JP2002015690A - X-ray image tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-Ray image tube having a small change in diameter of an output image, even if a viewing field is changed. SOLUTION: In the X-Ray image tube composed of an input section 12 equipped in a vacuum envelope 11 in which an X-Ray image is inputted, an output section 17 arranged on an output window 18 constituting one part of the vacuum envelope 11, converging electrodes 13 to 15 and an anode 16 arranged between the input section 12 and the output section 17, and a masking plate 19 prepared in the side of the input section 12 of the output section 17, one part of the masking plate 19 is fixed to a part of the output window 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray image tube in which a space between a masking plate disposed immediately before an output section and an output section is small.

[0002]

2. Description of the Related Art An X-ray image tube is an X-ray tube that transmits an
An electron tube that converts a line image into a visible light image and the like, and is used in medical diagnostic devices and the like.

Here, a conventional X-ray image tube will be described with reference to FIG. Reference numeral 41 denotes a vacuum envelope. The vacuum envelope 41 is made of metal or glass and has a substantially cylindrical shape. On one side inside the vacuum envelope 41, an input unit 42 for inputting an X-ray image from the outside is provided. The input unit 42 converts the X-ray image into an electronic image, for example, photoelectrons, and outputs it. The photoelectrons output from the input unit 42 are accelerated and focused by a plurality of electrodes, for example, an electron lens formed by the focusing electrodes 43 to 45 and the anode 46, and reach the output unit 47. The photoelectrons that have reached the output unit 47 are converted into a visible light image or the like, and output from the X-ray image tube through the output window 48.

The output section 47 is formed in close contact with a glass output window 48 constituting a part of the vacuum envelope 41. A masking plate 4 is provided on the input side of the output section 47.
The central opening P faces the output unit 47. The masking plate 49 blocks photoelectrons generated from portions other than the effective diameter of the input section 42, and prevents these photoelectrons from reaching the output section 47.

In the above configuration, the focusing electrodes 43 to 4
5 and by changing the voltage applied to the anode 46,
As indicated by reference numeral A or B, the size of the visual field of the X-ray image tube is adjusted.

Next, the structure near the output section 47 of the X-ray image tube will be described with reference to FIG. The vicinity of the output portion 47 has a structure symmetrical with respect to the tube axis m. Therefore, FIG. 5 shows only the left half. FIG.
Are denoted by the same reference numerals, and overlapping description will be partially omitted.

An output portion 47 is formed on the inner surface of an output window 48 made of glass which forms a part of the vacuum envelope 41. The output unit 47 includes a phosphor layer 471 formed on the output window 48.
And metal back layer 4 formed on phosphor layer 471
72. The metal back layer 472 covers the entire phosphor layer 471, and furthermore, the phosphor layer 47 on the outside thereof
The output window 48 having no 1 is formed. Also,
A masking plate 49 having an L-shaped cross section is disposed around the output portion 47, and the anode 46 having a cylindrical shape as a whole is integrally formed on the masking plate 49.

[0008]

In the conventional X-ray image tube, when adjusting the field of view, the focusing electrodes 43 to 45 and the anode 4 are required.
6 is changed. Also, the input unit 42
The photoelectrons outputted from the focusing electrodes 43 to 45 and the anode 46
The output part 4 is accelerated and focused by the electron lens formed by
Reach 7

At this time, the trajectory of the photoelectrons is
45 and the voltage applied to the anode 46. Therefore, the angle of incidence on the output unit 47 is different between the electron trajectory e1 when the visual field is large (A in FIG. 4) and the electron trajectory e2 when the visual field is small (B in FIG. 4). As a result, the diameter of the output image changes depending on the size of the visual field. The change in the diameter of the output image increases as the distance between the masking plate 49 and the output unit 47 increases. In order to reduce such a change in the diameter of the output image, it is desirable to make the space between the masking plate 49 and the output unit 47 as small as possible.

For example, in an X-ray image tube having an input surface size of 32 cm and an output image size of 30 mm, when the distance between the masking plate 49 and the output portion 47 is 0.6 mm, the diameter of the output image becomes about 0. It changes by 2 mm. The change in the output image diameter of the X-ray image tube is required to be suppressed to 0.1 mm or less, and in this case, the distance between the masking plate and the output section is 0.2 mm or less.

However, in the conventional X-ray image tube, a masking plate is fixed to a metal part of a vacuum envelope in which an output window is sealed, and there is a problem of parts accuracy.
It is difficult to keep the distance between them at 0.2 mm or less.

When the output image of the X-ray image tube is photographed by a television camera or the like and taken out, the photographing conditions are set according to the smaller output image in ordinary photographing. Therefore, when the diameter of the output image changes and the output image spreads,
There is a problem that information on the peripheral portion cannot be obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an X-ray image tube in which the diameter of an output image is small even if the size of a visual field changes.

[0014]

According to the present invention, there is provided an input section provided in the vacuum envelope for inputting an X-ray image and an output window constituting a part of the vacuum envelope. An X-ray image tube comprising: an output unit; a plurality of electrodes provided between the input unit and the output unit; and a masking plate provided on the input unit side of the output unit. A part is fixed to a portion of the output window.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. Reference numeral 11 denotes a vacuum envelope. The vacuum envelope 11 is made of metal or glass and has a substantially cylindrical shape. An input unit 12 to which an X-ray image is input from the outside is provided on one side in the vacuum envelope 11. The input unit 12 converts the X-ray image into an electronic image, for example, photoelectrons, and outputs the image. The photoelectrons output from the input unit 12 are accelerated and focused by an electron lens formed by a plurality of electrodes, for example, the focusing electrodes 13 to 15 and the anode 16, and reach the output unit 17. The photoelectrons that have reached the output unit 17 are converted into an output image such as a visible light image and output from the X-ray image tube through an output window 18 made of glass. The output window 18 is airtightly joined to, for example, a metal part of the vacuum envelope 11 to form a part of the vacuum envelope 11.

The output section 17 is formed in close contact with the inner surface of the output window 18. A masking plate 19 is arranged on the input side of the output unit 17, and its central opening P is
And is facing. The masking plate 19 is used for the input unit 1.
Photoelectrons generated from areas other than the effective diameter 2 are blocked, so that these photoelectrons do not reach the output unit 17. Also,
A part of the masking plate 19 contacts and is fixed to the output window 18.

In the above configuration, the focusing electrodes 13 to 1
When the voltage applied to the anode 5 and the anode 16 is changed, the size of the visual field of the X-ray image tube is adjusted, for example, as shown by the symbol A or B. For example, the electron trajectory when the field of view is large (symbol A in FIG. 1) is indicated by reference sign e1, and the electron trajectory when the visual field is small (symbol B in FIG. 4) is indicated by reference sign e2. For the tube, the output unit 17
2 will be described with reference to FIG. Since the vicinity of the output section 17 has a structure symmetrical with respect to the tube axis m, only the left half thereof is shown. Also, portions corresponding to those in FIG. 1 are denoted by the same reference numerals, and duplicate description will be partially omitted.

The output window 18 is hermetically sealed in, for example, a metal portion of the vacuum envelope 11, and an output portion 17 is provided on the inner surface thereof. The output unit 17 includes a phosphor layer 171 and a metal back layer 172 formed on the phosphor layer 171. The metal back layer 172 covers the entire phosphor layer 171, and extends to the outside on the output window 18 in a region where the phosphor layer 171 is not provided.

The anode 16 is formed in a substantially cylindrical shape as a whole, and its cross section has a flange-shaped tip portion 16a extending toward the tube axis m.
And a first intermediate portion 16b extending from the outer edge of the tip portion 16a along the tube axis m, a flange portion 16c extending in a direction opposite to the tube axis m from the first intermediate portion 16b, and a flange portion 16c extending along the tube axis m from the flange portion 16c. A second intermediate portion 16d extending from the second intermediate portion 16d, and a flange-shaped rear end portion 16e extending in a direction opposite to the tube axis m from the second intermediate portion 16d, and the rear end portion 16e is a vacuum envelope in which the output window 18 is sealed. 11 is fixed to, for example, a metal part.

The cylindrical second intermediate portion 16 of the anode 16
For example, a disk-shaped masking plate 19 having an opening P at the center is fitted inside d. The masking plate 19 has two planes, for example, an upper stage 19a located inside near the tube axis m, and a lower stage 19b located farther outside the input unit 12 than the upper stage 19a. It has become. And the upper stage 19a
Is in contact with, for example, the metal back layer 172 of the output unit 17, and the lower surface of the lower stage 19 b is on the output window 18, for example, in a region where the phosphor layer 171 is not provided.
Is in contact with and fixed.

An elastic member 20 having a spring property is arranged between the flange 16c of the anode 16 and the lower stage 19b of the masking plate 19. The upper end of the elastic member 20 is fixed to the flange portion 16c, the lower end is fixed to the lower step 19b, and the masking plate 19 is pressed toward the output window 18 to fix the masking plate 19.

According to the above-described structure, a part of the masking plate 19, for example, the lower part 19b thereof is formed in the output window 18
, And the upper portion 19 a shields the input side of the output unit 17. Therefore, if the interval between the lower stage 19b and the upper stage 19a of the masking plate 19 is configured to be small, the interval between the masking plate 19 and the output unit 17 can be reduced.
This interval can be set to a dimension of 0.2 mm or less necessary for practical use.

Next, another embodiment of the present invention will be described with reference to FIG.
Since the vicinity of the output unit 17 has a symmetric structure with respect to the tube axis m, only the left half thereof is shown as in FIG.
Are denoted by the same reference numerals, and overlapping description will be partially omitted.

In this embodiment, a holding part 31 is fixed to a metal part of the vacuum envelope 11 in which the output window 18 is sealed. The holding part 31 has a substantially cylindrical shape, and its cross section is a first flange-shaped portion 311 extending toward the tube axis m, a cylindrical portion 312 extending along the tube axis m, and opposite to the tube axis m from the lower end of the cylindrical portion 312. The second flange portion 313 extends in the direction, and the second flange portion 313 is joined and fixed to the metal portion of the vacuum envelope 11.

The anode 16 is provided inside the holding member 31 and has a cross section having a flange-shaped tip portion 161 extending in a direction perpendicular to the tube axis m, and an intermediate portion extending along the tube axis m from the outer edge of the tip portion 161. A portion 162 includes a rear end portion 163 extending from the intermediate portion 162 in a flange shape in a direction opposite to the tube axis m. Then, the outer edge of the rear end portion 163 is
Is fitted inside the intermediate portion 162 of the second member. Further, the rear end portion 163 is located on the output window 18, for example, the phosphor layer 171.
It is in contact with and fixed to the metal back layer 172 in the region where there is no. A disk-shaped masking plate 19 having an opening P at the center is integrally formed inside the intermediate portion 162 so as to protrude in a direction perpendicular to the tube axis m.

The first flange 31 of the holding part 31
An elastic member 20 having a spring property is disposed between the first member 1 and the rear end portion 163 of the anode 16. The upper end of the elastic member 20 is fixed to the flange portion 311, and the lower end is the rear end portion 163.
, And a part of the anode 16, for example, a rear end portion 163 is pressed toward the output window 18 and fixed. At this time,
For example, a portion of masking plate 19 contacts metal back layer 182.

In this case, the masking plate 1
9 forms one plane near the input side, the rear end portion 163 of the anode 16 forms another plane farther from the input side than the masking plate 19, and the rear end portion 163 forms the output window 18. The part is fixed. Therefore, the masking plate 19 and the rear end portion 1 of the anode 16
If the space between the surfaces formed by the 63 is made small, the space between the masking plate 19 and the output unit 17 becomes small, and this space can be set to 0.2 mm or less, which is necessary for practical use.

In the case of a structure in which the masking plate and the anode are integrated, the displacement between the center of the output image formed by the electron lens formed by the anode and the like and the center of the masking plate can be reduced.

In the above embodiment, a part of the masking plate and the anode is fixed to the metal back layer on the output window. However, when there is no metal back layer around the output window, a part of the masking plate or the anode is directly fixed to the output window surface.

According to the above configuration, the distance between the masking plate and the output section can be reduced, and the change in the diameter of the output image can be suppressed even when the size of the field of view is switched. Further, the information of the X-ray image input to the X-ray image tube can be effectively used.

[0031]

According to the present invention, it is possible to realize an X-ray image tube in which the change in the diameter of the output image is small even if the size of the visual field changes.

[Brief description of the drawings]

FIG. 1 is a schematic structural diagram for explaining an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing the vicinity of an output unit according to the present invention.

FIG. 3 is a schematic sectional view showing the vicinity of another output section of the present invention.

FIG. 4 is a schematic structural diagram for explaining a conventional example.

FIG. 5 is a schematic sectional view showing the vicinity of an output section of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Vacuum envelope 12 ... Input part 13-15 ... Focusing electrode 16 ... Anode 17 ... Output part 18 ... Output window 19 ... Masking plate e1 ... Trajectory of the electron which generate | occur | produced from the outermost periphery in the maximum view mode e2 ... Minimum view mode Orbits of electrons generated from the outermost periphery in

Claims (6)

[Claims] 1. An input unit provided in a vacuum envelope for inputting an X-ray image, an output unit provided on an output window constituting a part of the vacuum envelope, and the input unit In an X-ray image tube including a plurality of electrodes provided between the output units and a masking plate provided on the input unit side of the output unit, a part of the masking plate is provided at a part of the output window. An X-ray image tube which is fixed. 2. The X-ray image tube according to claim 1, wherein an elastic member is disposed between one of the plurality of electrodes and the masking plate. 3. The masking plate has two planes, a first plane having an opening and a second plane located farther from the input section than the first plane, and a portion of the second plane is an output window. The X-ray image tube according to claim 1, which is fixed to the portion. 4. An input unit provided in the vacuum envelope for inputting an X-ray image, an output unit provided on an output window constituting a part of the vacuum envelope, and the input unit In an X-ray image tube including a plurality of electrodes provided between the output units and a masking plate disposed on the input unit side of the output unit, the masking plate and one of the plurality of electrodes are integrally formed. And one of said plurality of electrodes
An X-ray image tube, wherein one part is fixed to the output window. 5. The masking plate forms a first plane, one part of the plurality of electrodes forms a second plane located farther from the input unit than the first plane, and the second plane forms a second plane. 5. The X-ray image tube according to claim 4, wherein the plane portion is fixed to the output window portion. 6. The X-ray according to claim 4, wherein a holding member fixed to the vacuum envelope is provided in the vacuum envelope, and an elastic member is disposed between the holding member and one of the plurality of electrodes. Image tube.