Research On Expansion Technology Of Dynamic Range Of Gradient-energy Digital Radiography Image

Nowadays，the proportion of X-ray detection in the application of non-destructiveexamination technology account for nearly half, is widely used in the fields of aerospace、defense and military、transportation security、medical diagnosis、industrial detection andother fields. But in the practical projects, most of the tested workpieces with characteristicsof irregular and complex structure, and uneven thickness, when X-ray of conventionalfixed-energy act on such workpieces, as the range of changes in the thickness of theworkpieces to be far beyond the scope of imaging device can record, result in a single scanimage will appear underexposed and overexposed of coexisting phenomenon, causing theloss of the detail information of thick or thin piece of the workpieces, the effective detectionof the workpiece quality can not be achieved through a single radiographic image.In this paper, aimed at the problem of X-ray detect the workpieces of complexstructure, based on the variable energy X-ray scanning and imaging technology, with someadjustments by a confirmed stepper to increase the voltage of X-ray, then the cylinder headwere continuous transilluminated, and a set of digital image sequence of various voltagescan be obtained. Then proceed this group of image sequence as follows: Firstly, each imagein the image sequence is divided into blocks; Secondly, on the basis of the imageinformation entropy to measure how much of each image block contains information;Thirdly, fusing the optimal image block that contains amount of information by using themethod of weighted fusion, and use genetic algorithm to parameter optimization for thefused image, to eliminate discontinuities between image block and the block, so that thefused image has good visual effect, and showing the structural information of the workpiecemore clearly; Finally, evaluating the results by using the method of image quality evaluation.The experimental results showed that, this method can be effectively integrated informationof each pictures in the image sequence, come into being a high dynamic range image, this fused image make full use of comprehensive information of source images, make up for thedeficiency of the single image’s information, the details and department of thin and thick ofthe measured workpiece are presented in an image at the same time, its structuralinformation is represented completely, to extend the dynamic range of the radiographicimage. At the same time, compared with the newer fusion method of DR image, it isconcluded that the feasibility of this method.