JP2003317996A - X-ray tube and x-ray apparatus using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-size X-ray apparatus having a microfocus X-ray tube, capable of high-magnification photography. <P>SOLUTION: The microfocus X-ray tube 20 adopts a neutral point grounding method. Grid voltages applied to a plurality of grid electrodes 106, 108, and 110 disposed for forming a microfocus are generated in a grid voltage generation circuit 24 by use of a voltage divided from a negative high voltage generation part of a high voltage generation circuit 22. The grid voltage generation circuit 24 is controlled by an optical signal from a grid voltage control part 42 of a control part 32. The grid voltage generation circuit 24 and the grid voltage control part 42 are connected by an optical cable 224. By adopting the neutral point grounding method to the X-ray tube 20, an interval between the focus and an X-ray radiation window (an envelope) can be reduced to enable the high-magnification photography. Use of an insulation transformer becomes unnecessary in the grid voltage generation circuit 24 to miniaturize the X-ray apparatus. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a micro focus (hereinafter,
The present invention relates to a technique for increasing the geometric magnification of X-ray photography in an X-ray tube having a micro focus) and an X-ray apparatus incorporating the same.

[0002]

2. Description of the Related Art An X-ray tube such as an ordinary X-ray machine for medical or industrial use, a radiography apparatus, an X-ray exposure apparatus or the like is often equipped with an X-ray tube as an X-ray radiation source. A high voltage having a necessary potential difference according to desired X-ray energy is applied between the cathode and the anode of those X-ray tubes. As a method of applying this high voltage, in a normal X-ray tube, a so-called neutral point grounding method is adopted in which a high voltage is applied to the anode and the cathode by positively and negatively distributed with respect to the ground potential. By adopting the neutral grounding method in this way, the X-ray apparatus is downsized.

On the other hand, when the object to be seen through is a minute object or an ultrafine object, the dimension of the X-ray generation source (focus) of the X-ray tube is required to be on the order of several μm. Such an X-ray tube having a micro focus on the order of several μm is called a microfocus X-ray tube. In order to obtain such a microfocus, the electron beam trajectory is focused on the cathode of the X-ray tube and the outer diameter of the electron beam itself is set to a few μm.
It is necessary to form it to a size of m order.

Conventionally, in a microfocus X-ray tube, a plurality of grid electrodes are arranged on the cathode, an electrostatic lens is formed by the electric field distribution formed by the voltage applied to these grid electrodes, and the electrostatic lens is used to generate an electron beam. The method of converging the orbit is adopted. At this time, different potential difference voltages are applied to the plurality of grid electrodes, and control is performed so that an arbitrary focus size can be formed. In the case of such an X-ray tube, since it is necessary to control the voltage applied to the grid electrode, the neutral point grounding method used in a normal X-ray tube is not adopted, and the cathode grounding method is mainly used. It is used.

X having such a micro focus
As a technique relating to a ray tube and an X-ray device incorporating the same, there are known techniques described in US Pat. No. 5,077,771, US Pat. No. 4,646,338, US Pat. No. 4,694,48, and JP-A-7-29532.

US Pat. No. 5,077,771 and US Pat. No. 4,646,338
No. 4,694,480, a portable X-ray tube consisting of an X-ray tube and a molded high voltage power supply and control circuit.
A line device is disclosed.

In these X-ray apparatuses, as a method of applying a voltage to the X-ray tube, a cathode ground, a target ground, or a method of varying the focus voltage is used.
However, neither method is suitable for a method of generating and controlling microfocus X-rays, which is an important requirement for an X-ray apparatus incorporating a microfocus X-ray tube.

Further, the voltage control system of the high voltage generating circuit of each part is a pulse width modulation (PWM) system, and the effective voltage is controlled by changing the pulse width of the control pulse. The followability on the high voltage (secondary coil) side was poor, and the fluctuation of the X-ray output was large.

Further, Japanese Patent Laid-Open No. 7-29532 discloses a technique for solving the above problem. That is, in the X-ray device of Japanese Patent Laid-Open No. 7-29532, first, an X-ray tube including a cathode, a target, a focus electrode having a ground potential, and an envelope having a ground potential, and a change in the voltage applied to the target are linked. And a control circuit that controls the voltage applied to the cathode to change at a constant ratio.The control circuit keeps the outer diameter of the electron beam that forms a minute focal point constant and changes the X-ray output. It's suppressed.

[0010]

In the above conventional microfocus X-ray tube, in order to easily control the voltage applied to the grid electrode, the reference potential of the entire cathode (cathode side is shared among the acceleration voltage of the electron beam is shared). Potential) is a ground potential or a low voltage potential that is considered to be substantially the ground potential compared to the desired X-ray tube voltage. A bias voltage is applied to each grid electrode based on this reference potential. Therefore, X to obtain the desired X-ray energy
Almost all of the tube voltage is borne by the anode side. Therefore, in order to safely maintain the withstand voltage characteristics between the envelope and the anode, which are at the ground potential, the distance between the two must be secured to a certain value or more.

On the other hand, the microfocus X-ray tube is required to have a higher geometrical magnifying power in order to magnify and photograph a fine object to be photographed. In order to obtain a high magnification in an X-ray tube, it is required to reduce the distance between the focus of the X-ray tube and the envelope (in particular, the position of the X-ray emission window). For this reason, it is difficult to reduce the distance between the focus and the envelope with an X-ray tube of a type in which the reference potential of the entire cathode is a ground potential or a low voltage close to it, and it is possible to obtain the above high magnification. Will be difficult.

In view of the above, it is an object of the present invention to provide a compact microfocus X-ray tube which can obtain a high magnification and an X-ray apparatus using the same.

[0013]

In order to achieve the above object, an X-ray tube of the present invention has a cathode electrode for emitting an electron beam and a plurality of grid electrodes for controlling the orbit and current amount of the electron beam. A cathode, an anode having a target that generates X-rays by the collision of the electron beam,
The cathode and the anode are hermetically sealed in a vacuum-tight manner, and are composed of an envelope having an X-ray emission window that radiates X-rays generated in the target to the outside, by controlling the grid voltage applied to the grid electrode. In an X-ray tube for obtaining a micro focus, the envelope is set to ground potential, the X-ray tube voltage is divided into two equal parts, and the negative high voltage is applied to the cathode electrode of the cathode.
The positive high voltage is applied to the anode (claim 1).

In this structure, the neutral point grounding system is adopted in which the envelope is set to the ground potential and the positive and negative high voltages are applied to the anode and the cathode in the microfocus X-ray tube.
Compared with the conventional microfocus X-ray tube with the same X-ray tube voltage, the voltage applied between the envelope and the anode is reduced to about 1/2, so it is possible to narrow the distance between the envelope and the anode. It will be possible. As a result, the distance between the focal point of the X-ray tube and the X-ray radiation window can be shortened, and the geometrical magnification rate at the time of magnifying imaging by microfocus can be increased, resulting in a fine image of a minute object. Can be obtained.

Further, in the X-ray tube of the present invention, an independent grid voltage is applied to each of the plurality of grid electrodes with a negative high voltage applied to the cathode electrode as a reference potential.

In this configuration, since the grid voltages applied to the plurality of grid electrodes are independent of each other, these independent grid voltages should be appropriately applied to the plurality of grid electrodes with reference to the potential of the cathode electrode. Due to
An appropriate electrostatic lens for focusing the electron beam can be easily formed on the front surface of the cathode electrode. As a result, focusing of the electron beam from the cathode electrode is facilitated, and microfocusing is facilitated.

Further, the X-ray apparatus of the present invention comprises the above-mentioned X-ray tube, a high voltage generating circuit for generating high positive and negative voltages for applying to the anode and the cathode of the X-ray tube, and the X-ray tube. A grid voltage generation circuit that generates a plurality of grid voltages to be applied to the grid electrode of the line tube, a control unit that controls the operations of the high voltage generation circuit and the grid voltage generation circuit, and control data to the control unit. And an container for storing at least the X-ray tube, the high voltage generating circuit and the grid voltage generating circuit in an insulated manner (Claim 2).

Since the X-ray apparatus of this construction is provided with a neutral-point grounding type microfocus X-ray tube, and a power supply and a control unit for driving and controlling the same, it is possible to perform a magnifying imaging examination of a subject. The distance between the focal point and the subject can be reduced and the geometric magnification can be increased as compared with the conventional microfocus X-ray apparatus. As a result, a fine image of the minute object of the subject can be obtained.

Further, in the X-ray apparatus of the present invention, the voltage used for generating the grid voltage in the grid voltage generating circuit is further divided from the high voltage generated in the negative high voltage generating section of the high voltage generating circuit. I'm using it.

In this configuration, since the high voltage generated in the negative high voltage generating section of the high voltage generating circuit is directly used after being divided for generating the grid voltage, the grid voltage is generated as in the conventional X-ray apparatus. Since it is not necessary to use an isolation transformer for, a compact X-ray device with an integrated power supply can be realized.

Further, in the X-ray apparatus of the present invention, the potential difference of the high voltage generated in the negative high voltage generating section of the high voltage generating circuit is more than that of the high voltage generated in the positive high voltage generating section. It's high.

In this structure, the potential difference generated in the negative high voltage generating section of the high voltage generating circuit used by dividing the voltage for generating the grid voltage is higher than the potential difference generated in the positive high voltage generating section. Therefore, it is possible to generate a potential lower than the potential of the cathode electrode, which is the reference potential on the cathode side of the X-ray tube, as the grid voltage that uses the high voltage generated by the negative high voltage generator. . As a result, since positive and negative grid voltages can be applied to the plurality of grid electrodes with respect to the reference potential on the cathode side, it is easy to form an electrostatic lens with high accuracy for the electron beam.

Further, in the X-ray apparatus of the present invention, the high voltage generating circuit is a cockcroft circuit, and the number of sets of capacitors and diodes is set so that the high voltage generated in the negative high voltage generating part of the cockcroft circuit is high. Is one or more than that of the positive high voltage generating section (hereinafter, the section in which the number of pairs of the capacitor and the diode is increased is abbreviated as an additional section).

In this configuration, since the high voltage generating circuit is the Cockcroft circuit, it is easy to provide the positive and negative high voltage generating portions, and the number of sets of capacitors and diodes in the positive and negative high voltage generating portions is large. It is also possible to easily change the voltage values generated by the two by changing. Further, since the additional portion is provided in the negative high voltage generation portion, the potential difference of the negative high voltage generation portion is higher than the potential difference of the positive high voltage generation portion.

Further, in the X-ray apparatus of the present invention, the voltage generated in the additional portion of the negative high voltage generating portion of the Cockcroft circuit is divided and used for generating the grid voltage of the grid voltage generating circuit. is there.

In this configuration, since the voltage generated in the additional portion of the negative high voltage generating portion of the Cockcroft circuit is used as the input voltage of the grid voltage generating circuit, it is not necessary to provide a separate power source for generating the grid voltage. The grid voltage generation circuit is simplified, which contributes to downsizing of the X-ray device.

Further, in the X-ray apparatus of the present invention, the grid voltage generated by the grid voltage generating circuit is further changed by an optical signal sent to the grid voltage generating circuit via an optical cable insulated from the control section. Controlled (Claim 3).

In this configuration, since the grid voltage is controlled by the optical signal sent from the control section through the optical cable, the grid voltage generating circuit and the control section are completely insulated. As a result, it is not necessary to use an insulating transformer for generating grid voltage as in the conventional case, which contributes to downsizing of the X-ray device.

Further, in the X-ray apparatus of the present invention, the grid voltage of the grid voltage generating circuit is further controlled by the optical signal controlled by the pulse width modulation (PWM) control method in the control section.

In this configuration, the voltage value of the grid voltage is
Since it is controlled by the PWM control method with small frequency fluctuation and high pulse width accuracy, the accuracy of the grid voltage value improves and becomes stable.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of an X-ray apparatus according to an embodiment of the present invention. The overall configuration of the X-ray apparatus will be described with reference to FIG.

In FIG. 1, an X-ray apparatus 10 according to the present invention is
An X-ray tube 20 provided with a micro focus, a high voltage generation circuit 22 for supplying a high voltage to the X-ray tube 20, and a grid voltage generation circuit 24 for supplying a grid voltage to a grid electrode forming the cathode of the X-ray tube 20. A cathode power supply circuit 26 for heating the cathode of the X-ray tube 20, a stator 28 for rotationally driving the anode of the X-ray tube 20, an anode rotating power supply 30 for energizing the stator 28, and these power supplies. A control unit 32 that controls the circuit and controls the operation of the X-ray tube 20, an interface unit 34 that allows an operator to input data to the control unit 32, and a storage container 36 that stores the X-ray tube 20 and various power sources. Etc.

Here, the control unit 32 includes a high voltage control unit (40) for controlling the high voltage generation circuit 22 and a grid voltage generation circuit.
A grid voltage control unit (42) for controlling 24, a cathode control unit (44) for controlling the cathode power supply circuit 26, an anode rotation control unit for controlling the anode rotation power supply 30, and other control units for performing other controls. Composed of. Of these control units, high voltage is involved except for the anode rotation control unit.

FIG. 2 shows an example of the arrangement of main components in the storage container in the X-ray apparatus of this embodiment. In FIG.
The storage container 36 is a rectangular parallelepiped housing made of a metal plate, and a lead plate for X-ray prevention is attached to a necessary portion of the inner surface. The shape of this housing may be another shape such as a cylindrical body. In the center of the storage container 36, the X-ray tube 20 is fixed to the lower wall of the storage container 36 with its anode end supported by a fixing member 62 mainly made of an insulating material. At this time,
The X-ray radiation window 136 of the X-ray tube 20 is dimensionally adjusted so as to be arranged close to the upper wall surface of the storage container 36. Also, X-ray tube 2
The cathode-side power supply unit 118 of 0 is arranged toward the left wall surface of the storage container 36.

Further, the high voltage generating circuit 22 is insulated and supported on the right side wall surface of the storage container 36, and the grid voltage generating circuit 24 and the cathode power supply circuit 26 are insulated and supported on the left side wall surface.
A stator 28 for rotating the rotating anode 120 is arranged on the outer periphery of the X-ray tube 20 on the anode side. The inside of the storage container 36 is filled with insulating oil 60 in order to insulate each component from each other. For this insulation, in addition to the insulating oil 60, other liquid insulation materials or gaseous insulation materials such as sulfur hexafluoride (SF ₆ ) may be used.

FIG. 3 is a structural view of an embodiment of the X-ray tube 20 according to the present invention, and FIG. 4 is an enlarged view of the cathode structure. In FIG. 3, the X-ray tube 20 equipped with a micro focus is arranged such that the cathode 100 that generates the electron beam 62 collides with the electron beam 62 and the X
It consists of a rotating anode 120 that generates a wire, and an envelope 130 that insulates and supports the cathode 100 and the rotating anode 120 and hermetically seals them in a vacuum. The X-ray tube 20 of the present embodiment is used in a neutral point grounding system, the envelope 130 is held at the ground potential, a positive high voltage is applied to the rotating anode 120, and a negative voltage is applied to the cathode 100. High voltage is applied respectively.

The cathode 100 includes a heater electrode 102, a cathode electrode 104, a grid electrode (hereinafter sometimes abbreviated as G1 or G1 electrode) 106, and a focus electrode (composed of two types of electrodes). The electrodes are distinguished from the second focus electrodes.
2, G3 or G2 electrode, sometimes abbreviated as G3 electrode) 10
8 and 110, and a cathode support 112. The grid electrode 106 and the focus electrodes 108 and 110 have different names due to their functional differences, but since they are both electrodes for focusing the electron beam 62, they are collectively referred to as grid electrodes in the following description, and G1, It may be distinguished by G2 and G3.

The cathode electrode 104 is a thermoelectron emission source, and an impregnated cathode is used in this embodiment. In this impregnated cathode, porous tungsten and barium oxide (Ba
O), calcium oxide (CaO), alumina (Al ₂ O ₃ ) is impregnated, and its electron emission surface is coated with osmium (Os), iridium (Ir), osmium / ruthenium alloy (Os / Ru), etc. . By coating with osmium (Os), the operating temperature of the cathode can be lowered by about 100 ° C compared to that without the coating, so the cathode has a longer life.

The heater electrode 102 is provided inside the cathode electrode 104.
Is provided, and thermionic electrons are emitted from the electron emission surface of the cathode electrode 104 by heating to a constant temperature by a heater voltage supplied from a heater power supply described later. The thermoelectrons generated at the cathode electrode 104 are focused by the grid electrode 106 and the focus electrodes 108 and 110 to form a narrow electron beam (X-ray tube current) 62.

3 and 4, the grid electrode 106 and the focus electrodes 108 and 110 are made of a metal material such as molybdenum (Mo) having excellent heat resistance and heat dissipation, and are concentric with the front surface of the cathode electrode 104 as shown. An electrostatic lens for focusing the electron beam 62 is formed by applying a bias potential supplied from a grid voltage generating circuit 24, which will be described later, at intervals. The grid electrode 106 and the focus electrodes 108 and 110 are provided with holes through which the electron beam 62 from the cathode electrode 104 is passed in order to form a desired fine focus, and the shape of each electrode is determined by applying a bias potential. It is designed to have an electron beam focusing effect.

The heater electrode 102, the cathode electrode 104, the grid electrode 106, the focus electrodes 108 and 110 are the cathode support 112.
Insulated and supported by. The cathode support 112 of this embodiment is composed of an insulating strut 114 and a stem 116.
Reference numeral 14 insulates and supports the outer peripheral portion of each electrode as shown in FIG. 4, and stem 116 supports the assembly of the insulating support 114 and each electrode as shown in FIG. The insulating pillar 114 is composed of a plurality of pillars (2 to 4 pieces) of an insulator such as multi-form glass, and the grid electrode 106 and the focus electrode 1 are formed on these pillars.
The outer peripheral portions of 08 and 110 are attached via metal fittings 111.

The stem 116 is made of an insulating material such as heat resistant glass, and the lead for supplying power to the grid electrode 106 and the like is enclosed therein. An assembly of the insulating support 114 and each electrode is attached to the stem 116 via a lead or the like, and wiring between each electrode and the lead is performed.

Next, referring to FIG. 3, the rotating anode 12 of the X-ray tube 20.
0 is a target 122 that collides with the electron beam 62 from the cathode 100 to generate X-rays, a rotating portion 124 that supports and rotates the target 122, and a fixed portion that rotatably supports the rotating portion 124.
It is composed of 126 and. Target 122 is tungsten
It is made of a refractory metal (or alloy) material having a high atomic number, such as (W) and tantalum (Ta), which has a high X-ray generation efficiency. Its shape is a truncated cone, and the inclination angle θ is provided in the X-ray radiation direction X. In this embodiment, the target 12
The inclination angle θ of 2 is about 25 degrees with respect to the plane perpendicular to the trajectory of the electron beam 62.

The rotating part 124 includes a target support shaft 124a for supporting the target 122, a rotor 124b which receives a rotating magnetic field from a stator 28 arranged outside the X-ray tube 20 and rotates, and a rotor 124b arranged inside the rotor 124b. And a bearing that rotatably supports the rotating shaft. The fixed portion 126 is
A fixed part main body having a terminal that supports the bearing of the rotating part 124 and receives a positive high voltage supplied from the high voltage generation circuit 22,
It is composed of a fixed part insulator that connects the fixed part 126 to the envelope 130.

The envelope 130 includes a body portion 132 that encloses the cathode 100 and the target 122 portion of the rotating anode 120, and the rotating anode.
It is composed of a rotating part 124 of 120 and an anode sealing part 134 that encloses the fixed part 126. The body portion 132 has a cylindrical shape with disk-shaped bottoms at both ends, and is mostly made of a metal material such as stainless steel or copper. A cathode support 112 of the cathode 100 is connected to a substantially central portion of the cylindrical portion 132a of the body portion 132 via a stem 116. The body part 132 and the stem 116 are
A metal material that matches the coefficient of thermal expansion with the insulators that make up 116
For example, the connection is made by interposing Kovar or the like, and consideration is given so that the insulation distance between the metal portion of the body portion 132 and the lead enclosed in the stem 116 is sufficient.

An X-ray radiation window 136 is attached to a portion of one disk-shaped portion 132b of the body portion 132 near the X-ray generation portion (hereinafter also referred to as a focus) 123 of the target 122. X-ray emission window 1
Beryllium (Be), which has a high X-ray transmittance, is used as the material of 36, and the thin plate of beryllium is brazed to a window frame made of a metal material such as stainless steel to form a body 132.
Is connected by welding or the like.

The opening 1 is formed in the other disk-shaped portion 132c of the body portion 132.
32d is provided, and one end of a cylindrical anode sealing portion 134 is connected to the opening 132d. Most of the cylindrical portion of the anode sealing portion 134 is made of an insulating material such as glass or ceramic, and is connected to the body portion 132 by interposing a metal material such as Kovar. The connection between the anode sealing portion 134 and the fixed portion 126 of the rotary anode 120 is similarly made.

Next, power feeding to the X-ray tube 20 will be described with reference to FIG. First, the rotating anode 120 and the cathode 10 of the X-ray tube 20.
High positive and negative high voltages are applied to 0 from the high voltage generation circuit 22. The positive high voltage is applied directly to the rotating anode 120 via the wiring 140, but the negative high voltage is applied to the cathode 100 via the wiring 142, the grid voltage generating circuit 24, and the wiring 144. Via the cathode electrode 104. cathode
Three grid voltages generated by the grid voltage generation circuit 24 are applied to the grid electrode 106 and the focus electrodes 108 and 110 of 100 through wirings 145, 146 and 147. Also, cathode 1
The voltage from the heater power supply is applied to the heater electrode 102 of 00 via the grid voltage generating circuit 24 and the wirings 144 and 148. At this time, the cathode electrode 104 and the heater electrode 102
One of the terminals has the same potential, and the common wiring 144 is used. Further, the power supply to the low voltage side of each high voltage circuit and the stator 28 is performed from the control unit 32.

FIG. 5 shows a schematic configuration of an embodiment of the high voltage generating circuit according to the present invention. FIG. 5 also shows the high voltage control unit, the X-ray tube, and the grid voltage generation circuit related to the high voltage generation circuit. In FIG. 5, a high voltage generating circuit 22 employs a Cockcroft-Walton circuit type voltage doubling circuit (hereinafter, abbreviated as Cockcroft circuit) including a combination of a capacitor and a diode. Although various values can be taken as the value of the high voltage generated by the high voltage generation circuit 22, in the case of the present embodiment, the maximum value of the X-ray tube voltage applied to the X-ray tube 20 is set to 150 kV, and the value is set to the anode side. + 75kV, -75 on the cathode side
It adopts the neutral point grounding method in which each voltage of kV is applied.

In the illustrated example, the Cockcroft circuit 150
Consists of an anode-side Cockcroft circuit 151 and a cathode-side Cockcroft circuit 152. The former is composed of a combination of four capacitors and four diodes, and the latter is composed of a combination of five capacitors and five diodes. The maximum value of the voltage generated by one set of capacitor and diode is about 18.75kV. With respect to the cathode-side Cockcroft circuit 152, one set of capacitors and diodes is added in order to divide the input voltage of the grid voltage generation circuit 24 and use it. It goes without saying that the number of sets of capacitors and diodes in the Cockcroft circuit 150 is not limited to the above and may be increased or decreased.

In the Cockcroft circuit 150, the transformer T
When the output voltage of the secondary side of 154 is Vm, the voltage value at each node of the anode-side Cockcroft circuit 151 and the cathode-side Cockcroft circuit 152 of the Cockcroft circuit 150 is Vm, 2 sequentially.
Vm, 3Vm, ... and increase. However, in the cathode-side Cockcroft circuit 152, it has a negative sign. Here, the maximum voltage value is 4 Vm on the anode side, whereas it is 5 Vm on the cathode side.

In the cathode-side Cockcroft circuit 152, in order to generate a voltage (grid voltage) to the grid electrode,
The voltage generated at the third node 156 and the fifth node 158 will be divided. The voltage −4Vm at the fourth node 157 is applied to the cathode electrode 104 as a reference potential on the cathode side. Third node 15
The voltage of 6 −3 Vm and the voltage of the fifth node 158 −5 Vm are used for the grid voltage. That is, a voltage of 2 Vm is input to the grid voltage generating circuit 24, where G1 voltage, G2 voltage, and G3 voltage are generated and applied to the electrodes of G1106, G2108, and G3110. At this time, regarding the G1, G2, and G3 voltages, the potential difference from the reference potential of the cathode electrode 104 is used for forming the electrostatic lens.

FIG. 6 shows a schematic structure of a high voltage control unit for controlling the high voltage generation circuit 22 shown in FIG. In FIG. 6, in order to facilitate understanding of the mutual relationship, in addition to the high voltage control unit 40, the X-ray tube 20 which is a part involved in high voltage generation, the high voltage generation circuit 22,
The interface unit 34 is also shown. The control of high voltage generation will be described below with reference to FIGS.

In FIG. 6, the high voltage generating circuit 22 includes an anode side high voltage generating section 22a and a cathode side high voltage generating section 22b, and an interface section 34 is a tube for an operator to input a set value of the X-ray tube voltage. A voltage setting unit 162 is provided. High voltage controller 40
Is an anode side voltage setting unit 164 that sets the voltage generated by the anode side high voltage generating unit 22a, a cathode side voltage setting unit 166 that sets the voltage generated by the cathode side high voltage generating unit 22b, and the anode side. Anode-side voltage detection unit 168 that detects the voltage generated by the high-voltage generation unit 22a, cathode-side voltage detection unit 170 that detects the voltage generated by the cathode-side high-voltage generation unit 22b, and anode-side voltage detection unit 168 Tube voltage determination unit 1 for determining the actually generated X-ray tube voltage by adding the output of the
72, and a comparison unit 174 that compares the actually measured X-ray tube voltage with the X-ray tube voltage set by the tube voltage setting unit 162.

In generating the high voltage X-ray tube voltage by the high voltage generating circuit 22 in FIG. 6, the operator first sets the set value of the X-ray tube voltage from the tube voltage setting section 162 of the interface section 34. input. Then, in the high voltage control unit 40, based on the X-ray tube voltage value set by the tube voltage setting unit 162, the anode side high voltage generation unit 22a and the cathode side high voltage generation unit 22b of the high voltage generation circuit 22 are set to the anode. Side voltage setting unit 164 and cathode side voltage setting unit 16
Control via 6 to generate the set X-ray tube voltage,
It is applied to the rotating anode 120 and the cathode 100 of the X-ray tube 20. For example, X
When generating a tube voltage of 150 kV, the tube voltage setting unit 16
This X-ray tube voltage is set at 2, and based on this, the anode side voltage setting section 164 and the cathode side voltage setting section 166 of the high voltage control section 40.
As a result, the secondary side output of the transformer T154 in FIG.
It is controlled to be 8.75kV (Vm), so that positive 75kV (4Vm) is on the output side of the anode side high voltage generator 22a and negative 75kV is on the output side of the cathode side high voltage generator 22b. (−4Vm) is generated respectively.

The voltage generated at the output side of the anode side high voltage generating section 22a and the cathode side high voltage generating section 22b is the anode side voltage detecting section 168.
Is detected by the cathode side voltage detection unit 170. 5, an anode-side Cockcroft circuit 151 of the Cockcroft circuit 150 (corresponding to the anode-side high voltage generator 22a of FIG. 6) and a cathode-side Cockcroft circuit 152 (cathode-side high voltage generator 22b of FIG. 6).
(Corresponding to the above) is connected to a resistance voltage divider (not shown) at the fourth nodes 155 and 157, which are the final stage. Anode-side voltage detection unit 168 and cathode-side voltage detection unit 170 of FIG. 6, using the resistance voltage divider, the voltage generated at the fourth node 155, 157 of the anode-side Cockcroft circuit 151 and the cathode-side Cockcroft circuit 152. Is divided and measured, and is output as the measured value of each voltage.

The tube voltage determining section 172 is composed of an anode side voltage detecting section 168.
Then, the actually measured value of the anode side voltage and the actually measured value of the cathode side voltage obtained from the cathode side voltage detection unit 170 are added by an adder circuit to determine the actually measured value of the X-ray tube voltage. The comparison unit 174 compares the measured value of the X-ray tube voltage obtained from the tube voltage determination unit 172 with the set value of the X-ray tube voltage input from the tube voltage setting unit 162 of the interface unit 34 by the comparator. As a result of comparison by the comparison unit 174, if the actual measurement value and the set value of the X-ray tube voltage match, the control to the high voltage generation circuit 22 is left unchanged, but if they do not match, Based on the comparison difference in the comparison unit 174, the tube voltage determination unit 172 to the anode side voltage setting unit 164 and the cathode side voltage setting unit 166 so that the two match.
The voltage applied to the primary side of the transformer T154 in FIG. 5 is controlled via.

Next, the control of the high voltage generation circuit 22 by the high voltage controller 40 will be specifically described with reference to FIG.
FIG. 7 shows a circuit that controls the input voltage to the high voltage generation circuit 22. In FIG. 7, the high voltage generation circuit 22
A power supply unit 180 including an AC power supply 182, a rectifier circuit 184, and an inverter circuit 186 is connected to the primary side of a transformer T154 that supplies a voltage to the Cockcroft circuit 150 that configures
The inverter circuit 186 is subjected to pulse width modulation (PWM) control (hereinafter abbreviated as PWM control) by the control circuit 188. Hereinafter, the control circuit 188 is also referred to as a PWM circuit.

In the PWM control of the inverter circuit 186, for example,
A pulse of about 25 kHz is used. When increasing the secondary voltage V ₂ of the transformer T154, the pulse width of the inverter circuit 186 is increased by the PWM circuit 188, and
Increase the average current flowing through the secondary coil to increase the primary voltage V
Increase ₁ On the contrary, when lowering the secondary voltage V ₂ , the pulse width of the inverter circuit 186 is reduced by the PWM circuit 188 to reduce the average current flowing through the primary coil of the transformer T154 to reduce the primary voltage V 2. Drop ₁

When the turns ratio of the primary side and the secondary side of the transformer T154 is set to, for example, 1: 100, when the X-ray tube voltage output from the Cockcroft circuit 150 is set to 150 kV, the voltage V ₂ on the secondary side is As mentioned above, it is 18.75kV, so the primary side voltage V ₁ is
Only 187.5V needs to be generated.

FIG. 8 shows an example of a block configuration diagram of a power source for generating a voltage applied to each electrode of the cathode of the X-ray tube and a control section for controlling the power source. In FIG. 8, the high voltage generating circuit 22, the grid voltage generating circuit 24, and the cathode power source circuit 26 are included as the power source of the cathode 100 of the X-ray tube 20. The high voltage generation circuit 22 supplies a negative high voltage to the cathode electrode 104, and the grid voltage generation circuit 24 uses three types of grid voltages,
That is, the G1 voltage is supplied to the G1 electrode 106, the G2 voltage is supplied to the G2 electrode 108, the G3 voltage is supplied to the G3 electrode 110, and the cathode power supply circuit 26 supplies the heater heating voltage to the heater electrode 102.

The power supply of the cathode 100 is controlled by the controller 32 and the interface 34. High voltage generator 22
As described above, the high voltage control unit 40 of the control unit 32 and the tube voltage setting unit 162 of the interface unit 34 control the three grid voltage generating units of the grid voltage generating circuit 24, that is, the G1 voltage generating units 190 and G2. Voltage generator 191, G3 voltage generator
192 is controlled by the G1 voltage control unit 193, the G2 voltage control unit 194, the G3 voltage control unit 195 of the grid voltage control unit 42 of the control unit 32 and the grid voltage setting unit 196 of the interface unit 34, and the cathode power supply circuit 26 is controlled. Cathode control unit 44 of unit 32
Controlled by.

Since the grid voltage is a high negative voltage like the cathode electrode 104 which is the reference potential of the cathode 100, the grid voltage generating circuit 24 itself is held at a high negative voltage, and its input voltage is the high voltage generating circuit 22. It is supplied from the cathode-side high voltage generator 22b. Therefore, in this embodiment, the control signal sent from the grid voltage control unit 42 for controlling the grid voltage generation circuit 24 is insulated by high voltage. Specifically, an optical signal is used as described in detail below.

In generating the grid voltage in FIG. 8, first, the operator sets the target values of the G1 voltage, the G2 voltage, and the G3 voltage from the grid voltage setting section 196 of the interface section 34, and the three kinds of grid voltages are set. Based on the set value of, the G1 voltage control unit 193, the G2 voltage control unit 194, and the G3 voltage control unit 195 of the grid voltage control unit 42 connect the G1 voltage generation unit 190, the G2 voltage generation unit 191, and the G3 voltage generation unit 192. Controlled by optical signal,
The respective grid voltage generators generate G1 voltage, G2 voltage and G3 voltage and apply them to the G1 electrode 106, G2 electrode 108 and G3 electrode 110.

Next, the cathode power supply circuit and its control will be described with reference to FIG. As described above, the cathode of the X-ray tube 20 is the cathode electrode 104 and the heater electrode 102 that heats the cathode electrode 104.
The high voltage generating circuit 22 is connected to the cathode electrode 104.
Is applied with a negative high voltage (voltage of −4 Vm), and the heater heating voltage from the cathode power supply circuit 26 is applied to the heater electrode 102. One terminal of the heater electrode 102 is connected to the cathode electrode 104 and has the same potential.

The cathode power supply circuit 26 mainly comprises a low potential heating circuit 198 and a heater heating insulation transformer Th200.
The heating circuit 198 generates a heater heating voltage Eh, inputs it to the primary side of the heater heating insulation transformer Th200, and outputs an insulated heater heating voltage of the same voltage value to its secondary side. As the heater heating voltage Eh, for example, an AC voltage of about 6.3V is used. With this heater heating voltage Eh, the heater electrode 10
2 is heated to heat the cathode electrode 104 to the desired temperature required for thermionic emission.

In the X-ray tube 20 of this embodiment, unlike the normal X-ray tube, the current value of the X-ray tube current is controlled by controlling the grid voltage. ,
ON / OFF control of the heater heating voltage in the heating circuit 198 is mainly performed according to the operating conditions of the X-ray tube 20.

Next, details of the grid voltage generating circuit and its control will be described with reference to FIGS. Figure 9
G1 voltage generator 190 of the grid voltage generator 24 of FIG. 8
10 is an example of the G1 voltage control unit 193 of the grid voltage control unit 42, FIG. 11 is an example of the optical control signal transmission / reception unit of the grid voltage control unit 42, and FIGS. FIG. 14 shows an example of control for increasing and decreasing the grid voltage, and FIG. 14 shows the relationship between the grid voltage value and the duty (Duty) of the light control signal.

As shown in FIG. 8, the grid voltage generating circuit 2
4 is a G1 voltage generator 190, a G2 voltage generator 192, and a G3 voltage generator 1
94 and the G1 voltage, G2 voltage, and G3 voltage generated by the respective grid voltage generators are applied to the G1 electrode 10 of the X-ray tube 20.
6, applied to the G2 electrode 108 and the G3 electrode 110. X in this example
As a specific method of applying a grid voltage to the cathode 100 of the line tube 20, a high-potential reference potential on the cathode side is applied to the cathode electrode 104, and each grid electrode is applied to the reference potential of the cathode electrode 104. A voltage added with positive and negative voltages is applied. The G1 electrode 106 receives a positive voltage, for example, a G1 voltage added with 0V to + 100V, and the G2 electrode 108 receives a positive voltage higher than the G1 voltage, such as a G2 voltage loaded with 0 to + 2,000V, applied to the G3 electrode 110. Is applied with a positive or negative voltage lower than the G2 voltage, for example, a G3 voltage added with −500V to + 500V. By applying such a grid voltage,
An electrostatic lens is formed on the front surface of the cathode electrode 104, and the thermoelectrons emitted from the cathode electrode 104 are accelerated and focused into an electron beam having a small outer diameter.

The three groups of the grid voltage generating circuit 24 described above are
Since the lid voltage generator has almost the same configuration,
The G1 voltage generator 190 is shown as a typical example. Figure 9 Smell
In the G1 voltage generator 190, the high voltage generator circuit 22
From the cathode side cockcroft circuit 152 of the blackcroft circuit 150
Divided voltage V_hG1 voltage V as input voltage_G1Generate
It Where input voltage V_hChanges in conjunction with the X-ray tube voltage
Therefore, if the operating conditions of the X-ray tube 20 change,
It changes in conjunction with this. Therefore, the G1 voltage of this embodiment is
In the generator 190, the voltage is divided from the cathode side Cockcroft circuit 152.
Input voltage V_hFurther resistance R₁, R_Two, R_ThreePartial pressure with
C Densa C₁It is charged to this charging voltage V_iThe grip
Optical control signal from the G1 voltage control unit 193 of the voltage control unit 42
Control G1 voltage V _G1Is being generated. Receives light control signal
Therefore, the photodiode P
D is placed between the G1 voltage control unit 193 and the photodiode PD.
An optical cable is installed in.

First, the input voltage V to the G1 voltage generator 190 is_hWhen
The third node 156 of the Cockcroft circuit 152 on the cathode side.
Capacitor C between node 5 and 158_K5Output voltage of 2V_mIs a node
It is given between A and node B. At this time, the potential of node A is
-5V_mAnd the potential of node B is -3V _mBecomes This input voltage V
_hIs resistance R₁, R_Two, R_ThreeDivided by the capacitor
C₁Charged to the charging voltage V_iOccurs. Capacitor C₁
Charging voltage V_iThe voltage value of is expressed by the following equation (1).

[Equation 1]

Further, the output voltage V _G1 from the G1 voltage generator 190
Is output as a potential difference between the nodes C and D, and the potential of the node D is applied to the G1 electrode 106. The potential of node C is the fifth node 1
It is the same as the potential of 58 and is -5V _m . G1 electrode 106
The voltage to be applied to the cathode electrode 104 is 0V to + 100V
Since the potential of the cathode electrode 104 is −4 V _m , G1
The potential range to be applied to the electrode 106 is -4V _m to -4V _m + 100V
Becomes From the above, the voltage value of the output voltage V _G1 changes in the range of V _m to V _m + 100V.

From the above, the G1 voltage generator 190
Input voltage V_h(= 2V_m) The output voltage V _G1(= V_m~ V_m+ 100V)
When converting and outputting, the resistance R₁, R_Two, R_Threeby
With the partial pressure, the voltage is dropped to about half the voltage. here,
Voltage V_mChanges depending on the operating conditions of the X-ray tube 20.
Power voltage V_hAnd the required G1 voltage V_G1X-ray tube 20 operating conditions
Fluctuates depending on. Input voltage V_hAnd the required G1 voltage V
_G1Conversion ratio α (G1) (= V_{G 1}/ V_h) Is expressed as
It becomes like the formula (2).

[Equation 2] In equation (2), the maximum value of α (G1) is 0.5 + 100 / V _m , and therefore occurs when V _m is the smallest, that is, when the X-ray tube voltage is the lowest. Therefore, in this embodiment, the resistance
R _1, as the partial pressure ratio of R _2, R ₃ by the partial pressure and to take the maximum value of the ratio of the G1 voltage V _G1 and the input voltage V _h is needed in the lowest operating voltage value of the X-ray tube voltage . By thus setting the maximum value of α (G1), a margin can be secured for the input voltage V _{h with} respect to the voltage in the region where α (G1) is low.

The above applies to the X-ray tube voltage usage range of 40k.
When applied to the X-ray tube 20 which is from V to 150 kV, the input voltage V _h when the X-ray tube voltage is 40 kV and the required G1 voltage V _G1
10kV and 5kV to 5.1kV, for 150kV they are 37.5kV and 1
It will be 8.75kV to 18.85kV. The ratio α (G1) of G1 voltage V _G1 and input voltage V _h is calculated to be 0.5 to 0.51 for 40 kV and 150 kV for 40 kV.
It will be 0.5 to 0.5027. Therefore, the maximum value 0.51 at 40 kV is adopted as the voltage division ratio by the resistors R ₁ , R ₂ , and R ₃ . As a result, the input voltage V _h becomes G1 in the region where the X-ray tube voltage is higher than 40 kV and the region where the bias voltage of the G1 electrode 106 is low.
There will be a margin for the voltage V _G1 .

Next, the voltage V _i of the capacitor C ₁ is controlled by receiving the optical control signal from the G1 voltage control unit 193 in the subsequent stage of the G1 voltage generation unit 190. Hereinafter, the procedure of generating the G1 voltage in the latter stage of the G1 voltage generating unit 190 will be described with reference to FIGS. 10 and 11. In FIG. 10, the G1 voltage control unit 193 is
The main components are a light emitting diode 216 that generates an optical control signal, an optical signal transmitter / receiver 218, and a light emitting diode 216.
It includes a power supply unit 220 that supplies a current for causing the light to be emitted, a pulse width modulation (PWM) circuit 234 that controls the power supply unit 220, and the like. The power supply unit 220 includes an AC power supply 228, a rectifier circuit 230, and an inverter circuit 232, and the PWM circuit 234 controls the pulse width of the output current of the inverter circuit 232.

FIG. 11 shows the details of the structure of the optical signal transmission / reception unit 218. The optical signal transmission / reception unit 218 is a light emitting diode 216.
The optical signal transmitting unit 222 that collects the optical signal generated by the optical cable 224 and sends the optical signal to the optical cable 224, and the optical cable 224 that transmits the optical signal with insulation
And an optical signal receiving unit 226 that receives an optical signal and irradiates the photodiode 210, and connectors 236 and 238 that connect the optical cable 224 to the optical signal transmitting unit 222 and the optical signal receiving unit 226.

In FIG. 9, while the capacitor C ₁ is charged with the voltage V _i , the photodiode (PD) 210 receives the voltage shown in FIGS.
When the light control signal from the light emitting diode 216 of the G1 voltage control unit 193 shown in is given, the photodiode 210 is ON (conducting), and the current is supplied to the base of the transistor T _5, the collector and the emitter of the transistor T ₅ Interval is ON
It becomes a state. This behavior, since the supply of the base current stops base potential of T ₃ is decreased, the transistor T
Between the collector and emitter of ₃ is turned off (non-conducting). The transistor T ₃ is turned OFF, since the base current is supplied the base potential of the transistor T ₄ rises, the collector-emitter of the transistor T ₄ is turned ON.

By turning on the transistor T ₄ ,
The charging voltage V _i of the capacitor C ₁ charges the capacitor C ₂ for generating the G1 voltage, and the G1 voltage V _G1 rises. This rise of the G1 voltage V _G1 continues while the light control signal from the light emitting diode 216 of the G1 voltage control unit 193 is input to the photodiode 210, and the maximum value of the G1 voltage V _G1 is the voltage V _{i of the} capacitor C _1. And the same value as.

On the other hand, the light emitting diode 2 of the G1 voltage control unit 193
If you stop the transmission of optical control signal to the photodiode 210 from 16, since the photodiode 210 is turned OFF, the collector-emitter of the transistor T ₅ is turned OFF.
As a result, the base potential of the transistor T ₃ rises and the collector-emitter turns on, so
The collector-emitter of T ₄ is turned off, the charging of the capacitor C ₂ from the voltage V _i of the capacitor C ₁ is stopped,
On the contrary, the capacitor C ₂ starts discharging through the resistors R ₉ , R ₁₀ and R ₁₁ . This discharge of the capacitor C ₂ causes the G1 voltage V _G1 to drop.

[0080] However, since the emitter side voltage of the transistor T ₃ (voltage across the resistor R ₈₎ is determined by the rated voltage of the constant voltage diode D2, the base voltage of the transistor T ₃ is the rated voltage of the constant voltage diode D2 transistor T ₃ until the ON operation continues. The rated voltage of the constant voltage diode D2 defines the minimum value of the drop of the G1 voltage V _G1 .

As described above, in the G1 voltage generator 190, the G1 voltage V _G1 rises while the light control signal is supplied to the photodiode 210, and when the supply of the light control signal to the photodiode 210 is stopped, G1 Since the voltage V _G1 is configured to drop, the G1 voltage control unit 193 controls the ON / OFF control of the optical control signal transmitted from the G1 voltage control unit 193.
The voltage value of one voltage V _G1 can be controlled.

In this embodiment, the PWM control method is used for ON / OFF control of the light control signal in the G1 voltage control unit 193. In the G1 voltage control unit 193 of FIG. 10, the power supply unit 220 of the light emitting diode 216 that is the generation source of the light control signal is similar to the power supply unit of the high voltage generation circuit 22 in the AC power supply 228 and the rectification circuit 230.
And an inverter circuit 232, and a pulse voltage which is the output of the inverter circuit 232 is applied to the light emitting diode 216. The pulse width of the output voltage of the inverter circuit 232 is controlled by the PWM circuit 234.

Next, the PWM control by the light control signal of the voltage G1 will be described with reference to FIGS. Figure 12 (a) and figure
13 (a) shows an example of changes over time of the optical control signal that has undergone PWM control, and FIGS. 12 (b) and 13 (b) show changes over time of the G1 voltage at that time. When the duty of the light control signal is large, the latter is when the duty of the light control signal is small. Further, FIG. 14 shows the relationship between the duty of the light control signal subjected to the PWM control and the final arriving voltage value of the G1 voltage.

The vertical axis of FIGS. 12A and 13A shows the amount of light, the horizontal axis shows the passage of time, and the vertical axes of FIGS. 12B and 13B show the grid voltage and the horizontal axis. Indicates the passage of time. FIG. 12 shows the case where the duty of the light control signal is about 0.72, which is large. As described above, when the duty is greater than 0.5, the ON time of the photodiode 210 of the G1 voltage generator 190 is longer than the OFF time, and therefore, as shown in FIG.
The voltage rises as a whole and is set to a high level. On the other hand, in Fig. 13, the duty of the optical control signal is about 0.
At 22, it is small. Thus the duty is 0.5
If it is smaller, the OFF time of the photodiode 210 becomes longer than the ON time, so that the G1 voltage as a whole drops and is set to a low level, as shown in FIG. 13 (b). Further, when the duty of the light control signal is 0.5, the time of the ON state of the photodiode 210 and the time of the OFF state become equal, so that the G1 voltage does not change as a whole,
Set to the same level.

FIG. 14 summarizes the relationship between the magnitude of the G1 voltage and the duty of the light control signal in the above.
The value of G1 voltage, the horizontal axis is the duty of the light control signal. In the figure, the G1 voltage has a linear relationship with the duty of the light control signal. When the duty is 0.5, it is the median value E ₀ , when the duty is 1, it is the highest value E _H , and when it is 0, it is the lowest value E _L. Become.

In FIG. 14, the maximum value E _H when the duty is 1 is almost the same as or slightly lower than the charging voltage V _i of the capacitor C ₁ , and the minimum value E _L when the duty is 0 is constant. a value slightly higher than approximately equal to the minimum value of the drop of the G1 voltage defined by the voltage diode D _2. Therefore, the maximum value E _H
And the minimum value E _L are set, and for the median value E ₀ , for example, a voltage value that is frequently used out of the required G1 voltage may be set.

Of the three types of grid voltages, only the generation of the G1 voltage has been described above, but the generation of the G2 voltage and the G3 voltage is performed in the same manner as the G1 voltage. The G2 voltage and the G3 voltage have different voltage values and their fluctuation ranges from the G1 voltage, so the parts related to them, such as the figure
The voltage division ratio due to the resistances R ₁ , R ₂ and R ₃ of 9 are different.

In this embodiment, the low voltage G1 voltage controller 193
Since the control signal transmitted from the high voltage G1 voltage generation unit 193 is an optical signal and the optical cable 224 is used for the transmission, an electrical connection between the G1 voltage control unit 193 and the G1 voltage generation unit 190 is made. Completely insulated. As a result, since the grid voltage can be obtained by controlling the high voltage divided from the Cockcroft circuit 150 in an insulated state, it is not necessary to use an insulation transformer or the like as in the conventional case. 24 can be miniaturized.

Next, the driving of the stator 28 will be described with reference to FIG. In this embodiment, the rotating anode 120 is adopted as the anode of the X-ray tube 20, and the rotating anode 120 is rotated by energizing the stator 28 arranged on the outer periphery of the rotating anode 120, so that the resistance of the X-ray tube 20 is increased. The loadability is improved. Since the stator 28 is held at a low voltage, the anode rotation power supply 30 and the anode rotation control unit 46 that supply rotation driving power to the stator 28 are included in the control unit 32. 100 as the anode rotating power supply 30
An AC power supply of about 200 to 200 V is used. The rotating anode 120 is rotated only during the time when a load is applied to the X-ray tube 20, as in the conventional medical X-ray apparatus. For this reason,
The drive control of the stator 28 by the anode rotation control unit 46 is performed by applying a rotation start voltage to the stator 28 before applying a load to the X-ray tube 20, applying a continuous rotation voltage during the load, and changing the drive voltage after the end of the load. Turn it off, or turn the drive voltage off after applying rotation braking voltage to stop rotation.

As shown in FIG. 3, the X-ray tube 20 of the present embodiment employs a neutral point grounding system, and the envelope 130 is set to the ground potential,
High positive and negative voltages are applied to the rotating anode 120 and the cathode 100. As a result, the potential difference between the rotating anode 120 and the envelope 130 can be reduced and the gap between the two can be narrowed as compared with the conventional microfocus X-ray tube having a similar X-ray tube voltage. It has become possible. In the X-ray tube with the maximum X-ray tube voltage of 150 kV, comparing the case of the cathode grounding method and the case of the neutral point grounding method, the voltage between the envelope and the anode is 150 kV in the former, whereas in the latter, It becomes 75kV. Figure 15 shows the result of calculating the change in the electric field strength E (kV / mm) when the distance d (mm) between the anode and the envelope is changed and a voltage of 150 kV and 75 kV is applied between them. , Fig. 15 (a) is for 150kV, Fig. 15 (b)
Is for 75 kV. At this time, the envelope side has a flat plate shape, but the anode side has its outer peripheral portion R-face processed to have R = 2 mm. In Fig. 15, when the limit electric field strength that can be safely used is E = 20 kV / mm, for example, d is about 50 mm in the cathode grounding method of Fig. 15 (a), while the neutral value of Fig. 15 (b) is neutral. In the point grounding method, d is about 10 mm, which is a significant reduction.

From the above, the distance between the focal point 123 formed on the rotating anode 120 and the X-ray emission window 136 of the envelope 130 can be greatly shortened as compared with the conventional microfocus X-ray tube. . By shortening the distance between the focal point 123 and the X-ray radiation window 136, the distance between the focal point 123 and the subject can be reduced during X-ray imaging, so that the geometric magnification of X-ray imaging can be increased as described below. It can be made larger than before.

Since the X-ray apparatus of this embodiment is provided with a microfocus X-ray tube as an internal X-ray tube, it is suitable for inspecting a minute object by magnifying radiography when used for nondestructive inspection. FIG. 16 shows an example of a layout diagram in magnified imaging by the X-ray apparatus of this embodiment. In FIG. 16, the X-ray inspection apparatus includes an X-ray tube 20, an object 240, and an X-ray detector 242.
Are arranged. The subject 240 is supported by a support plate (not shown) made of a material having good X-ray transparency. X
The X-rays 64 emitted from the focus 123 formed on the target 122 of the X-ray tube 20 are transmitted through the subject 240 and then received by the light receiving surface 244 of the X-ray detector 242. At the light receiving surface 244, the X-ray 64 is converted into an image signal, and a magnified image of the subject 240 is obtained.

When the distance between the focal point 123 of the X-ray tube 20 and the subject 240 is A and the distance from the subject 240 to the light receiving surface 244 of the X-ray detector 242 is B, the geometry of the captured image of the subject 240 is determined. The magnification ratio M is (A + B) / A. In the present invention, as described above, the X-ray tube 2
By setting 0 as the neutral point grounding system, the focus 123 of the X-ray tube 20, the envelope 130, and the X-ray emission window can be compared to the conventional cathode grounding system X-ray tube with the same X-ray tube voltage. Since the distance to 136 can be greatly shortened, the distance A between the focus 123 and the subject 240 can be made significantly smaller than in the conventional case. As a result, the geometrical enlargement ratio M of the captured image can be increased as compared with the conventional case, and it becomes possible to perform a precise inspection of a minute portion of the subject.

[0094]

As described above, according to the present invention, the microfocus X-ray tube is of the neutral point grounding type, and the X-ray tube voltage is shared by the rotating anode side and the cathode side. The insulation distance between the envelope and the rotating anode having the X-ray source in Fig. 2 could be made shorter than the conventional product. As a result, the distance between the focal point of the X-ray tube and the X-ray radiation window provided in the envelope can be shortened, and the geometric magnification of the image of the subject can be increased.

Further, according to the present invention, by using the optical signal for controlling the grid voltage supplied to the grid electrode forming the cathode of the microfocus X-ray tube, the insulation voltage of the grid voltage generating circuit is insulated. It is no longer necessary to use a vessel or the like. As a result, the grid voltage generating circuit can be downsized, and a small power-source integrated microfocus X-ray device can be realized.

[Brief description of drawings]

FIG. 1 is a schematic configuration of one embodiment of an X-ray apparatus according to the present invention.

FIG. 2 is an arrangement example of main components in a storage container in the X-ray apparatus of this embodiment.

FIG. 3 is a structural diagram of an embodiment of an X-ray tube according to the present invention.

FIG. 4 is an enlarged view of a cathode structure.

FIG. 5 is a schematic configuration of an embodiment of a high voltage generating circuit according to the present invention.

FIG. 6 is a schematic configuration of a high voltage control unit that controls a high voltage generation circuit.

FIG. 7 is a circuit for controlling an input voltage to a high voltage generation circuit.

FIG. 8 is an example of a block configuration diagram of a power supply that generates a voltage applied to each electrode of the cathode of the X-ray tube and a control unit that controls the power supply.

FIG. 9 shows an example of a G1 voltage generating unit in the grid voltage generating circuit.

FIG. 10 shows an example of a G1 voltage control unit of the grid voltage control unit.

FIG. 11 is an example of a structure of an optical signal transmission / reception unit.

FIG. 12 is a control example of boosting of the grid voltage.

FIG. 13 is a control example of step-down of grid voltage.

FIG. 14 shows the relationship between the grid voltage value and the duty of the light control signal.

FIG. 15 shows the relationship between the distance between the anode and the envelope and the electric field strength.

FIG. 16 is an example of a layout diagram in magnified imaging by the X-ray apparatus according to the present embodiment.

[Explanation of symbols]

10 ... X-ray equipment 20 ... X-ray tube 22 ... High voltage generator 24 ... Grid voltage generator 26 ... Cathode power circuit 28 ... Stator 30 ... Anode rotation power supply 32 ... Control unit 34 ... Interface section 36 ... Storage container 40 ... High voltage controller 42 ... Grid voltage controller 44 ... Cathode controller 60 ... Insulating oil 62 ... electron beam 64 ... X-ray 100 ... Cathode 102 ... Heater electrode 104 ... Cathode electrode 106 ... Grid electrode (G1) 108 ... Focus electrode (G2) 110 ... Focus electrode (G3) 111 ... metal fittings 112 ... Cathode support 114… Insulated columns 116 ... Stem 118 ... Cathode side power supply 120 ... Rotary anode 122 ... Target 123 ... X-ray generator (focus) 124 ... Rotating part 126 ... Fixed part 130… Enclosure 132 ... Body 134 ... Anode sealing part 136… X-ray emission window 140, 142, 144, 145, 146, 147, 148, 149 ... Wiring 150 ... Cockcroft circuit 151… Anode side Cockcroft circuit 152… Cathode side Cockcroft circuit 154 ... Transformer T 155, 157 ... 4th node 156 ... Third node 158 ... Fifth node 162 ... Tube voltage setting section 164 ... Anode side voltage setting section 166 ... Cathode side voltage setting section 168 ... Anode side voltage detector 170 ... Cathode side voltage detector 172 ... Tube voltage determination unit 174 ... Comparison section 180, 220 ... Power supply 182, 228 ... AC power supply 184, 230 ... Rectifier circuit 186, 232 ... Inverter circuit 188, 234 ... Control circuit (pulse width modulation (PWM) circuit) 190 ... G1 voltage generator 191 ... G2 voltage generator 192 ... G3 voltage generator 193 ... G1 voltage controller 194 ... G2 voltage controller 195 ... G3 voltage controller 196 ... Grid voltage setting section 198 ... Heater heating circuit 200… Insulation transformer for heater heating 210 ... Photodiode 216 ... Light emitting diode 218 ... Optical signal transmitter / receiver 222 ... Optical signal transmitter 224 ... Optical cable 226 ... Optical signal receiver 236, 238 ... Connector 240 ... Subject 242 ... X-ray detector 244 ... Light receiving surface

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Keiichi Tea Field, Inventor             1-chome 1-14-1 Kanda, Chiyoda-ku, Tokyo             Inside the Hitachi Medical Co. F-term (reference) 4C092 AA01 AB27 AC01 AC08 AC09                       BD06 CD02

Claims (3)

[Claims] 1. A cathode having a cathode electrode for emitting an electron beam, a plurality of grid electrodes for controlling the orbit and current amount of the electron beam, and X due to collision of the electron beam.
An anode having a target for generating rays, the cathode and the anode are hermetically sealed in a vacuum, and an envelope having an X-ray emission window for radiating the X-rays generated at the target to the outside, In an X-ray tube that obtains a fine focus by controlling the grid voltage applied to the grid electrode, the envelope is set to the ground potential, the X-ray tube voltage is divided into two equal parts, and the negative high voltage is the cathode electrode of the cathode. An X-ray tube characterized in that the positive high voltage is applied to the anode. 2. The X-ray tube according to claim 1, a high voltage generating circuit for generating a positive and negative high voltage for applying to an anode and a cathode of the X-ray tube, and an application to a grid electrode of the X-ray tube. Voltage generating circuit for generating a plurality of grid voltages for operating, a control unit for controlling operations of the high voltage generating circuit and the grid voltage generating circuit, and an interface unit for inputting control data to the control unit And at least the above X
A container for insulatingly containing the wire tube, the high voltage generating circuit, and the grid voltage generating circuit.
X-ray equipment. 3. The X-ray apparatus according to claim 2, wherein the grid voltage generated by the grid voltage generating circuit is transmitted to the grid voltage generating circuit via an optical cable insulated from the control unit. An X-ray device characterized by being controlled.