A method of 3-D information detection of weld seam facts based on X-ray image has been developed. There are problems in the fact detection on the X-ray 2-D projection of weld seam

which the cracks along the projection direction and the concave holes on the surface of weld seam may be recognized as the air holes and the thin area facts(the cracks and nonpenetrate solder) may not be detected. The problems can be avoided in the method of 3-D information detection. The paper discusses the imaging approaches and the light models. An iterative algorithm of 3-D information detection of the facts has been constructed. This algorithm has been simplified greatly by parameterization of the fact models using the form knowledge about the facts.