用蒙特卡罗法研究高散射介质中的成像

Monte-Carlo Method for Research on Imaging of Inhomogeneity in the Scattering Medium

用蒙特卡罗方法模拟了均匀介质中含有散射系数和吸收系数不同的物体时 ,物体的位置和大小对表面漫射强度时间响应函数的影响 ;在频率域分析了用幅度差和相位差成像时 ,物体位置和大小对成像质量的影响。结果表明相位的探测比幅度的探测灵敏 ,高频探测比低频探测灵敏 ;物体与光源的几何位置影响物体的像质 ,光源与物体共线时成像最灵敏 ,横向位置变化比纵向位置变化影响大 ;物体越大 ,成像效果越好 ,物体小到一定程度时 ,对幅度和相位的影响超出系统的探测能力 ,这决定成像系统的分辨率 。

Monte-Carlo simulation researches on the influence of the inhomogeneous object in the medium on time characteristics of ultrashort pulse light propagation are presented. In frequency domain, the influence of the position and the size on imaging is analyzed by use of the difference of amplitude or phase. The results show that the detection by the phase difference is more sensitive than that by the amplitude difference, and the higher frequency detection can achieve more sensitivity of imaging than the lower frequency detection. The geometric structure of light source and object has the influence on the imaging and the collinear structure has the best imaging effectiveness. The influence on imaging from changes of the lateral position of the object is more serious than the influence on imaging from changes of the longitudinal position of the object. The size of the object also influences imaging, that is, the larger size will achieve, the better imaging. The resolution of the imaging system is determined by many factors, such as the SNR of detection, the geometric structure and the optical properties of the object and so on.