Derivative Method for Edge Enhancement in Radiographic Testing

The definition of edge is essential for dimension extraction from radiographic testing. One of the straightforward techniques for edge enhancement is the use of the derivative operator. This technique is analyzed for various types of edges on the basis of general definition of the edge. The radiographic response is considered as a convolution of ideal image with a blurring function. The types of edges responding to the technique with sufficient accuracy are found, while in other cases this technique is not recommended. The derivative approach is demonstrated for the localization of edges in a calibrated reactor fuel element tested by neutron radiography. The radiograph is digitized with an automatic microdensitometer, and the limitations of the method are shown for pellet axial and radial edges.