JP2006214879A - X-ray tomographic imaging method and x-ray tomographic imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the total imaging time and a reconstructing and calculating time, by reducing the number of imaging sheets, while suppressing the reduction of the detailed degree of internal structure data corresponding to the feature of a subject, when the subject, markedly changed in a projection image with respect to angular displacement especially by an angle phase, is imaged. <P>SOLUTION: When the subject 30, markedly changed in the projection is imaged with respect to the angular displacement by the angle phase, the angular displacement of rotary means is set small only in the angle phase, wherein the change of the projection image with respect to the angular displacement is large and the angular displacement of the rotary means is largely set in the angle phase, wherein the change of the projection image with respect to the angular displacement is small for photographing the subject. With this constitution, the subject can be photographed, by reducing the angular displacement only with respect to the really required angle, range and an increase in the number of imaging sheets can be suppressed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an X-ray tomographic imaging method and apparatus suitable for inspecting the internal structure of an object to be inspected, such as a multilayer film plate, in which a projected image changes significantly with respect to angular displacement due to angular phase.

  Conventionally, in the field of research and development of semiconductor elements and the like, non-destructive three-dimensional analysis has been required in order to inspect cracks, disconnections, and the like that exist inside a minute object to be inspected. One of the non-destructive three-dimensional analysis methods is a tomographic imaging method using X-rays. This X-ray tomographic imaging method detects an X-ray source (an X-ray generator configured by an X-ray tube or the like) and X-rays irradiated from the X-ray source through an X-ray focal point and transmitted through an object to be inspected. The detector is used to image the transmitted X-rays of the test object placed between the X-ray source and the detector with the detector. Then, by processing and reconstructing the captured projection image as image data, internal structure data can be created, and the inside of the object to be inspected can be inspected and observed.

  In the method described above, X-rays are irradiated from various angles within the plane of the object to be inspected, and the intensity distribution of transmitted X-rays is detected and measured by a detector. Then, a predetermined calculation is performed based on the measured intensity distribution, and a tomographic image (projected image) of the inspection object in the X-ray irradiation plane is acquired. Furthermore, by obtaining a projection image while switching the X-ray irradiation plane, the internal structure of the object to be inspected can be observed three-dimensionally.

  In the X-ray tomographic imaging apparatus, the internal structure data is calculated from the captured projection image through the reconstruction calculation of the internal structure. The number of images to be imaged is the details of the internal structure data calculated by the reconstruction calculation. Greatly affects the degree. Although there is an upper limit for the number of captured images that does not change the level of detail, the level of detail of the internal structure data tends to increase as the number of images increases. However, at the same time, the increase in the number of captured images causes a problem of increasing the calculation time as well as the time required for capturing the projected image and the amount of reconstruction calculation of internal configuration data. Therefore, a device for reducing the number of captured images is required.

As a solution to this problem, for example, after confirming the outline of the internal structure data of the reconstructed object to be inspected, in order to reduce the total imaging time required when more detailed internal structure data is desired, For the internal structure data of the inspected object that has been reconstructed, perform imaging at a new angular position excluding the angular position of the previously captured projection image, and make use of the previously captured projection image Have been proposed (see, for example, Patent Document 1).
JP 2003-329615 A

  By the way, the internal structure data obtained by the reconstruction calculation tends to be dense at the center of rotation during imaging and sparse as the distance from the center increases. The degree of detail of the part away from the center of the internal structure data can be improved by reducing the angular displacement as long as it is greater than or equal to the minimum value of the detector pixels.

  However, in the conventional imaging method, the projected image of the object to be inspected is rotated by equiangular displacement, and the reduction of the angular displacement leads to an increase in the number of images and the associated imaging time. For example, when the object to be inspected has a cylindrical shape and the internal structure is uniform or has a rotationally symmetric shape, the change in the projected image with respect to the angular displacement is almost constant without depending on the angular phase. Therefore, in order to increase the level of detail of the entire internal structure data, it is only necessary to reduce the angular displacement by equiangular displacement and simply increase the number of images. The number of images to be captured, the imaging time, and the reconstruction calculation time increase.

  On the other hand, when imaging an object to be inspected that has a remarkable change in projected image due to angular displacement due to angular phase, such as a multilayer film plate, the angular displacement is reduced by equal angular displacement, and the number of images is increased. It is possible to increase the level of detail of the entire structure data. By the way, in the angle phase where the change of the projected image due to the angular displacement is small, even if the angular displacement at the time of imaging is large, the influence on the detail level reduction of the reconstruction calculation result is small. Nevertheless, in order to capture a detailed projection image for an angular phase in which the change in the projected image with respect to the angular displacement is large, by reducing the angular displacement even in an angular phase that originally does not require a small angular displacement, However, there was a problem that the imaging time was increased accordingly. That is, in the conventional imaging method, the degree of detail of the internal structure data, the number of images to be captured, the imaging time, and the reconstruction calculation time have a trade-off relationship.

  The present invention has been made in view of such points, and in the case of imaging an object to be inspected, in particular, when a projected image changes significantly with respect to angular displacement due to an angular phase, An object is to reduce the number of images while reducing the level of detail of the structure data, and to shorten the total imaging time and reconstruction calculation time associated therewith.

  In order to solve the above-described problems and achieve the object, the present invention provides an X-ray source, a two-dimensional detection means for imaging transmitted X-rays of an object to be inspected, A rotating means that is placed between the rotating means and rotates at an angular displacement set around a rotation axis perpendicular to a perpendicular line dropped from the X-ray focal point to the light receiving surface of the two-dimensional detection means, The internal structure data of the object to be inspected is reconstructed from the projection images taken for each angle phase, and the object to be inspected is in an angle phase in which the change of the projection image with respect to the angular displacement of the object is small. The rotating means for placing the object is rotated at the first angular displacement, a projected image is taken for each first angular displacement, and the angular phase in which the projected image changes greatly with respect to the angular displacement of the object to be inspected is obtained. The rotating means for placing the inspection object is smaller than the first angular displacement. The projection is rotated at the second angular displacement, and a projected image for each second angular displacement is captured. After the imaging is completed, the projection image captured at the first and second angular displacements is used to detect the inside of the inspection object. Reconstruct structural data.

  According to the present invention, when an object to be inspected that has a remarkable change in the projected image with respect to the angular displacement is picked up by the angular phase, the angular displacement of the rotating means is set to be small only in the angular phase in which the change in the projected image with respect to the angular displacement is large. In an angle phase where the change of the projected image with respect to the angular displacement is small, the angular displacement of the rotating means is set to be large and imaging is performed, so that the angular displacement is reduced only in the actually required angular range and the number of images is increased. be able to.

  The present invention also provides an X-ray source, a two-dimensional detection means for imaging transmitted X-rays of the object to be inspected, and an X-ray source disposed between the X-ray focal point of the X-ray source and the two-dimensional detection means. The rotation means rotating at an angular velocity set around the rotation axis perpendicular to the perpendicular line dropped from the X-ray focal point to the light receiving surface of the two-dimensional detection means The internal structure data of the inspection object is reconstructed, and the rotation means for mounting the inspection object is rotated at the first angular velocity at an angular phase where the change of the projected image with respect to the angular displacement of the inspection object is small. The rotation means for placing the object to be inspected at the second angular velocity smaller than the first angular velocity in an angle phase in which the projection image is picked up at regular intervals and the change in the projected image with respect to the angular displacement of the object is large. Rotate the After, than the projected image that has been captured by the first and second angular velocity, to reconstruct the internal structure data of the object to be inspected.

  According to the present invention, in addition to the above-described invention, the imaging process of the projected image is performed without stopping the rotating object to be inspected, so that the imaging time can be further greatly shortened.

  According to the present invention, when an object to be inspected that has a remarkable change in the projected image with respect to the angular displacement due to the angular phase, the angular displacement of the rotating means is set to be small only in the angular phase in which the change in the projected image with respect to the angular displacement is large, In the angle phase where the change of the projected image with respect to the angular displacement is small, the angular displacement of the rotating means is set larger than the above angular displacement and imaging is performed, so that the angular displacement is reduced only in the actually required angular range, and the number of images to be captured is reduced. The increase can be suppressed. Therefore, by setting an appropriate angular displacement according to the angle phase based on the characteristics of the inspected object shape, the number of images can be reduced while suppressing the reduction in the level of detail of the internal structure data, and the total imaging time associated therewith There is an effect that the reconstruction calculation time can be shortened.

  Further, when the projection image is picked up without stopping the rotating object to be inspected, there is an effect that the total image pickup time can be further shortened.

  Hereinafter, examples of embodiments of the present invention will be described with reference to the accompanying drawings.

  The X-ray tomographic imaging method according to the present invention is performed using an X-ray tomographic imaging apparatus using X-rays that is widely used among computer tomographic imaging apparatuses at present. The apparatus applied to the X-ray tomographic imaging apparatus is an apparatus that irradiates an object from multiple directions and reconstructs and calculates internal structure data from a plurality of projection data obtained by imaging the projection image. The present invention is applied to a tomographic imaging apparatus adopting an imaging method for imaging projection data by changing the angular displacement to be rotated according to the shape of the test object. Of course, the present invention can also be applied to a tomographic imaging apparatus using radiation other than X-rays.

First, an X-ray tomographic imaging apparatus used in this example will be described with reference to FIGS. 1 and 2. FIGS. 1A and 1B non-destructively inspect the internal structure of a micro-inspection object such as a semiconductor element or a multilayer thin film. It is the schematic of an example of an X-ray tomographic imaging apparatus. In FIG. 1, 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. Captured by the X-ray two-dimensional detector 2 functioning as means, a projection image is obtained.

  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 resolution of the X-ray tomographic imaging apparatus is determined by the focal size of the X-ray, it is preferable that the numerical value is smaller because a minute size damage or the like inside the inspection object can be observed.

  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).

  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 other examples of FPDs, as disclosed in, for example, JP-A-9-90048, X-rays are absorbed by a phosphor layer such as an intensifying screen to generate fluorescence, and the intensity of the fluorescence is photoelectrically detected. Some are detected by a conversion element. There are other methods for detecting fluorescence, such as a method using a CCD or C-MOS sensor. As described above, the X-ray two-dimensional detector 2 of this example may be any device that can detect an X-ray and process it for 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 of the rotation base 3, 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 above-mentioned rotary base 3 is supported by an air bearing 4, and is directly connected to the air bearing 4 coaxially and has an angular positioning accuracy of, for example, 0.2 minutes or less, and a servo motor and a rotational phase detection means (not shown). Thus, each angular displacement corresponding to the resolution of the servo motor and the rotation phase detecting means is stopped in synchronism with the projection data capturing period 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 anti-vibration table 10 mounts all the devices, members, and the like that constitute the X-ray tomographic imaging apparatus described above, and removes vibrations so that no error occurs in the irradiation position. And the shield cover 11 is comprised from the lead etc. which covers the whole so that an X-ray may not leak outside from an X-ray tomographic imaging apparatus. In addition, this X-ray tomographic imaging apparatus is an example, Comprising: It does not restrict to this example.

An example of the configuration of the X-ray tomographic imaging apparatus described above will be described with reference to FIG.
First, X-rays are irradiated from the X-ray tube 1 to the inspection object 7 placed on the rotating base 3. 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 7 on which the inspection object 7 is placed are passed through the mechanism control unit 21 which 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 inspection object 7 placed on the rotating base 3 is rotated to the angle phase designated by the control console 22, and the projection image is taken by the X-ray two-dimensional detector 2.

  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, input values, and the like, and processes input operation signals. And a control means including a processor or the like for performing predetermined calculation / control to be described later according to a program stored in a non-volatile memory (not shown) such as a ROM. Further, the control console 22 captures and displays information such as the X-ray intensity of the X-rays emitted from the X-ray tube 1 on the display means, and a mechanism control unit for appropriately positioning the object 7 to be inspected. A command is issued to the rotary base 3 through 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 types of projection image storage unit 23 including an optical recording medium and a removable recording medium such as a semiconductor memory can be applied. Can do.

  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 in the projection image storage unit 23 or an external recording medium. Further, it is output to a reconstruction result display device 25 as a display means via a display memory (not shown) and displayed on a display such as a CRT monitor. The computer 24 for reconstruction calculation only needs to be capable of collecting projection data and reconstructing internal structure data and having a calculation / control capability for performing predetermined control, and may be shared with the control console 22. 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) visually confirms the presence or absence of defects such as cracks and breaks inside 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 do.

Next, an outline of the X-ray tomographic imaging method according to the present invention will be described.
In FIG. 1, a case where 360 degrees of projection images are taken with the angular displacement of the rotating base 3 on which the inspected object 7 is placed being 1 ° is projected, and 1440 projections are made with the same angular displacement being 0.25 °. When an image is captured, the internal structure data obtained by performing reconstruction calculation has a much higher level of detail than 1440 projected images. However, when 1440 projected images are captured, the imaging time is quadrupled and the amount of data is also quadrupled and the reconstruction time is longer than that when 360 projected images are captured. .

  In the present invention, when imaging is performed using the X-ray tomographic imaging apparatus as described above, in the case of imaging an object to be examined in which the change in the projected image with respect to the angular displacement is significant due to the angular phase, Reduces the level of detail of internal structure data by acquiring a projection image with a small angular displacement only at an angular phase with a large change, and acquiring a projection image with a large angular displacement at an angular phase with a small change in the projection image relative to the angular displacement. While reducing the total number of captured images.

Here, an example of an object to be inspected in which the change in the projected image with respect to the angular displacement is noticeable due to the angular phase will be described with reference to FIG.
As an object to be inspected, in which the change in the projected image with respect to the angular displacement is remarkable due to the angular phase, a multilayer film plate 30 as shown in FIG. When the multilayer film plate 30 is swiveled around the rotation center axis direction 31 and a projection image is picked up, the projection image when X-rays are irradiated from the long axis direction 32 of the multilayer film plate 30 corresponds to a minute angular displacement. However, the projected image when irradiated with X-rays from the short axis direction 33 of the multilayer film plate 30 does not change so much.

  FIG. 4 shows the state of the multilayer film plate 30 when a projected image is captured. The direction in which the major axis direction 32 of the multilayer film plate 30 is perpendicular to the perpendicular line dropped from the X-ray focal point of the X-ray tube 1 to the light-receiving surface of the X-ray two-dimensional detector 2 is the initial angle phase of 0 °. The angle phase with the clockwise direction as the positive direction is represented by θ.

  5A and 5B are examples of projected images when the multilayer film plate 30 is imaged from the short axis direction 33 and the long axis direction 32, where A is a projected image with angular phases θ = 0 ° and θ = 2 °, and B is The projection images of θ = 90 ° and θ = 92 ° are shown. 5A and 5B, the projected image changes little when the multilayer plate 30 is in the short axis direction 33, that is, when the angle phase θ is around 0 °, and when the long axis direction 32, that is, when the angle phase θ is around 90 °, the projected image changes. It can be seen that the change is large.

FIG. 6 shows a position where a perpendicular line dropped from the X-ray focal point of the X-ray tube 1 to the light receiving surface of the two-dimensional detection means 2 passes through the inspection object for each angle phase when viewed in coordinates on the inspection object. A represents an equiangular displacement, and B represents a variable angular displacement.
FIG. 6A shows the conventional rotating base 3 rotated with a constant angular displacement. In the present invention, as shown in FIG. 6B, the angle phase θ changes the projected image with respect to the angular displacement. Rotate with smaller angular displacements at 90 ° and 270 ° angular phase where is prominent

FIG. 7 explains the setting of the angular displacement when rotating the inspection object in this example.
In this example, when photographing at an angular phase from the major axis direction where the change of the projected image with respect to the angular displacement is significant, for example, imaging is performed with an angular displacement of 0.25 ° within a range of ± 16 °, and at other angular phases. In the imaging, the angular displacement is set to 1 °. That is, as shown in FIG. 7, the angular phase from 0 ° to 74 ° is from the first angular displacement of 1 °, the angular phase from 74 ° to 106 ° is from the second angular displacement of 0.25 °, and the angular phase from 106 °. The first angular displacement is set to 1 ° up to 254 °, the second angular displacement is set to 0.25 ° from 254 ° to 286 °, and the first angular displacement is set to 1 ° from 286 ° to 360 °. . This setting content is stored in the nonvolatile memory in association with the type of the object to be inspected.

The imaging process of this example based on the above settings will be described with reference to the flowchart of FIG.
First, the control console 22 starts an imaging process by detecting an imaging instruction input from the operator. When the control console 22 detects an imaging instruction, the control console 22 stores the first or second angular displacement associated with the multilayer film plate 30 of the object to be inspected and the imaging range corresponding to these stored in the nonvolatile memory. Are acquired as imaging conditions for imaging (step S1).

  Note that the imaging conditions such as the angular displacement may be input and set by the operator directly at the start of imaging according to the characteristics of the object to be inspected. Alternatively, imaging conditions associated with the type of the object to be inspected are stored in advance in the nonvolatile memory. Then, when the operator inputs information such as the type of the object to be inspected, the control console 22 sets the setting corresponding to the object to be inspected from the nonvolatile memory based on the input information, for example, the angular displacement during rotation and its You may make it call the angle phase etc. to which an angular displacement is applied, and may image according to the kind of to-be-inspected object.

  After obtaining the imaging conditions, a projected image of the multilayer film plate 30 is taken at an initial angle of 0 ° (step S2). Next, the phase of the rotation base 3 is detected by the rotation phase detection means, and the current angle phase of the multilayer film plate 30 is acquired (step S3). Then, based on the contents of the imaging conditions stored in the nonvolatile memory, an angular displacement to be rotated next is selected from the current angular phase (step S4). Here, since the angular phase is 0 °, the first angular displacement of 1 ° is selected.

  Then, the selected angular displacement is added to the current angular phase, and it is determined whether or not the value after the addition exceeds the preset angular phase to be imaged, and the end of the imaging process is determined (step S5). . For example, when the multilayer film plate 30 is set to take an image of 360 °, and the angle phase after the addition is less than 360 °, the rotation base 3 on which the multilayer film plate 30 is placed is selected at the selected angle. Displacement, in this example, the first angular displacement is rotated by 1 ° (step S6), and a projected image of the multilayer film plate 30 at an angular phase of 1 ° is captured (step S7).

  After completing the imaging in step S7, the process returns to step S3 to acquire the current angle phase. Then, the above-described steps S3 to S7 are repeated until it is determined that the photographing process has been completed.

  Here, when the angular phase of the rotary base 3 is rotated to 73 °, the rotary base 3 is rotated by a first angular displacement of 1 °, and a projection image at an angular phase of 74 ° is captured. Next, since it is set to rotate at the second angular displacement, that is, 0.25 ° from the angle phase 74 ° to 106 °, the rotation base 3 is rotated by 0.25 ° and the angle phase 74.25. Take a projected image of °. Thereafter, the processes in steps S3 to S7 are repeated in the same manner, and a projected image is taken every angular displacement 0.25 ° up to an angular phase of 106 °. When the angle phase is rotated to 106 °, the second angular displacement is changed from 0.25 ° to the first angular displacement of 1 °. In this manner, the above-described imaging process is determined while switching to a predetermined angular displacement set in advance at the angular phase of 74 °, 106 °, 254 °, and 286 °, which is the switching point of the angular displacement. The processes in steps S3 to S7 are repeated.

  In the above-described determination step S5, when the angle phase reaches 360 ° or more, which is determined to be the end of the imaging process, the multilayer film plate 30 is returned to the initial angle phase, and the imaging process ends. After the imaging process of all the projected images is completed, the internal structure data is reconstructed while taking into account the set angular displacement.

  In this example, according to the imaging conditions described above, 74 projected images are captured with an angular displacement of 1 ° from the angular phase 0 ° to 74 °, and the angular displacement is 0.25 from the angular phase 74 ° to 106 °. (106−74) /0.25=128 projection images are taken at an angle. Further, 148 projection images are taken with an angular displacement of 1 ° from an angular phase of 106 ° to 254 °, and an angular displacement of 0.25 ° from an angular phase of 254 ° to 286 ° (286-254). /0.25=128 projected images are captured. From the angle phase 286 ° to 360 °, the angular displacement is set to 1 °, and 74 projected images are captured, and a total of 74 + 128 + 148 + 128 + 74 = 552 projected images are captured. These projection images are reconstructed and calculated, and the internal structure data of the multilayer film plate 30 is obtained.

Here, referring to FIG. 9 and FIG. 10, the internal structure data of the multilayer film plate 30 obtained by imaging with different imaging conditions, that is, the conventional equiangular displacement and the variable angular displacement of this example are compared.
FIG. 9 shows internal structure data of the multilayer film plate 30 as viewed from the long axis direction. 10A, B, C, and D are obtained by extracting the leading end portion 34 of the internal structure data for each imaging condition of the multilayer film plate 30 as viewed from the long axis direction. Specifically, FIGS. 10A, 10B, and 10D show internal structure data obtained by performing reconstruction calculation from projection images obtained by imaging 360, 552, and 1440 multi-layer film plates 30 per revolution with conventional equiangular displacement. FIG. 10C shows internal structure data obtained by performing reconstruction calculation from a projection image obtained by imaging 552 rounds with variable angular displacement based on the imaging conditions.

  The internal structure data (FIG. 10C) obtained from 552 projection images with variable angular displacement is more detailed than the internal structure data (FIG. 10D) obtained from 1440 projection images with equal angular displacement. The time taken for the imaging time is approximately the same as that in the case of 1440 projected images taken at equiangular displacement. Furthermore, when compared with the internal structure data (FIG. 10B) obtained from 552 projection images with equal angular displacement, the internal structure data (FIG. 10B) obtained from 552 projection images with variable angular displacement while maintaining the same number of images. 10C) shows that the level of detail is significantly improved.

  In the embodiment described above, when imaging an object to be inspected with a significant change in the projected image with respect to the angular displacement due to the angle phase, the rotational angular displacement of the object to be inspected is only with an angular phase in which the change in the projected image with respect to the angular displacement is large. When the angle phase is small and the change in the projected image with respect to the angular displacement is small, the angular displacement is increased and imaging is performed. In this way, by utilizing the characteristics of the shape of the object to be inspected and setting an appropriate angular displacement according to the angular phase, the number of images can be reduced while suppressing the reduction in the level of detail of the internal structure data, and the total imaging time Thus, the reconstruction calculation time can be shortened.

  Next, imaging processing according to another embodiment of the present invention will be described with reference to the flowchart of FIG. In this example, as the first rotation, a projected image of the object to be inspected is captured at a predetermined angular displacement, and the degree of detail of the internal structure data obtained by performing reconstruction calculation from the projected image is observed and evaluated. Then, when the level of detail of the internal structure data does not reach a desired level, the second rotation is obtained from the first and second rotations by imaging only the necessary angular range with a smaller angular displacement. In addition, the reconstructed calculation is performed by combining the respective projection images, and the internal structure data having a higher level of detail is obtained.

  In FIG. 11, first, the control console 22 starts an imaging process by detecting an imaging instruction input from the operator. When the control console 22 detects the imaging instruction, the control console 22 acquires the setting relating to the imaging condition during the first rotation stored in the nonvolatile memory (step S11). The imaging condition may be set by an operator directly inputting at the start of imaging according to the characteristics of the object to be inspected.

  After acquiring the imaging conditions, a projected image of the multilayer film plate 30 is captured at an initial angle of 0 ° (step S12). Subsequently, a projected image of 360 ° is captured with the first angular displacement based on the imaging condition (step S13). Then, the internal structure data obtained by reconstructing the 360 ° projection image by the reconstruction calculation computer 24 is displayed on the reconstruction result display device 25. The operator observes the internal structure data displayed on the reconstruction result display device 25 and evaluates the level of detail.

  Here, as a result of evaluating the level of detail of the internal structure data by the operator, if it is determined that the desired level of detail has not been reached, a change in the projected image with respect to the angular displacement occurs in an angular phase range where the desired level of detail cannot be obtained. A re-imaging instruction is issued after determining that the image is conspicuous. The control console 22 detects that an instruction to perform re-imaging is given by the operator (step S14), and a second angular displacement smaller than the first angular displacement with respect to the specific angular range of the object to be inspected. Then, the projection image is picked up again (step S15). Then, reconstruction calculation is performed by combining the projection image captured with the first angular displacement and the projection image within the predetermined angular range captured with the second angular displacement to obtain internal structure data with a higher degree of detail.

  The setting of the photographing range and the angular displacement at the time of the above re-imaging may use the setting contents stored in advance in the nonvolatile memory, or the operator observes the internal structure data and directly inputs the setting. You may make it do.

  According to such an embodiment, first, the internal structure data is reconstructed from a projection image obtained by imaging one round (360 °) of the inspection object with a certain angular displacement, and the operator determines the level of detail of the internal structure data. After the confirmation, only the necessary angular range is imaged again with a smaller angular displacement, so that the internal structure data having the level of detail desired by the operator can be obtained. In addition, the example shown in FIG. 11 has the same effects as the embodiment described with reference to FIG.

Next, imaging processing according to still another embodiment of the present invention will be described with reference to the flowchart of FIG.
In FIG. 12, first, the control console 22 starts an imaging process by detecting an imaging instruction input from the operator. When the control console 22 detects an imaging instruction, the control console 22 calls up settings such as an angular displacement and an imaging range, which are stored in the nonvolatile memory and associated with the characteristics of the object to be inspected, and obtains the imaging conditions (step S21). . Note that the imaging condition may be input and set by the operator directly at the start of imaging according to the characteristics of the object to be inspected.

  After obtaining the imaging conditions, a projected image of the multilayer film plate 30 is taken at an initial angle of 0 ° (step S22). Next, a 360 ° projection image is captured with the first angular displacement based on the imaging condition (step S23). Subsequently, the projection data obtained from the projection images of adjacent angular phases are compared (step S24), and an angular phase in which the image contents of the adjacent projection data differ by a predetermined ratio or more is detected (step S25). The value of this ratio is appropriately set according to the desired inspection accuracy. Then, a specific angular range including the detected angular phase is imaged again with a second angular displacement smaller than the first angular displacement (step S26). The projection image captured with the first angular displacement thus obtained and the projection image within the predetermined angular range captured with the second angular displacement are combined to perform reconstruction calculation to obtain internal structure data with a higher level of detail. .

  Note that various methods can be applied as a method for comparing whether or not the image contents of the projection data of adjacent angular phases differ by a predetermined ratio or more. For example, a method is conceivable in which the grayscale values of the projection data obtained at two angular phases are calculated and binarized based on a predetermined threshold value, and the black and white ratio of the two image data is compared. Alternatively, a method is also conceivable in which histograms are created from the gray values of projection data and the histograms are compared. Further, a method of detecting motion vectors of two image data is also conceivable.

  According to such an embodiment, first, a projected image of one round (360 °) of the object to be inspected is picked up, and the projection data of the projected image is compared to automatically set an angular range in which a change with respect to angular displacement is significant. Thus, only the angle range that requires more detailed projection data is imaged again with a smaller angular displacement, so that internal structure data with a desired level of detail can be obtained automatically. Further, the example shown in FIG. 12 has the same operational effects as the embodiment described with reference to FIG.

Furthermore, examples of other embodiments of the present invention will be described.
In the imaging methods according to the above-described three embodiments, the projected image is captured in a state where the rotation base is stopped, that is, in a state where the object to be inspected is stopped. As described above, when the subject to be inspected is picked up and an image is taken, an image with high accuracy without blurring is obtained because the subject to be picked up is stopped. However, the total imaging time becomes longer due to the stop time. Therefore, in the imaging method according to the present example, the angular velocity at which the rotary base 3 rotates is set as the imaging condition, and the angular velocity is set according to the type of object to be inspected or according to the degree of detail of the desired internal structure data. It is intended to be changed.

  For example, when an object to be inspected that has a remarkable change in the projected image with respect to the angular displacement due to the angular phase, such as the multilayer film plate 30, the rotation base 3 is set in a predetermined manner in an angular phase with a small change in the projected image due to the angular displacement. A projected image is taken at regular intervals while being rotated at the first angular velocity, and is rotated at a second angular velocity smaller than the first angular velocity in an angular phase where the change in the projected image with respect to the angular displacement is large. In the state, a projected image is taken at regular time intervals and stored in the projected image storage unit 23, respectively. Then, from the projected images captured at different angular velocities stored in the projected image storage unit 23 after the completion of imaging, reconstruction calculation is performed according to the angular velocities at each angular phase, and the internal structure data of the object to be inspected is obtained. get.

  According to such an embodiment, the angular velocity with a large change in the projected image with respect to the angular displacement is in a state where the angular velocity of the object to be rotated is small, and the angular velocity with respect to the angular phase in which the change in the projected image with respect to the angular displacement is small. Since the projection image is captured at a constant time in a large state, the angular displacement when the projection image is captured can be varied according to the shape of the inspection object. Furthermore, since the imaging process of the projected image is performed without stopping the rotating object to be inspected, the imaging time can be greatly shortened. In addition to this function and effect, this example has the same function and effect as the example of the embodiment described with reference to FIGS. Further, the imaging method of this example can be applied to each imaging process described with reference to FIG.

  Note that the angular displacements according to these embodiments described above are taken as two discrete values of a large angular displacement (first angular displacement) and a smaller angular displacement (second angular displacement). You may take the continuous value according to the angular displacement of a step, or the shape of a to-be-inspected object.

  Further, the rotation angle of the rotation base 3 in one imaging is not necessarily 360 °, and it is only necessary to obtain a projection image in a minimum angle range necessary for reconstructing the internal structure data. An angle range obtained by adding 180 ° to the opening angle α ° (see FIG. 4) of the emitted X-ray may be set, for example, 270 °.

It is the schematic which shows an example of the X-ray tomographic imaging apparatus by this invention, A is a top view, B is a side view. It is a block diagram which shows an example of the X-ray tomographic imaging apparatus by this invention. It is the schematic of the multilayer film board which is an example of the test object of the X-ray tomography apparatus by this invention. It is a figure where it uses for description of the X-ray tomographic imaging method by this invention. It is the schematic which shows the example of the projection image of the multilayer film board in each angle phase. It is a comparison figure of equiangular displacement and variable angular displacement. It is a figure where it uses for description of the setting of the angular displacement by this invention. It is a flowchart which shows the imaging process of one Embodiment of the X-ray tomographic imaging method by this invention. It is a figure which shows the example of internal structure data when a to-be-inspected object (multilayer film board) is seen from a major axis direction. AD is a figure which shows the example of the internal structure data of the multilayer-film board long axis direction in each imaging condition. It is a flowchart which shows the imaging process of other embodiment of the X-ray tomographic imaging method by this invention. It is a flowchart which shows the imaging process of other embodiment of the X-ray tomography method by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... X-ray tube, 2 ... X-ray two-dimensional detector, 3 ... Rotation base, 5 ... XY stage, 7 ... Test object, 8 ... Holding jig, 10 ... Vibration isolator, 11 ... Shield cover, 20 ... X-ray control unit, 21 ... mechanism control unit, 22 ... control console, 23 ... projection image storage unit, 24 ... computer for reconstruction calculation, 25 ... reconstruction result display device, 30 ... multilayer film plate, 31 ... rotation axis Direction, 32 ... major axis direction, 33 ... minor axis direction, tip 34

Claims (6)

An X-ray source, two-dimensional detection means for imaging transmitted X-rays of the object to be inspected, an X-ray focal point of the X-ray source and the two-dimensional detection means are placed on the object to be inspected From a projected image captured for each angular phase using a rotating means that rotates at an angular displacement set around a rotation axis that is perpendicular to a perpendicular line dropped from the X-ray focal point to the light receiving surface of the two-dimensional detection means. An X-ray tomography method for reconstructing internal structure data of the object to be examined,
In an angle phase in which the change in the projected image with respect to the angular displacement of the object to be inspected is small, the rotating means for placing the object to be inspected is rotated at the first angular displacement, and a projected image for each first angular displacement is captured. And
In an angular phase where the change in the projected image with respect to the angular displacement of the object to be inspected is large, the rotating means for placing the object to be inspected is rotated by a second angular displacement smaller than the first angular displacement, and the second Take a projected image for each angular displacement,
An X-ray tomographic imaging method comprising: reconstructing internal structure data of the object to be inspected from projection images imaged at the first and second angular displacements after imaging is completed. In the first rotation of the rotating means, a projected image is taken for each first angular displacement,
Reconstruction calculation of internal structure data from the captured projection image,
When a re-imaging instruction from an operator is detected after reconstructing the internal structure data, a second smaller than the first angular displacement is detected in the second rotation of the rotating means in the designated angular phase range. Image with the angular displacement of
2. The internal structure data of the object to be inspected is reconstructed from a projected image captured in the first rotation and a projected image captured in the second rotation after the imaging is completed. X-ray tomographic imaging method. An X-ray source, two-dimensional detection means for imaging transmitted X-rays of the object to be inspected, an X-ray focal point of the X-ray source and the two-dimensional detection means are placed on the object to be inspected A rotation unit that rotates at an angular velocity set around a rotation axis that is orthogonal to a perpendicular line that descends from the X-ray focal point to the light-receiving surface of the two-dimensional detection unit; An X-ray tomographic imaging method for reconstructing internal structure data of an examination object,
In an angular phase where the change in the projected image with respect to the angular displacement of the object to be inspected is small, the rotating means for placing the object to be inspected is rotated at the first angular velocity, and a projected image is taken at regular intervals,
In an angular phase where the change in the projected image with respect to the angular displacement of the object to be inspected is large, the rotating means for placing the object to be inspected is rotated at a second angular velocity smaller than the first angular velocity, and the projected image is displayed at regular intervals. Image
An X-ray tomographic imaging method comprising reconstructing internal structure data of the object to be inspected from projection images imaged at first and second angular velocities after completion of imaging. An X-ray source, two-dimensional detection means for imaging transmitted X-rays of the object to be inspected, an X-ray focal point of the X-ray source and the two-dimensional detection means are placed on the object to be inspected Rotating means that rotates with an angular displacement set around a rotation axis that is perpendicular to a perpendicular drawn from the X-ray focal point to the light receiving surface of the two-dimensional detection means, and a projection image captured for each angular phase. An X-ray tomographic imaging apparatus comprising a reconstruction means for reconstructing the internal structure data of an examination object,
In an angle phase in which the change in the projected image with respect to the angular displacement of the object to be inspected is small, the rotating means for placing the object to be inspected is rotated at the first angular displacement, and a projected image for each first angular displacement is captured. Then, in an angular phase where the change in the projected image with respect to the angular displacement of the object to be inspected is large, the rotating means for placing the object to be inspected is rotated by a second angular displacement smaller than the first angular displacement, and the first Control means for controlling to take a projected image for every two angular displacements;
An X-ray tomographic imaging apparatus characterized in that, after completion of imaging, the reconstruction means reconstructs the internal structure data of the object to be inspected from the projected images imaged at the first and second angular displacements. . The control means captures a projection image of the object to be inspected at each first angular displacement by a first rotation of the rotation means, and reconstructs internal structure data from the captured projection image to the reconstruction means. When the re-imaging instruction from the operator is detected after the configuration calculation, the second angular displacement smaller than the first angular displacement in the second rotation of the rotating means in the designated angular phase range. Instruct to take a picture,
After completion of imaging, the reconstruction means reconstructs the internal structure data of the object to be inspected from the projection image captured by the first rotation and the projection image captured by the second rotation. The X-ray tomographic imaging apparatus according to claim 4. An X-ray source, two-dimensional detection means for imaging transmitted X-rays of the object to be inspected, an X-ray focal point of the X-ray source and the two-dimensional detection means are placed on the object to be inspected From the X-ray focal point, a rotating means that rotates at an angular velocity set around a rotation axis that is orthogonal to a perpendicular line that descends on the light receiving surface of the two-dimensional detection means, and the object to be inspected from a projection image that is captured at regular intervals An X-ray tomographic imaging apparatus comprising a reconstruction means for reconstructing the internal structure data of
In an angular phase where the change in the projected image with respect to the angular displacement of the object to be inspected is small, the rotating means for placing the object to be inspected is rotated at a first angular velocity, and a projected image is taken at regular time intervals. In an angular phase where the change in the projected image with respect to the angular displacement of the body is large, the rotating means for placing the object to be inspected is rotated at a second angular velocity smaller than the first angular velocity, and a projected image is taken at regular intervals. Control means for controlling
An X-ray tomographic imaging apparatus characterized in that, after completion of imaging, the reconstruction means reconstructs internal structure data of the object to be inspected from projection images captured at the first and second angular velocities.