JPH0765741A - X-ray imaging tube - Google Patents

Abstract

(57) [Summary] [Object] To provide an X-ray imaging tube having a vibration-proof target. [Structure] A thin glass plate 32 constituting a target 3 was joined to a semi-circular support frame 9, and the support frame 9 was attached to a vacuum valve 2 via a bracket KB.

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 pickup tube for converting an X-ray image into an electric signal in an X-ray television system used for medical diagnosis or non-destructive material inspection.

[0002]

2. Description of the Related Art Recently, as an X-ray image pickup tube of this kind, a fluorescent surface for converting X-rays into visible light and a photoelectric conversion surface made of amorphous selenium are formed on both surfaces of a flat transparent plate so as to be in close contact with each other. An apparatus has been proposed which includes such a target and is configured to read out charges formed on a photoelectric conversion surface by scanning an electron beam.

The structure of this apparatus will be described with reference to FIGS. As shown in FIG. 5, the X-ray imaging tube 1 is configured such that a target 3 ′ is mounted inside a vacuum valve 2 via a bracket KB and an electron gun 4 is housed therein. A window 5 made of aluminum or the like is provided on the X-ray incident surface of the vacuum valve 2, and the X-ray XR transmitted through the subject M is incident on the target 3 ′ through the window 5.

The target 3'is, as shown in FIG.
In order from the incident side of the line XR, a phosphor screen 31 of CsI or the like, a flat glass thin plate 32, a transparent conductive film 33 such as an ITO film, and an amorphous selenium film 34 are formed in close contact with each other. That is, without providing the thin glass plate 32, the fluorescent screen 31 (usually Cs
When the conductive film 33 and the amorphous selenium film 34 are directly formed on I), since CsI has a needle-like crystal structure, the conductive film 33 and the amorphous selenium film 34 thereon are not flat, and as a result, amorphous selenium film is formed. This is because a local high electric field is generated in the film 34, which may cause a spark or the like to destroy the pixel.

When the X-ray XR transmitted through the subject M is incident on the target 3 through the window 5, the fluorescent surface 31 of the portion on which the X-ray XR is incident emits light, and the light is a glass thin plate 32 and a conductive film 33.
It enters the amorphous selenium film 34 through the. When light reaches this amorphous selenium film 34, electric charges are generated therein, and the conductivity of that portion is increased. Therefore, on the amorphous selenium film 34, a distribution of conductivity corresponding to the incident X-ray transmission image can be obtained. Conductive film 33 of target 3 '
A high voltage is applied between the electron gun 4 and the electron gun 4 to form a high electric field. Therefore, since a high electric field is applied to the amorphous selenium film 34, the avalanche effect is caused, the charges formed on the amorphous selenium film 34 exponentially increase, and the conductivity is amplified.

Amorphous selenium film thus formed
The two-dimensional distribution of conductivity on 34 is read by the electron beam e. That is, an electron beam e is emitted from the electron gun 4 toward the target 3 ', and a current proportional to the conductivity in the portion of the amorphous selenium film 34 hit by the electron beam e produces a current between the target 3'and the electron gun 4. Since it flows in between, a voltage signal is obtained across the resistor R.
Since the electron beam e is focused and deflected by the coil 6 and the like to scan the target 3'two-dimensionally, the conductivity distribution on the amorphous selenium film 34 is read out as an electric image signal. This electric signal becomes a video signal via the camera control unit 7, is sent to the television monitor device 8, and the X of the subject M is displayed on the screen.
A line transmission image is displayed.

According to the X-ray image pick-up tube 1 as described above, the X-ray image intensifier device and the television image pick-up tube, which are generally used conventionally, are used in the conversion process from the X-ray to the electric signal. The number of steps is smaller than that in the conversion process in the line television system, and as a result, noise generated during the conversion can be reduced. Therefore, the X-ray transmission image displayed on the television monitor device 8 has a large S / N ratio. Will be things. Also, due to the avalanche effect,
Since the conductivity on the amorphous selenium film 34 corresponding to the X-rays incident on the target 3'is amplified, a large electric signal can be obtained even with a small amount of incident X-rays, and the dynamic range becomes large. Furthermore, since it is possible to form the phosphor 31 and the amorphous selenium film 34 in a large area, it is possible to manufacture the X-ray image pickup tube 1 having a large diameter.

[0008]

However, the conventional example having such a structure has the following problems. A flat glass thin plate 32, which is interposed between the phosphor screen 31 and the conductive film 33 and serves as a support (substrate) for the phosphor 31, the conductive film 33, and the amorphous selenium film 34, thickens the light from the phosphor screen 31. Since it is transmitted in the vertical direction and diffused in the surface direction, increasing the thickness causes a decrease in resolution.

Therefore, from the viewpoint of resolution, the glass thin plate 32
It is necessary to make the thickness of 50 μm or less. Such thin glass sheets are vulnerable to mechanical vibration and are fragile,
There is a problem that it is difficult to handle.

In view of the above circumstances, it is an object of the present invention to provide an X-ray image pickup tube having a target that is strong against mechanical vibration.

[0011]

In order to achieve the above object, the present invention has the following constitution. That is,
According to the present invention, a fluorescent screen for converting X-rays into visible light is closely adhered to an X-ray incident surface of a flat glass thin plate, and a photoelectric conversion surface made of amorphous selenium is closely adhered to the other surface of the glass thin plate. In an X-ray image pickup tube having a target and a means for reading out charges formed on the photoelectric conversion surface by scanning an electron beam, the target is supported via a supporting means for bending and supporting a thin glass plate of the target. It is attached to a vacuum valve that accommodates.

[0012]

The operation of the present invention is as follows. The thin glass plate is curved and supported by the supporting means, whereby the target has a curved surface, so that the mechanical strength is increased and the vibration resistance is improved. Further, since the thin glass plate is supported by the supporting means, its handling becomes easy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of an X-ray image pickup tube according to an embodiment of the present invention, and FIG. 2 is a perspective view of a support frame (supporting means) for curvedly supporting a thin glass plate in FIG. In the figure, the parts indicated by the same reference numerals as in FIGS.
Since the configuration is the same as that of the conventional example, detailed description thereof is omitted here.

The feature of this embodiment is that, as shown in FIG. 2, a glass thin plate 32 is attached to a portion of the support frame 9 indicated by diagonal lines in the figure by an adhesive agent or the like on a support frame 9 having a semi-circular cross section in which an opening 9'is formed. It is joined and curved in a concave shape with respect to the X-ray incident direction, and a fluorescent screen 31 is formed on the X-ray incident surface, and a conductive film 33 and an amorphous selenium film 34 are sequentially formed on the other surface by vapor deposition or the like. .
The target thus configured is attached to the vacuum valve 2 via the bracket KB.

In the above description, after the glass thin plate 32 is bonded to the support frame 9, the fluorescent surface is adhered to one surface of the glass thin plate and the conductive film and the amorphous selenium film are adhered to the other surface to form the target 3. However, after providing a margin for joining to the support frame around the glass thin plate, forming the fluorescent screen, the conductive film, and the amorphous selenium film, the glass thin plate is joined to the support frame to create a curved target. May be.

[0016]

[Modification] In the above embodiment, the thin glass plate is joined to the support frame having a semi-cylindrical cross section and curved in a concave shape with respect to the X-ray incident direction, but it may be curved in a convex shape.

Further, the curved shape may not be a simple concave or convex shape, but may be a corrugated shape as shown in FIGS. 3 and 4.

[0018]

As is clear from the above description, according to the present invention, the thin glass plate is curved and supported by the supporting means. As a result, the target becomes a curved surface,
Since the mechanical strength is increased and a target having excellent vibration resistance can be obtained, an X-ray image pickup tube that is resistant to mechanical vibration can be obtained.

Therefore, by using the X-ray image pickup tube of the present invention, an X-ray transmission image free from image blur due to vibration can be obtained and displayed on the monitor device.

Further, since the thin glass plate is fixed to the supporting means, it becomes easy to prepare a target and handle it when assembling the X-ray image pickup tube.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of an X-ray image pickup tube according to an embodiment of the present invention.

FIG. 2 is a perspective view of a support frame that curvedly supports the thin glass plate of FIG.

FIG. 3 is a schematic diagram of a modified example.

FIG. 4 is a schematic view of still another modified example.

FIG. 5 is a cross-sectional view showing a configuration of an X-ray image pickup tube according to a conventional example.

FIG. 6 is a diagram schematically showing a configuration of a target of an X-ray image pickup tube.

[Explanation of symbols]

1 ... X-ray imaging tube 2 ... Vacuum valve 3 ... Target 4 ... Electron gun 6 ... Electron beam focusing / deflecting coil 9 ... Support frame (support means) 31 ... Phosphor (phosphor surface) 32 ... Glass thin plate 33 ... Conductivity Film 34 ... Amorphous selenium film (photoelectric conversion surface) e ... Electron beam

Claims (1)

[Claims] 1. An X-ray incident surface of a flat glass thin plate is provided with X
The fluorescent surface for converting the rays into visible light, the photoelectric conversion surface made of amorphous selenium on the other surface of the glass thin plate, the targets formed in close contact with each other, and the photoelectric conversion surface is placed inside the vacuum bulb. In an X-ray image pickup tube equipped with means for scanning and reading out charges formed on the photoelectric conversion surface by focusing and deflecting an electron beam by a coil, via a supporting means for bending and supporting the thin glass plate of the target. And an X-ray image pickup tube attached to the vacuum valve.