displacement of the target disk 14, the position where the X-ray 54 is generated (the incidence of the electron beam 12 in FIGS. 1 and 2). Position) is maintained at a predetermined position with reference to the case 18. Therefore, even when the energy of the X-ray 54 is switched, the optical path of the X-ray 54 can be kept constant.

  Further, by increasing the rotation speed of the motor 16, the energy of the X-ray 54 can be switched in a short cycle.

  In the present embodiment, the X-ray tube 51 capable of switching between two types of energy by the two types of irradiated portions 14a and 14b is shown. However, three or more types of energy are supplied by three or more types of irradiated portions. A configuration that can be switched may be used. If three or more types of irradiated portions are arranged along the circumferential direction of the target disk, each of the three or more types of energy can be generated periodically.

  In the present embodiment, the X-ray 54 is generated while the motor 16 is driven. However, the X-ray 54 is generated while the motor 16 is stopped, and the motor 16 is driven only when the energy is changed. May be. Such a method of use is suitable for applications that require changes in energy at any time but do not require high-speed switching. For example, such a use form can be considered as an X-ray source for fluoroscopy and various physical analyses.

(Embodiment 2)
Referring to FIG. 4, the X-ray tube of the present embodiment is partially different from X-ray tube 51 (FIG. 1). That is, instead of the target disk 14, the rotating shaft 15, the motor 16, and the filter disk 17, the piezo element 9 (drive unit), the spring 10, the mounting member 21, the target piece 24 (target), the filter piece 27 (filter), And a vibration axis adjusting portion 19b.

  The target piece 24 includes an irradiated portion 24a (first irradiated portion) and an irradiated portion 24b (second irradiated portion). The size of each of the irradiated portions 24a and 24b is, for example, about several tens of μm. Further, the target piece 24 is positioned opposite to the first surface (upper surface in FIG. 4) on which the electron beam is incident and the second surface that emits the first and second characteristic X-rays. And a surface (the lower surface in FIG. 4). Thereby, by reducing the dimension between the first and second surfaces, that is, by sufficiently reducing the thickness of the target piece 24, the thickness of the region where X-rays are generated can be reduced. . That is, the region where X-rays are generated can be made smaller.

  The filter piece 27 includes an absorption part 27a (first absorption part) for absorbing the above-described third characteristic X-ray, and an absorption part 27b (second absorption part) for absorbing the above-described fourth characteristic X-ray. Have The size of each of the absorbers 27a and 27b is, for example, several tens of μm.

  The piezo element 9 expands and contracts along the x direction as indicated by an arrow DP in the figure. The amplitude of vibration is several tens of μm, for example. Each of the target piece 24 and the filter piece 27 is attached to the piezo element 9. Specifically, each of the target piece 24 and the filter piece 27 facing each other is sandwiched between the spring 10 fixed to the mounting member 21 and the piezo element 9. With this configuration, the filter piece 27 is oscillated and displaced in conjunction with the target piece 24.

  The vibration axis adjusting portion 19b is fixed to the case 18 (FIG. 1) and supports the attachment member 21. The vibration axis adjusting unit 19b is configured to be able to adjust the position of the piezo element 9 in the y direction. Thereby, the place where the electron beam 12 is irradiated among the target pieces 24 can be adjusted. Thereby, since the wider range of the target piece 24 can be utilized, the lifetime of the target piece 24 can be extended. Moreover, the place where X-rays 54 are irradiated among the filter pieces 27 can be adjusted. Thereby, since the wider range of the filter piece 27 can be utilized, the lifetime of the filter piece 27 can be extended.

  Since the configuration other than the above is substantially the same as the configuration of the first embodiment described above, the same or corresponding elements are denoted by the same reference numerals, and description thereof is not repeated.

  According to the present embodiment, substantially the same effect as in the first embodiment can be obtained. Furthermore, according to the present embodiment, the space necessary for the displacement only needs to be secured along the x direction, so that it is not necessary to secure the space for the rotational displacement as in the first embodiment. Therefore, a smaller X-ray tube can be obtained.

(Embodiment 3)
Referring to FIG. 5, the X-ray inspection apparatus according to the present embodiment is resin piece inspection apparatus 100 having X-ray tube 51 according to Embodiment 1 or 2 described above. The resin piece inspection apparatus 100 further includes an X-ray detector 53 (detection unit), a conveyor 55 (holding unit), an air blow gun 56, containers 57 and 58, a resin piece supply device 59, and a calculation unit 62. And have. The X-ray detector 53 detects X-rays 54 from the X-ray tube 51, and preferably has high time resolution. The conveyor 55 positions a resin piece 52 (sample) between the X-ray tube 51 and the X-ray detector 53.

  The resin piece 52 is supplied from the resin piece supply device 59 to the conveyor 55 and moves to a position where the X-ray tube 51 and the X-ray detector 53 are arranged. X-rays 54 generated from the X-ray tube 51 partially pass through the resin piece 52, and a transmission image is detected by the X-ray detector 53. The signal is sent to the data processor 60, stored in the storage unit 61, and shaded by the calculation unit 62 to determine whether to activate the air blow gun 56. In the meantime, the resin piece 52 moves and is blown off into the container 57 when the air blow gun 56 is activated, and naturally falls into the container 58 when it is not activated.

  For example, in the separation of resin pieces containing bromine (Br), the contrast of light and dark with and without inclusion can be most effectively obtained by irradiating X-rays with energy slightly exceeding 13.5 keV that can excite K-shell electrons of bromine. Can do. In this case, the Ka line of strontium (Sr) having an energy of 14.16 keV is most suitable, and a transmissive target can be obtained by thinly applying strontium oxide powder to an aluminum plate or the like. On the other hand, when the X-ray energy is increased to, for example, 17 keV, the influence of X-ray absorption by bromine on the contrast of light and dark becomes small, and the influence of the thickness of the object becomes relatively large. As a target that gives such energy, a Ka line of molybdenum (Mo) corresponding to a characteristic X-ray of 17.48 keV energy is suitable, and it may be used as a thin metal foil. That is, when an aluminum plate coated with strontium oxide is A and a molybdenum foil is B, each characteristic X-ray can be emitted alternately if A and B are alternately exposed to the traveling path of the electron beam. . At this time, the Kb characteristic X-rays from strontium and molybdenum cause a decrease in contrast. In order to selectively absorb this, it is suitable to use a filter containing (Z-1) element, where Z is the atomic number of the element contained in the target. For strontium, rubidium (Rb), molybdenum is used. On the other hand, it is desirable to use niobium (Nb) as a filter material. Rubidium can be used as a foil coated with an oxide powder like strontium, and niobium can be used as a metal foil.

  According to the resin piece inspection apparatus 100 of the present embodiment, it is possible to perform inspection with each of a plurality of X-rays having different energies with one X-ray tube 51.

  Further, since it is possible to alternately irradiate X-rays 54 having different energies from one X-ray tube 51 within a short period of time, the contrast of the X-ray transmission image of the resin piece 52 passes while the resin piece 52 passes. The difference can be determined by one X-ray detector 53. Therefore, the configuration of the apparatus can be made simpler and smaller.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

  9 Piezo element (drive unit), 11 Filament (electron beam source), 12 Electron beam, 13 Electromagnetic lens, 14 Target disk (target), 14a Irradiated part (first irradiated part), 14b Irradiated part (second) Irradiated part), 15 rotating shaft, 16 motor (driving part), 17 filter disk (filter), 17a absorbing part (first absorbing part), 17b absorbing part (second absorbing part), 18 case, 18W X-ray window , 19a Rotation axis adjustment unit, 19b Vibration axis adjustment unit, 24 Target piece (target), 24a Irradiated part (first irradiated part), 24b Irradiated part (second irradiated part), 27 Filter piece (filter) 27a Absorber (first absorber), 27b Absorber (second absorber), 51 X-ray tube, 52 Resin piece (sample), 53 X-ray detector, 54 X-ray, 55 Conveyor (holder), 1 0 resin piece testing apparatus (X-ray inspection apparatus).

Claims (7)

A target including a first irradiated portion that emits a first characteristic X-ray by irradiation of an electron beam and a second irradiated portion that emits a second characteristic X-ray different from the first characteristic X-ray by irradiation of an electron beam When,
An electron beam source arranged to emit an electron beam and the emitted electron beam is incident on a predetermined position;
An X-ray tube comprising: a drive unit that displaces the target so as to switch a portion of the target irradiated with the electron beam at the predetermined position between the first and second irradiated units. The target is
A first surface on which the electron beam is incident;
2. The X-ray tube according to claim 1, further comprising: a second surface that is opposite to the first surface and that emits the first and second characteristic X-rays. The first irradiated part further emits a third characteristic X-ray different from the first characteristic X-ray by the incidence of an electron beam, and the second irradiated part is the second characteristic X by the incidence of an electron beam. A further emission of a fourth characteristic X-ray different from the line,
The X-ray tube further includes a filter,
The filter has a first absorption part for absorbing the third characteristic X-ray and a second absorption part for absorbing the fourth characteristic X-ray, and is displaced in conjunction with the target. The X-ray tube according to claim 1 or 2.   The X-ray tube according to claim 3, wherein the drive unit is configured to displace both the target and the filter.   The X-ray tube according to claim 1, wherein the drive unit rotates the target.   The X-ray tube according to claim 1, wherein the drive unit vibrates the target. With an X-ray tube,
The X-ray tube is
A target including a first irradiated portion that emits a first characteristic X-ray by irradiation of an electron beam and a second irradiated portion that emits a second characteristic X-ray different from the first characteristic X-ray by irradiation of an electron beam When,
An electron beam source arranged to emit an electron beam and the emitted electron beam is incident on a predetermined position;
A drive unit that displaces the target so as to switch a portion of the target irradiated with the electron beam at the predetermined position between the first and second irradiated units, and further from the X-ray tube A detection unit for detecting X-rays;
An X-ray inspection apparatus comprising: a holding unit that positions a sample between the X-ray tube and the detection unit.

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