JP4201933B2 - Radiation-excited phosphor screen processing method and processing apparatus, and image intensifier thereby - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image intensifier technique, and more particularly to a flattening technique of a scintillator surface that is a radiation-excited fluorescent surface of an image intensifier.
[0002]
[Prior art]
In general, an image intensifier is provided with an input unit having an input surface formed on the input side in the vacuum envelope, and an anode and an output surface provided on the output side. Further, a focusing electrode is disposed from the input side to the output side along the side wall in the vacuum envelope. By the way, the input unit is configured as shown in FIGS. FIG. 9 is an enlarged schematic view of the periphery of the input unit shown in FIG.
[0003]
That is, the input unit 71 is based on an input substrate 72 having a smooth surface and CsI (cesium iodide) formed on the input substrate 72 by a vapor deposition method under a low vacuum degree and activated with Na. The first fluorescent layer 73, the second fluorescent layer 74 formed on the first fluorescent layer 73 by a vapor deposition method under a high degree of vacuum, the first fluorescent layer 73, the second fluorescent layer 74, and the input substrate 72. Formed from an annular metal thin film 75 formed so as to cover the respective peripheral portions of each, and a photocathode (not shown) formed directly on the second fluorescent layer 74 or indirectly through another thin layer. Has been. The first fluorescent layer 73 and the second fluorescent layer 74 constitute a so-called input fluorescent layer 76.
[0004]
The annular metal film 75 has a function of electrically connecting the photocathode on the second fluorescent layer 74 and a metal thin plate electrode (not shown) formed on the input unit 71. . Further, the inner diameter of the annular metal thin film 75 is set to the value of the effective diameter of the input surface. As another function of the annular metal thin film 75, it also has a function of blocking electron emission due to fluorescence from a portion outside the effective diameter of the input fluorescent layer 76.
[0005]
The first fluorescent layer 73 is an aggregate of columnar crystals of CsI having an average diameter of 5 μm to 50 μm and grown substantially perpendicular to the input substrate 72, and a typical film thickness is about 400 μm. In this way, since the adjacent CsI columnar crystals are separated from each other by a minute gap, when the photocathode is formed directly on the half surface having high resolution characteristics, the photocathode is also the same. In other words, it is partitioned into small islands separated from each other, and electrical conduction in a direction parallel to the surface of the photocathode cannot be obtained. As a result, as the number of photoelectrons emitted from the photocathode increases, the photocathode potential cannot be kept constant, the electro-optical uniformity of the image intensifier is significantly impaired, and the output image is distorted. And degradation of resolution characteristics.
[0006]
Therefore, a second fluorescent layer 74 having a thickness of 10 μm to 30 μm is formed on the surface of the first fluorescent layer 73. Since the second fluorescent layer 74 has a relatively continuous surface, it is possible to ensure electrical conduction in a direction parallel to the surface of the photocathode formed on the surface.
[0007]
As a technique for flattening the photocathode of the input unit, Japanese Patent Laid-Open No. 57-136744 discloses a technique for flattening by a tumbler method using a stainless ball.
[0008]
[Problems to be solved by the invention]
As described above, the input unit of the image intensifier is a scintillator that is a photocathode by forming a hemispherical metal plate as an input substrate into a concave surface and vacuum-depositing a radiation-excited fluorescent material such as CsI on the concave surface. The surface was being manufactured. In order to improve the channel separation of the scintillator, CsI is grown into a columnar crystal and its wall surface is used as a separator.
[0009]
Therefore, irregularities at the tip of the columnar crystal remain on the scintillator surface, which causes a reduction in resolution of the X-ray image. Since CsI is a brittle material having a Mohs hardness of about 0.2, it is difficult to flatten by removal processing, and thus flattening processing is performed by plastic deformation. These are, for example, methods of flattening by a tumbler method using stainless balls as described above. However, it is difficult to uniformly flatten the entire processed surface by this method.
[0010]
The present invention was made based on those circumstances, and by applying a flattening process to the scintillator surface, which is the photoelectric surface of the image intensifier, to improve the resolution of the X-ray image, The object is to enable high-speed and stable image processing.
[0011]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a radiation-excited phosphor screen processing method in which the film surface of a workpiece having a film surface formed of a radiation-excited phosphor on the surface is formed flat using a roller. There ,
The film surface has a concave shape corresponding to an arc shape drawn by a tip of an arm arranged to hold the roller and turn around a fulcrum,
The roller is equipped with a heater inside,
A method for processing a radiation-excited phosphor screen, comprising the step of bringing the workpiece into a heated state and applying pressure with the roller while blowing hot air from the heater onto the roller .
[0012]
According to a second aspect of the present invention, there is provided the radiation-excited phosphor screen processing method, wherein the back surface of the workpiece is fixed by vacuum suction.
[0013]
According to a third aspect of the present invention , the back surface of the workpiece is fixed by a fixed body, and the fixed body has a spherical surface equal to the back surface of the workpiece to be formed on the front surface. when There being rotated about an axis passing through the spherical surface, pressing the workpiece the roller provided at a position opposed to the spherical surface is moved along the curved surface of the workpiece A method of processing a radiation-excited phosphor screen, characterized by pressing.
[0014]
According to a fourth aspect of the present invention, there is provided the radiation-excited phosphor screen processing method, wherein the roller is a barrel roller.
[0015]
According to a fifth aspect of the present invention, there is provided the radiation-excited phosphor screen processing method, wherein the roller is biased to the workpiece by an air spring .
[0016]
According to the means of the invention of claim 6, the air spring uses a bellows as a method for processing a radiation-excited phosphor screen.
[0017]
According to a seventh aspect of the present invention, the roller is in contact with the workpiece based on a result of measuring a distance from the workpiece surface by a non-contact sensor. This is a surface processing method.
[0018]
Further, according to the means according to the invention of claim 8, there is provided a radiation-excited phosphor screen processing method, wherein the roller processes the workpiece while vibration is applied by the vibration applying means.
[0019]
According to the means of the invention of claim 9, a radiation-excited phosphor screen processing apparatus for forming the film surface of the workpiece, on which the film surface of the radiation-excited phosphor material is formed flat, using a roller a is the fixed body rotating to fix the rear surface of the workpiece, an arm pivotally disposed about a fulcrum which holds the rollers, heater mounted inside the roller When a nozzle for blowing hot air of the heater to the roller, the roller possess a membrane surface following means for moving in contact with the membrane surface of said workpiece, said roller, said fixed body A processing apparatus for a radiation-excited phosphor screen, which is disposed at an opposed position and pressurizes and flattens the film surface .
[0020]
According to the means of the invention of claim 10, there is provided an image intensifier characterized by having a radiation-excited phosphor screen processed by the above-described method for processing a radiation-excited phosphor surface.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0022]
FIG. 1 is a cross-sectional view showing an outline of an image intensifier. The image intensifier is provided with an input unit 3 having an X-ray input surface 2 formed on the input side inside the vacuum envelope 1. An anode 4 and an output surface 5 are provided on the output side. Further, a focusing electrode 6 is arranged along the side wall in the vacuum envelope 1 from the input side to the output side. Therefore, photoelectrons emitted from the photocathode 7 of the scintillator (radiation-excited fluorescence) substance of the input unit 3 that receives and excites X-rays are converged by the focusing electrode 6 and made incident on the output surface.
[0023]
The input unit 3 is configured as shown in FIGS. FIG. 3 is an enlarged schematic diagram of the internal structure of the input unit 3 of FIG.
[0024]
As shown in FIG. 2, a layer of scintillator material is formed on the input substrate 8 having a smooth surface. The first fluorescent layer 9 is formed by vapor deposition under a low vacuum degree and is based on CsI activated by Na, and is formed on the first fluorescent layer 9 by vapor deposition under a high vacuum degree. The second fluorescent layer 10 or the like.
[0025]
The first fluorescent layer 9 is an aggregate of columnar crystals of CsI having an average diameter of 5 μm to 50 μm and grown substantially perpendicular to the input substrate 8, and a typical film thickness is about 400 μm. Thus, since the adjacent CsI columnar crystals are separated from each other by a minute gap, when the photocathode 7a is directly formed on the surface of the half surface having high resolution characteristics, the photocathode 7a is also the same. In other words, it is partitioned into small islands, and electrical conduction in a direction parallel to the surface of the photocathode 7a cannot be obtained.
[0026]
As a result, as the number of photoelectrons emitted from the photocathode 7a increases, the electric potential of the photocathode 7a cannot be kept constant, the electro-optical uniformity of the image intensifier is significantly impaired, and the output image Distortion and degradation of resolution characteristics are caused.
[0027]
Therefore, the second fluorescent layer 10 having a thickness of 10 μm to 30 μm is formed on the surface of the first fluorescent layer 9. Since the second fluorescent layer 10 has a relatively continuous surface, electrical conduction in a direction parallel to the surface of the photocathode 7 formed on this surface can be secured.
[0028]
In addition, scintillator materials such as CsI are selected according to the characteristics of each device because the maximum emission wavelength, attenuation time, reflection coefficient, density, light output ratio, temperature dependence of fluorescence efficiency, and the like are different. In addition, even with each selected material, the presence of foreign matter, dimensional accuracy, surface roughness, presence of a work-affected layer, and the like are checked in advance.
[0029]
Next, planarization of the scintillator surface (photoelectric surface 7) of the input unit 3 will be described.
[0030]
First, the CsI phosphor is evaporated under low vacuum while rotating the input substrate 8 shown in FIG. 2 in an upper vapor deposition tank (not shown) in advance, and the first fluorescent layer 9 is formed on the input substrate 8. Is formed with a film thickness of about 400 μm. Thereafter, the CsI phosphor is evaporated under high vacuum without returning the vapor deposition tank to atmospheric pressure, and the second fluorescent layer 10 is formed on the first fluorescent layer 9 to a thickness of 5 to 20 μm and input. A unit 3 is formed, and this input unit 3 is attached to the flattening device.
[0031]
As shown in the schematic side view of FIG. 4, the flattening device is composed of a fixed body 31 that fixes and rotates the input unit 3, and a processing section 32 that is provided to face the fixed body 31. .
[0032]
The fixed body 31 is formed with a spherical fixed surface 30 for sucking and fixing the input unit 3, and the fixed surface 30 is provided with suction holes 31a, 31b, 31c... 31n along the entire spherical surface. These suction holes 31a, 31b, 31c... 31n are connected to a vacuum source such as a vacuum pump (not shown) by piping. A rotation drive mechanism 33 that rotates the fixed body 31 is provided on the opposite side of the fixed surface 30.
[0033]
On the other hand, as the processing unit 32, a flattening roller 41 held by the scintillator following mechanism 34 is disposed at a position facing the fixed surface 30 of the fixed body 31. The scintillator following mechanism 34 has a configuration in which an arm 35 slidable in the axial direction is rotatable about a fulcrum 36, and the fulcrum 36 is pivotally attached to a rotation shaft (not shown) of a motor 37. In the slide structure of the arm 35, a slide shaft 39 is slidably fitted to the inner diameter of a pipe-shaped hollow shaft 38. The slide shaft 39 is structured to be attracted by a solenoid (not shown) provided in the hollow shaft 38, and moves in the direction of the fulcrum 36 when attracted by the solenoid. In addition, since a spring (not shown) is provided against this solenoid, the slide shaft 39 is always attached to the fixed body 31 side by the spring in a state where the solenoid is not activated (a state where the solenoid is not attracted). It is energized.
[0034]
A roller holding unit 40 is provided at the tip of the slide shaft 39, and a flattening roller 41 made of stainless steel is rotatably held by the roller holding unit 40. The outer shape of the flattening roller 41 is formed with a curvature matching the inner diameter of the input unit 3 to be processed, and a heater (not shown) is mounted inside.
[0035]
The operation of the apparatus having these configurations will be described with reference to FIGS. As described above, first, as shown in FIG. 5 (a), the input unit 3 is attached to the fixed surface 30 of the fixed body 31, and the suction holes 31a, 31b, 31c,. . In this state, the scintillator surface 7 of the input unit 3 is formed by vapor deposition on a spherical concave surface. However, since the spherical error of the metal input substrate 8 is large, the scintillator surface 7 also has an error following it. Therefore, the spherical error is corrected by fixing the input unit 3 using vacuum at the suction holes 31a, 31b, 31c... 31n formed on the hemispherical concave surface precisely processed of the fixed body 31.
[0036]
Next, as shown in FIG. 5B, the fixed body rotating mechanism 33 is rotated at about 100 rpm, and the fixed body 31 that holds the input unit 3 by suction is rotated. On the other hand, the scintillator surface following mechanism 34 is driven to gradually approach the scintillator surface 7 from the outer edge portion of the input unit 3, and the flattening roller 41 attached to the tip of the scintillator surface following mechanism 34 is rotating. Contact surface 7. Due to the contact pressure (about several hundred mg / inch), the flattening roller 41 moves on the rotating scintillator surface 7 in the direction of arrow A along the scintillator surface 7, and proceeds to the center of the scintillator surface 7. The flattening process is performed.
[0037]
Since the flattening roller 41 is constantly heated to about 150 ° C. by the action of a heater (not shown) mounted therein, the flattening process is performed by pressurization in a heated state.
[0038]
Further, the locus on the scintillator surface 7 of the flattening roller 41 during the flattening process becomes a spiral shape and proceeds to the central portion of the scintillator surface 7 and then flattened as shown in FIG. The roller 41 is lifted and separated from the scintillator surface 7 to finish the flattening process.
[0039]
In addition, the follow-up method of the scintillator surface follow-up mechanism 34 can be performed by using a passive force control by a spring or a method in which a distance from the scintillator surface is measured and position control is actively performed thereby.
[0040]
That is, as shown in FIG. 6, the passive force control by the spring is such that the flattening roller 41 a is provided at the tip of the arm 35 a of the scintillator surface following mechanism 34 a via the link mechanism 45. The link 46 is urged by a bellows 47, which is an air spring, to apply a certain force to the scintillator surface (not shown). The air spring can apply a constant force regardless of the stroke. The bellows 47 is connected to a buffer tank 49 through a pipe 48, and the buffer tank 49 is connected to a vacuum pump (not shown). Further, by using the bellows 47 for the air spring, the sliding resistance of the pneumatic piston can be eliminated.
[0041]
The method shown in FIG. 7 is a method based on position control. That is, a mounting base 51 is provided at the tip of the arm 35b of the scintillator surface following mechanism 34b, and the mounting base 51 is configured to reduce the distance between the flattening roller 41b mounted on the laminated piezoelectric body 52 and the scintillator surface. For example, a measurement terminal 53 of an ultrasonic sensor that is measured by contact is installed. Accordingly, a measuring device (not shown) measures the distance from the scintillator surface (not shown) by the measuring terminal 53, and the control device 54 causes the laminated piezoelectric body 52 to expand and contract based on the result, thereby the flattening roller 41b. Flattening is performed by controlling the position.
[0042]
Further, as the flattening method by the flattening roller 41, any one shown in FIGS. 8A to 8C can be used alone or in combination. In either method, the columnar crystals of the scintillator layer are flattened only on the surface without being destroyed.
[0043]
FIG. 8A shows a flattening method using a barrel roller 41 c as the flattening roller 41. A constant force or a fixed amount of pressing is applied to the barrel-shaped roller 41c from a scintillator surface following mechanism (not shown) to flatten the scintillator surface 7. Barrel roller 41c is a radius of curvature is or smaller formed equal to the radius of curvature of the scintillator surface 7. In addition, if the curvature of the flattening roller 41c is too small, regular irregularities are generated on the scintillator surface 7, which may cause moire in the captured image.
[0044]
FIG. 8B shows a planarization method by heating. The flattening roller 41d is heated by the heater 42 built in the flattening roller 41d, and hot air is blown onto the scintillator surface 7 by the nozzle 55, whereby the scintillator surface 7 is heated and softened to flatten the surface. If the nozzle 55 is arranged at a position where hot air blows to the flattening roller 41d, the flattening roller 41d can be cleaned together.
[0045]
FIG. 8C shows a planarization method by applying vibration. A vibrator 57 is installed at a portion of the roller receiver 56 that holds the flattening roller 41e. The vibrator 57 applies vibration to the flattening roller 41e to flatten the scintillator surface 7. In this case, by applying a shocking force, only the surface of the columnar crystal of the first fluorescent layer 9 can be crushed and flattened.
[0046]
In the above-described case, the heater 42 is provided in the flattening rollers 41 and 41d and is heated by the flattening rollers 41 to 41d. However, a heater (not shown) is provided inside the fixed body 31. May be embedded and heated accordingly.
[0047]
In each of the above cases, the scintillator surface is a curved surface. However, when the scintillator surface is a flat surface, the scintillator surface following mechanism is not placed in the polar coordinate system, but is scanned on a plane axis using an XY stage. Can be done.
[0048]
As described above, according to the present invention, a uniform finish with a stable flat surface can be expected as compared with the flat method using tumbling. Moreover, since a dust does not generate | occur | produce compared with the removal process like a buff process, a favorable processed surface is obtained.
[0049]
【The invention's effect】
According to the present invention, it is possible to improve the resolution of an X-ray image by obtaining a good flat surface on the scintillator surface of the image intensifier.
[0050]
Also, various devices equipped with the image intensifier can perform image processing stably at high speed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an outline of an image intensifier.
FIG. 2 is a schematic diagram showing a configuration of an input unit.
FIG. 3 is an enlarged schematic diagram of the internal structure of the input unit.
FIG. 4 is a schematic side view of the flattening device of the present invention.
FIGS. 5A to 5C are explanatory diagrams of a planarization operation by the planarization apparatus of the present invention.
FIG. 6 is an explanatory view of a scintillator surface following mechanism of the flattening device of the present invention.
FIG. 7 is an explanatory diagram of another scintillator surface following mechanism of the flattening device of the present invention.
8A to 8C are explanatory views of a pressurizing mechanism of the flattening device of the present invention.
FIG. 9 is an explanatory diagram showing a configuration of an input unit.
FIG. 10 is an enlarged schematic view of the periphery of the input unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 3 ... Input unit, 7 ... Photoelectric surface (scintillator surface), 9 ... 1st fluorescent layer, 10 ... 2nd fluorescent layer, 31 ... Fixed body, 34 ... Scintillator following mechanism, 41, 41a, 41b, 41c, 41d, 41e ... flattening roller, 42 ... heater

Claims (10)

A method of processing a radiation-excited fluorescent surface, wherein the film surface of a workpiece having a film surface formed of a radiation-excited fluorescent material on a surface is formed flat using a roller ,
The film surface has a concave shape corresponding to an arc shape drawn by a tip of an arm arranged to hold the roller and turn around a fulcrum,
The roller is equipped with a heater inside,
A method of processing a radiation-excited phosphor screen, comprising the step of bringing the workpiece into a heated state and applying pressure with the roller while blowing hot air from the heater onto the roller .   The method for processing a radiation-excited fluorescent screen according to claim 1, wherein the back surface of the workpiece is fixed by vacuum suction. The back surface of the workpiece is fixed by a fixed body, and the fixed body has a spherical surface formed on the front surface equal to the back surface of the workpiece, and the fixed body rotates around an axis passing through the spherical surface. 2. The radiation according to claim 1, wherein the roller provided at a position opposite to the spherical surface moves along a curved surface of the surface of the workpiece to pressurize the workpiece. Excitation phosphor surface processing method.   The method of processing a radiation-excited phosphor screen according to claim 1, wherein the roller is a barrel roller. 2. The method of processing a radiation-excited phosphor screen according to claim 1, wherein the roller is urged against the workpiece by an air spring . 6. The method of processing a radiation-excited phosphor screen according to claim 5, wherein the air spring uses a bellows .   2. The method for processing a radiation-excited phosphor screen according to claim 1, wherein the roller contacts the workpiece based on a result of measuring a distance from the workpiece surface by a non-contact sensor.   The radiation-excited phosphor screen processing method according to claim 1, wherein the roller processes the workpiece while vibration is applied by a vibration applying unit. A radiation-excited phosphor screen processing apparatus for forming the film surface of a workpiece, on which a film surface of a radiation-excited phosphor material is formed , using a roller,
A fixed body that rotates with fixing the back surface of the workpiece,
An arm that holds the roller and is arranged to be rotatable around a fulcrum;
A heater mounted inside the roller;
A nozzle for blowing hot air from the heater to the roller;
Possess a membrane surface following means for moving the roller in contact with the membrane surface of the workpiece,
The said roller is arrange | positioned in the position facing the said fixed body, pressurizes and planarizes the said film surface, The processing apparatus of the radiation excitation fluorescent screen characterized by the above-mentioned .   An image intensifier comprising a radiation-excited phosphor screen processed by the method for processing a radiation-excited phosphor surface according to claim 1.

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