Patent Grant
11114268
This application is a national phase application of international application PCT/JP2016/005252, filed on Dec. 28, 2016, and claims the benefit of, and priority to, Japanese Patent Application No. 2016-016375, filed Jan. 29, 2016, which applications are hereby incorporated by reference herein in their entireties.
The present disclosure relates to an X-ray generating apparatus that can be used in nondestructive radiography and so on in the fields of medical equipment and industrial equipment and to a radiography system equipped with the X-ray generating apparatus.
As semiconductor devices have been increasingly miniaturized and increased in layer, recent inspection of electronic devices typified by semiconductor integrated circuit substrates in an industrial field uses an X-ray inspection apparatus equipped with an X-ray generating tube.
A known example of an electron source that emits an electron beam to a target is an X-ray generating tube equipped with an electron gun projected toward the target along a tube axis.
PTL 1 discloses a technique for achieving high positional accuracy of a focus formed on a target and microfocusing using an electron gun including a plurality of grid electrodes near the target.
The plurality of grid electrodes of the electron gun are configured to be individually supported by insulating members so that the distance between the electrodes is determined and to be subjected to predetermined voltages.
PTL 2 discloses an X-ray generating tube including an electron gun in which a plurality of grid electrodes are supported at certain intervals by an insulating support extending along a tube axis for microfocusing.
PTL 1: Japanese Patent Laid-Open No. 2002-298772
PTL 2: Japanese Patent Laid-Open No. 2007-66694
A radiography system that uses an X-ray generating tube equipped with an electron gun including a plurality of grid electrodes supported by an insulating member can form a low-quality image.
A study by the inventor revealed that fluctuations in focal position or focal shape due to the operation history of the X-ray generating tube are responsible for the decrease in image quality.
The present disclosure provides a reliable X-ray generating tube and a reliable X-ray generating apparatus equipped with an electron gun including grid electrodes supported by an insulating member in which fluctuations in focal position or shape are reduced. The present disclosure also provides a radiography system including an X-ray generating apparatus according to an embodiment of the present disclosure so that high-image-quality radiography is allowed.
An X-ray generating tube according to a first aspect of the present disclosure includes a target and an electron gun. The target is configured to generate X rays under electronic irradiation. The electron gun includes an electron emitting portion that emits electrons, a plurality of grid electrodes that form an electron beam to be emitted toward the target, and an insulating support member that electrically insulates and supports at least two of the plurality of grid electrodes. The electron gun includes a conductive section that hides the insulating support member to prevent the insulating support member from being directly viewed from an electron through path of the electrons emitted from the electron emitting portion and passing through the grid electrodes.
An X-ray generating tube according to a second aspect of the present disclosure includes a target and an electron gun. The target is configured to generate X rays under electronic irradiation. The electron gun includes an electron emitting portion that emits electrons, a plurality of grid electrodes that form an electron beam to be emitted toward the target, and an insulating support member that electrically insulates and supports at least two of the plurality of grid electrodes. The plurality of grid electrodes define an electron through path through which the electrons emitted from the electron emitting portion are passed. The electron gun includes a conductive section that hides the insulating support member to prevent the insulating support member from being directly viewed from the electron through path of the electrons passing through the grid electrodes.
According to an embodiment of the present disclosure, since an electron gun of an X-ray generating tube includes a conductive section that hides an insulating support member so that the insulating support member is not directly viewed from an electron through path, an X-ray generating tube and an X-ray generating apparatus having high reliability can be provided in which fluctuations in the position or shape of the focus are reduced.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Embodiments of the present disclosure will be described in detail hereinbelow with reference to the drawings. It is to be understood that the sizes, materials, shapes, and relative dispositions of components described in the embodiments are not intended to limit the scope of the present disclosure. Known techniques of this technical field are applied to components or parts that are not particularly illustrated or described in this specification.
X-ray Generating Tube
In this embodiment, an electron beam emitted from an electron emitting portion 40 is applied to a target layer 5c to cause a target 5b to generate X rays. For that purpose, the target layer 5c is disposed on a surface of the support substrate 5d facing the electron gun 4b. In other words, the electron emitting portion 40 is disposed on a cathode 4 so as to oppose the target 5b. Electrons emitted from the electron emitting portion 40 are accelerated to incident energy necessary for generating X rays in the target layer 5c by an accelerating electric field formed between the cathode 4 and the anode 5 due to a tube voltage applied to the X-ray generating tube 1.
The anode 5 includes the target 5b and an anode member 5a connected to the target 5b and functions as an electrode that determines the anode potential of the X-ray generating tube 1.
The anode member 5a is made of a conductive material and is electrically connected to the target layer 5c. The anode member 5a is connected to the periphery of the support substrate 5d to hold the target 5b, as illustrated in
The target layer 5c contains target metal, such as tantalum, molybdenum, or tungsten, as a metallic element with a high atomic number, a high melting point, and a high specific gravity. The support substrate 5d may be made of a material having high X-ray transmissivity and high thermal conductivity, for example, diamond, silicon nitride, silicon carbide, aluminum nitride, graphite, and beryllium. In particular, diamond may be used as a support substrate material for a transmission-type target because it has high thermal conductivity due to sp3 bond and high radiation transmissivity.
The interior of the X-ray generating tube 1 is under vacuum to ensure an average free path of electron beams. The degree of vacuum of the X-ray generating tube 1 is preferably 1×10−4 Pa or less and is more preferably 1×10−6 Pa or less from the point of view of the stability of the electron emission characteristic of the electron emitting portion 40. In this embodiment, the electron emitting portion 40 and the target layer 5c are disposed in the internal space or on the inner surface of the X-ray generating tube 1.
The vacuum in the X-ray generating tube 1 is formed by evacuating air using an exhaust pipe and a vacuum pump (not shown) and then sealing the exhaust pipe. The interior of the X-ray generating tube 1 is sometimes provided with a getter (not shown) for the purpose of maintaining the degree of vacuum.
The X-ray generating tube 1 includes an insulating tube 2 between the anode member 5a and the cathode member 4a for the purpose of electrical insulation between the electron emitting portion 40 set at cathode potential and the target layer 5c set at anode potential. In other words, the insulating tube 2 is connected to the anode member 5a and the cathode member 4a at one end and the other end in the tube axis direction.
The insulating tube 2 is formed with an insulating material, such as a glass material or a ceramic material. The outer circumference of the insulating tube 2 made of ceramic is protected by a glass layer with a thickness of 0.1 μm to 100 μm to provide sufficient strength.
In this embodiment, the insulating tube 2, the cathode 4 including the electron emitting portion 40, and the anode 5 including the target 5b constitute an envelope having air tightness for maintaining the vacuum and robustness against atmospheric pressure. Thus, the cathode 4 and the anode 5 are connected to opposite ends of the insulating tube 2 in the tube axis direction to constitute part of the envelope. Likewise, the support substrate 5d functions as a transmission window through which X rays generated at the target layer 5c are extracted outside the X-ray generating tube 1 and constitutes part of the envelope.
Electron Gun
Next, an electron gun, which is a feature of the X-ray generating tube according to an embodiment of the present disclosure, will be described with reference to
The cathode 4 includes a cathode member 4a and an electron gun 4b including the electron emitting portion 40, a grid electrode 42, and an insulating support member 41 that supports the grid electrode 42. The target 5b and the electron emitting portion 40 are opposed to each other.
Examples of the electron emitting portion 40 include hot-cathode electron sources, such as a tungsten filament, an impregnated cathode, and an oxide cathode, and a cold-cathode electron source, such as a spindt cathode made of molybdenum.
The electron gun 4b of this embodiment projects from the cathode member 4a toward the anode 5, as illustrated in
The electron emitting portion 40 and the grid electrode 42 are disposed at a portion of the electron gun 4b projecting toward the anode 5. This portion is referred to as a head portion. A portion that supports the head portion with respect to the cathode member 4a is referred to as a neck portion. As illustrated in
As illustrated in
Both of the extraction grid electrode 43 and the focusing grid electrode 44 are similar in controlling the motion of electrons passing through the electron through path 7 and defining the diameter of the electron beam and are therefore collectively referred to as a grid electrode 42 in the present disclosure. The extraction grid electrode 43 is provided to chronologically control the amount of electrons emitted from the electron emitting portion 40 passing through the electron through hole 43f, to which a plurality of potentials are selectively applied from a voltage source (not shown). The focusing grid electrode 44 is provided to form a focusing electrical field for electrons to define the size of a focus 8 formed on the target 5b, to which a focusing grid potential having a predetermined potential difference from the electron emitting portion 40 is applied from a voltage source (not shown).
The electron through path 7 in this specification corresponds to a pathway through which electrons emitted from the electron emitting portion 40 pass through the focusing grid electrode 44. The electron through path 7 includes pathways of electrons passing through the grid electrode 42 (43 and 44).
The extraction grid electrode 43 has a circular portion 43a having an electron through hole 43f and extending in the radial direction and the circumferential direction. The extraction grid electrode 43 is supported at the outer rim of the circular portion 43a by four insulating support members 41a to 41d disposed at intervals of 90° around the electron through path 7.
The coefficient of linear expansion of the insulating support members 41a to 41d and the grid electrode 42 are matched to each other to reduce thermal stress at the connection to the grid electrode 42. If the grid electrode 42 is made of molybdenum (α=4.8×10−6K−1 at 300 K), the insulating support members 41a to 41d are made of alumina (α=7.0×10−6K−1 at 300 K) 3. The grid electrode 42 and the insulating support members 41a to 41d are joined together with a brazing filler (not shown).
In some embodiments, a plurality of extraction grid electrodes 43 and a plurality of focusing grid electrodes 44 are disposed (not shown). Thus, in some embodiments, three or more grid electrodes 42 are disposed (not shown). In such a configuration, the insulating support member 41 electrically insulates and supports at least two of the plurality of grid electrodes 42.
As illustrated in
The circular portions 43a and 44a do not need to be parallel to the radial direction (y-z plane). It is only required that the circular portions 43a and 44a have such a shape as to form an electrical field that defines the electron through path 7, for example, a cone shape. The circular portions 43a and 44a may have a discontinuous shape, such as a mesh, spiral shape, or a multi-circular shape.
Next, the X-ray generating tube 1 according to the first embodiment including a conductive section, which is a feature of the present disclosure, will be described in more detail with reference to
The grid electrode 42 of this embodiment includes the extraction grid electrode 43 near the electron emitting portion 40 and includes the focusing grid electrode 44 far from the electron emitting portion 40. The extraction grid electrode 43 includes tubular portions 43b and 43c extending along the tube axis. In other words, the tubular portions 43b and 43c extend in a direction intersecting the tube radius direction. The tubular portions 43b and 43c are tubular projections projecting from the circular portion 43a toward the electron emitting portion 40 and the focusing grid electrode 44, respectively. The tubular portions 43b and 43c are part of the extraction grid electrode 43 and are electrically connected to a voltage source (not shown) together with the circular portion 43a and are regulated in potential.
The focusing grid electrode 44 is supported at the outer rim of the circular portion 44a by the four insulating support members 41a to 41d disposed at intervals of 90° around the electron through path 7. The circular portion 44a is opposed to the target 5b.
The focusing grid electrode 44 of this embodiment includes tubular portions 44b and 44c extending along the tube axis. In other words, the tubular portions 44b and 44c extend in a direction intersecting the radial direction. The tubular portions 44b and 44c are tubular projections projecting toward the electron emitting portion 40 and the anode 5, respectively. The tubular portions 44b and 44c are part of the focusing grid electrode 44 and are electrically connected to a voltage source (not shown) together with the circular portion 44a and are regulated in potential.
As illustrated in
The tubular portion 43c and the tubular portion 44b project in opposite directions in the tube axis direction in such a manner as to overlap in the tube axis direction so that the insulating support member 41 is not directly viewed from the electron through path 7, as illustrated in
The extraction grid electrode 43 and the focusing grid electrode 44 are a pair of grid electrodes 42 whose circular portions 43a and 44a face in the tube axis direction and whose tubular portions 43c and 44b face in the tube radius direction, as illustrated in
The tubular portion 43c is located inside the tubular portion 44b in the tube radius direction. In other words, the tubular portion 43c of the extraction grid electrode 43 whose circular portion 43a is located near the electron emitting portion 40 is located more inside in the tube radius direction than the tubular portion 44b of the focusing grid electrode 44 whose circular portion 44a is located far from the electron emitting portion 40.
The conductive section 6 (the tubular portions 43b, 43c, and 44b) plays a role in preventing metal particles scattered through the electron through path 7 from depositing on the insulating support member 41 to maintain the insulating performance of the insulating support member 41. This allows the electron emitting portion 40 and the grid electrode 42 (43 and 44) to be regulated at their respective predetermined potentials with stability. This allows the X-ray generating tube 1 of this embodiment to reduce in fluctuations in the size, position, and shape of the focus 8 due to the operation history, thus offering high reliability.
The conductive section 6 (the tubular portions 43b, 43c, and 44b) of this embodiment is part of the grid electrode 42 (43 and 44) and has electrical conductivity. For that reason, deposition of metal particles on the conductive section 6 (the tubular portions 43b, 43c, and 44b) in a range in which the adjacent electron emitting portion 40 and the grid electrode 42 (43 and 44) are not short-circuited will not cause fluctuations in the electric-field regulating operation of the grid electrode 42.
With the X-ray generating tube 1 of this embodiment, the electron gun 4b has the conductive section 6 (the tubular portions 43b, 43c, and 44b) that hides the insulating support member 41 so that it is not directly viewed from the electron through path 7, This ensures the insulating performance of the insulating support member 41. The presence of the electron gun 4b including the conductive section 6 (the tubular portions 43b and 43c, 44b) allows providing the reliable X-ray generating tube 1 in which fluctuations in the size, position, and shape of the focus 8 are reduced or eliminated.
In this embodiment, the conductive section 6 (the tubular portions 43b, 43c, and 44b) is part of the grid electrode 42 (43 and 44). In some embodiments, the grid electrode 42 (43 and 44) has a configuration in which electrically separated metal materials are disposed. To prevent a short circuit between the conductive section 6 and the grid electrode 42 or a short circuit between the conductive section 6 and the electron emitting portion 40 in a space in which the grid electrode 42 (43 and 44) is disposed, the conductive section 6 may be part of the grid electrode 42, as in this embodiment.
In this embodiment, the conductive section 6 (the tubular portions 43b, 43c, and 44b) is tubular in shape so as to hide the insulating support members 41a to 41d so that they are not directly viewed from the electron through path 7, as illustrated in
A mechanism in which metal particles are scattered from the electron through path 7 onto the insulating support members 41a to 41d will be described later.
The inventor has observed fluctuations in focus diameter with the operation history of the X-ray generating tube including an electron gun having grid electrodes supported by an insulating support member.
From a result of assiduous study, the inventor observed the following five facts about fluctuations in focus diameter with the operational history of an X-ray generating tube including an electron gun having grid electrodes supported by an insulating support member.
Fluctuations in focus diameter are not corrected after a down period and are irreversible.
The square R2 of a correlation coefficient of fluctuations in focus diameter is expressed as follows: tube voltage<emission intensity (approximately equal to) the amount of electron beam emitted<filament current from an electron emitting source.
An analysis of an electron gun of an X-ray generating tube in which significant fluctuations are observed shows decreases in internode resistance between grid electrodes and between grid electrodes and the electron gun.
An analysis of an electron gun of an X-ray generating tube in which significant fluctuations are observed shows an increase of specific metal in the surface composition of an insulating support member.
A predominant component of the metal increased in amount is barium (Ba) caused by an electron emitting portion.
From the above observations, the inventor presumes that the cause of fluctuations in focus diameter is deposition of scattered metal particles onto an insulating support member 341 associated with the operation of the X-ray generating tube.
Elementary Process of Generation of Scattered Metal Particles
Referring next to
The X-ray generating tube 301 contains inevitably remaining gas and floating metal particles. Such metal particles are regarded as part of the components of an electron emitting portion 340 and a target layer 305c, released into the vacuum space. The process for releasing the metal particles may include evaporation from the electron emitting portion 340 and spattering to the target layer 305c and a grid electrode 342 from the result of observation based on the exposure from the X-ray generating tube and the electron emitting operation of the electron gun, as illustrated in
Since the floating metal particles have a kinetic energy of several electron volts or less, almost all of the metal particles are captured at their origin or in the vicinity thereof, while the remainder become cations under emission of electrons and irradiation with X rays, as shown in
The process of ionization of barium particles emitted from the electron emitting portion 340 will be described in (Chem. 1) and (Chem. 2) using the impregnated-type electron emitting portion 340 impregnated with barium oxide as an example.
Ba (incidence of X-ray)→Ba++e (Chem. 1)
Ba (incidence of +e)→Ba+2e (Chem. 2)
The generated metal ions are moved toward the cathode 304 by electrostatic force received from an electric field in the electron gun 304b or the X-ray generating tube 301, as shown in
Ba+ e→Ba (Chem. 3)
The metal deposited on the cathode 304 can be tolerated because it has no influence on the electric-field regulating performance of the cathode member 304a and the electron emitting portion 340 that constitute the cathode 304.
The remainder of the metal ions recombine with scattered electrons and the electron beam before being captured by the cathode 304, as shown in
Such scattered metal particles are not influenced by the electric field and can move in the tube radius direction (y-z plane), and are therefore fixed on the surface of the insulating support member 341 to deposit a metal layer, as illustrated in
In this embodiment, the circumferential tubular portion 44e also serves as the power feeding unit 44d of the focusing grid electrode 44, that is, part of the focusing grid electrode 44 (the grid electrode 42).
A conductive section 6 (the tubular portions 43b, 43c, and 44b) located inside the electron gun 4b hides the insulating support members 41a to 41d as viewed from the electron through path 7. In contrast, a conductive section 6 (the tubular portion 44e) located outside the electron gun 4b hides the insulating support members 41a to 41d as viewed from an area between the electron gun 4b and the insulating tube 2.
Referring to
Scattered Metal Particles Coming from Backscattered Electrons
Electrons released from the electron emitting portion 40 pass through the electron through path 7 substantially at an initial velocity of 0 and are then accelerated under the electrostatic potential of a tube voltage Va onto the target 5b at a kinetic energy of Va (eV).
At the target 5b, the electrons are converted to thermal energy, secondary electrons, and Auger electrons in the target layer 5c, and the remainder are converted to X rays. Since the secondary electrons and Auger electrons, which interact with the target metal in the target layer 5c to slow down, are emitted toward the back of the target layer 5c only with a kinetic energy of 0 to 500 (eV), almost all of them enter the anode 5 again and are captured therein.
About 20% to 40% of the incident electrons are elastically scattered from the surface of the target layer 5c. The backscattered electrons elastically scattered from the surface of the target layer 5c have a kinetic energy of Va (eV) and therefore can reach an area on an equipotential surface of the electron emitting portion 40.
In the X-ray generating tube 1 including the electron gun 4b projecting from the cathode member 4a toward the anode 5, the electric field between the cathode 4 and the anode 5 is deformed near the cathode 4 by the electron gun 4b, as shown in
The backscattered electrons elastically scattered from the target layer 5c have a scattering angle distribution, in which not only components scattered toward the electron gun 4b but also components that reach the space between the electron gun 4b and the insulating tube 2 are present.
Since the electrostatic potential of the electron emitting portion 40 is expressed as:
cathode potential—Va (eV), backscattered electrons that move along X2 (y=−ψ/4) reach the cathode member 4a from the electron emitting portion 40.
Therefore, the backscattered electrons that reach the space between the electron gun 4b and the insulating tube 2 recombine with a trace quantity of metal (positive) ions contained in the internal space of the X-ray generating tube 1 to change to neutral scattered metal particles. In other words, the backscattered electrons that have reached the space between the electron gun 4b and the insulating tube 2 seem to cause scattered metal particles to be generated in the space between the electron gun 4b and the insulating tube 2 to deposit on the insulating support member 41.
The circumferential tubular portion 44e (the conductive section) of this embodiment prevents scattered metal particles generated in the space between the electron gun 4b and the insulating tube 2 from depositing on the insulating support members 41a to 41d to reduce the resistance of the insulating support member 41. Thus, the electron emitting portion 40 and the grid electrode 42 (43 and 44) are regulated at their respective predetermined potentials with stability. This allows the X-ray generating tube 1 according to this embodiment to be further reduced in fluctuations in the size, position, and shape of the focus 8 with the operation history, as shown in
In other words, the circumferential tubular portion 44e serves as a conductive section provided outside the insulating support members 41a to 41d to prevent scattered metal particles from depositing on the insulating support members 41a to 41d from outside the tube radius direction.
The X-ray generating tubes 1 according to the first and second embodiments are transmission-type X-ray generating tubes including a transmission-type target. In some embodiments, a reflection-type X-ray generating tube including a reflection-type target is used in an X-ray generating tube including an electron gun in which grid electrodes are supported by an insulating support member.
This disposition prevents a phenomenon in which reflected electrons (not shown) scattered backward from the circular portion 44a of the focusing grid electrode 44 enter the tubular portion 43c of the extraction grid electrode 43, reducing or eliminating fluctuations in the potential of the extraction grid electrode 43.
The X-ray generating tube 1 of this embodiment prevents not only a decrease in the insulating performance of the insulating support members 41a to 41d with the emitting operation history but also an influence of the reflected electrons incident on the grid electrode 42. This provides a further reliable X-ray generating tube in which the center 8c of the focus 8 is further stabilized, as illustrated in
X-ray Generating Apparatus
Referring next to
The driving circuit 106 includes a tube voltage circuit 106a that applies a tube voltage between the cathode and the anode and an electron-amount control circuit 106b that controls the amount of electrons to be emitted from the electron gun 4b. The tube voltage circuit 106a forms an accelerating electric field between the target layer 5c and the electron emitting portion 40. Appropriately setting the tube voltage Va according to the thickness and metal kind of the target layer 5c allows selection of the kind of radiation necessary for radiography.
The casing 107 of the X-ray generating tube 1 and the driving circuit 106 may have sufficient strength for the casing and high heat dissipation performance. Examples of the constituent material include metal materials, such as brass, iron, and stainless steel.
The casing 107 of this embodiment is electrically connected to the anode 5 of the X-ray generating tube 1 and is set at a grounding potential 16.
A space in the casing 107 excluding the X-ray generating tube 1 and the driving circuit 106 is filled with insulating fluid 108 to ensure electrical insulation between the casing 107 and the components in the casing 107. The components in the casing 107 include the X-ray generating tube 1, the driving circuit 106, and wiring lines (not shown).
The insulating fluid 108 is liquid having electrical insulation properties and has a function of maintaining electrical insulation in the casing 107 and a function as a cooling medium for the X-ray generating tube 1. Examples of the insulating fluid 108 include electrical insulation oil, such as mineral oil, silicone oil, and perfluoro-base oil, and insulating gas, such as sulfur hexafluoride (SF6).
Since the X-ray generating apparatus 101 of this embodiment includes at least the X-ray generating tube 1 according to one of the first 1 to third embodiments and therefore includes an electron gun in which stability of an electron beam focusing function is ensured, it has high reliability because fluctuations in the focus 8 are reduced.
Radiography System
Referring next to
The driving circuit 106 outputs various control signals to the X-ray generating tube 1 under the control of the system control unit 202. In response to the control signals output from the driving circuit 106, the emission state of an X-ray beam emitted from the X-ray generating apparatus 101 is controlled.
The X-ray beam emitted from the X-ray generating apparatus 101 passes through the object 204 and is detected by an X-ray detector 206. The X-ray detector 206 converts the detected X rays to an image signal and outputs the image signal to a signal processing unit 205.
The signal processing unit 205 performs predetermined signal processing on the image signal under the control of the system control unit 202 and outputs the processed image signal to the system control unit 202.
The system control unit 202 outputs a display signal for displaying an image on a display unit 203 to the display unit 203 based on the processed image signal. The display unit 203 displays an image based on the display signal on a screen as a captured image of the object 204.
Because of the presence of the X-ray generating apparatus 101 according to the fourth embodiment, the radiography system 200 of this embodiment can acquire a high-quality image with high reproductivity in which fluctuations in the focus 8 are reduced. The radiography system 200 is used for nondestructive inspection of industrial products and pathological diagnosis of human bodies and animals.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2016-016375, filed Jan. 29, 2016, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2016-016375 | Jan 2016 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/005252 | 12/28/2016 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2017/130262 | 8/3/2017 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4621213 | Rand | Nov 1986 | A |
| 4879518 | Broadhurst | Nov 1989 | A |
| 20040090166 | Sanders | May 2004 | A1 |
| 20110114830 | Reijonen | May 2011 | A1 |
| 20170199283 | Hu | Jul 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| S47-31054 | Dec 1972 | JP |
| H01143198 | Jun 1989 | JP |
| 2002-298772 | Oct 2002 | JP |
| 2007-66694 | Mar 2007 | JP |
| 2011134498 | Jul 2011 | JP |
| 2015135722 | Jul 2015 | JP |
| 1481870 | May 1989 | SU |
| Number | Date | Country | |
|---|---|---|---|
| 20190035593 A1 | Jan 2019 | US |
