JP2023001428A - CT image generation method - Google Patents

Abstract

To provide a CT image generation method capable of generating a CT image being more accurate in an X-ray inspection device that obliquely irradiates an object to be inspected with X-rays to obtain X-ray images of the object to be inspected and generates a CT image on the basis of the obtained multiple X-ray images.SOLUTION: The CT image generation method includes: a sphere image acquisition step of rotating a table 5 at every constant angle in such a state that an X-ray optical axis OA is tilted with respect to a rotation center axis CR at the same angle θ as a tilt angle when acquiring X-ray images of the object to be inspected and acquiring X-ray images of a sphere 22 on a constant angle basis; a trajectory identification step of identifying a sphere center trajectory that is a trajectory of the center of the sphere 22 during one rotation of the table 5 on the basis of the multiple X-ray images of the sphere 22 acquired in the sphere image acquisition step; and a CT image generation step of performing a predetermined correction based on the sphere center trajectory so as to generate a CT image of the object to be inspected.SELECTED DRAWING: Figure 3

Description

The present invention relates to a CT image generation method for generating a CT image in an X-ray inspection apparatus for nondestructively inspecting an object to be inspected such as an industrial product.

Conventionally, there is known a tomography apparatus that captures a tomographic image of an object to be inspected using X-rays (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100003). The tomography apparatus described in Patent Document 1 includes an X-ray tube, an X-ray detector, a table on which an object to be inspected is placed, and rotates the table around a rotation center axis parallel to the vertical direction. A rotating mechanism and a detector moving mechanism for moving the X-ray detector are provided. In this tomography apparatus, the X-ray detector is moved by the detector moving mechanism to change the Lamino angle, which is the angle between the rotation center axis of the table and the X-ray optical axis, within the range of 0° to about 70°. is possible.

In the tomography apparatus described in Patent Literature 1, when inspecting an object to be inspected, the table is rotated around the rotation center axis, and an X-ray image of the object to be inspected is captured by the X-ray detector over 360°. to get At this time, the Lamino angle is set to an angle exceeding 0°. That is, in this tomography apparatus, the lamina angle is an acute angle when inspecting an object to be inspected, and the object to be inspected is irradiated with X-rays from an oblique direction.

In the tomography apparatus disclosed in Patent Document 1, prior to inspection of the object to be inspected, the Lamino angle is set to 0°, and instead of the object to be inspected, a reference object to be inspected is placed near the rotation center axis of the table. Then, the table is rotated around the central axis of rotation, and the X-ray image of the reference object to be inspected is acquired over 360° with the X-ray detector. The reference object to be inspected is, for example, a plate that easily transmits X-rays and on which a metal ball that does not easily transmit X-rays is adhered, and the metal ball is arranged near the central axis of rotation.

In the tomography apparatus described in Patent Document 1, the deflection of the center of gravity of the metal ball when the table is rotated 360° is obtained from the X-ray image of the reference object and stored in a memory. More specifically, as described above, in this tomography apparatus, the Lamino angle is set to 0° when acquiring the X-ray image of the reference object, so the X-ray image of the reference object , the horizontal deflection of the center of gravity of the metal ball when the table rotates 360° is obtained and stored in the memory. During inspection of the object to be inspected, the X-ray image of the object to be inspected obtained by the X-ray detector is corrected based on the horizontal deflection of the center of gravity of the metal ball stored in the memory.

Japanese Patent No. 5060862

The inventor of the present application has developed an X-ray inspection apparatus for nondestructively inspecting an object to be inspected such as an industrial product. Specifically, the inventor of the present application has developed an X-ray inspection apparatus in which the Lamino angle is set to an acute angle when inspecting an object to be inspected, like the tomography apparatus described in Patent Document 1. That is, the inventor of the present application has developed an X-ray inspection apparatus that irradiates an object to be inspected with X-rays from an oblique direction and obtains an X-ray image of the object to be inspected. In this X-ray inspection apparatus, predetermined calculations are performed based on a plurality of X-ray images of an object to be inspected obtained by an X-ray detector to generate a CT image. In this X-ray inspection apparatus, it is preferable to generate a CT image with higher accuracy in order to increase the inspection accuracy of the object to be inspected.

Accordingly, an object of the present invention is to obtain an X-ray image of an object to be inspected by irradiating the object to be inspected with X-rays from an oblique direction, and to generate a CT image based on a plurality of acquired X-ray images. An object of the present invention is to provide a CT image generation method that enables an inspection apparatus to generate a CT image with higher accuracy.

In order to solve the above problems, the inventors of the present application firstly performed mechanical adjustment of a rotating mechanism for rotating a table on which an object to be inspected is placed so that the object to be inspected rotates together with the table. We decided to suppress the vibration of the object to be inspected in the horizontal direction. In addition, the inventor of the present application performed a mechanical adjustment of the rotation mechanism to suppress horizontal deflection of the object to be inspected rotating together with the table, and then rotated the table to detect the object to be inspected by the X-ray detector. I decided to acquire an X-ray image and confirm the acquired X-ray image.

In this process, the inventor of the present application found that when the horizontal deflection of the object rotating together with the table was suppressed, the vertical (vertical) deflection of the object rotating together with the table was suppressed. has a greater influence on the X-ray image of the object to be inspected, making it difficult to improve the accuracy of the X-ray image of the object to be inspected, and as a result, it becomes difficult to generate a more accurate CT image. I came to know that. Further, the inventors of the present application have found that the vertical vibration of the object to be inspected rotating together with the table has a greater influence on the X-ray image of the object to be inspected, and the accuracy of the X-ray image of the object to be inspected can be improved. Even if it becomes difficult, when generating a CT image based on a plurality of X-ray images, it is possible not only to correct the horizontal vibration of the object to be inspected that rotates with the table, but also to correct the vertical direction of the object to be inspected. It has been found that correcting the shake makes it possible to generate a CT image with higher accuracy.

The CT image generation method of the present invention is based on such new knowledge, and includes an X-ray generator, an X-ray detector arranged to sandwich an object to be inspected between the X-ray generator, An X-ray optical axis that is the optical axis of X-rays emitted by an X-ray generator, comprising a table on which an object to be inspected is placed and a rotation mechanism that rotates the table around a rotation center axis parallel to the vertical direction. A CT image generation method for generating a CT image with an X-ray inspection apparatus in which an acute angle is formed between an X-ray generator and an object to be inspected by the rotation center axis and the X-ray generator, the method comprising: The table is rotated while the sphere is placed and the X-ray optical axis is tilted with respect to the rotation center axis at the same angle as the tilt angle when acquiring the X-ray image of the object to be inspected. A spherical image acquisition step of causing an X-ray detector to acquire X-ray images of a sphere at regular intervals by irradiating rays, and a table based on a plurality of X-ray images of the sphere acquired in the spherical image acquisition step. A trajectory specifying step of specifying a sphere center trajectory, which is the trajectory of the center of the sphere during one rotation; an image acquisition step of causing an X-ray detector to acquire an X-ray image of an object to be inspected at each constant angle; and a CT image generation step of generating a CT image of the body, wherein the CT image generation step performs a predetermined correction based on the sphere center locus to generate the CT image of the subject.

In the CT image generation method of the present invention, in the spherical image acquisition step, the table is rotated with the X-ray optical axis tilted with respect to the central axis of rotation parallel to the vertical direction, and the spherical body is projected onto the X-ray detector at regular intervals. In the trajectory specifying step, the sphere center trajectory, which is the trajectory of the center of the sphere during one rotation of the table, is determined based on the multiple X-ray images of the sphere acquired in the sphere image acquisition step. have specified. Therefore, in the present invention, an X-ray image of the sphere including the vertical vibration of the sphere in addition to the horizontal vibration of the sphere that rotates together with the table is acquired, and the horizontal vibration of the sphere that rotates together with the table is acquired. It is possible to acquire the sphere center locus including the vertical vibration and the vertical vibration.

Further, in the present invention, in the spherical image acquisition step, the table is rotated while the X-ray optical axis is tilted with respect to the rotation center axis at the same angle as the tilt angle at which the X-ray image of the object to be inspected is acquired. Therefore, when an X-ray image of the object to be inspected is acquired, it is possible to acquire a locus of the center of the sphere that includes horizontal and vertical shakes of the object to be inspected rotating together with the table. be possible.

Furthermore, in the present invention, in the CT image generation step for generating a CT image of the object to be inspected, the center of the sphere containing the same degree of vibration as the horizontal and vertical vibrations of the object to be inspected rotating together with the table. A CT image of the object to be inspected is generated by performing a predetermined correction based on the trajectory. Therefore, in the present invention, when a CT image of an object to be inspected is generated based on a plurality of X-ray images of the object to be inspected, it is only necessary to correct the vibration in the horizontal direction of the object to be inspected that rotates together with the table. Therefore, it is possible to correct the vibration of the object to be inspected in the vertical direction. Therefore, if a CT image is generated by the CT image generating method of the present invention, it becomes possible to generate a CT image with higher precision.

In the present invention, in the CT image generation step, for example, a virtual circle whose radius is the average distance between the center of gravity of the sphere center locus and the center of the sphere center trajectory and whose center is the center of gravity of the sphere center locus, or a virtual circle inscribed in the sphere center locus Alternatively, a CT image of the object to be inspected is generated by correcting the difference between the distance from the center of the virtual circle circumscribing the sphere center locus to the sphere center locus and the radius of the virtual circle. In this case, it is possible to reduce the amount of correction in the CT image generation step.

In the present invention, in the sphere image acquisition step, the sphere is placed near the center axis of rotation, and in the CT image generation step, the distance between the center of gravity of the sphere center trajectory and the sphere center trajectory is corrected. of CT images may be generated.

As described above, if a CT image is generated by the CT image generating method of the present invention, the object to be inspected is irradiated with X-rays from an oblique direction to acquire an X-ray image of the object to be inspected, and a plurality of acquired X-ray images are obtained. An X-ray inspection apparatus that generates a CT image based on a line image can generate a CT image with higher accuracy.

1 is a diagram for explaining a schematic configuration of an X-ray inspection apparatus that generates a CT image by a CT image generating method according to an embodiment of the present invention; FIG. FIG. 2 is a plan view of the holding member shown in FIG. 1; FIG. 4 is a schematic diagram for explaining a spherical image acquisition step of the CT image generation method according to the embodiment of the present invention; (A) is a diagram for explaining a CT image generation method according to an embodiment of the present invention; (B) and (C) are diagrams for explaining a CT image generation method according to another embodiment of the present invention; It is a figure for explaining.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Configuration of X-ray inspection device)
FIG. 1 is a diagram for explaining a schematic configuration of an X-ray inspection apparatus 1 that generates a CT image using a CT image generation method according to an embodiment of the present invention. 2 is a plan view of the holding member 11 shown in FIG. 1. FIG.

The CT image generation method of this embodiment is a method for generating a CT image in an X-ray inspection apparatus 1 for nondestructively inspecting an object 2 to be inspected such as an industrial product. The object to be inspected 2 is, for example, a board (circuit board) such as a glass epoxy board formed in a flat plate shape. An electronic component such as an IC chip is mounted on the substrate, which is the object to be inspected 2, and the X-ray inspection apparatus 1 inspects the joint portion between the substrate and the electronic component. Therefore, the inspection by the X-ray inspection apparatus 1 requires high inspection accuracy, for example, on the order of microns.

An X-ray inspection apparatus 1 is arranged so as to sandwich an object 2 to be inspected between an X-ray generator 3 that irradiates an object 2 to be inspected with X-rays. An X-ray detector 4 that acquires an X-ray image, a table 5 on which an object to be inspected 2 is placed, and a rotation that rotates the table 5 around a rotation center axis CR parallel to the vertical direction (vertical direction). It comprises a mechanism 6 and a personal computer (PC) 7 for capturing and processing X-ray images acquired by the X-ray detector 4 .

In the X-ray inspection apparatus 1, the X-ray optical axis OA, which is the optical axis of the X-rays emitted by the X-ray generator 3, is tilted with respect to the horizontal direction and the vertical direction. Specifically, in the X-ray inspection apparatus 1, the angle (Lamino angle) θ formed between the X-ray optical axis OA and the rotation center axis CR between the X-ray generator 3 and the object to be inspected 2 is an acute angle. there is That is, the X-ray inspection apparatus 1 is a so-called oblique CT apparatus. The angle θ is, for example, 45° to 60°.

The X-ray generator 3 emits conical X-rays toward the object 2 to be inspected. The X-ray detector 4 is a two-dimensional X-ray detector (area sensor). The X-ray detector 4 is arranged such that the light receiving surface of the X-ray detector 4 faces the X-ray generator 3 side. The X-ray optical axis OA is orthogonal to the light receiving surface of the X-ray detector 4 . A fluoroscopic image of the object 2 to be inspected is projected onto the X-ray detector 4 . Between the X-ray generator 3 and the X-ray detector 4, for example, a part of the inspected object 2 is sandwiched. The table 5 is attached to the upper end of the rotating mechanism 6 and arranged above the rotating mechanism 6 . The X-ray generator 3 is arranged above the object 2 to be inspected. The X-ray detector 4 is arranged below the rotating mechanism 6 .

The table 5 is a so-called XY table, and the object 2 to be inspected placed on the table 5 is movable in the X direction orthogonal to the vertical direction and the Y direction orthogonal to the vertical direction and the X direction. there is The substrate, which is the object to be inspected 2, is placed on the table 5 so that the thickness direction of the substrate is aligned with the vertical direction. A through hole is formed in the table 5 for passing X-rays emitted from the X-ray generator 3 .

The rotating mechanism 6 includes a rotating member 10 to which the table 5 is attached and which rotates together with the table 5 , a holding member 11 which rotatably holds the rotating member 10 , and which is arranged between the rotating member 10 and the holding member 11 . A rolling bearing 12 is provided. The rotating mechanism 6 also includes a drive mechanism (not shown) that rotates the rotating member 10 . The drive mechanism includes, for example, a motor as a drive source and a power transmission mechanism that transmits power of the motor to the rotating member 10 . The motor is fixed to the holding member 11 . The power transmission mechanism includes, for example, a driving gear fixed to the output shaft of the motor and an annular large-diameter driven gear fixed to the rotating member 10 .

The rolling bearing 12 (hereinafter referred to as "bearing 12") is a cross roller bearing. The bearing 12 includes an annular inner ring 14 fixed to the rotating member 10, an annular outer ring 15 fixed to the holding member 11, and a plurality of rollers arranged between the inner ring 14 and the outer ring 15. and The bearing 12 is a relatively large bearing, and the inner diameter of the inner ring 14 is, for example, 500 mm. In addition, the bearing 12 may be a roller bearing (roller bearing) other than the cross roller bearing, or may be a ball bearing (ball bearing).

The rotating member 10 is arranged on the inner peripheral side of the inner ring 14 . The rotating member 10 is formed in an annular shape. X-rays emitted from the X-ray generator 3 pass through the inner peripheral side of the rotating member 10 formed in an annular shape. The holding member 11 is formed in an annular shape. X-rays emitted from the X-ray generator 3 pass through the inner peripheral side of the holding member 11 formed in an annular shape. The holding member 11 is formed with a mounting surface 11a on which the outer ring 15 is mounted. The mounting surface 11a is formed in an annular shape with the center of the holding member 11 formed in an annular shape as the center of curvature. Moreover, the mounting surface 11a is a plane perpendicular to the vertical direction. The outer ring 15 mounted on the mounting surface 11 a is fixed to the holding member 11 by a plurality of fixing screws arranged in the circumferential direction of the bearing 12 .

(CT image generation method)
FIG. 3 is a schematic diagram for explaining the spherical image acquisition step of the CT image generation method according to the embodiment of the present invention. FIG. 4A is a diagram for explaining the CT image generation method according to the embodiment of the present invention.

The X-ray inspection apparatus 1 generates a CT image of the object 2 to be inspected as follows. First, before acquiring an X-ray image of the object 2 to be inspected, the spherical body 22 is placed on the table 5 and X-rays are scanned at the same angle θ as the angle of inclination when acquiring the X-ray image of the object 2 to be inspected. The table 5 is rotated while the optical axis OA is tilted with respect to the central axis of rotation CR, and the X-ray generator 3 is irradiated with X-rays. An X-ray image of the sphere 22 is acquired (sphere image acquisition step).

The sphere 22 placed on the table 5 in the sphere image acquisition step is a metal ball through which X-rays are difficult to pass (or through which X-rays do not pass). The sphere 22 is, for example, a steel ball made of steel, and the sphericity of the sphere 22 is high. The diameter of the sphere 22 is, for example, 0.3 mm. The sphere 22 is placed in the vicinity of the rotation center axis CR by an operator who inspects the object 2 to be inspected.

In the spherical image acquisition step, the rotating mechanism 6 rotates the table 5 on which the spherical body 22 is placed by at least 360° at a constant speed, and the X-ray generator 3 rotates the spherical body 22 rotated at a constant speed by the rotating mechanism 6. is irradiated with X-rays. The X-ray detector 4 continuously acquires a plurality of two-dimensional X-ray images showing the fluoroscopic image of the sphere 22 each time the table 5 rotates by a constant angle. For example, the X-ray detector 4 continuously acquires 1000 X-ray images each time the table 5 rotates by 0.36°. The multiple X-ray images of the sphere 22 acquired by the X-ray detector 4 are captured by the PC 7 . In this embodiment, the same number of X-ray images of the sphere 22 as the number of X-ray images of the object to be inspected 2 acquired in the image acquisition step described later are acquired.

In this embodiment, mechanical adjustment of the rotating mechanism 6 is performed before the spherical image acquisition step. For example, the rotation mechanism 6 is precisely adjusted so that the horizontal deflection of the sphere 22 rotating together with the table 5 is about 5 μm and the vertical deflection of the sphere 22 rotating together with the table 5 is about 10 μm. is being done.

When the X-ray image of the sphere 22 is acquired in the spherical image acquisition step, based on the multiple X-ray images of the sphere 22 acquired in the spherical image acquisition step, while the table 5 rotates once (360° rotation ) is specified as the trajectory of the center (center of gravity) of the sphere 22 (trajectory specifying step). In the trajectory specifying step, the PC 7 specifies the sphere center trajectory BT based on the multiple X-ray images of the sphere 22 captured by the PC 7 . The sphere center locus BT varies according to the rotation angle of the table 5, for example, as shown in FIG. 4(A).

After the spherical object image acquisition step, the spherical object 22 is lowered from the table 5, the object 2 to be inspected is placed on the table 5, the table 5 is rotated, and the X-ray generator 3 is caused to irradiate the X-rays. The X-ray detector 4 acquires an X-ray image of the inspection object 2 at regular angles in the rotation direction of 5 (image acquisition step). In the image acquisition step, the rotating mechanism 6 rotates the table 5 on which the object to be inspected 2 is placed by at least 360° at a constant speed, and the X-ray generator 3 rotates the object rotated at a constant speed by the rotating mechanism 6. X-rays are applied to the object 2 to be inspected. The X-ray detector 4 continuously acquires a plurality of two-dimensional X-ray images showing a fluoroscopic image of the object 2 to be inspected each time the table 5 rotates by a constant angle. A plurality of X-ray images of the object to be inspected 2 acquired by the X-ray detector 4 are captured by the PC 7 .

When the X-ray image of the object 2 to be inspected is acquired in the image acquiring step, a CT image of the object 2 to be inspected is obtained by performing a predetermined calculation based on the plurality of X-ray images of the object 2 acquired in the image acquiring step. (CT image generation step). In the CT image generation step, the PC 7 performs predetermined arithmetic processing based on the plurality of X-ray images of the object 2 to be inspected and generates a CT image of the object 2 to be inspected. In the CT image generating step, a CT image of the object 2 to be inspected is generated by performing a predetermined correction based on the sphere center locus BT.

Let the average distance between the center of gravity of the sphere center locus BT and the sphere center locus BT (the average value of the distance between the center of gravity of the sphere center locus BT and the sphere center locus BT) be the radius r, and let the center of gravity of the sphere center locus BT be the center C. Assuming that the circle is a virtual circle VC (see FIG. 4A), in the present embodiment, in the CT image generation step, the difference between the distance from the center C of the virtual circle VC to the sphere center locus BT and the radius r of the virtual circle VC A CT image of the object 2 to be inspected is generated by performing correction for d. Specifically, as described above, in the image acquisition step, a plurality of X-ray images of the subject 2 are acquired at regular angles in the rotation direction of the table 5, and in the CT image generation step, the table 5 The X-ray image of the subject 2 at each rotation angle is corrected by the difference d calculated at that rotation angle to generate a CT image of the subject 2 .

For example, in the CT image generation step, the X-ray image of the object 2 to be inspected at each rotation angle of the table 5 is corrected in a predetermined direction by the difference d. In this case, if the distance from the center C of the virtual circle VC to the sphere center locus BT is greater than the radius r of the virtual circle VC, the X-ray image of the object to be inspected 2 is shifted in the negative direction by the amount of the difference d. If the distance from the center C of the circle VC to the sphere center locus BT is smaller than the radius r of the virtual circle VC, the X-ray image of the object 2 to be inspected is shifted in the positive direction by the difference d.

Alternatively, in the CT image generation step, correction is performed for the difference d calculated at each rotation angle of the table 5 when performing predetermined calculations on a plurality of X-ray images. In the present embodiment, the state of the rotating member 10, the holding member 11, the bearing 12, etc. in the spherical image acquisition step and the state of the rotating member 10, the holding member 11, the bearing 12, etc. in the image acquisition step depend on the environmental temperature fluctuation. In order to minimize the influence of fluctuations in the states of the rotating member 10, the holding member 11, the bearing 12, etc. on the CT image, the image is acquired immediately after the spherical image acquisition step. Acquisition step.

(Main effects of this form)
As described above, in this embodiment, in the spherical image acquisition step, the table 5 is rotated with the X-ray optical axis OA tilted with respect to the rotation center axis CR parallel to the vertical direction, and the spherical body 22 is rotated at regular intervals. In the trajectory specifying step, based on the X-ray images of the plurality of spheres 22 acquired in the sphere image acquisition step, a sphere that is the trajectory of the center of the sphere 22 during one rotation of the table 5 A central locus BT is specified. Therefore, in this embodiment, an X-ray image of the sphere 22 including vertical vibration of the sphere 22 in addition to the horizontal vibration of the sphere 22 rotating together with the table 5 is obtained, and the sphere 22 rotates together with the table 5. It is possible to obtain the sphere center locus BT including the horizontal and vertical deflections of the sphere 22 that is moving.

Further, in this embodiment, in the spherical image acquisition step, the table is tilted with the X-ray optical axis OA tilted with respect to the rotation center axis CR at the same angle θ as the tilt angle when acquiring the X-ray image of the object 2 to be inspected. 5 is rotated, the X-ray image of the object 2 to be inspected includes vibrations of the same degree as the horizontal and vertical vibrations of the object 2 rotating together with the table 5. It becomes possible to acquire the sphere center locus BT.

Furthermore, in the present embodiment, in the CT image generation step, a predetermined correction based on the sphere center locus BT including horizontal and vertical vibrations of the object to be inspected 2 rotating together with the table 5 is performed. is performed to generate a CT image of the object 2 to be inspected. Therefore, in this embodiment, when a CT image of the subject 2 is generated based on a plurality of X-ray images of the subject 2, the vibration of the subject 2 rotating together with the table 5 is corrected. In addition to correction, it is possible to correct vertical vibration of the object to be inspected 2 . Therefore, if a CT image is generated by the CT image generation method of this embodiment, it becomes possible to generate a CT image with higher accuracy.

In addition, in this embodiment, the bearing 12 is a relatively large bearing, and the inner diameter of the inner ring 14 is relatively large. Further, in this embodiment, the rotating member 10 and the holding member 11 are formed in an annular shape so that the X-rays emitted from the X-ray generator 3 pass through the inner peripheral sides of the rotating member 10 and the holding member 11. . Therefore, in this embodiment, the rigidity of the rotating member 10, the holding member 11, and the bearing 12 is relatively low, and the inspection object 2 rotating together with the table 5 tends to vibrate in the vertical direction. Then, even if the object to be inspected 2 rotating together with the table 5 is likely to vibrate in the vertical direction, it is possible to generate a CT image with higher accuracy.

In this embodiment, in the CT image generating step, the CT image of the subject 2 is corrected by correcting the difference d between the distance from the center C of the virtual circle VC to the sphere center locus BT and the radius r of the virtual circle VC. are generating. Therefore, in this embodiment, it is possible to reduce the amount of correction in the CT image generation step compared to the case of performing correction for the distance between the center of gravity of the sphere center locus BT and the sphere center locus BT.

(Other embodiments)
In the embodiment described above, the virtual circle VC may be an inscribed circle inscribed in the sphere center locus BT as shown in FIG. It may be a circumscribed circle that circumscribes BT. Even in this case, in the CT image generation step, correction is performed for the difference d between the distance from the center C of the virtual circle VC to the sphere center locus BT and the radius r of the virtual circle VC. Generate a CT image. Even in this case, it is possible to reduce the amount of correction in the CT image generation step. Further, in the above embodiment, when the radius r of the virtual circle VC is sufficiently small, in the CT image generation step, the center of gravity of the sphere center locus BT and the distance between the sphere center locus BT and the center of gravity of the sphere center locus BT are corrected. A CT image of body 2 may be generated.

In the embodiment described above, when acquiring an X-ray image of the object 2 to be inspected in the image acquiring step, the X-ray detector 4 sequentially moves the object 2 to be inspected while temporarily stopping the table 5 at equally divided positions of 360°. X-ray image may be acquired. In the above embodiment, when acquiring the X-ray image of the sphere 22 in the spherical image acquiring step, the X-ray detector 4 sequentially moves the sphere 22 while temporarily stopping the table 5 at equally divided positions of 360°. An X-ray image may be acquired.

In the embodiment described above, the spherical image acquisition step may be performed after the image acquisition step. In this case, it is preferable to perform the spherical image acquisition step immediately after the image acquisition step. Further, in the above-described embodiment, the number of X-ray images of the object to be inspected 2 acquired in the image acquisition step and the number of X-ray images of the sphere 22 acquired in the spherical image acquisition step may be different. Furthermore, in the embodiment described above, the X-ray detector 4 may be arranged above the subject 2 and the X-ray generator 3 may be arranged below the rotating mechanism 6 . Moreover, in the above embodiment, the object 2 to be inspected by the X-ray inspection apparatus 1 may be something other than a substrate.

1 X-ray inspection device 2 Subject to be inspected 3 X-ray generator 4 X-ray detector 5 Table 6 Rotation mechanism 22 Sphere BT Sphere center locus C Center of virtual circle CR Rotation center axis d From the center of the virtual circle to the sphere center locus Difference between distance and radius of virtual circle OA X-ray optical axis r Radius of virtual circle VC Virtual circle

Claims (3)

An X-ray generator, an X-ray detector arranged to sandwich an object to be inspected between the X-ray generator, a table on which the object to be inspected is placed, and a rotation center parallel to the vertical direction. and a rotation mechanism for rotating the table around an axis, wherein the X-ray optical axis, which is the optical axis of the X-ray emitted by the X-ray generator, and the rotation center axis are aligned with the X-ray generator and the subject. A CT image generation method for generating a CT image with an X-ray inspection apparatus having an acute angle with an object to be inspected,
A spherical body is placed on the table, and the table is moved while the X-ray optical axis is tilted with respect to the rotation center axis at the same angle as the tilt angle at which the X-ray image of the object to be inspected is acquired. a sphere image acquisition step of rotating and irradiating the X-ray generator with X-rays to cause the X-ray detector to acquire an X-ray image of the sphere at regular intervals;
a trajectory identifying step of identifying a sphere center trajectory, which is a trajectory of the center of the sphere during one rotation of the table, based on the plurality of X-ray images of the sphere acquired in the spherical image acquisition step;
The object to be inspected is placed on the table, the table is rotated, the X-ray generator is irradiated with X-rays, and the X-ray image of the object to be inspected is transmitted to the X-ray detector at regular intervals. an image acquisition step to be acquired;
a CT image generating step of generating a CT image of the subject by performing a predetermined calculation based on the plurality of X-ray images of the subject obtained in the image obtaining step;
In the CT image generating step, a CT image of the object to be inspected is generated by performing a predetermined correction based on the spherical center locus. In the CT image generating step, a virtual circle having a radius equal to the average distance between the center of gravity of the sphere center locus and the center of gravity of the sphere center locus, or a virtual circle inscribed in the sphere center locus, Alternatively, the CT image of the object to be inspected is generated by correcting the difference between the distance from the center of a virtual circle circumscribing the sphere center locus to the sphere center locus and the radius of the virtual circle. The CT image generating method according to claim 1, wherein In the sphere image acquisition step, the sphere is placed in the vicinity of the rotation center axis,
2. The CT image according to claim 1, wherein in said CT image generation step, the CT image of said object to be inspected is generated by correcting the distance between the center of gravity of said spherical center locus and said spherical center locus. generation method.

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