WO2018212377A1

WO2018212377A1 - X-ray tube

Info

Publication number: WO2018212377A1
Application number: PCT/KR2017/005202
Authority: WO
Inventors: 윤중석; 손유주
Original assignee: 주식회사 쎄크
Priority date: 2017-05-19
Filing date: 2017-05-19
Publication date: 2018-11-22
Also published as: KR102268608B1; KR20190133770A

Abstract

An X-ray tube is disclosed. The disclosed X-ray tube comprises: a vacuum chamber; an electron generation unit connected to the vacuum chamber; an anode located inside the vacuum chamber and having a target mounted on one end thereof; a cathode which is located inside the electron generation unit and emits electrons toward the target; and a focal distance adjustment unit which is located between the vacuum chamber and the electron generation unit and sealed therewith and moves the electron generation unit so as to adjust the focus.

Description

X-ray tube

The present invention relates to an x-ray tube, and more particularly, to an x-ray tube for adjusting the focal length by changing the position of the cathode and grid after sealing the x-ray tube.

In general, X-ray tube is divided into a closed type supplied for single use and an open type for exchanging a filament or a target, which can be made arbitrarily, and a vacuum.

The X-ray tube has a cathode, an anode, and a target attached to the anode inside the vacuum chamber decompressed with high vacuum, and generates an X-ray by injecting electrons generated from the cathode into a target, and emits the generated X-ray through the X-ray window. Device.

In general operation of an X-ray tube, current flows through the filament of the cathode, and heat electrons are generated when heat is generated in the filament.

In order to obtain a clear transmission image, the focal size of the electrons colliding with the target should be small. The focal length must be adjusted to reduce the focal size. Conventionally, after adjusting the focal size of the former, the X-ray tube was sealed. In this case, there is a problem that an error due to deformation due to heat or an error due to bonding occurs due to the sealing operation. Because of this, there was a problem in manufacturing a high-resolution X-ray tube of the product reliability.

In order to solve the above problems, an object of the present invention is to provide an X-ray tube after sealing the X-ray tube, to adjust the focal length to prevent errors due to the bonding process and deformation due to heat.

In order to achieve the above object, a vacuum chamber, the electron generating unit is connected and sealed to the vacuum chamber and the internal space, the anode is located inside the vacuum chamber, the target is installed at one end, and located inside the electron generating unit, And a cathode for emitting electrons to the target, and a focal length adjusting unit disposed in the electron generating unit and adjusting the focal size by moving the electron generating unit.

The focal length adjusting unit may include a bellows member disposed in the electron generating unit, and the bellows member may contact one end of the vacuum chamber.

The focal length adjusting unit may include a control pin which is fastened to a fastening groove formed at one end of the vacuum chamber and moves along the fastening groove toward the target to compress the bellows member.

The control pin may be rotatably coupled to the electron generating unit.

The fastening groove is a screw groove is formed, the adjusting pin is formed with a screw line corresponding to the screw groove, it is possible to adjust the compression of the bellows by the rotation of the adjusting pin.

The bellows member may be a metal material.

The bellows member may be installed on an inner surface of the electron generating unit.

The electron generating unit, the grid for controlling the amount of electrons emitted from the cathode; And a cylindrical grid cap focusing electrons passing through the grid to the target and including a window through which the electrons pass.

The electron generator may include an electrode part electrically connected to the grid and the cathode and protruding outside the electron generator.

The focal length adjusting part may include a bellows member surrounding a part of the electrode part and a control pin installed at an end of the electrode part to adjust a length of the electrode part.

The focal size of the electrons reaching the target may be determined according to the size of the window of the grid.

The window may be rectangular.

The distance between the target and the grid may be adjusted by the focal length adjusting unit.

As described above, in the present invention, after sealing the X-ray tube, the focal length may be adjusted by moving the electron generating unit by using the focal length adjusting device, thereby preventing the error due to the bonding or heat caused by the sealing process.

1 is a perspective view showing an x-ray tube according to an embodiment of the present invention.

Figure 2 is an exploded perspective view showing an x-ray tube according to an embodiment of the present invention.

Figure 3 is a cross-sectional view showing an x-ray tube according to an embodiment of the present invention.

4 is an enlarged view illustrating a portion A shown in FIG. 3.

FIG. 5 is a diagram illustrating an electron generating unit illustrated in FIG. 3.

6 is a cross-sectional view of an x-ray tube according to another embodiment of the present invention.

FIG. 7 is a diagram illustrating an electron generating unit illustrated in FIG. 6.

FIG. 8 is a diagram illustrating the grid cap shown in FIG. 5.

Hereinafter, various embodiments of the present disclosure will be described with reference to the accompanying drawings. However, this is not intended to limit the techniques described in this document to specific embodiments, but should be understood to cover various modifications, equivalents, and / or alternatives to the embodiments of this document. In connection with the description of the drawings, similar reference numerals may be used for similar components.

In addition, the expressions "first," "second," and the like used in this document may modify various components in any order and / or importance, and may distinguish one component from another. Used only and do not limit the components. For example, the first user device and the second user device may represent different user devices regardless of the order or importance. For example, without departing from the scope of rights described in this document, the first component may be called a second component, and similarly, the second component may be renamed to the first component.

The terminology used herein is for the purpose of describing particular embodiments only and may not be intended to limit the scope of other embodiments. Singular expressions may include plural expressions unless the context clearly indicates otherwise. The terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the art. Among the terms used in this document, terms defined in the general dictionary may be interpreted as having the same or similar meaning as the meaning in the context of the related art, and ideally or excessively formal meanings are not clearly defined in this document. Not interpreted as In some cases, even if terms are defined in the specification, they may not be interpreted to exclude embodiments of the present disclosure.

Hereinafter, with reference to the accompanying drawings, the configuration of the X-ray tube according to an embodiment of the present invention.

1 is a perspective view showing an x-ray tube according to an embodiment of the present invention, Figure 2 is an exploded perspective view showing an x-ray tube according to an embodiment of the present invention.

Referring to FIG. 1, the X-ray tube 1 includes an electron generator 100 and a vacuum chamber 200. The electron generator 100 and the vacuum chamber 200 may include a cathode 130 (see FIG. 2) and an anode 210 (see FIG. 2). The electron generating unit 100 may include a plurality of electrode units 120, and the plurality of electrode units 120 may protrude out of the electron generating unit 100 to receive a current. In addition, in order to facilitate the emission of electrons, the electron generating unit 100 and the vacuum chamber 200 are vacuumed. The current is supplied to the cathode 130 by the current supplied through the electrode unit 120, and the cathode 130 emits electrons.

The adjustment pin 155 may adjust the distance between the electron generating unit 100 and the vacuum chamber 200 to adjust the focal length for focusing the electrons emitted from the cathode 130 to the anode 210. After the electron generating unit 100 and the vacuum chamber 200 are sealed with the bellows member 150 (refer to FIG. 2), the insertion of the electron generating unit 100 disposed inside the vacuum chamber 200 with the adjusting pin 155 is performed. When the distance is adjusted, the bellows member 150 is compressed or tensioned to control the distance between the electron generating unit 100 and the vacuum chamber 200.

Referring to FIG. 2, the electron generating unit 100 may include an electrode unit 120, a cathode 130, and a bellows member 150. The electrode unit 120 is inserted into and fixed to the opening 126 formed in the electron generating unit 100. The opening 126 is formed in the insulator 125, and the electrode part 120 is cut off from the case 160 of the electron generating unit 100 by the insulator 125. In general, the electron generating unit 100 may be formed of a metal material, and thus, it is necessary to block the energization between the electrode unit 120 and the case 160 of the electron generating unit 100.

The electrode part 120 includes a pair of first electrode parts 121 connected to the cathode 130 and a plurality of second electrode parts 122 connected to the grid 173. When a current is applied to the plurality of first and

second electrode parts

121 and 122 exposed to the outside of the electron generator 100, the first electrode part 121 applies a current to the filament of the cathode 130. The cathode 130 generates electrons by the applied current. When a current is applied to the second electrode part 122, the second electrode part 122 forms an electric field by flowing an electric current through the grid 173, and electrons are emitted into the internal space 172 of the grid cap 170. May be adjusted to face the target 220 of the anode 210 (see FIG. 3).

The bellows member 150 and the adjusting pin 155 serve to adjust the position of the electron generating unit 100 to serve as a focal length adjusting unit for adjusting the focal length. The bellows member 150 is installed at a stepped portion formed inside of the electron generating unit 100 to be described later, and a protrusion 226 protruding from one end 227 of the cylinder 230 extending from the side of the vacuum chamber 200. Is installed on. Bellows member 150 is wrinkled is formed, it can be compressed and tensioned. Compression and tension of the bellows member 150 may control the gap between the vacuum chamber 200 and the electron generating unit 100.

The adjusting pin 155 is fastened to the fastening groove 225 of the vacuum chamber 200 by passing through the hole 110 of the electron generating unit 100. Although the adjusting pin 155 passes through the hole 110, the movement in the longitudinal direction in the electron generating unit 100 is restricted, there is no movement along the longitudinal direction of the electron generating unit 100, and the fastening groove 225 is closed. Can be moved longitudinally. This adjusts the distance between the electron generating unit 100 and the vacuum chamber 200.

The vacuum chamber 200 includes an anode 210 therein. A high voltage is applied to the anode 210 to accelerate the electrons emitted from the cathode 130, so that the electrons collide with the target 220 disposed inside the anode 210. As the voltage applied to the anode 210 is higher, electrons are accelerated, and electrons collided with the target 220 generate X-rays having high transmittance.

Electrons emitted from the cathode 130 are directed to the anode 21 through the grid 173 and the grid cap 170 disposed inside the cylinder 230, and the electrons are moved to the electron opening 215 formed in the anode 210. It collides with the target 220 through. Electrons impinging on the target 220 are emitted to the X-ray transmission window 250 through the X-ray passing opening 216.

3 is a cross-sectional view illustrating an X-ray tube according to an exemplary embodiment of the present invention, FIG. 4 is an enlarged view illustrating a portion A shown in FIG. 3, and FIG. 5 is a diagram illustrating the electron generating unit illustrated in FIG. 3.

3 and 5, the cathode 130, the grid 173, and the grid cap 170 of the electron generating unit 100 are disposed inside the cylinder 230 of the vacuum chamber 200, and electron generation is performed. The bellows member 150 is disposed between the part 100 and the vacuum chamber 200.

One end of the bellows member 150 is in contact with the stepped portion 111 formed in the case 160 of the electron generating unit 100, and the other end of the bellows member 150 is a cylinder 230 of the vacuum chamber 200. Contact with the protrusion 226 formed at one end 227. One end and the other end of the bellows member 150 are sealed to the stepped portion 111 and the protrusion 226, respectively, so that the electron generating portion 100 and the vacuum chamber 200 are sealed to each other. The case 160 and the vacuum chamber 200 are formed of a vacuum inside, and are made of a material having sufficient rigidity to withstand the pressure difference between the inside and the outside. The case 160 and the vacuum chamber 200 may be made of a metal material. However, the case 160 and the vacuum chamber 200 may be formed of a metal material.

In addition, the bellows member 150 is wrinkled is formed on the outer surface to be compressed and tensioned. When the bellows member 150 is compressed, since the electron generating unit 100 moves toward the vacuum chamber 200, the cathode 130, the grid 173, and the grid cap 170 move toward the anode 210.

When the bellows member 150 is tensioned, since the electron generating unit 100 moves away from the vacuum chamber 200, the cathode 130, the grid 173, and the grid cap 170 are moved from the anode 210. Move away

Although the bellows member 150 has been described as being formed on the inner surface of the case 160 in the drawings of the present invention, the present invention is not limited thereto, and the bellows member 150 may be disposed outside or sealed inside the case 160 and may be sealed. It may be sealed in contact with the outer surface. That is, the stepped portion may be formed on the outer surface of the case 160 of the electron generating unit 100, and the stepped portion or the protrusion may be formed on the outer surface of the vacuum chamber 200. Even when the bellows member 150 is coupled to the stepped portion or the protrusion of the case 160 and the vacuum chamber 200, the distance between the electron generator 100 and the vacuum chamber 200 may be adjusted. In addition, the bellows member 150 may be installed in the second electrode part 122, which will be described later with reference to FIGS. 6 and 7.

An opening formed in the grid 173 controls the amount of electrons emitted from the cathode 130 and serves to guide the electrons to the grid cap 170. An insulating member 175 is installed to prevent the grid 173 and the grid cap 170 from energizing. Through this, the cathode 130 and the grid 173 has a negative potential, the potential of the grid cap is maintained at 0V. Due to the potential difference between grid 173 and grid cap 170, electrons emitted from cathode 130 are first accelerated at grid cap 170 through grid 173.

The grid cap 170 and the grid 173 are located inside the cylinder 230, and the moving direction is guided by the cylinder 230. The cathode 130 and the grid 173 are electrically connected by the first and

second electrode portions

121 and 122, and are also physically fixed. The first and

second electrode parts

121 and 122 are formed of a rod having a length, and one end of the first and

second electrode parts

121 and 122 protrudes out of the case 160 of the electron generating part 100. It is fixed to the case. The first and

second electrode parts

121 and 122 pass through the opening 126 formed of the insulator 125 and are fixed to the case 160 in order to prevent power supply to the case 160.

In addition, the other end of the first electrode part 121 is connected to the filament by the filament of the cathode 130 and the coupling member 135 inside the case 160 of the electron generating unit 100. Through this, the cathode 130 moves in response to the movement of the electron generating unit 100. The other end of the second electrode part 122 is coupled to one surface of the grid cap 170, and the grid cap 170 moves in response to the movement of the electron generator 100.

The anode 210 includes a target 220, an electron transfer opening 215, and an x-ray passing opening 216. Electrons emitted from the cathode 130 are focused on the target 220 through the electron moving opening 215 through the window 171. The target 220 is disposed with an inclination, and the X-rays generated by the target 220 travel outside the anode 210 through the X-ray passing opening 216.

The filament of the cathode 130 may be formed of tungsten with good thermal properties. According to the thermal properties of tungsten, when a current flows through the filament, the filament is heated to a temperature where electrons can be generated. At this time, if the voltage applied to the filament is changed, the filament current changes and electrons are emitted.

Referring to FIG. 4, the adjustment pin 155 passes through the hole 110 formed in the case 160 and is rotatably coupled to the hole 110. One end of the adjustment pin 155 is inserted into the fastening groove 225 formed in the cylinder 230 of the vacuum chamber 200. Both ends of the bellows member 150 are sealed and coupled to the case 160 of the electron generating unit 100 and the cylinder 230 of the vacuum chamber 200, so that the adjustment pin 155 is provided to the end of the fastening groove 225. When combined, the distance between the electron generating unit 100 and the vacuum chamber 200 is closest. On the contrary, the shorter the distance that the adjustment pin 155 is inserted into the fastening groove 225, the farther the distance between the electron generating unit 100 and the vacuum chamber 200.

The bellows member 150 is preferably formed of a metal to withstand the internal space formed by the vacuum. However, if the material has a rigidity that can withstand vacuum, the bellows member 150 may not be limited to metal.

The adjusting pin 155 may have a screw line for coupling with the fastening groove 225 at one end, and the fastening groove may have a screw groove corresponding to the screw line of the adjusting pin 155.

Since the adjusting pin 155 having a screw thread is rotatably coupled to the hole 110, by the rotation of the adjusting pin 155, the adjusting pin 155 is inserted into the fastening groove 225 having the screw groove. It can be adjusted, and through this, it is possible to adjust the moving distance of the electron generating unit 100, the cathode 130, the grid 173 and the grid cap 170.

Although the adjusting pin 155 has a screw line and the fastening groove 225 has a screw groove, it is not limited thereto. The adjusting pin 155 and the fastening groove 225 may have a groove and a protrusion to snap to each other. Has a projection on the adjustment pin 155, the locking groove may be formed in the longitudinal direction of the fastening groove 225. In this case, when the adjustment pin 155 moves in the longitudinal direction, the projection of the adjustment pin 155 can be caught and fixed in the locking groove 225, the inner locking groove, if adjustment is necessary, the adjustment pin 155 again Can be adjusted by moving in the longitudinal direction.

6 is a cross-sectional view of an X-ray tube according to another exemplary embodiment of the present invention, and FIG. 7 is a diagram illustrating an electron generating unit illustrated in FIG. 6.

6 and 7, the plurality of bellows members 151 are installed in the first and

second electrode portions

121 and 122. The installation position of the bellows member 151 and the structure other than the first and

second electrode portions

121 and 122 have the same configuration as the X-ray tube of FIGS. 2 to 5. 6 and 7, the bellows member 150 of the focal length adjusting unit may be disposed in the electron generating unit 100.

The bellows member 151 provided in the electrode part 120 will be described based on the second electrode part 122 connected to the grid 173.

The bellows member 151 is installed between the outer tube 122a of the second electrode portion 122 and the connection rod 122b. The adjusting pin 156 is inserted into the outer tube 122a.

The adjusting pin 156 and the connecting rod 122b may be integrally formed. When the adjusting pin 156 is pulled, the bellows member 151 is compressed, and the case 160 and the vacuum of the electron generating unit 100 are vacuumed. The lengths of the first and

second electrode parts

121 and 122 disposed inside the chamber 200 are shortened. Through this, the cathode 130, the grid 173, and the grid cap 170 may be moved away from the target.

In the X-ray tube of the present invention, as described above, the bellows member 150 is sealed between the electron generating unit 100 and the vacuum chamber 200, or the bellows member 151 surrounds a part of the electrode unit 120. As described above, the present invention is not limited thereto, and the

bellows members

150 and 151 may be installed where compression or tension is required by installing a portion for adjusting the focal length.

FIG. 8 is a diagram illustrating the grid cap shown in FIG. 5.

Referring to FIG. 8, the grid cap 170 has a cup shape. The grid cap 170 is formed of a metal material and receives a current from the second electrode part 122.

The grid cap 170 has an empty space inside, and a window 171 is formed in the direction toward the anode 210. Electrons emitted into the grid cap 170 are transferred to the anode 210 through the window 171.

The grid cap 170 receives a current from the second electrode unit 122 to form an electric field therein, thereby causing electrons to travel to the target 220, and to focus the electrons. The grid 173 may be composed of a focusing coil and a deflection coil therein. The grid cap 170 surrounding the electron path toward the anode 210 prevents the electrons from dispersing while the electrons move and forms a magnetic field for focusing the electrons.

The focal size at which electrons are focused on the target 220 is small, and the closer to the circle, the higher the sharpness. What affects the focal size is affected by the size of the window 171 of the grid cap 170 and the distance between the window 171 and the target 220. As the size of the window 171 increases, the distance between the target 220 and the grid 173, the grid cap 170, and the window 171 should be increased to reduce the focus size. Therefore, the focal length should be set differently according to the size of the window 171. Even if the cathode 130, the grid cap 170, and the grid 173 are installed at the focal length, additional errors occur due to the bonding error and deformation due to heat during the sealing process. Since the sharpness may deteriorate, it is necessary to adjust the focal length after sealing.

In addition, since the shape of the vacuum chamber 200 is not perfectly symmetrical and the target 220 disposed on the anode 210 is inclined, when the window 171 is formed in a square shape, the electrons collide with the target 220. The shape is not circular. Therefore, in order to adjust electrons colliding with the target 220 to a certain density and to form a circle close to a circular shape, a rectangular window 171 is required. Therefore, the aspect ratio of the window 171 is determined so that the focal point of the electrons colliding with the target 220 is circular.

The window 171 is formed in a rectangular shape so that the shape of the focus is circular, and the electron generating unit 100 and the vacuum chamber 200 are formed by using the focal length adjusting member formed of the bellows member 150 and the adjusting pin 155. You can increase the sharpness of the X-ray device by adjusting the distance between the

Hereinafter, a method of manufacturing and operating an X-ray tube according to an embodiment of the present invention will be described.

Referring to FIG. 2, the anode 210 including the target 220 is installed in the vacuum chamber 200. The bellows member 150 may be installed on an inner surface of the case 160 of the electron generating unit 100. The bellows member 150 is coupled to the stepped portion 111 inside the case 160 and then sealed. The electrode unit 120 is installed through the opening 126 of the insulator 125 formed on the outer surface of the case 160 of the electron generating unit 100. The cathode 130 coupled to one end of the first electrode portion 121 and the grid 173 coupled to one end of the second electrode portion 122 are also fixed to the electron generator 100. Thereafter, the adjustment pin 155 is rotatably installed through the hole 110 formed in the case 160.

In order to couple the electron generating unit 100 and the vacuum chamber 200, the cylinder 230 extending from the side of the vacuum chamber 200 is brought into contact with the case 160 of the electron generating unit 100. In this case, the grid cap 170, the grid 173, and the cathode 130 are inserted into the cylinder 230.

The bellows member 150 installed in the electron generating unit 100 is disposed in contact with the protrusion 226 of the cylinder 230, and then sealed. Thereafter, the adjustment pin 155 is inserted into the fastening groove 225 to be combined to produce an X-ray tube.

X-ray tubes are manufactured with focal length at the time of assembly.

However, when depressurizing the inside of the vacuum chamber 200 in the sealing process, heat may be applied to approach the vacuum state. In this case, the positions of the anode 210, the target 220, the cathode 130, the grid 173, the grid cap 170, and the like may be modified by the applied heat. Therefore, an error may occur in the focal length at the time of assembly. If an error occurs in the focal length, the focal size is changed. Therefore, the focal length adjustment process is necessary because it may affect the resolution of the X-ray tube.

Therefore, there is an error in the sealing process and the bonding process in order to control this, in order to determine whether there is an error of the set focal length, the X-ray tube 1 is commissioned.

If there is an error in the focal length, the adjusting pin 155 is adjusted to move the grid 173, the grid cap 170, and the cathode 130 into the cylinder 230, or the distance from the target 220 is increased. Finally, the X-ray tube 1 is manufactured.

6 and 7, in the manufacturing process of the X-ray tube according to another exemplary embodiment of the present invention, the bellows member 150 includes the case 160 of the electron generating unit 100 and the cylinder 230 of the vacuum chamber 200. ), The case 160 and the cylinder 230 are sealed. The bellows member 151 and the adjusting pin 156 are inserted into the opening 126 of the insulating member 125 attached to the case 160 in the form of being installed in the electrode unit 120. The adjusting pin 156 may be pulled or pushed to adjust the inner length of the case 160 of the first and

second electrode parts

121 and 122, and the outer tube 122a and the adjusting pin 156 may be screwed to each other. The inner length of the case 160 of the first and

second electrode parts

121 and 122 may be adjusted by the rotation of the adjustment pin 156.

Hereinafter, an operation process of the manufactured x-ray tube 1 will be described.

The electrode unit 120 of the X-ray tube 1 receives a current. The current applied to the second electrode portion 122 flows along the second electrode portion 122 to the grid 173. In the grid 173 an electric field is formed due to the applied current. In addition, the grid 173 and the grid cap 170 are insulated by the insulating member 175, so that a potential difference is generated.

The current applied to the first electrode part 121 is transferred to the cathode 130. The cathode 130 is formed of a filament, and the electron generator 100 and the interior of the vacuum chamber 200 are decompressed with high vacuum. The filament of the cathode 130 is heated by the current, and heated to generate hot electrons.

Due to the potential difference between grid 173 and grid cap 170, the emitted electrons are primarily accelerated. When a high voltage is applied to the anode 210 included in the vacuum chamber 200 to further accelerate the electrons, the moving speed of the electrons generated from the cathode 130 is increased. When electrons collide with the target 220 located in the anode 210, an X-ray is generated.

When a current is applied to the grid 173, it serves as an electrostatic lens that focuses the emitted electrons to one point of the target. That is, the grid 173 may focus electrons on the target with a small focal size in order to increase the sharpness of the transmitted image of the X-ray.

If the focal size is large, the grid 173, the grid cap 170, and the cathode 130 are moved back and forth in the cylinder 230 to achieve an optimal focal length and then installed in an X-ray imaging apparatus.

As described above, the X-ray tube according to an embodiment of the present invention may adjust the focal length after sealing the electron generating unit 100 and the vacuum chamber 200 constituting the X-ray tube. Therefore, when the distance is adjusted using the adjustment pins 155 and 156 after sealing the error of the focal length generated during the sealing process, the electron generating unit 100 and the vacuum chamber are deformed by the deformation of the

bellows members

150 and 151. The distance of 200 can be adjusted. As a result, the sharpness of the X-ray apparatus in which the X-ray tube 1 is installed may be improved by adjusting the focal size at which electrons emitted from the cathode 130 are focused on the target 220 through the grid 173.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

Claims

A vacuum chamber;

An electron generating unit in which the vacuum chamber and the internal space are connected and sealed;

An anode located inside the vacuum chamber and having a target installed at one end thereof;

A cathode positioned inside the electron generating unit and emitting electrons to the target; And

A focal length adjusting unit disposed in the electron generating unit and adjusting the focal size by moving the electron generating unit.
The method of claim 1,

The focal length adjusting unit includes a bellows member disposed in the electron generating unit, and the bellows member is in contact with one end of the vacuum chamber.
The method of claim 2,

The focal length adjusting unit,

And a control pin which is fastened to a fastening groove formed at one end of the vacuum chamber and moves along the fastening groove toward the target to compress the bellows member.
The method of claim 3,

The control pin is an X-ray tube rotatably coupled to the electron generator.
The method of claim 3,

The fastening groove is a screw groove is formed,

The adjusting pin is a screw line corresponding to the screw groove is formed, X-ray tube for adjusting the compression of the bellows by the rotation of the adjusting pin.
The method of claim 2,

The bellows member is a metal X-ray tube.
The method of claim 2,

The bellows member is an X-ray tube installed on the inner surface of the electron generating unit.
The method of claim 1,

The electron generating unit,

A grid for controlling the amount of electrons emitted from the cathode; And a cylindrical grid cap focusing electrons passing through the grid to the target and including a window through which the electrons pass.
The method of claim 8,

The electron generating unit,

And an electrode part electrically connected to the grid and the cathode and protruding outside the electron generator.
The method of claim 9,

The focal length adjusting unit,

A bellows member surrounding a part of the electrode part; And an adjusting pin installed at the end of the electrode to adjust the length of the electrode.
The method of claim 8,

The focal size of the electrons reaching the target is determined according to the size of the window of the grid.
The method of claim 8,

The window is a rectangular x-ray tube.
The method of claim 8,

The grid,

The x-ray tube is adjusted to the distance between the target by the focal length adjusting unit.