X-ray inspection apparatus and X-ray inspection method

An inspection method performed by an X-ray inspection apparatus, the apparatus comprising:

• an X-ray generator provided with an X-ray detector having a point-shaped tube focal spot, the X-ray detector generating an X-ray beam from the tube focal spot, the X-ray beam having a given cone angle in a scan direction and a predetermined fan angle in a direction which is along a section perpendicular to the scan direction;
• and
• an X-ray detector provided with a plurality of pixels two-dimensionally arrayed and configured to output at a predetermined frame rate frame data presenting strength of the X-ray beam incident on the pixels, the X-ray detector having a detection surface, the pixels providing a rectangular shape as a whole thereof in the detection surface and being arranged to be oblique to the scan direction as a whole of the rectangular shape, the X-ray detector being arranged to be opposed and separated to and from the X-ray tube with a space provided therebetween, an object being inspected being positioned in the space,
• wherein the method comprising steps of:
• either a pair of the X-ray tube and the X-ray detector or the object is moved relatively to the other in the scan direction, the X-ray detector being arranged to be opposed and separated to and from the X-ray tube with a space provided therebetween, an object being inspected being positioned in the space, wherein either the pair of the X-ray tube and the X-ray detector or the object is moved such that a center line of the X-ray beam in a width direction thereof crosses with each of a plurality of tomographic planes virtually set in the space and
• parallel to the scan direction, a crossing length in each of the tomographic planes being always constant, the frame data outputted from the X-ray detector being acquired while either the pair of the X-ray tube and the X-ray detector or the object is moved relatively to the other;
• generating, based on the frame data, frame data of each of a plurality of tomographic planes depending on a spread of the fan-shaped X-ray beam and positional differences of the plurality of tomographic planes in a perpendicular direction to the tomographic planes, the tomographic planes being set in the space and parallel to the scan direction;
• generating tomographic images of the tomographic planes by applying a laminography method to the generated frame data of the tomographic planes;
• generating a three-dimensional distribution of edge information based on calculating, every pixel of each of the tomographic images, edge information showing changes in pixel values of the respective tomographic images generated;
• correcting, at each of the tomographic planes, the edge information in accordance with a difference in distances, the distances i) being taken between a center position, in the scan direction, of the rectangular shape provided by arrangement of the plurality of pixels and a position of each of the plurality of pixels and ii) depending on a height position in a radiation direction of the X-ray beam;
• and
• generating a single composite image through searching every pixel a three-dimensional distribution of the torsion-corrected edge information in a direction passing through the tomographic planes to detect a pixel showing a maximum of the edge information, selecting, at a pixel position corresponding to the detected pixel, only pixels of the tomographic images or other tomographic images generated from the tomographic images, and combining the selected pixels, the single composite image showing an inside state of the object.