JPH10162758A - X-ray image tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray image tube capable of improving a contrast ratio without degrading brightness characteristics and of easy manufacturing. SOLUTION: This X-ray imaging tube 41 has a vacuum envelope 51, an X-ray input face, and an image output part 55. The image output part 55 has a fluorescent output face (output screen) 55a formed inside an output window 51a of the vacuum envelope, and a band pass filter 57 formed outside the output window. The band pass filter 57 does not always pass a spectrum of 400nm or less and a spectrum of 650nm or more, and trnasmission rate of a spectrum of 450nm and 600nm is appropriately 50%. Thereby, a luminous spectrum and a spectrum in the vicinity thereof to be required to be captured as a visible light beam can be acquired at a high contrast ratio without undesirably lowering brightness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray converter for converting an image obtained by X-rays into a visible light image or an electric image signal.
The present invention relates to an X-ray image tube, and more particularly, to an output screen substrate or an output window of an X-ray image tube.

[0002]

2. Description of the Related Art An X-ray image tube is useful for examining the internal structure of a human body or an object. Used to convert to an image signal.

An X-ray image tube comprises an X-ray input portion (input surface), an output fluorescent screen, and a photoelectric conversion surface arranged in a vacuum envelope. An X-ray that has passed, ie, an X-ray projection image, is captured by an X-ray input portion, ie, an input phosphor screen, and light emitted from the input phosphor screen is converted into electrons on a photocathode and formed by electrodes provided in the X-ray image tube. The electrons are accelerated and focused on the output fluorescent screen by the electrostatic electron lens system, and converted into a visible light image on the output fluorescent screen and output to the outside.

[0004] It is known that the contrast ratio of an image output to the outside of an X-ray image tube as a visible light image has a large effect on a portion where the X-ray image tube emits the brightest light, that is, on an output fluorescent screen (output portion). Therefore, in order to increase the contrast ratio of the output image of the X-ray image tube, for example, the transmittance of the output screen (or the substrate forming the output screen) is significantly reduced to about 20% to 80%, so that the output brightness is reduced. There is an example in which the contrast ratio is improved by lowering the contrast ratio.

In order to improve the contrast ratio of the output image of the X-ray image tube without lowering the brightness of the output image of the X-ray image tube, it is useful to increase the thickness of the glass of the output window. However, when the thickness of the window glass is changed, the focusing power (power) of the imaging lens for inputting the output X-ray image to the imaging device arranged at the subsequent stage is changed, or the imaging lens is changed. It is necessary to optimize the refractive index of the material.

Japanese Patent Application Laid-Open No. Sho 63-105449 discloses that the number of glass substrates for forming an output screen and an output window forming a vacuum envelope is reduced so that light emitted from the output screen is reduced. An example is disclosed that reduces the number of interfaces that reflect.

On the other hand, Japanese Patent Application Laid-Open No. 49-128672 discloses a reflection made of an alkali noble earth fluoride compound so that light output from an X-ray image tube is not reflected back by the X-ray image tube. An example in which a prevention film is formed is disclosed.

[0008]

As described above, remarkably lowering the luminance of the X-ray image tube to improve the contrast ratio does not only sacrifice the luminance characteristics of the X-ray image tube but also increases the X-ray image tube. There is a problem that the visible light image output from the line image tube cannot be fully utilized.

Further, as disclosed in Japanese Patent Application Laid-Open No. 63-105449, a method for reducing the number of glass sheets on a substrate for forming an output screen and an output window forming a vacuum envelope is disclosed in Japanese Patent Application Laid-Open No. 63-105449. The face plate needs to be glued. The face plate must be closely attached to the vacuum envelope, which requires a complicated bonding process and has a problem of reducing the yield.

On the other hand, when an anti-reflection film is used as disclosed in JP-A-49-128672, the anti-reflection film has an extremely small anti-reflection effect for light incident from a position other than perpendicular, and therefore X When focusing an electron using an electrostatic electron lens system like a line image tube, there is a problem that it does not function sufficiently. When the antireflection film is disposed on the glass surface, uniform characteristics are required in a wide range corresponding to the area of the output image of the X-ray image tube, so that there is a problem that its manufacture becomes difficult.

Further, in the method of improving the contrast ratio of the output image by increasing the thickness of the glass of the output window of the X-ray image tube, it is necessary to redesign the imaging lens located at the subsequent stage. Or an unusable lens arrangement such that the lens and the output window come into contact with each other.

An object of the present invention is to provide an X-ray image tube capable of improving the contrast ratio without lowering the luminance characteristics of the X-ray image tube and avoiding a problem in manufacturing the X-ray image tube. To provide.

[0013]

SUMMARY OF THE INVENTION The present invention has been made based on the above problems, and has an input screen in an input side in a vacuum envelope, an output screen and an anode in an output side, and a vacuum. In an X-ray image tube provided with a focusing electrode along the side wall of the envelope, the transmittance of a glass serving as a substrate of the output screen or an output window forming a part of the vacuum envelope is at least the output power. X, which has a transmittance of 10% or less through the emission spectrum of the screen and other spectrums.
A line image tube is provided.

According to the present invention, an input screen is arranged on an input side in a vacuum envelope, an output screen and an anode are arranged on an output side, and a focusing electrode is provided along a side wall of the vacuum envelope. In the X-ray image tube, the transmittance of the output window forming a part of the glass or the vacuum envelope serving as the substrate of the output screen is determined by a transmission spectrum regulating member externally attached to the output window. 10% transmittance at least for the emission spectrum of the output screen and the other spectrum
The present invention provides an X-ray image tube characterized in that the transmittance is regulated as follows.

Further, according to the present invention, an input screen is arranged on an input side in a vacuum envelope, an output screen and an anode are arranged on an output side, and a focusing electrode is provided along a side wall of the vacuum envelope. In an X-ray image tube, the transmittance of an output window forming a part of the glass or the vacuum envelope of the substrate of the output screen is determined by a band-pass filter externally attached to the output window. 10% transmission through the spectrum of the light emitted by the screen and the other spectrum
The present invention provides an X-ray image tube characterized in that the transmittance is regulated as follows.

Further, according to the present invention, the transmission spectrum restricting member externally attached to the output window may be a glass serving as a substrate of the output screen or an output window forming a part of the vacuum envelope. Formed by glass having a refractive index substantially equal to the refractive index, and an adhesive having a refractive index substantially equal to the refractive index of glass serving as a substrate of the output screen or an output window forming a part of the vacuum envelope. It is fixed to the output window.

Further, according to the present invention, the transmittance of the band-pass filter is approximately 50% at 450 nm and 600 nm, and approximately 90% at 525 nm.
%.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of an X-ray image tube having a radiation-excited fluorescent screen, that is, an X-ray input plane, manufactured according to an embodiment of the present invention.

As shown in FIG. 1, an X-ray image tube 1
Is a cylindrical vacuum envelope 11 formed of glass or the like,
An X-ray input surface 1 formed of aluminum (Al) or an aluminum alloy and capturing an X-ray emitted from an X-ray source (not shown) and passing through an object, that is, an X-ray projection image.
3. An image output unit 15 disposed at the other end of the vacuum envelope 11 facing the X-ray input surface 13 and outputting a visible light image corresponding to the X-rays captured by the X-ray input surface 13 I have.

According to the X-ray image tube 1 described above, the X-ray image incident on the input surface 13 is transmitted through the substrate 13a to excite the phosphor on the fluorescent surface 13b,
The fluorescence corresponding to the line image is emitted. The fluorescent light emitted from the fluorescent screen 13b is converted into photoelectrons 7 by the photoelectric screen 13c and is focused by the focusing electrode 17 while being accelerated by the accelerating electrode 19.
(Anode) and guided to the output unit 15.

The X-ray input surface 13 has a substrate 13a having a convex surface protruding toward an X-ray source (not shown).
On the back surface of the convex surface of the substrate 13a, for example, a phosphor screen 13b on which a phosphor layer is formed by vapor deposition or the like and a photoelectric screen 13c added to the phosphor screen 13b, and the X-rays 5 transmitted through the subject 3, Captured as an X-ray image.

The output unit 15 is, specifically, a vacuum envelope 11
Has an output screen or fluorescent output surface 15a located inside the output window 11a which forms a part of the output window 11a. In addition,
The output window 11a is formed so as to transmit at least the emission spectrum of the light output from the fluorescent light output surface 15a, and to have a transmittance of 10% or less in other areas. Such characteristics can be easily obtained by including a specific impurity in a portion of the vacuum envelope 11 corresponding to the output window 11a. Note that, as an example, the output screen 15a is
For example, in the case of zinc sulfide, the emission spectrum is 5
With a peak at 25 nanometers (hereinafter referred to as nm),
Since it is between approximately 400 nm and 650 nm, by including a transition metal (iron-based) in the portion corresponding to the output window 11a, the transmittance of the emission spectrum of less than 400 nm and 650 nm or more is reduced to the peak of 525 nm. The transmittance is reduced to 10% or less as compared with the transmittance.

FIG. 2 shows a modification of the X-ray image tube shown in FIG. 1, and is a partially enlarged view showing the vicinity of the output window. The same components as those of the X-ray image tube shown in FIG. 1 are denoted by the same reference numerals, and detailed description will be omitted.

As shown in FIG. 2, the X-ray image tube 2
1 is a cylindrical vacuum envelope 3 made of glass or the like
1. An X-ray input surface 13, which is formed of aluminum (Al) or an aluminum alloy and captures X-rays emitted from an X-ray source (not shown) and passing through an object, that is, an X-ray projection image, facing the X-ray input surface 13. An image output unit 35 is provided at the other end of the vacuum envelope 11 to output a visible light image corresponding to the X-rays captured by the X-ray input surface 13.

The image output section 35 includes a fluorescent output surface (output screen) 35 a formed inside the output window 31 a of the vacuum envelope 31, that is, inside the vacuum envelope 31, and the output window 3.
It has a transmission spectrum restricting member 37 formed outside of 1a.

The transmission spectrum restricting member 37 includes a glass plate 37a having a refractive index substantially equal to the refractive index of the glass material of the output window 31a of the vacuum envelope 31, and a portion corresponding to the output window 11a of FIG. Similarly, it is provided by containing a specific impurity and fixing it with an adhesive having a refractive index substantially equal to the refractive index of the glass material of the output window 31a.

According to this structure, as compared with the X-ray image tube shown in FIG. 1, no special processing is required for the output window 31a, so that the cost and yield of the vacuum envelope 31 alone can be reduced. Can be improved. Further, the transmission spectrum restricting member 37 may be adhered to the output window 31a. Even if the transmission spectrum of the transmission spectrum restricting member 37 does not satisfy the required spectrum, the vacuum envelope 31 may be used. Can be reused.

FIG. 3 shows a modification of the X-ray image tube shown in FIG. 1, and is a partially enlarged view showing the vicinity of the output window. The same components as those of the X-ray image tube shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 3, the X-ray image tube 4
1 is a cylindrical vacuum envelope formed of glass or the like.
1. An X-ray input surface 13, which is formed of aluminum (Al) or an aluminum alloy and captures X-rays emitted from an X-ray source (not shown) and passing through an object, that is, an X-ray projection image, facing the X-ray input surface 13. An image output unit 55 is provided at the other end of the vacuum envelope 11 to output a visible light image corresponding to the X-rays captured by the X-ray input surface 13.

The image output unit 55 includes a fluorescent output surface (output screen) 55 a formed inside the output window 51 a of the vacuum envelope 51, that is, inside the vacuum envelope 51, and the output window 5.
It has a band-pass filter 57 formed outside 1a.

The band-pass filter 57 is easily provided, for example, by alternately stacking at least one or more filters of sharp cut filter B56 (made of Hoya glass, trade name) and Y44 (made of Hoya glass, trade name). You.
In this case, 5 which is the peak of the spectrum described in FIG.
The transmittance at 25 nm is 90% or more, and the decrease in luminance conventionally caused does not substantially occur. According to the above-described filter 57, transmission of a spectrum of 400 nm or less and a spectrum of 650 nm or more is hardly measured. The transmittance of the spectrum at 450 nm and 600 nm is approximately 50%.

On the other hand, when the incident field of view is 40 cm (hereinafter referred to as cm) in a 40-inch X-ray image tube, the 10 mm diameter contrast ratio (see JISZ4721) is 15 to 16, and
The 10% area contrast ratio (see JISZ) has been improved from 25 to 30 respectively. According to the above-described embodiment, since the thickness of the glass of the output window 11a is not affected, the output image of the output window 11a is formed on the imaging device arranged at the subsequent stage of the X-ray image tube 1. There is no need to change the focusing power or power of the imaging lens to be imaged or to optimize the refractive index of the material of the imaging lens. This is very useful in reducing the design cost of the X-ray image tube 1.

[0033]

As described above, according to the X-ray image tube of the present invention, without undesirably lowering the luminance,
An emission spectrum that needs to be captured as a visible light image and a spectrum in the vicinity thereof can be obtained with a high contrast ratio. Thereby, the intensity of the X-ray irradiated on the target can be minimized.

Further, since the transmission spectrum regulating member or the band-pass filter is arranged separately from the vacuum envelope outside the output window of the X-ray image tube, the vacuum envelope alone and the X-ray image tube are not provided. Total cost is reduced.

Further, the contrast ratio of the output image can be increased without changing the thickness of the glass of the output window of the X-ray image tube, and the output image is formed on the image pickup device located at the subsequent stage of the X-ray image tube. The complicated design work for changing the power of the imaging lens to be imaged or optimizing the refractive index of the material of the lens and the cost thereof are reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an X-ray image tube to which an embodiment of the present invention is applied.

FIG. 2 is a schematic diagram showing another example of the output unit of the X-ray image tube shown in FIG.

FIG. 3 is a schematic diagram showing another example of the output unit of the X-ray image tube shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... X-ray image tube, 11 ... Vacuum envelope, 11a ... Output window, 13 ... X-ray input surface, 15 ... Image output part, 15a ... Fluorescence output surface, 17 ... Focusing electrode, 19 ... Acceleration electrode, 35 ... Image output unit, 35a: fluorescent output surface, 37: transmission spectrum regulating member, 55: image output unit, 55a: fluorescent output surface, 57: band-pass filter.

Claims (5)

[Claims] An X-ray image in which an input screen is arranged on an input side in a vacuum envelope, an output screen and an anode are arranged on an output side, and a focusing electrode is provided along a side wall of the vacuum envelope. In the tube, the transmittance of a glass serving as a substrate of the output screen or an output window forming a part of the vacuum envelope passes at least through the emission spectrum of the output screen, and the transmittance of the other spectrum is 10%. An X-ray image tube characterized by the following. 2. An X-ray image in which an input screen is arranged on an input side in a vacuum envelope, an output screen and an anode are arranged on an output side, and a focusing electrode is provided along a side wall of the vacuum envelope. In the tube, the transmittance of a glass serving as a substrate of the output screen or an output window forming a part of the vacuum envelope is at least the output screen provided by a transmission spectrum regulating member externally attached to the output window. And the transmittance for the other spectrum is 1
An X-ray image tube characterized in that the transmittance is regulated so as to be 0% or less. 3. An X-ray image in which an input screen is arranged on an input side in a vacuum envelope, an output screen and an anode are arranged on an output side, and a focusing electrode is provided along a side wall of the vacuum envelope. In the tube, the transmittance of a glass serving as a substrate of the output screen or an output window forming a part of the vacuum envelope is emitted by at least the output screen by a bandpass filter externally attached to the output window. Pass through the spectrum of light, and the transmittance for the other spectrum is 1
An X-ray image tube characterized in that the transmittance is regulated so as to be 0% or less. 4. The output screen, wherein the regulating member is formed of glass serving as a substrate of the output screen or glass having a refractive index substantially equal to a refractive index of an output window forming a part of the vacuum envelope. 3. The fixing device according to claim 2, wherein said glass is fixed to said output window by an adhesive having a refractive index substantially equal to that of an output window forming a part of said vacuum envelope. Line image tube. 5. The band-pass filter has a transmittance of 45.
For 0 nm and 600 nm, roughly 50%, 52
The X-ray image tube according to claim 3, wherein the X-ray image tube has a wavelength of approximately 90% at 5 nm.