1. College of Physics and Electronic Science, Hunan University of Arts and Science, Changde 415000, China 2. College of Automation, Chongqing University, Chongqing 400030, China 3. College of Science, Chongqing University, Chongqing 400030, China
Abstract：Since energy spectrum of X-ray is polychromatic source in X-ray industrial computerized tomography, the variation of attenuation coefficient with energy leads to the lower energy of X-ray radiation being absorbed preferentially when X-ray is transmitting the materials. And the higher the energy of X-ray, the lower the attenuation coefficient of X-ray. With the increase in the X-ray transmission thickness, it becomes easier for the X-ray to transmit the matter. Thus, the phenomenon of energy spectrum hardening of X-ray takes place, resulting from the interaction between X-ray and the materials. This results in false images in the reconstruction of X-ray industrial computerized tomography. Therefore, hardening correction of energy spectrum of X-ray has to be done. In the present paper, not only is the hardening phenomenon of X-ray transmitting the materials analyzed, but also the relation between the X-ray beam sum and the transmission thickness of X-ray is discussed. And according to the Beer law and the characteristics of interaction when X-ray is transmitting material, and by getting the data of X-ray beam sum, the relation equation is fitted between the X-ray beam sum and X-ray transmission thickness. Then, the relation and the method of equivalence are carried out for X-ray beam sum being corrected. Finally, the equivalent and monochromatic attenuation coefficient fitted value for X-ray transmitting the material is reasoned out. The attenuation coefficient fitted value is used for product back-projection image reconstruction in X-ray industrial computerized tomography. Thus, the effect caused by X-ray beam hardening is wiped off effectively in X-ray industrial computerized tomography.
Key words：X-ray;Industrial computerized tomography;Hardening correction;Beam sum
[1] Krohn Barbara R, Silver Michael D. Materials Evaluation, 1990, 49(10): 1296. [2] de Paiva Rogerio Ferreira, Lynch John, Rosenberg Elisabeth, et al. NDT & International, 1998, 31(1): 17. [3] PENG Guang-han, YANG Xue-heng, HAN Zhong, et al(彭光含，杨学恒，韩 忠, 等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2005, 25(11)：1880. [4] Hanke R, Bobel F. NDT & International, 1992, 25(2): 87. [5] PENG Guang-han, YANG Xue-heng, CAI Xin-hua, et al(彭光含，杨学恒，蔡新华, 等). Spectroscopy and Spectral Analysis(光谱学与光谱分析）, 2007, 27(4): 823. [6] Guy M J, Castellano-Smith I A, Flower M A, et al. IEEE, Transaction on Nuclear Science, 1998, 45(3): 1261. [7] ZHANG Li-ming, WEI Cai-ping, ZHENG Shi-rong(张李明, 魏彩屏, 郑世荣). Journal of China University of Science and Technology(中国科学技术大学学报), 1996, 26(4): 510. [8] PENG Guang-han, CAI Xin-hua, HAN Zhong, et al(彭光含，蔡新华，韩 忠，等). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2007，27(9)：1882.
