JPH069047U - X-ray tube - Google Patents

Abstract

(57) [Abstract] [Purpose] To make the electron beam density distribution in the focal length direction of the X-ray tube a Gaussian distribution. [Structure] The winding pitch of a filament coil of an X-ray tube is made dense at the central part and coarse at both ends. [Effect] The electron beam density distribution in the focal length direction becomes a Gaussian distribution, which contributes to improving the image quality of X-ray photographs and the like.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to improvement of electron beam density distribution in the focal length direction of an X-ray tube.

[0002]

[Prior art]

 Various studies have been conducted on the improvement of the density distribution of the electron beam at the focus of the conventional X-ray tube, but most of them are related to the improvement of the density distribution of the electron beam in the focal width direction, and most of them are related to the improvement of the electron beam density distribution in the focal length direction. There is little work on improving the electron beam density distribution. An example of the latter is, for example, Japanese Utility Model Publication No. 2-124652. This publication describes the improvement of the shape of the opening of the focusing electrode of the cathode, and is characterized in that the length of the opening in the filament length direction is shorter than the length of the filament.

[0003]

[Problems to be solved by the device]

 In the case of the above-mentioned prior art, the electron beam density distribution in the focal length direction of the X-ray tube is rectangular or unimodal as shown in FIGS. The electron beam density distribution shown in FIG. 5 is generated when the winding pitch of the filament coil is dense, and the electron beam density distribution shown in FIG. 6 is generated when the winding pitch of the filament coil is coarse. The response functions of these electron beam density distributions are similar to those of the bimodal shape or the unimodal shape of FIG. 8 (b), and are inferior in characteristics to those of the Gaussian distribution type.

An object of the present invention is to provide an X-ray tube having a Gaussian distribution shape as shown in FIG. 4 by improving the electron beam density distribution in the focal length direction of the X-ray tube.

[0005]

[Means for Solving the Problems]

 To achieve the above object, the present invention comprises a cathode part and an anode part supported in a vacuum envelope, the cathode part supporting a coiled filament and focusing an electron emitted from the coiled filament. In an X-ray tube having a target in which the accelerated and focused electrons from the cathode collide with the anode part, the winding pitch of the coiled filament is made dense in the central part and roughened at both ends. The density distribution of electron beams in the winding and focal length directions is Gaussian.

[0006]

[Action]

 FIG. 8 shows various electron beam density distribution shapes and corresponding response functions. As is clear from this figure, when the electron beam density distribution is Gaussian, it shows the best response function up to the high spatial frequency region. Therefore, by changing the winding pitch of the filament coil so that the electron beam density distribution in the focal length direction becomes a Gaussian distribution, a good response function can be obtained at a high spatial frequency, and an X-ray photograph with good image quality can be obtained.

[0007]

【Example】

 An embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a vertical sectional view of the X-ray tube. In the X-ray tube, the anode part 4 and the cathode part 6 are arranged so as to face each other in the envelope 3, and the inside of the envelope 3 is maintained in vacuum. The cathode part 6 comprises a focusing electrode 2 in which a coiled filament 1 is arranged. Further, the anode part 4 is provided with a target 5 which is focused by the electron beam from the cathode part 6 to form a focus.

FIG. 1 shows a coil winding method of a coiled filament 1 according to an embodiment of the present invention, and FIG. 2 shows a state in which the coiled filament 1 of FIG. 1 is attached to a focusing electrode 2. It is a thing. In FIG. 3, the electrons emitted from the heated coiled filament 1 are accelerated by the high voltage applied between the negative and positive electrodes and are focused by the focusing electrode 2 to collide with the target 5 of the opposing anode part 4. And emit X-rays. The focal point is a portion where the electron beam on the target 5 concentrates and collides, and emits X-rays. At the focal point of the X-ray tube, the longitudinal direction of the filament coil is called the focal length direction, and the direction perpendicular thereto is called the focal width direction. The target of the present invention is the former electron beam density distribution in the focal length direction.

In FIG. 1, the winding pitch of the coiled filament 1 is dense at the center and coarse at both ends. For example, the central portion has 80 turns / inch (dense) and both ends have 50 turns / inch (dense). Since the winding pitch of the filament coil can be changed by changing the gear ratio when winding the coil, a fine and fine pitch combination can be freely realized. 5 and 6 are shown as an example of the electron beam density distribution in the focal length direction when the filament is wound in the conventional single winding pitch, the example of FIG. 5 is 80 windings / inch (dense) It is a case of winding, and the example of FIG. 6 is a case of winding at 50 turns / inch (dense). On the other hand, the electron beam density distribution when wound as in the embodiment of the present invention is as shown in FIG. Comparing the three, (1) In the case of dense winding with a single pitch, the electron beam density distribution becomes rectangular as shown in Fig. 5, and the response function is also poor (close to a bimodal shape), which is not preferable in terms of image quality. . (2) In the case of coarse winding with a single pitch, the electron beam density distribution has a single-peaked shape as shown in Fig. 6, but the efficiency of thermionic emission of the filament is extremely reduced, and it is 1/2 of that of close winding. It is about 1/3 and not practical. (3) When the central portion is densely roughened at both ends as in the case of the present invention, as shown in FIG. 7, a Gaussian distribution is obtained by combining FIG. 5 and FIG. The response function at this time is good, and the image quality is also preferable. In the above embodiment, the case of the fixed anode X-ray tube has been described, but it goes without saying that the same applies to the rotating anode X-ray tube and the like.

[0010]

[Effect of device]

 According to the present invention, the electron beam density distribution in the focal length direction can be made into a Gaussian distribution simply by changing the winding pitch of the filament coil, and an X-ray photograph with high image quality can be provided.

[Brief description of drawings]

FIG. 1 shows a method of winding a coil of a coiled filament which is an embodiment of the present invention.

FIG. 2 shows a state in which the coiled filament of FIG. 1 is attached to a focusing electrode.

FIG. 3 is a vertical sectional view of an X-ray tube according to an embodiment of the present invention.

FIG. 4 is a characteristic diagram of the electron beam density distribution in the focal length direction of the X-ray tube of the present invention.

FIG. 5 is a characteristic diagram of an electron beam density distribution when the winding pitch of the filament coil is dense.

FIG. 6 is a characteristic diagram of an electron beam density distribution when the winding pitch of the filament coil is coarse.

FIG. 7 is a characteristic diagram of an electron beam density distribution when the winding pitch of the filament coil is densely formed in the central portion and roughened at both ends.

FIG. 8 shows various electron beam density distribution shapes (a) and corresponding response functions (b) for comparison.

[Explanation of symbols]

 1 Coiled filament 2 Focusing electrode 3 Envelope 4 Anode part 5 Target 6 Cathode part

Claims (1)

[Scope of utility model registration request] 1. A vacuum envelope is provided with a cathode part and an anode part, and the cathode part has a focusing electrode that supports a coiled filament and focuses electrons emitted from the coiled filament. In an X-ray tube having a target where accelerated electrons from the cathode part and focused electrons collide with the anode part,
An X-ray tube, characterized in that a coiled filament is wound densely at a central portion and coarsely wound at both ends to make a density distribution of an electron beam in a focal length direction a Gaussian distribution.