X-ray photographing device and method for adjusting current supplied to filament

Abstract

To provide an X-ray photographing device that can prevent a usable period of a filament from being reduced due to processing of searching for an appropriate current value supplied to the filament, and a method for adjusting a current supplied to a filament.SOLUTION: The X-ray photographing device 100 comprises: an X-ray tube 1 that includes a target 10 and an electron emission unit 11 provided with a filament 19; an X-ray detector 2 that detects an X-ray 9 emitted from the X-ray tube 1; a storage unit 22 that stores current information 30 acquired in advance in which the total supply time of a current supplied to the filament 19 to emit electrons from the filament 19, and an appropriate current value supplied to the filament 19 to emit electrons from the filament 19 are associated with each other; and a control unit 21 that performs control of adjusting the current supplied to the filament 19 on the basis of the current information 30 at a time later than the first total supply time as the predetermined total supply time.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an X-ray imaging apparatus and a method for adjusting a current supplied to a filament. [Background technology]

[0002] BACKGROUND ART Conventionally, an X-ray imaging apparatus is known (see, for example, Patent Document 1).

[0003] The above-mentioned Patent Document 1 discloses an X-ray inspection device (X-ray imaging device) including an X-ray tube, an X-ray detector, and a control unit. The X-ray tube includes a target and an electron emitter with a filament. The X-ray tube is configured to focus an electron beam emitted from the filament using a magnetic lens and strike the target within a vacuum chamber, while emitting X-rays generated at the target. The filament emits thermoelectrons when heated by supplying current. In X-ray inspection, if the current supplied to the filament is too small, sufficient tube current cannot be obtained, and the desired X-ray brightness cannot be achieved. On the other hand, if the current supplied to the filament is too large, the filament will burn out and become unusable, thereby shortening its lifespan. The above-mentioned Patent Document 1 discloses that, before performing X-ray inspection, the current supplied to the filament is gradually increased to search for a current value (saturation filament current) at which the brightness value based on the X-ray detection signal stops changing and reaches a saturation range, and a current equal to or less than the searched saturation filament current is supplied to the filament, thereby performing X-ray inspection. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-251300 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even during the process of searching for a saturation filament current before X-ray inspection, a current is supplied to the filament. Therefore, even during this process, the filament burnout progresses, shortening its lifespan. The present inventors discovered that, with regard to filament breakage due to the progression of filament burnout, the filament is more likely to break during this process than during X-ray imaging, which is performed by supplying a current equal to or lower than the searched saturation filament current value. The present inventors then discovered a problem of how to prevent the shortening of the usable life of a filament due to the process of searching for an appropriate current value to be supplied to the filament.

[0006] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide an X-ray imaging device and a method for adjusting the current supplied to the filament that can prevent the usable period of the filament from being shortened due to the process of searching for an appropriate current value to be supplied to the filament. [Means for solving the problem]

[0007] An X-ray imaging device according to a first aspect of the present invention includes an X-ray tube including a target, an electron emitter provided with a filament and emitting electrons toward the target, an X-ray detector for detecting X-rays emitted from the X-ray tube, a memory unit storing previously acquired current information that associates a total supply time of current supplied to the filament to emit electrons from the filament with an appropriate current value that is supplied to the filament to emit electrons from the filament, and a control unit that performs control to adjust the current supplied to the filament based on the current information after a first total supply time as a predetermined total supply time.

[0008] A method for adjusting a current supplied to a filament in a second aspect of the present invention is a method for adjusting a current supplied to a filament in an X-ray imaging device equipped with an X-ray tube including a target and an electron emitter provided with a filament and emitting electrons to the target, and includes the steps of: acquiring in advance current information that associates a total supply time of current supplied to the filament to emit electrons from the filament with an appropriate current value that is supplied to the filament to emit electrons from the filament; and adjusting the current supplied to the filament based on the current information after a first total supply time as a predetermined total supply time. [Effects of the Invention]

[0009] In the X-ray imaging apparatus according to the first aspect and the method for adjusting a current supplied to a filament according to the second aspect, current information is acquired in advance, which associates a total supply time of a current supplied to the filament to emit electrons from the filament with an appropriate current value to be supplied to the filament to emit electrons from the filament. After a first total supply time, which is a predetermined total supply time, the current supplied to the filament is adjusted based on the current information. As a result, after the first total supply time, the current supplied to the filament is adjusted based on the previously acquired current information without performing a process for obtaining an appropriate current value to be supplied to the filament by supplying current to the filament. Therefore, after the first total supply time, the process for supplying current to the filament to search for an appropriate current value is not performed, and the supply of current to the filament due to the process is suppressed. As a result, a shortening of the usable life of the filament due to the process is suppressed. Furthermore, after the first total supply time, the current supplied to the filament can be appropriately adjusted based on the previously acquired current information without performing the process. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a schematic diagram showing the overall configuration of an X-ray imaging apparatus according to an embodiment. [Figure 2] FIG. 1 is a schematic diagram illustrating a configuration of an X-ray tube according to an embodiment. [Figure 3] 10 is a graph illustrating an appropriate current value obtained in a process of searching for an appropriate current value. [Figure 4] 10 is a graph illustrating an example of current information. [Figure 5] FIG. 10 is a flow chart for explaining control of adjustment of current supplied to a filament. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0012] (Configuration of X-ray equipment) The configuration of an X-ray imaging apparatus 100 according to this embodiment will be described with reference to FIGS.

[0013] 1, the X-ray imaging apparatus 100 is an apparatus that captures an X-ray image of a subject 90. The X-ray imaging apparatus 100 of this embodiment is used, for example, for non-destructive testing of the subject 90. In this case, the subject 90 is a sample to be inspected.

[0014] The X-ray imaging apparatus 100 includes an X-ray tube 1, an X-ray detector 2, a subject installation unit 3, an installation unit moving mechanism 4, and a control device 20.

[0015] The X-ray tube 1 is configured to irradiate X-rays 9 onto a subject 90 placed on a subject placement unit 3. The X-ray tube 1 is configured to generate X-rays 9 when a high voltage is applied to it. The X-ray tube 1 faces an X-ray detector 2 via the subject placement unit 3. In this embodiment, the X-ray tube 1, subject placement unit 3, and detector are arranged side by side in the horizontal direction.

[0016] 2, the X-ray tube 1 includes an electron emitter 11 serving as a cathode, a grid electrode 12, an anode 13, an electron lens 14, an aperture 15, a target 10, a vacuum vessel 16, a first power supply circuit 17, and a second power supply circuit 18. The electron emitter 11, the grid electrode 12, the anode 13, the electron lens 14, and the target 10 are housed in the vacuum vessel 16.

[0017] The electron emitter 11 is configured to irradiate the target 10 with an electron beam 8. The electron emitter 11 generates electrons when a current is applied from a second power supply circuit 18. The electron emitter 11 is also configured to emit the generated electrons toward the target 10 to which a high voltage is applied. The electron emitter 11 includes a filament 19, which is, for example, a heavy metal formed into a coil or foil shape. The filament 19 is formed of, for example, tungsten or the like.

[0018] A predetermined voltage is applied between the electron emitter 11 and the target 10 by a first power supply circuit 17. Specifically, the electron emitter 11 and the target 10 are connected to the first power supply circuit 17 via wiring. The electron emitter 11 is also connected to a second power supply circuit 18 via wiring. A filament 19 of the electron emitter 11 is heated by being energized by the second power supply circuit 18. This generates an electron beam 8 (thermal electrons) that travels from the electron emitter 11 toward the target 10. A current supplied to the filament 19 by a control unit 21 is adjusted via the second power supply circuit 18.

[0019] The grid electrode 12 is configured to control the amount of current of the emitted electron beam 8. The grid electrode 12 is provided in the vicinity of the electron emitting portion 11.

[0020] The anode 13 is configured to accelerate the electrons emitted from the electron emitting portion 11 when a voltage is applied thereto. The anode 13 is provided between the electron emitting portion 11 and the target 10.

[0021] The electron lens 14 is configured to focus the electron beam 8 emitted from the electron emitter 11. The electron lens 14 is also configured to make the electron beam 8 emitted from the electron emitter 11 incident on the surface of the target 10 approximately perpendicularly. The electron lens 14 is provided between the electron emitter 11 and the target 10. In this embodiment, the electron lens 14 is an electromagnetic lens. The electromagnetic lens is an electromagnet that uses a coil and has a magnetic pole (pole piece) (not shown) that is formed to protrude toward the center of the coil hole. The electrons emitted from the electron emitter 11 pass through the area (hole) surrounded by the pole piece. The electron lens 14 for focusing the electron beam 8 need not be an electromagnetic lens, but may be an electrostatic lens or another known lens.

[0022] Aperture 15 is configured to be able to adjust the range through which electrons pass. Aperture 15 has apertures 15a. Aperture 15 is provided between electron emitter 11 and target 10. Electrons emitted from electron emitter 11 and passing through apertures 15a of aperture 15 collide with target 10.

[0023] The target 10 is configured to generate X-rays 9 when struck by the electron beam 8 (thermal electrons) emitted from the electron emitter 11. The target 10 is formed from a metal material such as tungsten, molybdenum, copper, cobalt, chromium, iron, or silver. The target 10 is a reflective target. A reflective target is a target that emits X-rays 9 so that the X-rays 9 are reflected by the surface in a direction different from the direction in which the electron beam 8 travels. The target 10 may also be a transmissive target. A transmissive target has a pair of surfaces (front and back) that are perpendicular to the electron beam 8, and when electrons strike one surface, the X-rays 9 are emitted from the other surface so as to pass through the target 10.

[0024] An electron emitter 11 and a target 10 are disposed inside a vacuum vessel 16. The inside of the vacuum vessel 16 is sealed in a substantially vacuum state. The vacuum vessel 16 is formed of a non-magnetic metal material such as stainless steel (SUS). The vacuum vessel 16 is also provided with a window (not shown) that emits X-rays 9 to the outside.

[0025] As shown in FIG. 1, the X-ray detector 2 is configured to detect X-rays 9 emitted from the X-ray tube 1. The X-rays 9 emitted from the X-ray tube 1 pass through a subject 90 and are incident on the detection surface of the X-ray detector 2. The X-ray detector 2 is configured to convert the detected X-rays 9 into an electrical signal. This allows an X-ray image to be obtained that reflects the transmission of the X-rays 9 through the subject 90. The X-ray detector 2 is, for example, an FPD (Flat Panel Detector). The X-ray detector 2 is configured with a plurality of conversion elements (not shown) and pixel electrodes (not shown) arranged on the plurality of conversion elements. The plurality of conversion elements and pixel electrodes are arranged in a matrix on the detection surface at a predetermined period (pixel pitch). A detection signal (image signal) of the X-ray detector 2 is sent to an image processing unit 5.

[0026] The subject placement unit 3 is disposed between the X-ray tube 1 and the X-ray detector 2, and is configured to support the subject 90. The subject placement unit 3 is configured by a stage on which the subject 90 is placed. The subject 90 may be placed on the subject placement unit 3 via a holder (not shown) for holding the subject 90.

[0027] The installation unit moving mechanism 4 is configured to move the subject installation unit 3 in two mutually perpendicular directions within a horizontal plane or in the vertical direction. The installation unit moving mechanism 4 includes a motor (not shown) for moving the subject installation unit 3, which is a stage.

[0028] The control device 20 is configured by, for example, a PC (personal computer). The control device 20 includes a control unit 21, an image processing unit 5, a storage unit 22, and an input / output unit 23. The control device 20 is connected to a display device 24 and an input device 25.

[0029] The control unit 21 is configured with a processor such as a CPU (Central Processing Unit), and executes application programs stored in the storage unit 22 to set imaging conditions in the X-ray imaging apparatus 100, control the start and stop of imaging, control the operation of the X-ray tube 1, and control the process of searching for an appropriate current value. Details of the above processes will be described later.

[0030] Furthermore, the control unit 21 is configured to adjust the current supplied to the filament 19 based on the current information 30 after a first total supply time as a predetermined total supply time. Specifically, the control unit 21 is configured to adjust the current supplied to the filament 19 based on an appropriate current value acquired by processing to search for an appropriate current value until the first total supply time, and to adjust the current supplied to the filament 19 based on the current information 30 during a second total supply time after the first total supply time. Details of the current information 30 and the control of the adjustment of the current supplied to the filament 19 based on the current information 30 will be described later.

[0031] The image processing unit 5 is configured with a processor such as a GPU (Graphics Processing Unit) or an FPGA (Field-Programmable Gate Array) configured for image processing. The image processing unit 5 acquires X-ray image data from the X-ray detector 2. The image processing unit 5 is configured to perform predetermined image processing on the acquired X-ray image data.

[0032] The storage unit 22 includes a volatile storage device and a non-volatile storage device. The storage unit 22 stores various programs. The storage unit 22 also stores previously acquired current information 30, an offset value table, and a correction value table. In this specification, the term "previously acquired" in "previously acquired current information 30" does not mean "acquired before the first X-ray inspection is started after the manufacture of the X-ray imaging device 100 or after the shipment of the X-ray imaging device 100," but rather means, for example, "acquired by the manufacturer of the X-ray imaging device 100 through experiments in common for each model and product number of the X-ray imaging device 100." Details of the offset value table and the correction value table will be described later.

[0033] The input / output unit 23 is composed of various interfaces for inputting and outputting signals to and from the control device 20. The input / output unit 23 is connected to a display device 24 and an input device 25. The display device 24 is, for example, a liquid crystal display device. The input device 25 includes a keyboard, a mouse, and the like. The image processing unit 5 acquires a detection signal (image signal) from the X-ray detector 2 via the input / output unit 23.

[0034] (Process to search for appropriate current value) The process of searching for an appropriate current value will now be described.

[0035] In X-ray imaging, it is important to set the current supplied to the filament 19 to an appropriate value in order to obtain an image with the desired X-ray brightness. If the current supplied to the filament 19 is too small, a sufficient tube current cannot be obtained, and the desired X-ray brightness cannot be obtained. On the other hand, if the current supplied to the filament 19 is too large, the filament 19 may burn out and become unusable, thereby shortening its lifespan. Therefore, the control unit 21 performs a process to obtain an appropriate current value to be supplied to the filament 19 by supplying current to the filament 19. The above process is performed at predetermined third total supply time intervals. The total supply time means the total supply time of current supplied to the filament 19 to emit electrons from the filament 19. The above process may be performed based on an input operation by the user.

[0036] The control unit 21 acquires an appropriate current value by a process of searching for an appropriate current value from the start of use of the filament 19 until the first total supply time. Here, an oxide film is formed on the filament 19 before use. Due to the formed oxide film, the appropriate current value of the filament 19 is not stable immediately after use. The control unit 21 performs the above process until the first total supply time and acquires an appropriate current value to be supplied to the filament 19 by supplying current to the filament 19. The first total supply time is a total supply time during which fluctuations in the appropriate current value acquired by the above process are predicted to stabilize as the oxide film of the filament 19 peels off during use. The first total supply time is, for example, 96 hours. Note that the first total supply time is not limited to 96 hours and may be shorter or longer than 96 hours.

[0037] In the process of searching for an appropriate current value, the control unit 21 gradually increases the current supplied to the filament 19 via the second power supply circuit 18, and acquires the change in the brightness value based on the X-ray detection signal acquired by the X-ray detector 2 in response to the increase in the current supplied to the filament 19. FIG. 3 is a diagram showing the relationship between the current supplied to the filament 19 and the X-ray brightness. When the current supplied to the filament 19 is small, as the current supplied to the filament 19 increases, the brightness value based on the X-ray detection signal also increases. As the current supplied to the filament 19 increases, the amount of change in the brightness value based on the X-ray detection signal eventually becomes minimal and tends to reach a saturation range. When a current exceeding the current value that reaches the saturation range is supplied to the filament 19, the X-ray brightness remains almost unchanged, but the temperature of the filament 19 increases, accelerating evaporation and wear of the filament 19 and shortening the life of the filament 19.

[0038] For example, when measuring brightness values based on X-ray detection signals while gradually increasing the current supplied to the filament 19, the control unit 21 determines that the current value has reached the saturated region when the measurement values at several consecutive measurement points fall within a preset allowable fluctuation range. Then, the control unit 21 acquires, as the appropriate current value, a current value that is 80% of the current value at which the saturated region has been reached.

[0039] The process of searching for an appropriate current value requires obtaining a brightness value based on an X-ray detection signal when the subject 90 is not captured in the X-ray image. Therefore, the above process obtains brightness values based on the X-ray detection signal obtained by the X-ray detector 2 while gradually increasing the current supplied to the filament 19 in a state where the subject 90 is not placed on the stage. Therefore, while the above process is being performed, X-ray photography for non-destructive testing in which the subject 90 is placed on the stage is suspended.

[0040] (Adjustment of current supplied to filament up to first total supply time) The control unit 21 adjusts the current supplied to the filament 19 based on the appropriate current value acquired by the process of searching for the appropriate current value until the first total supply time elapses.

[0041] The control unit 21 acquires an appropriate current value by searching for an appropriate current value at each predetermined third total supply time interval from the start of use of the filament 19 until the first total supply time. The predetermined third total supply time interval is, for example, a 24-hour (total supply time) interval. The predetermined third total supply time interval is not limited to 24 hours, and may be shorter or longer than 24 hours.

[0042] Here, when the diameter of the diaphragm hole 15a provided in the aperture 15 is small, the X-ray focal point of the target 10 becomes smaller than when the diameter of the diaphragm hole 15a is large. Therefore, by limiting the direction in which the X-rays 9 are irradiated, an X-ray image with clearer contours and improved resolution can be generated, but because the X-ray amount is reduced, an X-ray image with a low brightness value is generated.

[0043] Therefore, to increase the brightness value, an offset value for finely adjusting the appropriate current value is preset according to the diameter of the aperture 15a provided in the aperture 15. The memory unit 22 stores an offset value table in which the diameter of the aperture 15a provided in the aperture 15 is associated with an offset value for an appropriate current value obtained by a process for searching for an appropriate current value. The control unit 21 refers to the offset value table to adjust the current supplied to the filament 19 based on the appropriate current value obtained by the above process and the offset value based on the diameter of the aperture 15a provided in the aperture 15. Specifically, the control unit 21 adds the offset value to the obtained appropriate current value to adjust the current supplied to the filament 19. That is, the control unit 21 obtains the appropriate current value by the above process at predetermined third total supply time intervals from the start of use of the filament 19 until the first total supply time, and adjusts the current supplied to the filament 19 by adding the offset value to the obtained appropriate current value.

[0044] (Current information) The current information 30 will be described with reference to FIG.

[0045] The current information 30 is information in which a total supply time of a current supplied to the filament 19 to emit electrons is associated with an appropriate current value supplied to the filament 19 to emit electrons. Specifically, the current information 30 is information in which a total supply time is associated with an appropriate current value acquired based on a luminance value based on an X-ray detection signal detected by the X-ray detector 2 while supplying a current to the filament 19 and increasing the supplied current for each predetermined second total supply time interval. The current information 30 is acquired in advance and stored in the storage unit 22. The current information 30 may be stored in the storage unit 22 before or after shipping of the X-ray imaging apparatus 100. The current information 30 stored in the storage unit 22 may be configured to be updatable or to be replaced with new current information 30.

[0046] The current information 30 is information on an appropriate current value obtained by a process of searching for an appropriate current value for the total supply time of the current supplied to the filament 19, which is obtained based on actual measurement data. Specifically, the current information 30 is an approximate curve calculated based on a plot of appropriate current values for the total supply time in a graph in which the vertical axis represents information on appropriate current values for the total supply time of the current supplied to the filament 19 and the horizontal axis represents the total supply time of the current supplied to the filament 19.

[0047] The process of searching for an appropriate current value when acquiring the current information 30 in advance is performed at a predetermined second total supply time interval. That is, an appropriate current value is acquired by the above process performed at each predetermined second total supply time interval. The predetermined second total supply time interval is, for example, a two-hour (total supply time) interval. Note that the predetermined second total supply time interval is not limited to two hours, and may be shorter or longer than two hours. For example, the predetermined second total supply time interval may be 0.5 hours, 1 hour, 4 hours, or 8 hours.

[0048] In acquiring the current information 30, actual measurement data in which the filament 19 was not cut before reaching the predicted maximum usable time of the filament 19 (the predicted life of the filament 19) is used. In acquiring the current information 30, actual measurement data in which the filament 19 was cut and became unusable before reaching the predicted maximum usable time of the filament 19 is not used.

[0049] The initial value is set as an appropriate current value for the total supply time acquired by the first process of searching for an appropriate current value when acquiring the current information 30 in advance. As an example, "160" is set as the initial value as an appropriate current value for the acquired total supply time. Note that the initial value is not limited to "160".

[0050] Then, an approximate curve is calculated for the plot representing the appropriate current value obtained by the process of searching for the appropriate current value performed at each predetermined second total supply time interval. The calculated approximate curve is stored in the storage unit 22 as current information 30.

[0051] Two pieces of current information 30 are acquired: one piece of current information 30 acquired based on actual measurement data acquired under conditions where the tube voltage of the X-ray tube 1 is 120 kV and the tube current is 50 μA, and the other piece of current information 30 acquired based on actual measurement data acquired under conditions where the tube voltage of the X-ray tube 1 is 120 kV and the tube current is 100 μA. The two pieces of current information 30 acquired are stored in the storage unit 22.

[0052] (Adjustment of current supplied to filament during second total supply time after first total supply time) The control unit 21 acquires an appropriate current value by a process of searching for an appropriate current value during the first total supply time, and adjusts the current supplied to the filament 19 during a second total supply time that is after the first total supply time, based on the appropriate current value acquired during the first total supply time and current information 30 that has been acquired in advance and stored in the memory unit 22.

[0053] In non-destructive testing using the X-ray imaging device 100, if X-ray imaging is performed under the same X-ray imaging conditions as either of the two pieces of current information 30, the control unit 21 adjusts the current supplied to the filament 19 based on the current information 30 of the same X-ray imaging conditions during a second total supply time that is later than the first total supply time. Also, in non-destructive testing using the X-ray imaging device 100, if X-ray imaging is performed using tube currents different from 50 μA and 100 μA, the control unit 21 performs linear interpolation processing on the two pieces of current information 30 and adjusts the current supplied to the filament 19 based on the current information 30 that has been linearly interpolated during a second total supply time that is later than the first total supply time.

[0054] After acquiring the appropriate current value for the first total supply time, the control unit 21 acquires a correction value based on the acquired appropriate current value and the appropriate current value in the current information 30 for the first total supply time.

[0055] The control unit 21 acquires the correction value based on, for example, the difference between the appropriate current value acquired during the first total supply time and the appropriate current value in the current information 30 for the first total supply time, the diameter of the aperture 15a of the aperture 15 of the X-ray tube 1, and an offset value based on the diameter of the aperture 15a of the aperture 15. The storage unit 22 stores a correction value table in which the above-mentioned appropriate current value difference, the diameter of the aperture 15a, the offset value based on the diameter of the aperture 15a, and the correction value are associated with each other. The control unit 21 acquires the correction value by referring to the correction value table. Note that the items associated with the correction value in the correction value table are not limited to those described above. Alternatively, the control unit 21 may acquire the correction value using a relational expression in which the correction value is calculated based on the above-mentioned appropriate current value difference, the diameter of the aperture 15a, and the offset value based on the diameter of the aperture 15a, instead of using the correction value table.

[0056] Then, the control unit 21 adjusts the current supplied to the filament 19 during the second total supply time based on the acquired correction value and the appropriate current value during the second total supply time in the current information 30. Specifically, the control unit 21 adjusts the current supplied to the filament 19 by adding or subtracting the acquired correction value from or dividing the appropriate current value during the second total supply time in the current information 30.

[0057] Furthermore, after the first total supply time, the control unit 21 adjusts the current supplied to the filament 19 at each predetermined first total supply time interval based on the acquired correction value and the appropriate current value in the current information 30. The predetermined first total supply time interval is, for example, a two-hour interval (total supply time). Note that the predetermined first total supply time interval is not limited to two hours, and may be an interval shorter or longer than two hours.

[0058] Furthermore, after the first total supply time, the control unit 21 shortens the first total supply time interval for adjusting the current supplied to the filament 19 as the total supply time increases. For example, the predetermined first total supply time interval is set to 2 hours (total supply time) until the total supply time reaches 500 hours, at which the slope of the appropriate current value acquired by the process of searching for an appropriate current value in the actual measurement data relative to the total supply time is small. After 500 hours, at which the slope is large, the predetermined first total supply time interval is changed to 0.5 hours (total supply time), and the control unit 21 adjusts the current supplied to the filament 19 at each predetermined first total supply time interval. The timing for changing the predetermined first total supply time interval is not limited to a total supply time of 500 hours, and may be shorter or longer than 500 hours. The predetermined first total supply time interval may also be changed multiple times, rather than just once. Furthermore, the changed predetermined first total supply time interval is not limited to 0.5 hour intervals, and may be an interval shorter than 0.5 hour intervals or an interval longer than 0.5 hour intervals.

[0059] Therefore, after the first total supply time, the control unit 21 adjusts the current supplied to the filament 19 by adding or subtracting the acquired correction value from the appropriate current value for the second total supply time in the current information 30 at each predetermined first total supply time interval. That is, after the first total supply time, the control unit 21 adjusts the current supplied to the filament 19 based on the current information 30 without performing a process of searching for an appropriate current value. Therefore, the subject 90 placed on the stage does not need to be moved from the stage when adjusting the current supplied to the filament 19. Furthermore, the control unit 21 can perform the adjustment process of the current supplied to the filament 19 in the background. For these reasons, after the first total supply time, it is not necessary to interrupt X-ray imaging for nondestructive testing for the adjustment process of the current supplied to the filament 19.

[0060] (control of the adjustment of the current supplied to the filament) 5, the control of the control unit 21 for adjusting the current supplied to the filament 19 (X-ray imaging method) will be described. Current information 30 is stored in advance in the storage unit 22. When an input operation for ending X-ray imaging is accepted, the control of the control unit 21 for adjusting the current supplied to the filament 19 and the control of X-ray imaging are terminated. The order of the steps can be reversed or executed simultaneously as long as there is no mutual contradiction.

[0061] In step S1, with no subject 90 placed on the stage, control unit 21 obtains an appropriate current value by processing to search for an appropriate current value, and then proceeds to step S2.

[0062] In step S2, the control unit 21 adjusts the current supplied to the filament 19 based on the appropriate current value acquired through the above process. Then, the process proceeds to step S3.

[0063] In step S3, with subject 90 placed on the stage, control unit 21 performs X-ray photography, and then the process proceeds to step S4.

[0064] In step S4, the control unit 21 determines whether a predetermined third total supply time interval has elapsed since the above processing. If the predetermined third total supply time interval has elapsed since the above processing (Yes in step S4), the process proceeds to step S5, and if the predetermined third total supply time interval has not elapsed since the above processing (No in step S4), the process proceeds to step S3.

[0065] In step S5, the control unit 21 determines whether the total supply time from the start of use of the filament 19 has reached the first total supply time. If it has reached the first total supply time (Yes in step S5), the process proceeds to step S6, and if it has not reached the first total supply time (No in step S5), the process proceeds to step S1.

[0066] In step S6, with subject 90 not placed on the stage, control unit 21 obtains an appropriate current value by processing to search for an appropriate current value, and then proceeds to step S7.

[0067] In step S7, the control unit 21 adjusts the current supplied to the filament 19 based on the appropriate current value acquired through the above process. Then, the process proceeds to step S8.

[0068] In step S8, the control unit 21 determines whether or not a predetermined first total supply time interval has elapsed since the previous adjustment of the current supplied to the filament 19. If the predetermined first total supply time interval has elapsed since the previous adjustment of the current supplied to the filament 19 (Yes in step S8), the process proceeds to step S9, and if the predetermined first total supply time interval has not elapsed since the previous adjustment of the current supplied to the filament 19 (No in step S8), the process proceeds to step S8.

[0069] In step S9, the control unit 21 adjusts the current supplied to the filament 19 based on the current information 30. After that, the process proceeds to step S8.

[0070] (Effects of this embodiment) In this embodiment, the following effects can be obtained.

[0071] In the X-ray imaging apparatus 100 and the method for adjusting the current supplied to the filament 19 according to this embodiment, current information 30 is acquired in advance, which associates a total supply time of current supplied to the filament 19 to emit electrons from the filament 19 with an appropriate current value to be supplied to the filament 19 to emit electrons from the filament 19. The current supplied to the filament 19 is adjusted based on the current information 30 after a first total supply time, which is a predetermined total supply time. As a result, after the first total supply time, the current supplied to the filament 19 is adjusted based on the previously acquired current information 30 without performing a process for obtaining an appropriate current value to be supplied to the filament 19 by supplying current to the filament 19. Therefore, after the first total supply time, the process for supplying current to the filament 19 to search for an appropriate current value is not performed, and thus the supply of current to the filament 19 due to the above process can be suppressed. As a result, the usable life of the filament 19 can be prevented from being shortened due to the above process. Furthermore, after the first total supply time, the current supplied to the filament 19 can be appropriately adjusted based on the previously acquired current information 30 without performing the above process.

[0072] Furthermore, the X-ray imaging apparatus 100 according to the above embodiment has the following configuration, thereby providing the following additional effects.

[0073] That is, in this embodiment, as described above, the control unit 21 is configured to adjust the current supplied to the filament 19 based on the appropriate current value acquired by the process of acquiring the appropriate current value to be supplied to the filament 19 by supplying current to the filament 19 until the first total supply time, and to adjust the current supplied to the filament 19 based on the current information 30 during the second total supply time after the first total supply time. As a result, since the appropriate current value is not stable until the first total supply time, the current supplied to the filament 19 can be adjusted based on the appropriate current value acquired by the above process for the filament 19 currently in use. Furthermore, since the appropriate current value is stable during the second total supply time after the first total supply time, the current supplied to the filament 19 can be adjusted based on the current information 30 acquired in advance.

[0074] Furthermore, in this embodiment, as described above, the control unit 21 is configured to acquire an appropriate current value by the above processing during the first total supply time, and to adjust the current supplied to the filament 19 during the second total supply time based on the appropriate current value acquired during the first total supply time and the current information 30. This makes it possible to accurately adjust the current supplied to the filament 19 based on the appropriate current value acquired by the above processing that is actually measured during the first total supply time, and the current information 30 that is acquired in advance.

[0075] Furthermore, in this embodiment, as described above, the control unit 21 is configured to acquire a correction value based on the appropriate current value acquired for the first total supply time and the appropriate current value in the current information 30 for the first total supply time, and to adjust the current supplied to the filament 19 for the second total supply time based on the acquired correction value and the appropriate current value for the second total supply time in the current information 30. This makes it possible to accurately adjust the current supplied to the filament 19 for the second total supply time based on the acquired correction value and the appropriate current value for the second total supply time in the current information 30.

[0076] Furthermore, in this embodiment, as described above, the control unit 21 is configured to adjust the current supplied to the filament 19 at each predetermined first total supply time interval after the first total supply time, based on the appropriate current value in the current information 30. As a result, the current supplied to the filament 19 is adjusted at each predetermined first total supply time interval based on the appropriate current value in the current information 30, and therefore, it is possible to effectively prevent the usable period of the filament 19 from being shortened due to the above processing.

[0077] Furthermore, in this embodiment, as described above, the control unit 21 is configured to shorten the first total supply time interval for adjusting the current supplied to the filament 19 as the total supply time increases after the first total supply time. This shortens the first total supply time interval to adjust the current supplied to the filament 19 for the filament 19, whose wire diameter gradually decreases as the total supply time increases, and therefore makes it possible to more effectively prevent the usable period of the filament 19 from being shortened due to the above process.

[0078] Furthermore, in this embodiment, as described above, the current information 30 is information on an appropriate current value for the total supply time that is acquired in advance based on actual measurement data, and the control unit 21 is configured to adjust the current supplied to the filament 19 after the first total supply time based on the current value information acquired in advance based on actual measurement data. This makes it possible to accurately adjust the current supplied to the filament 19 using the current information 30 acquired in advance based on actual measurement data.

[0079] Furthermore, in this embodiment, as described above, the current information 30 is information in which the total supply time is associated with an appropriate current value acquired based on a brightness value based on an X-ray detection signal detected by the X-ray detector 2 while supplying current to the filament 19 at predetermined second total supply time intervals and increasing the supplied current, and the control unit 21 is configured to adjust the current supplied to the filament 19 after the first total supply time based on the current information 30. This makes it possible to more accurately adjust the current supplied to the filament 19 after the first total supply time based on the current information 30 in which the total supply time is associated with an appropriate current value.

[0080] Furthermore, in this embodiment, as described above, the first total supply time is the total supply time predicted to stabilize the appropriate fluctuation in the current value acquired by the above process as a result of peeling off the oxide film of the filament 19, and the control unit 21 is configured to adjust the current supplied to the filament 19 after the first total supply time based on the current information 30. This makes it possible to appropriately adjust the current supplied to the filament 19 based on the current information 30 after the first total supply time when the appropriate fluctuation in the current value stabilizes.

[0081] [Variations] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than the above description of the embodiments, and further includes all modifications (variations) within the meaning and scope of the claims.

[0082] For example, in the above embodiment, an example was shown in which the X-ray imaging device is used for non-destructive testing, but the present invention is not limited to this. For example, the X-ray imaging device may be configured to be used for medical purposes. In this case, the subject is a living body to be inspected.

[0083] In addition, although the above embodiment shows an example in which there are two pieces of current information, the present invention is not limited to this. For example, the current information may include only one standard piece of current information, or may include three or more different pieces of current information.

[0084] Furthermore, in the above embodiment, an example was shown in which two pieces of current information were acquired: current information acquired based on actual measurement data acquired under conditions of an X-ray tube voltage of 120 kV and a tube current of 50 μA, and current information acquired based on actual measurement data acquired under conditions of an X-ray tube voltage of 120 kV and a tube current of 100 μA. However, the present invention is not limited to this. For example, the values of the tube voltage and tube current under the conditions of the actual measurement data of the current information are not limited to those described above, and the values of the tube voltage and tube current under the conditions of the actual measurement data of the current information may be other values.

[0085] In the above embodiment, the control unit adjusts the current supplied to the filament based on an appropriate current value acquired by a process of searching for an appropriate current value up to the first total supply time, but the present invention is not limited to this. For example, the control unit may not adjust the current supplied to the filament up to the first total supply time, or may be configured to adjust the current supplied to the filament based on an appropriate current value acquired by another known method up to the first total supply time.

[0086] In the above embodiment, the control unit adjusts the current supplied to the filament based on the appropriate current value and current information acquired by the process of searching for an appropriate current value during the first total supply time, but the present invention is not limited to this. For example, the control unit may be configured to adjust the current supplied to the filament based on the appropriate current value and current information acquired by the process before the first total supply time.

[0087] In the above embodiment, the control unit acquires a correction value based on the appropriate current difference, the diameter of the aperture, and the offset value, and adjusts the current supplied to the filament based on the acquired correction value and current information, but the present invention is not limited to this. For example, the control unit may be configured to acquire an appropriate current difference, and adjust the current supplied to the filament based on the acquired appropriate current difference and current information.

[0088] In the above embodiment, the control unit shortens the first total supply time interval as the total supply time increases, but the present invention is not limited to this. For example, the first total supply time interval after the first total supply time may be constant.

[0089] In the above embodiment, the current information is information in which the total supply time is associated with an appropriate current value acquired based on a luminance value based on an X-ray detection signal while supplying and increasing a current to the filament at each predetermined second total supply time interval, but the present invention is not limited to this. For example, the appropriate current value in the current information does not have to be acquired based on a luminance value based on an X-ray detection signal while supplying and increasing a current to the filament at each predetermined second total supply time interval.

[0090] In the above embodiment, the current information is an approximate curve calculated based on a plot of appropriate current values for a total supply time previously obtained based on actual measurement data. However, the present invention is not limited to this. For example, the current information may be a table in which appropriate current values are associated with total supply times previously obtained based on actual measurement data. For example, the current information may be configured to input data such as X-ray imaging conditions into a trained model previously created using various machine learning techniques, including deep learning, and output an appropriate current value for the total supply time.

[0091] [Aspect] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0092] (Item 1) an X-ray tube including a target and an electron emitter provided with a filament and emitting electrons toward the target; an X-ray detector that detects X-rays emitted from the X-ray tube; a storage unit that stores previously acquired current information that associates a total supply time of a current that is supplied to the filament in order to emit electrons from the filament with an appropriate current value that is supplied to the filament in order to emit electrons from the filament; and a control unit that performs control to adjust the current supplied to the filament based on the current information after a first total supply time as the predetermined total supply time.

[0093] (Item 2) 2. The X-ray imaging apparatus according to claim 1, wherein the control unit is configured to adjust the current supplied to the filament based on the appropriate current value acquired by a process of acquiring the appropriate current value supplied to the filament by supplying current to the filament until the first total supply time, and to adjust the current supplied to the filament based on the current information during a second total supply time that is after the first total supply time.

[0094] (Item 3) 3. The X-ray imaging apparatus according to item 2, wherein the control unit is configured to acquire the appropriate current value by the processing during the first total supply time, and to adjust the current supplied to the filament during the second total supply time based on the appropriate current value acquired during the first total supply time and the current information.

[0095] (Item 4) Item 4. The X-ray imaging apparatus according to item 3, wherein the control unit is configured to acquire a correction value based on the appropriate current value acquired for the first total supply time and the appropriate current value in the current information for the first total supply time, and to adjust the current supplied to the filament for the second total supply time based on the acquired correction value and the appropriate current value for the second total supply time in the current information.

[0096] (Item 5) 5. The X-ray imaging device according to any one of items 1 to 4, wherein the control unit is configured to adjust the current supplied to the filament based on the appropriate current value in the current information for each predetermined first total supply time interval after the first total supply time.

[0097] (Item 6) 6. The X-ray imaging apparatus according to item 5, wherein the control unit is configured to, after the first total supply time, shorten the first total supply time interval for adjusting the current supplied to the filament as the total supply time becomes longer.

[0098] (Item 7) the current information is information on the appropriate current value for the total supply time, which is acquired in advance based on actual measurement data, 7. The X-ray imaging device according to any one of items 1 to 6, wherein the control unit is configured to adjust the current supplied to the filament after the first total supply time based on information about the current value acquired in advance based on actual measurement data.

[0099] (Item 8) the current information is information in which the total supply time is associated with the appropriate current value acquired based on a luminance value based on an X-ray detection signal detected by the X-ray detector while supplying a current to the filament and increasing the supplied current at each predetermined second total supply time interval, 8. The X-ray imaging apparatus according to item 7, wherein the control unit is configured to adjust the current supplied to the filament based on the current information after the first total supply time.

[0100] (Item 9) the first total supply time is a total supply time predicted to stabilize fluctuations in the appropriate current value obtained by the process as a result of peeling off the oxide film of the filament, 5. The X-ray imaging device according to any one of items 2 to 4, wherein the control unit is configured to adjust the current supplied to the filament based on the current information after the first total supply time.

[0101] (Item 10) 1. A method for adjusting a current supplied to a filament in an X-ray imaging device equipped with an X-ray tube including a target and an electron emitter provided with a filament and emitting electrons to the target, comprising: a step of previously acquiring current information in which a total supply time of a current supplied to the filament for emitting electrons from the filament is associated with an appropriate current value supplied to the filament for emitting electrons from the filament; a step of adjusting the current supplied to the filament based on the current information after a first total supply time as the predetermined total supply time. [Explanation of symbols]

[0102] 1 X-ray tube 2 X-ray detector 9 X-ray 10 Target 11 Electron emission part 19 Filaments 21 Control section 22 Memory section 30 Current information 100 X-ray equipment

Claims

1. an X-ray tube including a target and an electron emitter provided with a filament and emitting electrons toward the target; an X-ray detector that detects X-rays emitted from the X-ray tube; a storage unit that stores previously acquired current information that associates a total supply time of a current that is supplied to the filament in order to emit electrons from the filament with an appropriate current value that is supplied to the filament in order to emit electrons from the filament; and a control unit that performs control to adjust the current supplied to the filament based on the current information after a first total supply time as the predetermined total supply time.

2. 2. The X-ray imaging apparatus according to claim 1, wherein the control unit is configured to adjust the current supplied to the filament based on the appropriate current value acquired by a process of acquiring the appropriate current value supplied to the filament by supplying current to the filament until the first total supply time, and to adjust the current supplied to the filament based on the current information during a second total supply time that is after the first total supply time.

3. 3. The X-ray imaging device according to claim 2, wherein the control unit is configured to acquire the appropriate current value by the processing during the first total supply time, and to adjust the current supplied to the filament during the second total supply time based on the appropriate current value acquired during the first total supply time and the current information.

4. 4. The X-ray imaging device according to claim 3, wherein the control unit is configured to acquire a correction value based on the appropriate current value acquired for the first total supply time and the appropriate current value in the current information for the first total supply time, and to adjust the current supplied to the filament for the second total supply time based on the acquired correction value and the appropriate current value for the second total supply time in the current information.

5. 2. The X-ray imaging apparatus according to claim 1, wherein the control unit is configured to adjust the current supplied to the filament based on the appropriate current value in the current information for each predetermined first total supply time interval after the first total supply time.

6. 6. The X-ray imaging apparatus according to claim 5, wherein the control unit is configured to, after the first total supply time, shorten the first total supply time interval for adjusting the current supplied to the filament as the total supply time becomes longer.

7. the current information is information on the appropriate current value for the total supply time, which is acquired in advance based on actual measurement data, 2. The X-ray imaging apparatus according to claim 1, wherein the control unit is configured to adjust the current supplied to the filament after the first total supply time based on information about the current value acquired in advance based on actual measurement data.

8. the current information is information in which the total supply time is associated with the appropriate current value acquired based on a luminance value based on an X-ray detection signal detected by the X-ray detector while supplying a current to the filament and increasing the supplied current at each predetermined second total supply time interval, The X-ray imaging apparatus according to claim 7 , wherein the control unit is configured to adjust the current supplied to the filament based on the current information after the first total supply time.

9. the first total supply time is a total supply time predicted to stabilize fluctuations in the appropriate current value obtained by the process as a result of peeling off the oxide film of the filament, The X-ray imaging apparatus according to claim 2 , wherein the control unit is configured to adjust the current supplied to the filament based on the current information after the first total supply time.

10. 1. A method for adjusting a current supplied to a filament in an X-ray imaging apparatus equipped with an X-ray tube including a target and an electron emitter provided with a filament and emitting electrons toward the target, comprising: a step of acquiring current information in advance, in which a total supply time of a current supplied to the filament for emitting electrons from the filament is associated with an appropriate current value supplied to the filament for emitting electrons from the filament; a step of adjusting the current supplied to the filament based on the current information after a first total supply time as the predetermined total supply time.

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