Contaminant detection using X-ray imaging

摘要

An X-ray scanning apparatus for locating a contaminant in a product 5 comprises means 1, 2 for generating an X-ray image of the product; means for assigning a grey scale value to pixels in the image; means for identifying suspect pixels in the image; means, which for each suspect pixel: selects two neighbouring (i.e. adjacent or closely spaced) pixels in a first direction lying on opposed sides of the suspect pixel and determines which of the first direction pixels has the lower grey value; selects two neighbouring pixels in a second direction lying on opposed sides of the suspect pixel and determines which of the second direction pixels has the lower grey value; determines a first direction difference value by taking the grey value difference between the lower grey value first direction pixel and the grey value of the suspect pixel; determines a second direction difference value by taking the grey value difference between the lower grey value second direction pixel and the grey value of the suspect pixel; determines first and second direction scores from the first and second direction difference values respectively; compares the scores with a threshold value; and identifies the suspect pixel as representing a contaminant if the threshold value is exceeded.