This paper presents an effective approach for online testing the assembly structures inside products using multiple views technique and X-ray digital radiography system based on spatial sampling criteria and variable step sampling mechanism. Although there are some objects inside one product to be tested, there must be a maximal rotary step for an object within which the least structural size to be tested is predictable. In offline learning process, Rotating the object by the step and imaging it and so on until a complete cycle is completed, an image sequence is obtained that includes the full structural information for recognition. The maximal rotary step is restricted by the least structural size and the inherent resolution of the imaging system. During online inspection process, the program firstly finds the optimum solutions to all different target parts in the standard sequence, i.e., finds their exact angles in one cycle. Aiming at the issue of most sizes of other targets in product are larger than that of the least structure, the paper adopts variable step-size sampling mechanism to rotate the product specific angles with different steps according to different objects inside the product and match. Experimental results show that the variable step-size method can greatly save time compared with the traditional fixed-step inspection method while the recognition accuracy is guaranteed.
The present paper reviews the X-ray grating imaging systems at home and abroad from the aspects of technological
characterizations and the newest researching focus. First, not only the imaging principles and the frameworks of the typical
X-ray grating imaging system based on Talbot-Lau interferometry method, but also the algorithms of retrieving the signals
of attenuation, refraction and small-angle scattering are introduced. Second, the system optimizing methods are discussed,
which involves mainly the relaxing the requirement of high positioning resolution and strict circumstances for gratings and
designing large field of view with high resolution. Third, two and four-dimensional grating-based X-ray imaging techniques
are introduced. Moreover, the trends of X-ray grating based imaging technology are discussed, especially the multiple
information fusions are tried with attenuation, refraction and scattering obtained synchronously.
This paper proposes an effective approach for online inspecting and recognizing the assembly structure inside three-dimensional
objects using multiple views technique and X-ray digital radiography system. During the offline study
process, the paper obtains a gray image sequence of a standard sample in multiple circumferential orientations. Utilizing
the idea of classifying identification, the paper locates and extracts different characters of different parts in each image of
the sequence and establishes corresponding character sequence libraries. In online detection stage, the program finds the
optimum solutions to all different target parts in the library with bisearch method and carries out exactness image
matching with correlation coefficient weighted of multi-character via Bayes decision. Aiming at the issue of some
objects may be occluded by others in a scene, the paper puts forward to rotate the product some certain angles and re-match.
Furthermore, the paper analyzes the relationships of misjudgment ratio with product assembling tolerance, the
size of target part and identifying velocity. Based on this approach, the first domestic X-ray automatism detection system
has been developed and it is successfully applied in online detecting some axis symmetric products which assembly
structures inside are complex.