JP4898364B2 - Radiation inspection apparatus, radiation inspection method, and radiation inspection program - Google Patents

Description

  The present invention relates to a radiation inspection apparatus, a radiation inspection method, and a radiation inspection program.

Conventionally, a radiation inspection apparatus has been used for quality inspection of cast products and the like. For example, Patent Document 1 discloses a radiation CT that obtains a three-dimensional distribution of defects by irradiating an inspection target with radiation from a plurality of directions and performing a reconstruction operation based on the plurality of transmitted radiations.
JP 2005-91288 A

In the conventional radiation inspection apparatus described above, a highly reliable inspection can be performed by acquiring a three-dimensional distribution of defects, but a highly reliable inspection cannot be performed at a very high speed.
That is, the above-described radiation inspection apparatus requires reconstruction calculation as described above, and it is difficult to increase the speed. In particular, when a large number of parts such as automobile parts are inspected in a factory, it is necessary to execute a highly reliable inspection at high speed.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique for executing a highly reliable inspection at high speed.

  In order to achieve the above object, in the present invention, in a radiation inspection apparatus that inspects a defect by irradiating the inspection object with a radiation generator, the inspection object is rotated relative to the imaging system to obtain a plurality of inspection objects. The transmission radiation image of the inspection object is taken from the angle. Then, based on the obtained plurality of transmitted radiation images, it is determined whether or not a defect exists within a specific range centered on the rotation axis. That is, in the transmitted radiation image, the defect image is present at a position that reflects the position of the defect in the inspection object. If a plurality of transmitted radiation images having different rotation angles are referred to, the defect image changes. The relative relationship between the defect and the axis of rotation can be estimated. Therefore, it can be determined whether or not a defect exists within a specific range around the axis of rotation.

  Further, since the transmitted radiation image is information indicating the intensity of the transmitted radiation on a two-dimensional plane, information on a three-dimensional structure cannot be obtained with only one transmitted radiation image. For this reason, even if two or more defects are arranged along the traveling direction of the radiation, they cannot be distinguished. However, if a plurality of transmitted radiation images are compared, the defect image changes reflecting the difference in the relative relationship between each defect and the rotation axis, so that the defect can be distinguished. Therefore, when determining whether or not a certain defect exists within a specific range, the influence of the image of another defect can be eliminated, and the inspection can be executed accurately.

  In the above configuration, it is determined whether or not there is a defect in a specific range of the inspection target around the rotation axis, and by appropriately selecting the specific range, It becomes possible to carry out inspections necessary for ensuring reliability, and it is possible to perform highly reliable inspections. In other words, in order to ensure the reliability of industrial products such as automobile parts, there are rare cases where it is required that no defect exists in all parts to be inspected. In most cases, the reliability of a product can be ensured by confirming that there is no defect in a specific part such as a part where a large force acts on the inspection target.

  Therefore, a highly reliable inspection can be performed by performing an inspection so that a portion that is required to have no defect in the inspection object is included in the specific range. In addition, since the present invention can perform inspection based on image fluctuations in a transmitted radiation image as described above, it is not necessary to perform high-load processing as in radiation CT, and inspection can be performed at high speed. Can be executed. Therefore, it is possible to operate the factory while inspecting without stopping the mass production line of industrial products, and the inspection does not hinder the shipment of products.

  Here, the radiation irradiating means only needs to be able to irradiate the inspection object with radiation, and the inspection object arranging means only needs to be able to arrange the inspection object in the irradiation direction of the radiation, and the radiation passes through the inspection object by these means. What is necessary is just to comprise. Therefore, the radiation irradiating means may be an open tube or a sealed tube, and is not particularly limited. Further, the inspection object arranging means may be an XY stage that arranges the inspection object in the radiation irradiation range, or may be a robot that holds and conveys the inspection object, and can adopt various configurations. It is.

  The radiation detection means only needs to be able to detect the intensity of transmitted radiation that has passed through the inspection target, and various configurations can be employed. For example, a sensor such as a CCD or CMOS sensor may be two-dimensionally arranged, or scanning may be performed by a one-dimensionally arranged sensor.

  In the rotating means, it is only necessary that the inspection object can be rotated relative to the imaging system. That is, it is only necessary that the position of the defect image in the plurality of transmission radiation images can be changed by changing the posture of the inspection object within the radiation irradiation range and changing the relative relationship between the rotation axis and the defect. As a configuration for this, a configuration in which an inspection object is rotated with respect to a specific rotation axis may be adopted, or an imaging system including the radiation generator and the radiation detector is rotated with respect to a specific rotation axis. You may employ | adopt the structure to make it rotate, and of course, you may rotate both.

  The rotation axis in the rotation is not particularly limited and can be set at an arbitrary position. That is, the defect image included in the transmitted radiation image changes reflecting the rotational movement of the defect included in the predetermined range around the rotation axis, and whether the defect exists within a specific range based on this change What is necessary is just to be able to determine whether or not. Therefore, the axis of rotation may be set so as to penetrate the inspection object, or may be set so as not to overlap the inspection object.

  The determination unit only needs to acquire a plurality of transmitted radiation images taken at different rotation angles and analyze the variation of the defect image included in these transmitted radiation images. Accordingly, it is only necessary to identify the defect image based on the intensity of the radiation indicated by the transmitted radiation image and to identify the variation thereof. Of course, since the transmitted radiation image is a two-dimensional image, when two or more defects are arranged along the radiation traveling direction, the two or more defects cannot be distinguished as described above. It is possible to distinguish between two or more defects by acquiring a plurality of transmitted radiation images and analyzing the defect image. Accordingly, it is not essential for the determination means to accurately acquire the shape, image duplication, and the like from the defect image in each transmitted radiation image, and it is sufficient to simply specify the presence or absence of the defect image.

  Further, the determination unit only needs to be able to determine whether or not a defect exists within a specific range centered on the axis of rotation based on the variation in the defect image included in the transmitted radiation image. That is, if the behavior when the defect in the inspection object rotates and moves with the rotation is specified in advance based on the distance between the axis of rotation and the defect, the defect is determined based on the defect behavior in the transmitted radiation image. Can be determined whether or not exists within the specific range.

  In addition, it is preferable to employ a configuration in which the axis of rotation is substantially perpendicular to the traveling direction of the radiation because the image of the same defect can be analyzed more easily as it fluctuates greatly in a plurality of transmitted radiation images. . According to this configuration, an image corresponding to a specific range around the rotation axis can be defined as an image within a predetermined range in the transmitted radiation image. Therefore, when there is no defect image in the predetermined range, it can be immediately determined that there is no defect in a specific range around the rotation axis. Furthermore, even if two or more defects are arranged in parallel in the radiation traveling direction in a certain posture, and two or more defect images are overlapped in a certain transmission radiation image, It is possible to reliably inspect the image and accurately inspect it.

  Furthermore, the determination means only needs to be able to make a determination based on the fluctuation of the defect image. For example, the determination may be made based on the amount of movement of the defect image. That is, the rotational movement of the defect with respect to a specific rotational axis is a linear movement in the transmitted radiation image that is the projection image. Therefore, if the amount of movement of the defect image is obtained from a plurality of transmitted radiation images, it is possible to estimate the relative relationship between the defect and the rotation axis. For example, the amount of rotational movement of the defect increases as the distance from the rotation axis increases. Therefore, when the amount of movement of the defect image exceeds a predetermined threshold, it can be determined that there is no defect within the specific range.

  Furthermore, the maximum amount of movement on the transmitted radiation image when a defect within a specific range moves by the rotation of the rotation angle can be adopted as an example of this threshold value. That is, as described above, the amount of rotational movement of the defect increases as the distance from the rotation axis increases. Therefore, the maximum amount of movement on the transmitted radiation image corresponding to the maximum amount of rotational movement of a defect within a specific range (a sector arc having a radius from the rotation axis to the boundary of the specific range) is a threshold value. By doing so, it is possible to determine whether or not a defect exists at least in a specific range.

  Furthermore, the present invention can be applied to all inspection objects that can be inspected by determining whether or not a defect exists in a specific range. As a preferable application example thereof, a cylindrical portion is cited. be able to. In other words, a cylindrical part such as a boss often inserts a shaft or bolt into the cylinder, and in order to ensure its reliability, it is determined whether or not a defect exists within a specific distance from the inner wall of the cylinder. do it. Therefore, it is possible to easily determine whether or not there is a defect in a region at a specific distance from the inner periphery of the cylinder by performing an inspection with the axis of the cylindrical portion coincident with the rotation axis of the rotating means. It is possible.

  Although the case where the present invention is realized as an apparatus has been described above, the present invention can be realized as a method and program for realizing the apparatus and a medium recording the program. In addition, the radiation inspection apparatus as described above may be realized alone, applied to a certain method, or used in a state where the method is incorporated in another device. However, the present invention is not limited to this and includes various modes. Therefore, it can be changed as appropriate, such as software or hardware. The software recording medium may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium to be developed in the future.

Here, embodiments of the present invention will be described in the following order.
(1) Configuration of the present invention:
(2) X-ray inspection process:
(3) Other embodiments:

(1) Configuration of the present invention:
FIG. 1 is a schematic block diagram of an X-ray inspection apparatus according to an embodiment of the present invention. In the figure, the X-ray inspection apparatus includes an X-ray imaging mechanism unit 10 and an X-ray imaging control unit 20. The X-ray imaging mechanism unit 10 includes an X-ray generator 11, a rotation mechanism 12, and an X-ray detector 13. The X-ray imaging control unit 20 includes an X-ray control unit 21, a rotation mechanism control unit 22, a transmission X-ray image acquisition unit 23, a CPU 24, an input unit 25, an output unit 26, and a memory 27. In this configuration, the CPU 24 can execute a program (not shown) recorded in the memory 27, control each unit, and perform predetermined arithmetic processing.

  The memory 27 is a storage medium capable of storing data, and threshold data 27a, rotation axis data 27b, and imaging condition data 27c are recorded in advance. The threshold value data 27 a is data indicating a threshold value that is referred to in processing described later, and is determined in advance and recorded in the memory 27. In the present embodiment, a configuration is adopted in which the inspection object is rotated around the rotation axis of the boss to be inspected, and the rotation axis data 27b is data indicating the rotation axis of the rotation. The imaging condition data 27c is data indicating conditions when X-rays are generated by the X-ray generator 11, and includes an applied voltage to the X-ray tube, imaging time, and the like. The memory 27 only needs to be able to store data, and various storage media such as RAM, EEPROM, and HDD can be adopted.

  The X-ray control unit 21 can control the X-ray generator 11 based on the imaging condition data 27c to generate predetermined X-rays. The rotation mechanism control unit 22 is connected to the rotation mechanism 12 and controls the rotation mechanism 12. The rotation mechanism 12 is a multi-axis robot, clamps the casting product 12a that is sequentially conveyed, and takes a desired posture within the X-ray irradiation range. The multi-axis robot in the present embodiment is configured to perform at least inspection object placement work for transporting the cast product 12a to the X-ray irradiation range and rotation work for rotating the cast product 12a around the rotation axis. ing.

  The transmitted X-ray image acquisition unit 23 is connected to the X-ray detector 13, and detects the intensity of the X-ray transmitted through the casting product 12 a based on the detection value output from the X-ray detector 13. The X-ray detector 13 in the present embodiment includes a two-dimensionally distributed sensor, and can generate transmission X-ray image data indicating a two-dimensional X-ray distribution from the detected X-rays. In the present embodiment, the transmitted X-ray image acquisition unit 23 expresses the intensity of the X-rays in shades, and performs image processing so that the intensity decreases as the intensity decreases.

  The output unit 26 is a display that displays the transmitted X-ray image and the like in the CPU 24, and the input unit 25 is an operation input device that receives user input. That is, the user can execute various inputs via the input unit 25, and various output results obtained by the processing of the CPU 24, transmitted X-ray image data, quality determination results of the cast product 12a, and the like are output to the output unit 26. Can be displayed.

  The CPU 24 can execute predetermined arithmetic processing in accordance with various control programs stored in the memory 27, and in order to determine the quality of the cast product 12a, the rotation control unit 24a, the defect detection unit 24b shown in FIG. The control calculation in the calculation part 24c and the quality determination part 24d is performed. The rotation control unit 24 a performs posture control of the inspection target by the rotation mechanism 12. The defect detector 24b detects a defect in the cast product 12a based on the transmitted X-ray image data. The movement amount calculation unit 24c compares a plurality of transmitted X-ray images and detects the movement amount by which the detected defect has moved. The quality determination unit 24d determines whether a defect exists in a predetermined area around the boss based on the detected defect, and determines whether the cast product 12a is a good product or a defective product. .

(2) X-ray inspection process:
In this embodiment, the quality of the inspection object is determined according to the flowchart shown in FIG. In this process, the inspection object produced on the production line of the factory is sequentially conveyed, the casting product 12a is clamped by the rotating mechanism 12, and the inspection process for this inspection object is started. In the inspection process, first, the CPU 24 controls each part to set the inspection part of the cast product 12a in the X-ray irradiation range (step S100). That is, the CPU 24 acquires the rotation axis data 27 b and passes it to the rotation mechanism control unit 22. The rotation mechanism control unit 22 refers to the rotation axis data 27b and controls the rotation mechanism 12 so that the rotation axis is included in the X-ray irradiation range.

  FIG. 3 is a diagram schematically showing the relative relationship among the X-ray generator 11, the X-ray detector 13, and the inspection object. FIG. 3 shows an example in which it is determined whether or not a defect exists within a predetermined range around the axis of the boss 12b. In this example, the X-ray detector 13 from the focal point of the X-ray generator 11 is shown. The direction of travel D of X-rays going to is indicated by an arrow. Further, in this drawing, a boss 12b which is a part of the casting product 12a to be inspected is extracted, and the relationship between the axis A of the boss 12b and the X-ray traveling direction D is shown.

  That is, in the present embodiment, when the rotating mechanism 12 sets the cast product 12a within the X-ray irradiation range, the boss 12b is within the X-ray irradiation range, and the axis A and the X-ray of the boss 12b. It arrange | positions so that the advancing direction D may orthogonally cross. In this example, the axis A of the boss 12b coincides with the rotation axis of the rotation mechanism 12.

  When the cast product 12a is set within the X-ray irradiation range in step S100, the CPU 24 executes the rotation control unit 24a and acquires transmission X-ray images at a plurality of rotation angles. That is, the rotation control unit 24a first sets the rotation angle of the boss 12b to an initial value. Then, the imaging condition data 27 c is transferred to the X-ray control unit 21. The X-ray control unit 21 sets conditions in the X-ray generator 11 according to the imaging condition data 27c, and irradiates X-rays. Since the irradiated X-rays pass through the casting product 12a and reach the X-ray detector 13, the rotation control unit 24a controls the transmission X-ray image acquisition unit 23 to acquire transmission X-ray image data (step S105). ).

  When the transmission X-ray image data is acquired, the CPU 24 executes the defect detection unit 24b and detects a defect based on the transmission X-ray image (step S110). That is, when a defect such as a cast hole is generated in the cast product 12a, a shadow is generated in the transmitted X-ray image according to the difference in the amount of X-ray absorption between the air and the cast product 12a. Therefore, an image of a defect is specified by extracting a dark portion in the image of the cast product 12a as compared with the surroundings.

  Next, the rotation control unit 24a determines whether or not the predetermined number of transmission X-ray images have been captured (step S115), and if the predetermined number of times (in this example, three times) has not been completed. The boss 12b is rotated around the axis A at a predetermined rotation angle (10 ° in this example) (step S120). Then, the processes in and after step S105 are repeated until it is determined in step S115 that the predetermined number of shootings has been completed. Here, the first, second, and third images are referred to in the order in which the transmission X-ray images are captured.

  When it is determined in step S115 that the predetermined number of times of imaging has been completed, the CPU 24 executes the pass / fail determination unit 24d, and the defect detected in the first transmission X-ray image is within the predetermined range. (Step S120), and if it is not determined that the defect exists within the predetermined range, it is determined that the cast product 12a is a non-defective product (step S125).

  FIG. 4 schematically shows an X-ray traveling path from the X-ray generator 11 to the X-ray detector 13. In this figure, the boss is arranged such that the rotation axis A is oriented in a direction perpendicular to the paper surface. 12b is shown. FIG. 5 schematically shows a transmitted X-ray image. In the image 120b of the boss 12b, the outer periphery of the boss and the inner wall of the boss are indicated by solid lines. In the present embodiment, a specific range for determining the presence of a defect is set to a range of a distance r from the rotation axis A (a range indicated by a broken-line circle in FIG. 4). In other words, in the present embodiment, the absence of defects in a predetermined range around the boss 12b is a condition for guaranteeing the quality of the cast product 12a.

  On the detection surface of the X-ray detector 13, a two-dimensional distribution of the intensity of the X-ray output from the X-ray generator 11 and transmitted through the boss 12 b is obtained. The image is included in a specific area on the detection surface. Therefore, if this range is set as the default range in step S120 as shown in FIGS. 4 and 5, a defect exists in the range of the distance r from the rotation axis A when there is no defect in the predetermined range. It can be determined not to. Therefore, in the present embodiment, it is determined whether or not a defect exists in a predetermined range in the first transmission X-ray image, and when there is no defect, it is determined that the cast product 12a is a non-defective product.

  On the other hand, since the X-ray detector 13 detects a two-dimensional distribution of transmitted X-ray intensity, if the predetermined range of the transmitted X-ray image includes a defect image, the defect is detected from the rotation axis A. It cannot be determined whether or not it is included in the range of the distance r. Therefore, in the present embodiment, when a plurality of transmission X-ray images having different rotation angles are compared and it is confirmed that the defect is not at least within the range of the distance r from the rotation axis A based on the movement distance of the defect. Further, it is assumed that the cast product 12a is a non-defective product.

  That is, when the distance between the rotation axis A and the defect is R inside the boss 12b, the defect rotates by the distance Rθ by rotating the rotation axis A around the angle θ (rad) (FIG. 4). reference). Since the rotational movement distance Rθ increases as the distance R from the rotational axis A increases, the maximum movement distance of defects within the range of the distance r from the rotational axis A is rθ. Therefore, if the movement distance of the defect due to the rotation of the angle θ is equal to or greater than rθ, it can be said that the defect does not exist within the range of the distance r from the rotation axis A.

  Therefore, in the present embodiment, the maximum movement amount on the detection surface when the movement locus of the maximum movement distance at each rotation angle is projected on the detection surface of the X-ray detector 13 is set as the above-described threshold value. That is, the maximum movement amount on the detection surface corresponding to the rotation angles of 10 ° and 20 ° is set as a threshold value, and the movement amount based on the threshold value is determined in steps S130 and S135.

  In other words, when it is determined in step S120 that the defect detected in the first transmission X-ray image is within the predetermined range, the CPU 24 activates the movement amount calculation unit 24c and activates the first transmission X-ray. The distance (distance L shown in the example of FIG. 5) that the defect image has moved between the image and the second transmitted X-ray image is acquired. Then, the quality determination unit 24d determines whether or not the amount of movement of the defect image on the transmission X-ray image exceeds a threshold corresponding to the rotation angle of 10 ° (step S130). In step S125, it is determined that the cast product 12a is a non-defective product.

  In the present embodiment, three transmission X-ray images are taken in order to improve the accuracy of pass / fail judgment, and the amount of movement of the defect image on the transmission X-ray image in step S130 is the rotation angle. If it is not determined that the threshold corresponding to 10 ° is exceeded, a determination is further made based on the first transmitted X-ray image and the third transmitted X-ray image (step S135). That is, the movement amount calculation unit 24c acquires the distance that the defect image has moved between the first transmission X-ray image and the third transmission X-ray image, and the pass / fail determination unit 24d determines that the movement amount is the rotation angle. It is determined whether or not the threshold corresponding to 20 ° is exceeded. If the amount of movement exceeds the threshold, it is determined in step S125 that the cast product 12a is a non-defective product. If the amount of movement is not determined to exceed the threshold, the cast product 12a is defective. It is determined that However, even when the defect is out of the predetermined range in steps S130 and S135, the movement amount of the defect is determined to be equal to or greater than the threshold value, and the good determination is made in step S125.

  According to the above processing, a highly reliable inspection can be executed at high speed. In other words, in the present embodiment, it is determined whether or not a defect exists within a specific range around the rotation axis, based on transmitted X-ray images taken at a plurality of rotation angles. Accordingly, when a defect X image is included in the predetermined range in one transmission X-ray image, it is determined whether or not there is no defect in the range of the distance r from the rotation axis A. Therefore, it is possible to suppress the occurrence of oversight that causes the non-defective casting product 12a to be determined as a defective product to an extremely low rate. Further, since the quality determination is performed based on extremely simple parameters such as the position of the defect image and the amount of movement of the defect image, the quality determination can be performed at a very high speed.

(3) Other embodiments:
In the present invention, it is only necessary to determine whether or not a defect exists within a specific range around the rotation axis based on transmission X-ray images taken at a plurality of rotation angles. Various other embodiments can be employed. In addition to the configuration in which the casting product 12a to be inspected is a rotation target, a configuration in which the X-ray generator 11 and the X-ray detector 13 are paired and rotated around a specific rotation axis may be adopted. Both may be rotated. That is, as long as it is possible to determine whether or not a defect exists within a specific range from the variation of the defect image in the transmission X-ray image, using the fact that the rotational movement distance varies depending on the distance from the rotation axis. Various configurations can be employed. Further, a single cast product may be inspected with a plurality of parts as inspection targets, and the center of the rotating shaft may not be hollow in the inspection target.

  Furthermore, the processing order is not limited to the above-described embodiment. For example, after the first transmission X-ray image is captured, the determination process in step S120 is performed, and the second transmission X-ray image is captured. After that, the determination processing in step S130 may be performed, and the determination processing in step S135 may be performed after the third transmission X-ray image is captured. Of course, it suffices if the number of times of photographing is plural, and it may be two times or four times or more, and the rotation angle may be an angle other than 10 °. The pass / fail judgment may be performed using a threshold corresponding to the rotation angle. Furthermore, in the above embodiment, the case where X-rays are used as the radiation has been illustrated, but the usable radiation is not limited to X-rays, and may be γ-rays. There may be.

1 is a schematic block diagram of an X-ray inspection apparatus according to the present invention. It is a flowchart of a X-ray inspection process. It is the figure which showed typically the relative relationship between a X-ray generator, a X-ray detector, and a test object. It is the figure which showed typically the relationship between a test object and a detection surface. It is the figure which showed the transmission X-ray image typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... X-ray imaging mechanism part 11 ... X-ray generator 12 ... Rotation mechanism 12a ... Cast product 12b ... Boss 13 ... X-ray detector 20 ... X-ray imaging control part 21 ... X-ray control part 22 ... Rotation mechanism control part 23 ... Transmission X-ray image acquisition unit 24a ... Rotation control unit 24b ... Defect detection unit 24c ... Movement amount calculation unit 24d ... Quality determination unit 25 ... Input unit 26 ... Output unit 27 ... Memory 27a ... Threshold data 27b ... Rotation axis data 27c ... Imaging condition data

Claims (6)

Radiation irradiating means for irradiating the examination object with radiation by a radiation generator;
Inspection object placement means for placing the inspection object in the radiation irradiation range;
Radiation detection means for acquiring a transmission radiation image of the transmission radiation transmitted through the inspection object by a radiation detector;
A rotating means for rotating the inspection object relative to an imaging system comprising the radiation generator and the radiation detector;
The rotation means is controlled to acquire the transmission radiation images at a plurality of rotation angles, and a plurality of the transmission radiation images are compared. When the movement amount of the defect image exceeds a threshold, the rotation axis is set as the center. A radiation inspection apparatus comprising: a determination unit that determines that no defect exists within a specific range.   The radiation inspection apparatus according to claim 1, wherein an axis of rotation of the rotating unit is substantially perpendicular to a traveling direction of the radiation irradiated from the radiation irradiating unit.   The threshold value is a maximum movement amount on a transmission radiation image when a defect within the specific range moves by the rotation of the rotation angle. The radiation inspection apparatus described.   The inspection object comprises a cylindrical part, and the rotating means rotates the inspection object with the axis of the cylindrical part as the axis of rotation. The radiation inspection apparatus described.   A radiation irradiation step of irradiating the inspection object with radiation by a radiation generator;
  An inspection object arrangement step of arranging the inspection object in an irradiation range of the radiation;
  A radiation detection step of acquiring a transmission radiation image of the transmission radiation transmitted through the inspection object by a radiation detector;
  A rotation step of rotating the inspection object relative to an imaging system composed of the radiation generator and the radiation detector;
  The rotation means is controlled to acquire the transmission radiation images at a plurality of rotation angles, and a plurality of the transmission radiation images are compared. When the movement amount of the defect image exceeds a threshold, the rotation axis is set as the center. And a determination step of determining that no defect exists within a specific range.   Radiation irradiating means for irradiating the examination object with radiation by a radiation generator;
  Inspection object placement means for placing the inspection object in the radiation irradiation range;
  Radiation detection means for acquiring a transmission radiation image of the transmission radiation transmitted through the inspection object by a radiation detector;
  In a computer for controlling rotation means for rotating the inspection object relative to an imaging system comprising the radiation generator and the radiation detector,
  The rotation means is controlled to acquire the transmission radiation images at a plurality of rotation angles, and a plurality of the transmission radiation images are compared. When the movement amount of the defect image exceeds a threshold, the rotation axis is set as the center. A radiation inspection program for realizing a determination function for determining that a defect does not exist within a specific range.

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