JP4788272B2 - X-ray tomographic imaging apparatus and X-ray tomographic imaging method - Google Patents

Description

  The present invention relates to an X-ray tomographic imaging apparatus and an X-ray tomographic imaging method for inspecting internal structure data of an object to be examined using X-rays or the like.

  Conventionally, non-destructive three-dimensional analysis is required in the field of research and development of semiconductor elements and the like in order to inspect cracks, breaks, and the like that exist inside a micro-inspection object. As one of the methods, there is a method using a computed tomography apparatus using X-rays (hereinafter referred to as an X-ray tomography apparatus).

  The X-ray tomographic imaging apparatus is, for example, an X-ray source (an X-ray generator configured by an X-ray tube or the like) and an X-ray focus from this X-ray source to irradiate a subject to be examined in the form of a cone beam. A two-dimensional detection means for detecting the detected X-ray, and a rotation axis orthogonal to the perpendicular line dropped from the X-ray focal point to the detection surface of the detection means while being placed between the detection means and the detection means It has a rotating base that rotates with an angular displacement based on it. The X-ray source irradiates the object to be inspected with X-rays, the transmission X-ray projection image of the object to be inspected is picked up by the two-dimensional detection means, processed as a plurality of image data for each angle phase, By reconstructing the internal structure data from the image data, it becomes easier to inspect and observe the inside of the inspection object.

  In the calculation for reconstructing the internal structure data described above, it is desirable that the projected image of the object to be inspected is within the width direction of the detection surface of the two-dimensional detection means. It is required to take an image by means.

  For example, as a means for artificially expanding the width of a finite two-dimensional detection means, there is a method described in Patent Document 1.

  An outline of a technique for artificially expanding the width of the two-dimensional detection means described in Patent Document 1 will be described with reference to FIGS. 10 and 11. FIG. 10 is a schematic diagram (bird's eye view) for explaining a method of imaging by moving a conventional X-ray two-dimensional detector in parallel. FIG. 11 is a top view of FIG.

As shown in FIGS. 10 and 11, the initial position of the X-ray two-dimensional detector 102 is set at an inspected object 107 disposed between the X-ray focal point of the X-ray tube 101 and the X-ray two-dimensional detector 102. The position passes through the center of rotation and is perpendicular to the detection surface of the X-ray two-dimensional detector 102 from the X-ray focal point. The X-ray two-dimensional detector 102 is translated in parallel with the positions 102a, 102b, and 102c in a plane parallel to the detection surface, and a plurality of obtained projection images are synthesized to obtain a virtually wide projection image.
JP 9-327453 A

  However, the X-ray two-dimensional detector 102 is placed in a device (shield cover) that prevents X-ray leakage, and the amount of parallel movement is largely limited by the size of the device. Further, when the amount of parallel movement of the X-ray two-dimensional detector 102 increases as in the positions 102a and 102c, the distance from the perpendicular drawn from the X-ray focal point to the X-ray two-dimensional detector 102 gradually increases, and the X-ray two-dimensional The projection image captured by the detector 102 cannot obtain sufficient brightness.

  The present invention has been made in view of such points, and uses an X-ray two-dimensional detector placed in an apparatus having a limited space to capture an image while suppressing the attenuation of the brightness of the projected image. The objective is to improve the magnification of the projected image obtained in this way.

In order to solve the above-described problems, the present invention provides an X-ray source capable of obtaining a cone beam-shaped irradiation field , a two-dimensional detection means having a flat detection surface for imaging transmitted X-rays of an object to be inspected, and an X-ray source. angle set around a rotation axis perpendicular to the perpendicular dropped to the test exit face of the deployed two-dimensional detector from X-ray focal point by placing the object to be tested between the X-ray focal point and the two-dimensional detection means X-ray tomographic imaging comprising: a rotating means that rotates by displacement ; and a control means that performs reconstruction calculation from a projection image captured for each angular phase and performs control to reconstruct the internal structure data of the object to be inspected In performing X-ray tomography with the device,
The X-ray source and the two-dimensional detection unit are placed on the rotation unit while the mutual positions of the X-ray source and the two-dimensional detection unit are fixed so that a part of the inspection object is imaged by the two-dimensional detection unit by the control unit . A vertical line that is lowered from the X-ray focal point to the detection surface of the two-dimensional detection unit with respect to a rotational axis that passes through the X-ray focal point in parallel with the rotational axis of the inspection object, The angle formed by the straight line connecting the rotation axis of the object to be inspected from the X-ray focal point is at three imaging positions of θ degrees, 0 degrees, and −θ degrees, and each time a predetermined number of projected images are captured at each imaging position, Swivel with the same radius,
At each imaging position, the initial angle phase of the object to be inspected is set to −θ degrees, 0 degrees, and θ degrees, respectively, and the predetermined number of projection images are captured for each angle phase;
Projected images obtained at the respective imaging positions are perpendicular to the rotation axis passing through the X-ray focal point in parallel with the rotation axis of the object to be inspected, and the radius is lowered from the X-ray focal point to the two-dimensional detection means. Projective transformation to a virtual cylindrical surface with the length of
The projection images of the same angle phase are synthesized in the order of imaging at the respective imaging positions subjected to the projective transformation, and the reconstruction calculation is performed from the projection images synthesized for each angle phase to reconstruct the internal structure data of the object to be inspected. It is characterized by that.

According to the present invention, the X-ray source and the two-dimensional detection means having a flat detection surface do not require the process of moving the two-dimensional detection means while fixing the mutual position of the two-dimensional detection means. The structure can be simplified and the apparatus size can be reduced. Further, since the distance between the X-ray source and the two-dimensional detection means is constant, attenuation of the brightness of the projected image is prevented. In addition, since it is possible to capture an image without changing the positional relationship between the X-ray focal point and the two-dimensional detection means, it is possible to perform imaging at each imaging position only by performing calibration once. In addition, since the imaging can be performed while the two-dimensional detection unit is fixed, it is easy to maintain the geometric positional relationship without bending the surface plate, and higher-accuracy imaging can be realized.

  According to the present invention, by using an X-ray two-dimensional detector placed in a limited space, it is possible to improve the magnification of a projected image obtained by imaging while suppressing the attenuation of the brightness of the projected image. With the goal.

  Examples of the best mode for carrying out the present invention will be described below, but the present invention is not limited to the following examples.

  That is, an X-ray tomographic imaging apparatus that is widely used among tomographic imaging apparatuses will be described as an example. However, the present invention irradiates an object with X-rays and other radiations from multiple directions, and displays a projection image thereof. The present invention can be applied to a tomographic imaging apparatus that reconstructs internal structure data from a plurality of captured projection data.

  1A and 1B are schematic views showing an embodiment of an X-ray tomographic imaging apparatus according to the present invention, in which A is a front view and B is a side view. 1A and 1B, an X-ray tube 1 is an X-ray generator that functions as an X-ray source that generates, for example, cone-beam X-rays. The X-ray tube 1 irradiates the entire inspection object 7 with X-rays, the projected image of the inspection object 7 is picked up by the irradiated X-rays, and the transmitted X-rays of the inspection object 7 are two-dimensionally detected. A projection image is obtained by detection with an X-ray two-dimensional detector 2 functioning as a means.

  The X-rays irradiated from the X-ray tube 1 are configured to form a very small X-ray focal point having a focal size of about 1 μm or less, for example. Since the X-ray focal spot size is a large factor that determines the resolution of the X-ray tomographic imaging apparatus, the smaller the numerical value, the more preferable it is possible to observe a minute size of damage inside the object to be inspected.

  The X-ray two-dimensional detector 2 is composed of, for example, a flat panel detector (FPD), and the vertical line drawn from the X-ray focal point of the X-ray tube 1 is irradiated to the center of the X-ray two-dimensional detector 2. The line two-dimensional detector drive mechanism 14 can adjust the movement in the left and right and up and down directions (XYZ directions). Furthermore, the X-ray two-dimensional detector 2 can be rotated about the axis parallel to the Z-axis by the X-ray two-dimensional detector rotation drive mechanism 15.

  An example of the FPD is disclosed in Japanese Patent Laid-Open No. 6-342098 (hereinafter referred to as “Document 1”). In this FPD, X-rays transmitted through a subject are absorbed by a photoconductive layer to generate charges corresponding to the X-ray intensity, and the amount of charges is detected for each pixel. In the FPD of the method disclosed in Document 1, since the X-ray dose is directly converted into the charge amount for each pixel, the sharpness degradation in the FPD is small and an image with excellent sharpness can be obtained. As an example of other types of FPDs, as disclosed in, for example, JP-A-9-90048, X-rays are absorbed in a phosphor layer such as an intensifying screen to generate fluorescence, and the intensity of the fluorescence Is detected by a photoelectric conversion element.

  As other fluorescence detection means, there is a method using a CCD (Charge Coupled Devices) or a C-MOS (Complementary-Metal Oxide Semiconductor) sensor. As described above, the X-ray two-dimensional detector 2 of this example may be anything that can detect the transmitted X-rays of the object to be inspected and process each pixel to obtain an image signal.

  The rotation base 3 is a rotating means for placing the inspection object 7 and rotating the inspection object 7. Hereinafter, the entire rotation base portion including a motor for rotating the rotation base portion and a bearing described later is referred to as a rotation base. The rotary base 3 is provided with a Z-axis drive mechanism 3a for moving the rotary base 3 in the direction parallel to the rotation axis that rotates itself, that is, in the Z-axis direction as shown in FIG. 1B. Further, a Y-axis drive mechanism 6 for moving the device under test 7 in the Y-axis direction is provided. The inspected object 7 is held and fixed by a holding jig 8 on the rotary base.

  The rotary base 3 is supported by an air bearing 4 and is directly connected to the air bearing 4 coaxially by a servo motor (not shown) having an angular positioning accuracy of, for example, 0.2 minutes or less, and a rotational phase detecting means. In each angular displacement corresponding to the resolution of the servo motor and the rotational phase detection means, the stationary motion is synchronized with the period of taking in the projection data necessary for reconstruction.

  The rotation axis of the bearing 4 that supports the rotation base 3 is orthogonal to a perpendicular line that descends from the focal point of the X-ray tube 1 to the vicinity of the center of the X-ray two-dimensional detector 2. In this example, the bearing 4 is composed of an air bearing capable of controlling the rotational base 3 with a minute angular displacement. However, the bearing 4 is not limited to this. That's fine.

  The XY table 5 moves the X-ray tube 1 of the mounted X-ray source on a plane orthogonal to the rotation axis of the bearing 4. The turning radius of the inspected object 7 is appropriately fed back to the XY table 5, and projection data can be acquired in a state where the inspected object 7 and the XY table 5 are in close proximity as necessary. The highest element that controls the enlargement ratio is the distance between the X-ray focal point and the object 7 to be inspected held on the rotating base 3. If the enlargement ratio is large, the internal structure of a finer part is analyzed. It becomes possible to do.

  The vibration isolation table 10 mounts all the devices, members, and the like that constitute the above-described X-ray tomographic imaging apparatus, and removes vibrations so that no error occurs in the X-ray irradiation position. The shield cover 11 is made of lead or the like, and covers the entire apparatus so that X-rays do not leak outside the X-ray tomographic imaging apparatus.

  FIG. 2 is a diagram illustrating an example of a main part of FIG. 1A. The X-ray 12 radiated from the X-ray tube 1 has a high luminance at the center, and the luminance is attenuated as the distance from the perpendicular drawn from the X-ray focal point to the X-ray two-dimensional detector 2 increases. Therefore, it is desired to capture a projection image of the inspection object 7 using the X-ray 12a near the center of the cone-beam X-ray 12.

  Next, an example of a block configuration of the above-described X-ray tomographic imaging apparatus will be described with reference to FIG.

  First, the X-ray tube 1 irradiates the inspection object 7 placed on the rotating base 3 with X-rays as described above. The intensity and quality of the X-rays irradiated at this time are controlled by the control console 22 through the X-ray control unit 20 which is an X-ray control means.

  The position, rotation angle displacement, initial angle phase, and the like of the rotation base 3 on which the inspection object 7 is placed are passed through a mechanism control unit 21 that is a mechanism control means for controlling the movement of the rotation base 3 and the XY stage 5. It is controlled by the control console 22. The inspected object 7 placed on the rotating base 3 is rotated to an angle phase designated by a control signal from the control console 22, and the projection image is taken by the X-ray two-dimensional detector 2. Further, the mechanism control unit 21 controls the X-ray two-dimensional detector driving mechanism 14 and the X-ray two-dimensional detector rotation driving mechanism 15 based on a command from the control console 22 to drive the X-ray two-dimensional detector 2. Is controlled.

  The control console 22 is connected to input means such as a keyboard and a mouse, and display means (not shown) having a GUI (Graphical User Interface) for displaying device operation states and input values. Further, a processor (control means) that performs processing and control of tomographic imaging processing, which will be described later, in accordance with a program stored in a nonvolatile memory (not shown) such as a ROM (Read Only Memory), and processing of input operation signals from the input means ).

  Further, the control console 22 takes in information such as the X-ray intensity of the X-rays emitted from the X-ray tube 1 and displays the information on the display means, and controls the mechanism for appropriately positioning the object 7 to be inspected. A command is issued to the rotary base 3 through the unit 21.

  X-rays transmitted through the inspection object 7 are detected by the X-ray two-dimensional detector 2. The X-ray two-dimensional detector 2 converts the projection image, which is detected X-ray information, into digital data, and the projection data, which is digital data, includes a large-capacity magnetic recording device or the like and functions as an imaging storage unit. The data is sent to the unit 23.

  The sent projection image (according to an instruction from the control console 22) is stored in the projection image storage unit 23 in correspondence with information such as the angle phase, angular displacement, initial angle phase, and X-ray intensity at the time of imaging. The The projection image storage unit 23 is not limited to this as long as it has a recording capacity capable of recording projection data, and various projection image storage units such as an optical recording medium and a removable recording medium such as a semiconductor memory are applicable. be able to.

  And the projection data memorize | stored in the projection image memory | storage part 23 are sent out to the computer 24 for a reconstruction calculation which functions as a reconstruction means connected with this. The reconstruction calculation computer 24 reconstructs the internal structure data of the object to be inspected from the input projection data, and stores the reconstructed internal structure data (reconstruction data) in the projection image storage unit 23 or an external recording medium. To do. Further, it is output to a reconstruction result display device 25 which is a display means via a display memory (not shown) and displayed on a display such as a CRT (Cathode Ray Tube) monitor.

  The computer 24 for reconstruction calculation only needs to be able to collect projection data and reconstruct the internal structure data and have a calculation / control capability for performing predetermined control. The projection image storage unit 23 is configured in the control console 22. May be. The reconstruction result display device 25 may be shared with the display means of the control console 22.

  With the above configuration, the internal structure data of the device under test 7 is input to the reconstruction result display device 25 and the internal structure is displayed. The operator (operator) can visually check the presence / absence of defects such as cracks and breaks in the object to be inspected, such as multilayer film plates and minute electronic component elements, by the internal structure displayed on the reconstruction result display device 25. Can be confirmed.

  Next, an X-ray tomographic imaging method performed by the X-ray tomographic imaging apparatus having the above configuration will be described.

  4 and 5, the X-ray two-dimensional detector 2 passes through the focal position of the X-ray tube 1 and is rotated at three positions about an axis parallel to the rotation center axis of the inspection object 7. A method of imaging while moving will be described. FIG. 4 is a schematic diagram (bird's-eye view) illustrating a method of imaging by rotating the X-ray two-dimensional detector. FIG. 5 is a schematic diagram (top view) for explaining a method for imaging by rotating the X-ray two-dimensional detector.

  4 and 5, the three imaging positions 31 a, 31 b, and 31 c are positions that are rotated with respect to an axis that passes through the focal position of the X-ray tube 1 and is parallel to the rotation center axis of the inspection object 7. The plane 30 is a plane parallel to the detection surface of the X-ray two-dimensional detector 2 at the initial position 31b, and is between the X-ray focal point of the X-ray tube 1 and the X-ray two-dimensional detector 2. A straight line drawn through the X-ray focal point from the X-ray focal point to the X-ray two-dimensional detector 2 passes through the rotation center of the inspection object 7 arranged. At this time, a point where a straight line drawn from the X-ray focal point intersects the plane 30 perpendicularly is defined as O ′. The cylindrical surface 31 has a central axis that passes through the focal position of the X-ray tube 1 and is parallel to the rotational central axis of the device under test 7.

  First, the X-ray two-dimensional detector 2 is moved to the position 31a, and the inspected object 7 is rotated for each designated angular phase to capture a projected image. Here, the turning angle 41 of the position 31a with respect to the position 31b is selected so that the detection surfaces of the X-ray two-dimensional detector 2 slightly overlap at the positions 31b and 31c.

  Then, the X-ray two-dimensional detector 2 is moved to the position 31b and then to the position 31c, and a projected image is captured in the same manner as the imaging at the position 31a. The turning angle of the position 31c with respect to the position 31b is also the same amount as the turning angle 41. Projecting three projected images taken by the X-ray two-dimensional detector 2 at the positions 31a, 31b, and 31c onto the plane 30 or the cylindrical surface 31 with the same angle phase and the inspected object 7 in consideration of the overlap. Then, a virtually wide projection image is calculated. The projection onto the cylindrical surface is performed by using the X-ray source to obtain pixel information obtained by the elements that are irradiated from the focal position of the X-ray source and transmitted through the object to be inspected 7 and arranged at equal intervals on the flat detector. It is to convert the information into equiangular information with the focal point as the origin.

  Here, a specific method for calculating a virtual wide projection image will be described by taking the case of projecting onto the cylindrical surface 31 as an example. FIG. 6 is a diagram (XYZ coordinate system) for explaining projective transformation to a cylindrical surface according to an embodiment of the present invention. FIG. 7 is a diagram (XY coordinate system) for explaining projective transformation to a cylindrical surface according to an embodiment of the present invention.

6 and 7, the focal position of the X-ray source is set to O, and the same X, Y, and Z axes as those in the apparatus schematic diagram of FIG. 1 are set. Let N be a perpendicular line drawn from the focal position O to the center line of the X-ray two-dimensional detector 2. If the X-ray two-dimensional detector 2 is at a position | N | away from the focal position O and turned by an angle φ,
N = (Nx, Ny, 0)
= (-Ncosφ, Nsinφ, 0)
It becomes.

となる。
これら３つのベクトルＮ，Ｕ，Ｖにより、Ｘ線二次元検出器２上の任意の点Ｑは、
Ｎ＋αＵ＋βＶ
として表せる。 Here, unit vectors U and V perpendicular to the vector N are prepared in the X-ray two-dimensional detector 2 plane. Since V is parallel to the Z axis and opposite to the Z axis,
V = (0, 0, -1)
It is.
When the vector U is calculated from the vectors N and V,

It becomes.
With these three vectors N, U, and V, an arbitrary point Q on the X-ray two-dimensional detector 2 is
N + αU + βV
It can be expressed as

On the other hand, an arbitrary point on the virtual detection surface formed on the cylindrical surface 31 is represented by a vector P.
P = (− Rcos (mΔθ), Rsin (mΔθ), nΔZ)
Here, the pixel pitch of the virtual detection surface on the cylindrical surface 31 is represented as Δθ and ΔZ, each pixel position is (m, n), and the distance from the X-ray focal point O to the end point of the vector P on the cylindrical surface 31 is R. And

The problem of where the extension line of the vector P intersects the detection surface of the X-ray two-dimensional detector 2 is
N + αU + βV = kP
This results in the problem of finding α, β, and k.

N + αU + βV = kP

When the pixel pitch of the X-ray two-dimensional detector 2 is Δh and Δw, each pixel position of the X-ray two-dimensional detector 2 is represented by (α ′, β ′).
α ′ = αΔh
β ′ = βΔw
The relationship between the pixel of the X-ray two-dimensional detector 2 and the pixel on the virtual cylindrical surface 31 is obtained from the relationship of (m, n) and (α ′, β ′), and the two-dimensional X-ray The projection image of the detector 2 can be projected onto the cylindrical surface.

  Further, the projection conversion of the projection image of the X-ray two-dimensional detector 2 onto the plane 30 can be realized in the same manner as the projection conversion onto the cylindrical surface 31.

  Then, a plurality of projection images at each imaging position (also referred to as a turning position or position) of the X-ray two-dimensional detector 2 are projectively transformed to the plane 30 or the cylindrical surface 31, respectively, and then combined into one wide projection image. . Alternatively, a wide projection image may be generated by projectively converting a plurality of projection images at each imaging position directly onto one wide cylindrical surface 31.

  Finally, reconstruction calculation can be performed on a plurality of wide projection images obtained after projective transformation to obtain internal structure data of the object to be inspected.

  Note that the position of the cylindrical surface 31 to be projected is preferably close to the position of the original X-ray two-dimensional detector 2 for the convenience of resampling at the time of projective transformation. The surface that is inscribed in the detection surface of the X-ray two-dimensional detector 2 that has been swung to the right is selected, but this is not necessarily the case.

According to the above-described embodiment, it is possible to realize further improvement in the geometric enlargement ratio as compared with the method of synthesizing a wide projection image by translating a conventional X-ray two-dimensional detector.
In addition, when trying to obtain a wide projection image by the conventional method, the further away from the straight line connecting the X-ray source and the center of the object to be inspected, the more the X-ray source and the X-ray two-dimensional detector are located. Although the distance is increased and the brightness of the projected image is attenuated, such a problem does not occur because the distance between the X-ray source 1 and the X-ray two-dimensional detector 2 is constant in the above-described configuration.
Further, when the projection image of the X-ray two-dimensional detector 2 is projected onto the cylindrical surface 31, the distance difference between the actual detection surface of the X-ray two-dimensional detector 2 and the virtual cylindrical surface 31 is the virtual plane. It can be expected that an image with less conversion error than that projected onto the image 30 can be obtained.

  In the imaging method according to the above-described embodiment, the X-ray two-dimensional detector 2 is turned to the positions 31a, 31b, and 31c, but the X-ray two-dimensional detector 2 is not turned to the initial position 31b. By setting the position of the inspection object 7 and the initial angle phase so as to maintain the same geometric position as when the X-ray two-dimensional detector 2 is rotated while being placed, imaging of the inspection object is performed. The method of performing will be described.

  FIG. 8 is a diagram (top view) for explaining a method for capturing a projection image by moving the object to be inspected without rotating the X-ray two-dimensional detector according to another embodiment of the present invention. It is. FIG. 9 is an enlarged view of a main part of FIG.

  In FIG. 8, the focal position of the X-ray source 1 is the origin O, and the X axis and Y axis are set. If the distance from the X-ray focal point of the X-ray source 1 to the center point at the initial position 7b of the inspection object 7 is S, the position of the inspection object 7 is expressed as (−S, 0).

  A state A is defined when the X-ray two-dimensional detector 2 is turned by θ at the turning angle 41 to the position 31a while the inspection object 7 is placed at the position 7b. Reference numeral 40 denotes a half angle of the projection region of the X-ray two-dimensional detector. The positional relationship between the X-ray focal point of the X-ray source 1 in the state A, the inspected object 7 and the X-ray two-dimensional detector 2 does not move the X-ray source 1 and does not rotate the X-ray two-dimensional detector 2. While placed at the initial position 31b, the center of the inspection object 7 is moved to the position 7a, that is, the position of (−Scos θ, −Ssin θ), and the angular phase of the inspection object 7 is offset by −θ (state) B). Accordingly, the projection image captured in the state A and the projection image captured in the state B can obtain substantially the same projection image.

  As shown in FIG. 9, the offset of the angle phase shift is such that a straight line passing through the X-ray focal point and the center of the inspection object 7 defines the reference point 7 b 1 on the inspection object 7 after moving the inspection object 7 to the position 7 a. This can be done by rotating the inspection object 7 so as to pass.

  Similarly, the inspection subject 7 is placed at the position 7c by moving the inspection subject 7 to the position 7c, that is, the position of (−Scos θ, Ssin θ), and further offsetting the angular phase of the inspection subject 7 by θ. As it is, a projection image substantially the same as the projection image picked up by rotating the X-ray two-dimensional detector 2 to the position 31c by θ is obtained.

  Therefore, first, while the X-ray two-dimensional detector 2 is placed at the position 31b, the object to be inspected 7 is moved to the position 7a, offset by −θ, and rotated by the specified angular displacement. An angle phase projection image is captured. Next, the object to be inspected 7 is moved to the position 7b and rotated by the designated angular displacement, and a projected image of each angular phase is captured.

  Then, the object to be inspected 7 is moved to the position 7c, offset by θ, and rotated by the designated angular displacement, and a projected image of each angular phase is captured. Projecting three projected images taken with the inspected object 7 at the same angular phase and the inspected object 7 at the positions 7a, 7b and 7c onto the plane 30 or the cylindrical surface 31 in consideration of the overlap. Then, a virtually wide projection image is calculated. The internal structure data of the inspected object 7 is obtained from a plurality of wide projection images of each angular phase obtained through reconstruction calculation.

  According to the other embodiment described above, the same effects as the above-described embodiment can be obtained, and the following effects can be newly obtained.

First, the method of moving the position of the inspection object 7 without rotating the X-ray two-dimensional detector 2 does not require a means for moving the X-ray two-dimensional detector 2, so X-ray tomographic imaging. The structure of the apparatus can be simplified, and the apparatus size can be reduced.
In addition, some X-ray two-dimensional detectors require calibration based on a white image or a black image in which nothing is shown, and this calibration is performed at the focus of the X-ray source. This must be done every time the positional relationship between the position and the X-ray two-dimensional detector changes. However, in the other embodiments described above, since it is possible to capture an image without changing the position of the X-ray two-dimensional detector 2, it is possible to perform imaging at each position (imaging position) with only one calibration.
In addition, since the imaging can be performed while the X-ray two-dimensional detector 2 is fixed, it is easy to maintain the geometric positional relationship without bending the surface plate, and more accurate imaging can be realized. The configuration of the line tomography apparatus is also simplified.

  In the above embodiment, the rotation angle of the rotation base 3 is not necessarily 360 °, and may be 270 °, for example.

  The means for capturing the projected image of the object to be inspected is not limited to the X-ray two-dimensional detector, but may be a one-dimensional detector such as a line sensor.

  Further, the X-ray tomographic imaging method of the present invention may be applied when imaging a projection image of an inspection object with the rotation axis of the inspection object inclined.

  In the present invention, the position (imaging position) of the X-ray two-dimensional detector and the object to be inspected is described as 3 positions, but it can be increased to 4 positions and 5 positions.

  The present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the X-ray tomographic imaging apparatus which concerns on the example of 1 embodiment of this invention, A represents a front view, B represents a side view. It is a figure which shows an example of the principal part of the X-ray tomographic imaging apparatus shown in FIG. 1 is a block configuration diagram of an X-ray tomographic imaging apparatus according to an embodiment of the present invention. It is the schematic (bird's-eye view) explaining the method of rotating the X-ray two-dimensional detector based on one embodiment of this invention, and imaging. It is the schematic (top view) explaining the method of revolving and moving the X-ray two-dimensional detector according to the embodiment of the present invention. It is a figure (XYZ coordinate system) explaining the projective transformation to a cylindrical surface according to an embodiment of the present invention. It is a figure (XY coordinate system) explaining the projective transformation to a cylindrical surface based on one embodiment of the present invention. It is a figure (top view) explaining the method to move and image an to-be-inspected object, without rotating the X-ray two-dimensional detector based on the other embodiment of this invention. It is a figure which shows an example of the principal part of the X-ray tomographic imaging apparatus shown in FIG. It is the schematic (bird's-eye view) explaining the method to translate and image the conventional X-ray two-dimensional detector. It is the schematic (top view) explaining the method to translate and image the conventional X-ray two-dimensional detector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... X-ray tube, 2 ... X-ray two-dimensional detector, 3 ... Rotation base, 7 ... Test object, 7a, 7b, 7c ... Moving position of test object, 11 ... Shield cover, 15 ... Rotation center axis , 22 ... control console, 23 ... projection image storage unit, 24 ... computer for reconstruction calculation, 25 ... reconstruction result display device, 30 ... virtual plane, 31 ... virtual cylindrical surface, 31a, 31b, 31c ... two X-rays Dimensional detector moving position, 41 ... Swivel angle of X-ray two-dimensional detector

Claims (2)

An X-ray source capable of obtaining a cone-beam-like irradiation field , a two-dimensional detection means having a flat detection surface for imaging transmitted X-rays of an object to be inspected, an X-ray focal point of the X-ray source, and the two-dimensional detection means rotating means for rotating at arranged a rotating shaft angular displacement which is set around a perpendicular from the X-ray focal point by placing the inspection object on the perpendicular line to the test exit face of the two-dimensional detection means between the And an X-ray tomographic imaging apparatus having control means for performing reconstruction calculation from the projection image captured for each angular phase and performing control to reconstruct the internal structure data of the object to be inspected ,
The control means is placed on the rotating means while fixing the mutual position of the X-ray source and the two-dimensional detection means so that a part of the object to be inspected is imaged by the two-dimensional detection means. A vertical line that is lowered from the X-ray focal point to the detection surface of the two-dimensional detection unit with respect to a rotational axis that passes through the X-ray focal point in parallel with the rotational axis of the inspection object, The angle formed by the straight line connecting the rotation axis of the object to be inspected from the X-ray focal point is at three imaging positions of θ degrees, 0 degrees, and −θ degrees, and each time a predetermined number of projected images are captured at each imaging position, Swivel with the same radius,
At each imaging position, the initial angle phase of the object to be inspected is set to −θ degrees, 0 degrees, and θ degrees, respectively, and the predetermined number of projection images are captured for each angle phase;
Projected images obtained at the respective imaging positions are perpendicular to the rotation axis passing through the X-ray focal point in parallel with the rotation axis of the object to be inspected, and the radius is lowered from the X-ray focal point to the two-dimensional detection means. Projective transformation to a virtual cylindrical surface with the length of
The projection images of the same angle phase are synthesized in the order of imaging at the respective imaging positions subjected to the projective transformation, and the reconstruction calculation is performed from the projection images synthesized for each angle phase to reconstruct the internal structure data of the object to be inspected. X-ray tomographic imaging apparatus. An X-ray source capable of obtaining a cone-beam-like irradiation field , a two-dimensional detection means having a flat detection surface for imaging transmitted X-rays of an object to be inspected, an X-ray focal point of the X-ray source, and the two-dimensional detection means rotating means for rotating at arranged a rotating shaft angular displacement which is set around a perpendicular from the X-ray focal point by placing the inspection object on the perpendicular line to the test exit face of the two-dimensional detection means between the X-ray tomographic imaging of an X-ray tomographic imaging apparatus comprising: and control means for performing reconstruction calculation from a projection image captured for each angle phase and reconstructing internal structure data of the object to be inspected In the method
The X-ray source and the two-dimensional detection unit are placed on the rotation unit while the mutual positions of the X-ray source and the two-dimensional detection unit are fixed so that a part of the inspection object is imaged by the two-dimensional detection unit by the control unit . A vertical line that is lowered from the X-ray focal point to the detection surface of the two-dimensional detection unit with respect to a rotational axis that passes through the X-ray focal point in parallel with the rotational axis of the inspection object, The angle formed by the straight line connecting the rotation axis of the object to be inspected from the X-ray focal point is at three imaging positions of θ degrees, 0 degrees, and −θ degrees, and each time a predetermined number of projected images are captured at each imaging position, Swivel with the same radius,
At each imaging position, the initial angle phase of the object to be inspected is set to −θ degrees, 0 degrees, and θ degrees, respectively, and the predetermined number of projection images are captured for each angle phase;
Projected images obtained at the respective imaging positions are perpendicular to the rotation axis passing through the X-ray focal point in parallel with the rotation axis of the object to be inspected, and the radius is lowered from the X-ray focal point to the two-dimensional detection means. Projective transformation to a virtual cylindrical surface with the length of
The projection images of the same angle phase are synthesized in the order of imaging at the respective imaging positions subjected to the projective transformation, and the reconstruction calculation is performed from the projection images synthesized for each angle phase to reconstruct the internal structure data of the object to be inspected. X-ray tomographic imaging method.

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