X-ray laminography and digital tomosynthesis which can form a cross-sectional image within 3-D objects promise to be good solutions for inspecting interior defects of products in industries. In this paper, an analysis and design of X-ray digital tomosynthesis system including image synthesizing method are presented. The system is composed of a scanned beam X-ray source, a image intensifier with a large input screen, and a high resolution CCD camera. The performance of the system such as projection angle, distortion and resolution of the system are discussed including the way for correcting the distortion caused by spherical input screen of image intensifier. The quality of images acquired from the system varies according to image synthesizing methods and X-ray projection angles. To get clear and accurate cross-sectional images, a new image synthesizing method named 'log-root method' is proposed, which can reduce both artifact and blurring generated by materials out of focal plane. To evaluate the quality of cross-sectional images, two evaluating criteria : (1) shape accuracy and (2) clearness are defined. Simulation results are shown which tell the good performance of the new synthesizing method over the existing ones such as averaging and minimum.
