IMAGE SUBTRACTION METHOD IN DIGITAL RADIOGRAPHY OF WELDING

摘要

In order to improve contrast resolution in X-ray digital radiography, an image subtraction method was developed. Using a conventional image intensifier, welding lines of thick steel parts were tested. First the X-ray image was integrated in the image flame of an image processor used to minimize the random noise from X-ray statistic distribution. Next the image detector was slightly moved and again the X-ray image was taken, where the second image was subtracted from the first integrated image, which gave us significantly spatial noise reduction and extracting the images of only defects of welding. The contrast enhancement was possible to maximum level, so that the detectability of defects was greatly improved, being about 0.1% of detectability was obtained.