Image Stitching for Radiography

X-Ray based nondestructive evaluation is widely used for detecting defects in materials. X-rays are made to pass through the object under inspection. The x-rays transmitted by the object are collected by a detector, which generates a digital image. If defect is present in the material, it will manifest as a change in the contrast in the digital image at that location. Typically for obtaining a digital x-ray image, digital radiography panel or computed radiology plate is used as detector. Digital radiography is used both for inspection during manufacturing and in service. Few of the scenarios in which digital radiography is used are inspection of (1) casting (2) welding on pipes

(3) assembly of components (4) components of rotatory machinery.

Sometimes the size of the object is larger than the detector itself. In such cases, multiple digital x-ray images at adjacent locations are acquired one after another to completely cover the object. In such cases, conventionally, these images are evaluated individually to qualify the part.

In this paper, we describe methods for stitching these individual x-ray images to make a composite image. The boundary at each of the image is correlated with each other and the matching boundary is identified. The images are rotated and/or translated and/or scaled so that the boundary aligns with each other. The essence of the paper involves the aligning the images by matching the boundaries as intelligent visual system does and then stitching the images to get the complete larger image. Results on different combinations of one set of data are presented.

Methods for stitching specific to digital radiography panel and computed radiography plate are also described.

Keywords: Digital Radiography, Image Stitching, X-Ray