高质量赝热光源是实现X光关联成像技术在显微领域应用的关键。X光傅里叶变换关联成像的赝热光源通过随机孔屏调制X光获得,在此基于统计光学分析了调制后X光散斑场的统计特性,并通过数值模拟分析了随机孔屏参数对散斑场特性及成像质量的影响。结果表明,随机孔屏引入的相位差变化为π时,关联成像对比度达到最优值。对于振幅型随机孔屏,成像对比度随着占空比的减小而增大;对于相位型随机孔屏,成像对比度随着占空比的减小而减小。实际X光傅里叶变换关联成像系统中使用的复振幅型随机分布金属孔屏,通过选择合适的透过率和占空比可以实现高对比度关联成像。
High quality pseudo-thermal sources are essential in X-ray ghost imaging microscopic applications. The pseudo-thermal source used in X-ray Fourier-transform ghost imaging is obtained by modulating X-ray with a screen full of randomly distributed holes. The statistical properties of the X-ray speckle fields are analyzed based on the statistical optics, and the influence of the screen parameters is explored by numerical simulations. Results show that the optimum contrast for ghost imaging can be achieved when the phase difference introduced by the screen is n. For random amplitude screens, the imaging contrast increases with the decrease of the duty cycle, while for random phase screens, the imaging contrast decreases with the decrease of the duty cycle. In practical X-ray Fourier- transform ghost imaging systems, the screen made of metal can be treated as a complex amplitude screen, and the high-contrast ghost imaging can be realized by choosing appropriate transmittance and duty cycle of the screen.