Development of a low cost industrial X-ray film scanner
Digitization of industrial radiographs provide many advantages: digital archiving, quantitative evaluation, image processing and enhancement, automated image evaluation. However, due to the high dynamic range and high spatial resolution of industrial X-ray film, only laser scanner and line-scan CCD-based scanner are capable of reproducing faithfully all diagnostic information contained in the original radiograph. These equipment are expensive due to the need for film transport and the lack of volume for such product. In order to meet the needs for film digitization for small volume of work where cost is the primary concern, this thesis describes a film digitization system that uses low-cost CCD camera to digitize industrial radiograph. To effectively utilize low-cost camera with limited dynamic range, the system alters the illumination of the lightbox, and then digitize the radiograph at each of these lightbox illuminations. By combining these subimages using simple algorithm, one can obtain a composite image with quality rivaling those obtained from expensive laser-based scanning system. To overcome the 8-bit display limitation of most computer monitors, a 16-bit viewer is designed to facilitate viewing of data with arbitrary bit-depth and to provide windowing capability to view subset of film density data. Finally, the capability of the system is demonstrated by digitizing real world radiographs and industrial X-ray standards radiographs.