Source: https://patents.justia.com/patent/20050163284
Timestamp: 2019-08-22 18:15:28
Document Index: 448928669

Matched Legal Cases: ['art 21', 'art 21', 'art 21', 'art 21', 'art 21', 'art 21', 'art 21', 'art 21', 'art 21', 'art 21', 'art 21', 'art 21', 'art 21']

US Patent Application for X-ray generator Patent Application (Application #20050163284 issued July 28, 2005) - Justia Patents Search
Justia Patents US Patent Application for X-ray generator Patent Application (Application #20050163284)
An X-ray generator of this invention has an X-ray monitor that monitors a state of an X-ray emitted from a target. Hence the state of the X-ray can be monitored in real time to maintain the X-ray in a constant state. The X-ray monitor is positioned off the path on which an X-ray transmitted from a first exit window travels. Hence, when the X-ray is emitted from the first exit window to an object to be inspected, the X-ray monitor does not obstruct the approaching of the object to the first exit window. This makes it possible to acquire X-ray images of high magnification.
This invention relates to an X-ray generator for irradiating a target with an electron beam to generate X-rays.
The inspection device which irradiates an object to be inspected with X-rays and taking an image of the X-rays transmitted through the object has been known previously. An X-ray generator can be used as an X-ray source for such an inspection device. The X-ray generator generates X-rays by irradiating a target with an electron beam. The X-ray dosage varies according to the acceleration voltage applied to the electron beam, the current value of the electron beam or the like, as well as according to the damage of the target, the thermal deformation of the target supporting member, etc.
In recent years, inspections of electronic parts and other compact, high-density objects by means of X-rays have come to be carried out, and in accompaniment, the obtaining of X-ray images of high magnification has come to be desired. However, with the X-ray generator of Japanese Published Unexamined Patent Application No. S55-124997, though the variation of the X-ray dosage can be reduced, it is difficult to obtain X-ray images of high magnification.
FIG. 1 is a partial sectional view showing a non-destructive inspection system having an X-ray generator of a first embodiment.
Embodiments of this invention will now be described in detail with reference to the attached drawings. In the description of the drawings, the same elements will be provided with the same symbols and redundant description will be omitted.
FIG. 1 is a schematic view showing a non-destructive inspection system having an X-ray generator of the first embodiment of the invention. This non-destructive inspection system 80 is for non-destructive inspection of an object 5 to be inspected. System 80 has a moving stage 2, a microfocusing type X-ray generator 100, and an X-ray camera 1. Moving stage 2 is able to be moved in horizontal directions, and a plurality of objects 5 to be inspected are placed on the top of moving stage 2. X-ray generator 100 is installed below moving stage 2 and irradiates the moving stage 2 with X-rays. X-ray camera 1 detects the X-rays transmitted through moving stage 2 and object 5 to acquire X-ray images.
The outer shell of X-ray tube 10 is configured as a vacuum enclosure 20 of substantially cylindrical shape. Vacuum enclosure 20 extends vertically and is sealed to be maintained in a substantially vacuum state. The upper part of vacuum enclosure 20 is a main enclosure body 21 which is formed of copper or other metal. Main enclosure body 21 has a trunk part 21a which has a vertically cylindrical shape and houses reflection type target 27. Main enclosure body 21 also includes an electron gun housing cylinder 21b which has a horizontally cylindrical shape and is connected perpendicularly to trunk part 21a. Trunk part 21a and electron gun housing cylinder 21b are in communication with each other.
A ceramic stem plate 24 is installed at the end of electron gun housing cylinder 21b at the side away from the trunk part 21a. As will be described later, stem plate 24 allows the transmission of the X-rays emitted from target 27. In electron gun housing cylinder 21b, an electron gun 23 which emits an electron beam substantially horizontally towards the central axis of trunk part 21 is installed. Electron gun 23 is supported by a stem pin 25 held by stem plate 24 while extending through stem plate 24. Stem pin 25 is a terminal for supplying the driving power for electron gun 23. Stem pin 25 is electrically coupled to an electrode, filament, etc., inside electron gun 23 and is electrically coupled to current and voltage controller 40. Current and voltage controller 40 supplies the predetermined current and voltage to electron gun 23 via stem pin 25 to drive electron gun 23.
The lower part of enclosure 20 is a valve 22 which is formed of glass, ceramic, or other electric insulator. Valve 22 has a substantially cylindrical shape that is coaxial to trunk part 21a, and is connected to trunk part 21a. An electrically conductive target support 26 of substantially cylindrical form is inserted in valve 22 along the central axis of valve 22 from the lower end of valve 22. Target support 26 extends to the vicinity of the upper end of trunk part 21a.
A portion of target support 26 at its upper end on which the electron beam from electron gun 23 is incident and the surroundings of this portion form a surface inclined downward and facing electron gun 23. Reflection type target 27, formed of tungsten, etc., is installed on this inclined surface.
A first exit window 31 is disposed on a part of the upper wall of trunk part 21a that faces target 27. The X-rays generated from target 27 are transmitted through first exit window 31 and emitted upward out of vacuum enclosure 20. Hereinafter, the upper surface of first exit window 31 from which the X-rays are emitted will be referred to as “X-ray exit surface 31a.”
As shown in FIG. 1 and FIG. 2, X-ray generator 100 has X-ray monitor 30 for monitoring the dosage of the X-rays generated from target 27. X-ray monitor 30 is installed outside vacuum enclosure 20 and opposes stem plate 24. As shown in FIG. 1, X-ray monitor 30 is positioned off the path on which the X-rays emitted through first exit window 31 travel, and is positioned so as not to protrude beyond X-ray exit surface 31a. The upper surface of X-ray monitor 30 is placed below X-ray exit surface 31a, that is, at the side of target 27 from X-ray exit surface 31a. X-ray monitor 30 detects the X-rays transmitted through stem plate 24 from target 27 and measures the dosage of these X-rays in real time.
The X-rays emitted from target 27 are transmitted through first exit window 31 in a direction that is rotated by substantially 90° with respect to the traveling direction of the electron beam and then transmitted through moving stage 2 and object 5. The transmitted X-rays are detected by X-ray camera 1 and an X-ray image is taken. By visual inspection of this X-ray image or by application of a binarization process or other image processing on the X-ray image, non-destructive inspection of object 5 is carried out.
Since X-ray monitor 30 is positioned so as not to protrude beyond X-ray exit surface 31a, X-ray monitor 30 will not obstruct moving stage 2 and object 5, which oppose X-ray exit surface 31a, from approaching X-ray exit surface 31a. This enables moving stage 2 and object 5 to be positioned close to X-ray exit surface 31a. Hence X-ray images of high magnification can be acquired using X-ray camera 1. This is especially beneficial for non-destructive inspection of electronic components or other compact, high-density objects.
An X-ray generator 200 of the second embodiment will now be described with reference to FIGS. 3 and 4. X-ray generator 200 differs from X-ray generator 100 of the first embodiment in having an X-ray tube 11 in place of X-ray tube 10. X-ray tube 11 has a second exit window 50 for transmitting X-rays from reflection type target 27 to the outside. Accordingly, X-ray monitor 30 does not oppose stem plate 24 but opposes second exit window 50.
Second exit window 50 is formed of Be or other substance with high X-ray transmittance and is fitted into a side wall of trunk part 21a of vacuum enclosure 20. The position of second exit window 50 is not restricted in particular; however, it is preferably installed at a position that faces the portion of the surface of target 27 on which the electron beam is incident so that X-rays with adequate intensity emerges through it.
A preferable arrangement of second exit window 50 and X-ray monitor 30 is shown specifically in FIG. 4. X-ray monitor 30 is preferably located at a position where the angle formed by a straight line 61 extending between target 27 and electron gun 23 and a straight line 62 extending between target 27 and X-ray monitor 30 is in the range of ±90° when X-ray tube 11 is viewed from above. Second exit window 50 is preferably located at a position where straight line 62 passes when straight line 62 is positioned within ±90° from straight line 61.
An X-ray generator 300 of the third embodiment will now be described with reference to FIG. 5. X-ray generator 300 differs from the second embodiment in having a transmission type X-ray tube 12 in place of reflection type X-ray tube 11. X-ray tube 12 has, in place of reflection type target 27 and first exit window 31 in X-ray tube 11, a transmission type target 60 which is fitted into the upper wall of trunk part 21a in substantially horizontal arrangement. Transmission type target 60 acts as both target 27 and first exit window 31 in the second embodiment. The upper surface of target 60 is an X-ray exit surface 60a and the lower surface is an electron beam incidence surface 60b.
Correspondingly, electron gun 23 is positioned below target 60 in the interior of trunk part 21a and is installed so as to emit an electron beam upward towards electron beam incidence surface 60b. Second exit window 50 is installed in the side wall of trunk part 21a so as to face electron beam incidence surface 60b.
In X-ray generator 300, the electron beam emitted from electron gun 23 enters electron beam incidence surface 60b of target 60. The X-rays generated from target 60 are emitted from X-ray exit surface 60a. Also, part of the X-rays generated from target 60 is transmitted through second exit window 50 to enter X-ray monitor 30. The dosage of the X-rays is thereby detected. Hence X-ray generator 300 with the transmission type X-ray tube 12 provides the same merits as those of the second embodiment.
An X-ray generator 400 of the fourth embodiment will now be described with reference to FIG. 6. X-ray generator 400 differs from the second and third embodiments in equipping a shutter 70 between second exit window 50 and X-ray monitor 30. Shutter 70 can block, as necessary, the X-rays emitted from second exit window 50.
An X-ray generator 500 of the fifth embodiment will now be described with reference to FIG. 7. X-ray generator 500 differs from the third and fourth embodiments in having an open enclosure 101 in place of vacuum enclosure 20 which is sealed in a vacuum state. Open enclosure 101 houses electronic beam incidence surface 60b of transmission type target 60. The interior of open enclosure 101 may be put into a vacuum state or be opened under atmospheric pressure as necessary. Open enclosure 101 is made, for example, of stainless steel.
X-ray generator 500 also differs from the third and fourth embodiments in that X-ray monitor 30 is housed inside enclosure 101. X-ray monitor 30 is preferably installed at a position facing electron beam incidence surface 60b of transmission type target 60 in the present embodiment as well.
As described above, X-ray generators in accordance with the present invention can monitor the state of the X-rays emitted from the target in real time using the X-ray monitor. It is possible to maintain the X-rays generated from the target in a constant state by controlling the current and voltage applied to the electron gun and the target, or moving the electron beam incidence position on the target, or other regulation, according to the state of the X-rays acquired by the X-ray monitor. Consequently, the generators can emit stable X-rays from the first exit window.
an X-ray generating target positioned so that the electron beam from said electron gun is incident thereon;
a first exit window transmitting an X-ray emitted from said target in response to the incidence of said electron beam; and
an X-ray monitor receiving another X-ray from said target to monitor a state of the other X-ray, said X-ray monitor being positioned off a path on which the X-ray transmitted through said first exit window travels.
2. The X-ray generator according to claim 1, wherein said first exit window has an exit surface from which the X-ray from said target is emitted, and
wherein said X-ray monitor is positioned so as not to protrude beyond the exit surface.
3. The X-ray generator according to claim 1, further comprising a second exit window transmitting the other X-ray from said target,
said second exit window being positioned on an X-ray path different from an X-ray path extending from said target to said first exit window,
said X-ray monitor receiving the other X-ray transmitted through said second exit window.
4. The X-ray generator according to claim 3, wherein said second exit window is positioned so as to face a portion of a surface of said target on which the electron beam is incident.
5. The X-ray generator according to claim 3, wherein said second exit window is a stem plate holding a terminal of said electron gun and through which said terminal extends.
6. The X-ray generator according to claim 3, wherein a shutter able to block the X-ray is installed between said second exit window and said X-ray monitor.
7. The X-ray generator according to claim 1, further comprising a housing in which said X-ray monitor, said electron gun, said first exit window, and said target are installed.
8. The X-ray generator according to claim 1, wherein said electron gun, said X-ray monitor, and a portion of a surface of said target on which the electron beam is incident are housed in an enclosure capable of being maintained under vacuum.
9. The X-ray generator according to claim 8, wherein said X-ray monitor is installed in the enclosure so as to face the portion of the surface of said target on which the electron beam is incident.
10. The X-ray generator according to claim 1, further comprising an X-ray state controller to maintain the X-ray generated from said target in a constant state based on the state of the other X-ray monitored by said X-ray monitor.
Publication number: 20050163284
Patent Grant number: 7298826
Inventor: Tutomu Inazuru (Shizuoka)
Application Number: 10/513,610
Current U.S. Class: 378/108.000; 378/119.000