| 摘要 |
<p>A transfer unit (2) moves an object (1) in a predetermined transfer direction. An x-ray source (3) is for applying x-rays to the object (1) being moved by the transfer unit (2). An x-ray detector (4) detects x-rays transmitted through the object and provided with an x-ray detecting element which is directed perpendicularly to the predetermined object transfer direction, and which has a predetermined width. A memory (5) stores the two-dimensional distribution of x-ray intensity for every picture element detected by the x-ray detector, as a transmission image. An average value calculator (7) calculates an average region value of a local region which has more than 7 x 7 picture elements including the object elements, more than 9 x 9 picture elements including the object elements, or more than 11 x 11 picture elements including the object elements, and has picture elements equal to the product of the number of picture elements corresponding to 1/2 of the predetermined detector width by the number of picture elements corresponding to 1/2 of the predetermined detector width, by performing product-sum operation by means of a predetermined coefficient matrix, for every picture element of the transmission image stored in the memory. A difference calculator (8) calculates the difference between the x-ray intensity value with respect to the object picture elements in the transmission image stored in the memory and the average region value with respect to the object picture elements calculated by the average value calculator. A judgement unit (9) compares the difference calculated by the difference calculator with a preset reference judgement value and judges whether foreign matter is present in the object or not.</p> |
