KR20010026637A - An Apparatus for Xray Tomography - Google Patents

Abstract

PURPOSE: An X-ray tomography equipment is provided to obtain rapidly a clear tomography image by simplifying a structure of an existing X-ray tomography equipment. CONSTITUTION: A table(21) fixes a location of a subject for photography. An X-ray generator(24) projects an X-ray to an axis point of the subject fixed on the table(21). The X-ray generator(24) is rotated along a constant circular orbit(23) in order to project the X-ray to a tomography angle. A photomultiplier tubes(26) are installed according to a uniformal interval on a constant circular orbit(25).

Description

X-ray tomography imaging device {An Apparatus for Xray Tomography}

The present invention relates to an X-ray tomography imaging apparatus, and more particularly, to an X-ray tomography imaging apparatus adapted for imaging a tomography quickly and clearly.

X-ray tomography apparatus has been used for a long time in the medical field, there are many kinds.

Recently, X-ray tomography imaging apparatus has been required as an inspection and measurement device for observing the state of PCB components and the structure of semiconductors not only in the medical field but also in the electronics industry. Because the line widths of electronic components and semiconductor products are indistinguishable with the naked eye, and some semiconductor packages are not able to see the leads from outside after they are attached to the PCB, It is to check for defects by acquiring tomography images and discriminating them.

Conventional X-ray tomography apparatuses include many apparatuses using various types of tomography imaging, such as linear tomography, circular tomography, elliptical tomography, eight-shaped tomography, and the like. A device using a circular tomography method as shown in Fig. 1 is mentioned.

The device using the circular tomography using X-rays rotates the X-ray generator 10 and the subject 11 at a constant speed, which makes it possible to rotate X-rays at a predetermined angle with respect to the reference line Z. The rotary table 12 for controlling the image, an image multiplier 13 for converting the image of X-rays passing through the subject into visible light, and a video camera 15 for converting the image of the image multiplier into a video image signal. There is).

The conventional X-ray tomography imaging apparatus rotates an object by rotating the X-ray generator at a predetermined angle with respect to the reference line while rotating the subject in synchronization with the X-ray generator. This generates an X-ray image of the subject in the image multiplier, which is captured by the camera and stored or processed by a computer to obtain a tomographic image of the subject. A tomographic image is obtained by overlapping by spatially matching a plurality of images generated while rotating. The principle that a tomographic image is obtained by overlapping a plurality of X-ray images is that a tomographic image is obtained by digitally superimposing a video image as a general tomographic imaging apparatus displays a plurality of images on one film.

Since the light-receiving surface is a curved surface, the image produced by the conventional X-ray tomography imaging apparatus is distorted in shape and distorted in strength, so that it is difficult to perform distortion correction in software, and it is difficult to perform rapid inspection.

An object of the present invention is to provide an X-ray tomography imaging apparatus which can quickly obtain a clear tomography image by supplementing the disadvantages of the conventional X-ray tomography imaging apparatus.

In order to achieve the above object, the present invention provides a table for positioning and fixing a subject photographing an X-ray tomography image, and rotating along a predetermined circular trajectory to project X-rays at a constant tomography angle to an axis point of the subject fixed to the table. Four or more X-ray generators and at least four equally spaced intervals are provided in a constant circular track that the X-rays generated by the X-ray generator are passed through the object, the light receiving surface is perpendicular to the radiation direction of the X-rays An X-ray tomography imaging device comprising an image multiplier. It is preferable that eight image multipliers are installed at intervals of 45 degrees with respect to the center of the circular track.

An image multiplier that receives visible X-rays to produce a visible light image includes a cold cathode in the form of a plate which generates electrons when X-rays are irradiated, and a first electrode on an electron generating surface of the cold cathode, insulated from the cold cathode. And a carbon electrode having a second electrode opposite to the first electrode, the carbon electrode having a plurality of through holes penetrating between the first electrode and the second electrode, and insulated from the carbon electrode and disposed adjacent to the second electrode. An electrode, a space between the cold cathode, the carbon electrode, and the transmissive fluorescent electrode is sealed and vacuumed, and the cold cathode, the first electrode of the carbon electrode, the second electrode of the carbon electrode, and the transparent fluorescent electrode The electrodes are provided so as to be insulated from each other, and the electrodes are configured such that a voltage is gradually applied from the cold cathode. The cold cathode, the first electrode of the carbon electrode, the second electrode of the carbon electrode, and the transparent fluorescent electrode are insulated by insulators in the form of a ring, and the insulators, the cold electrode, the first electrode of the carbon electrode, and the carbon electrode The second electrode and the transparent fluorescent electrode are sealed by a sealing material, and a high voltage generating circuit for supplying a high voltage to the electrodes is positioned around the insulators and the electrodes, and the outer case is configured to protect the surroundings.

1 is a view for explaining the principle of operation of a conventional X-ray tomography imaging apparatus.

2 is a view for explaining the principle of operation of the X-ray tomography imaging apparatus of the present invention.

Figure 3 is a plan view for explaining the position of the image multiplier of the present invention.

Figure 4 is a partial cross-sectional view of the image multiplier of the present invention

5 is a schematic cross-sectional view of an image multiplier of the present invention.

※ Explanation of symbols for main parts of drawing ※

Figure 2 is a schematic view showing the apparatus of the present invention, Figure 3 is a plan view for explaining the position where the image multiplier pipe is installed.

The X-ray tomography apparatus of the present invention has a table 21 for fixing the subject 22 to be photographed, and a constant circular trajectory for projecting X-rays at a constant tomography angle to an axis point of the subject fixed to the table 21. X-ray generator 24 rotating along 23 and X-rays generated by X-ray generator 24 are installed at equal intervals on a constant circular track 25 reached through the subject 22, Four or more image multipliers (26) provided with a light receiving surface perpendicular to the radiation direction of the X-rays.

In the illustrated embodiment, eight image boosters 26 are provided at intervals of 45 degrees with respect to the center of the circular track 25.

The table 21 may use an XY table, an XYZ table, a turn table, or the like. The image multiplier creates a visible light image according to its intensity when the X-rays are irradiated, so that the human eye can observe it. In the embodiment, the visible line image is captured by a video camera, and the video signal is converted into a digital signal to be processed by a control device using a computer.

Such a control device is general and is not shown in the drawings. In addition, the control device controls the overall system operation by controlling the position of the table or the X-ray generator.

A process of photographing a tomography image using the present invention will be described.

If the subject is fixed, and the X-ray generator is started to rotate from the position 26-1 as the initial position as the image multiplier reached by generating the X-rays, the first generated X-ray is the image multiplier 26-1. In the first X-ray transmission image is formed. Subsequently, when the X-ray generator rotates 45 degrees, the second X-ray image is formed in the image multiplier 26-2, and the third X-ray image is formed in the image multiplier 26-3. An 8X image will be imaged in the image multiplier 26-8.

These eight images are images with phase difference of 45 degrees because the subject is fixed.These images are digitally processed and rotated by 45 degrees by the controller (computer) so that they are all in the same phase. As a result, when the images are overlapped, the X-ray images of the focal plane at the axial point are summed together to make it clear, and all the X-ray images positioned outside the focal plane are blurred. (The image of the focal plane has a higher resolution and the other portions have a lower resolution, which eventually blurs, which is already used in tomography.)

In the conventional tomography imaging apparatus shown in FIG. 1, in addition to the operation of correcting the phase angle of the X-ray image, since the light receiving surface is inclined to the spherical surface, the amount of work required to correct all of them is about the same, so the speed is very slow. Only the calibration is required, so it can be processed very quickly. Because the image multipliers are all the same and installed so that they are all perpendicular to the X-ray radiation direction, there is no need for correction of the inclined and curved light receiving surface.

The image multiplier used in the present invention is as shown in Figs.

The image multiplier has a planar shape as shown in FIG. 3, and has a schematic cross-sectional shape as shown in FIG. 5, which is composed of an image generating unit 51 and an outer case 52, and inside the outer case. The high voltage generator is mounted on a ring-type PCB and is installed in a hermetic seal with silicone resin. The image generator 51 has a cold cathode 41, a carbon electrode 42 and a transparent fluorescent electrode 43.

The image generating unit has a cross section as specifically shown in FIG.

The image generating unit receives the cold cathode 41 which generates electrons according to the intensity of X-rays to be irradiated, the carbon electrode 42 which multiplies the electrons generated by the cold cathode, and the electrons that are multiplied by the carbon electrode to receive a large amount of visible light. It comprises a transparent fluorescent electrode 43 for generating a, it is sealed so that the electron transfer passage is a vacuum.

The cold cathode 41 is made of a high strength metal plate such as titanium to form the cold cathode 41 and has a thickness of about 0.25 mm.

The carbon electrode 42 is located about 10 mm from the cold cathode, and the carbon electrode has many small holes 48 of about 20 mm per hole. A metal film (for example, a platinum film) is attached to both sides of the carbon electrode to be used as the first electrode 47 and the second electrode 48.

The transparent fluorescent film 43 is formed by forming a transparent electrode 45 through which visible light passes through the glass substrate 44, and a fluorescent film 46 that emits fluorescence when electrons are incident thereon.

Between the cold cathode and the carbon electrode is provided with a ring-shaped insulator spacer (49-1) spaced about 10 mm apart, the first electrode and the second electrode of the carbon electrode is insulated by the insulator ring (49-2), Between the two electrodes and the transparent fluorescent electrode, the insulating ring 49-3 is spaced about 1 mm apart. Each electrode and the insulating ring may be joined by forming a screw and attaching with an adhesive. After the air is completely sealed, a vacuum pump is used to evacuate the gas inside to the exhaust hole (not shown) to obtain a vacuum. The transparent fluorescent electrode hardly bends because the thick glass sustains the vacuum force, but the cold cathode is a thin plate that is slightly concave spherically by the force of the vacuum.

The diameter of each electrode to be vacuumed is about 50 mm, a voltage of about 7 kv is applied between the cold cathode and the first electrode of the carbon electrode, and about 0,5 kv is applied between the first electrode and the second electrode. When a voltage of about 10 kv is applied between the second electrode and the transparent fluorescent electrode, a current of about 1.5 to 2.0 micro amps flows.

This high voltage is generated in the high voltage generating circuit 53, and is connected to each electrode by a lead wire in the high voltage generating circuit.

In this image multiplier, the X-ray image is converted into visible light on the fluorescent surface as follows.

When X-rays are incident on the cold cathode, electrons are emitted. Although the amount of this electron is small and the energy is small, it is accelerated to high energy by about 7 kv voltage applied between the carbon electrode and the cold cathode, and is attracted to the carbon electrode, some of which is absorbed by hitting the first electrode, and some of the holes of the carbon electrode It is injected into it and hits the carbon electrode wall in the hole to generate secondary electrons. These secondary electrons hit a wall again and generate many secondary electrons. Since a voltage of about 0.5 kv is applied to both sides of the carbon electrode, secondary electrons generated in the hole of the carbon electrode are attracted to the second electrode, and electrons drawn to the surface of the second electrode come out of the hole and are drawn to the transparent fluorescent electrode. Goes. Since a transparent fluorescent electrode is applied with a voltage of about 10 kv, electrons receive high energy and hit the phosphor at a small distance of about 1 mm, thereby causing the phosphor to emit light.

The image multiplier has the advantage of less distortion of the image because electrons from the cold cathode without the electronic lens are drawn toward the transparent electrode by an almost equal electric field.

Compared with the conventional X-ray tomography apparatus, the apparatus of the present invention described above has the advantage that a simple structure and a clear and high-resolution tomography image can be viewed quickly. Since it is slightly concave, it is at the same distance from the X-ray source to the spherical surface, the distortion is small, the structure is simple, and the hole of the carbon electrode is fine, so high resolution can be obtained.

Claims (5)

An apparatus for obtaining an X-ray tomography image, A table for fixing the position to photograph the X-ray tomography image, An X-ray generator that rotates along a constant circular trajectory to project X-rays at a constant tomography angle to an axial point of a subject fixed to the table; Including at least four image multiplier pipes are installed at equal intervals in a constant circular orbit reached by the X-ray generator passing through the subject, and the light receiving surface is installed perpendicular to the radiation direction of the X-rays; X-ray tomography imaging device The method according to claim 1, X-ray tomography imaging apparatus, characterized in that the eight image multipliers are installed at intervals of 45 degrees with respect to the center of the circular orbit The method according to claim 1, The image multiplier is an X-ray tomography imaging device, characterized in that the X-ray image forming surface is concave with respect to the focal point of the X-rays. As an image multiplier that receives X-rays and produces visible light images, The plate-shaped cold cathode that generates electrons when the X-rays are irradiated, A carbon electrode made of a carbon plate having a plurality of fine through holes, and having a first electrode attached to an electron generating surface side of the cold cathode and a second electrode attached to a surface opposite the first electrode; It is provided adjacent to the second electrode and provided with a transparent fluorescent electrode for generating fluorescence by electrons, The space between the cold cathode, the carbon electrode, and the transmissive fluorescent electrode is sealed and vacuumed, and the cold cathode, the first electrode of the carbon electrode, the second electrode of the carbon electrode, and the transparent fluorescent electrode are respectively insulated and installed. And the voltage of which the voltage gradually increases from the cold cathode in turn to this electrode. The method according to claim 4, The cold cathode, the first electrode of the carbon electrode, the second electrode of the carbon electrode, and the transparent fluorescent electrode are insulated by ring-shaped insulators, the insulators, the cold electrode, the first electrode of the carbon electrode, and the carbon electrode. The second electrode, and the transparent fluorescent electrode are sealed by a sealing material, A high voltage generating circuit for supplying a high voltage to the electrodes is located at the outer circumference of the insulators and the electrodes, and the image multiplier tube is configured to protect the outer case around the insulator.