Statistical Properties of Dynamic Multiple Scattering Phenomena of Laser Light

该项目的目的是揭示运动中高度无序介质散射的激光的统计特性，并开发新的技术来提取有关多个散射物体的结构和运动的信息。(1)多扩散器的动态光散射：在菲涅耳衍射近似下，从理论上研究了运动随机相位屏级联散射光的时间特性。结果表明，通过成像系统检测到的散射光具有自由空间传播几何结构所不能观测到的一些重要特征。(2)颗粒介质的动态光散射：实验研究了流动颗粒悬浮液的动态光散射，将颗粒的体积密度从单散射状态改变为多次散射状态。实验揭示了在多重散射状态下散射光的时间特性与散射体内部形成的散射体积之间的密切关系。此外，还发现通过控制用于检测的成像系统的数值孔径可以改变光的强度波动对粒子扩散和集体运动的敏感性。(3)多次散射光的光谱相关测量：利用集中流动微球进行布朗运动，测量不同波长散射光强度的相互关系。结果表明，强度波动的相关系数主要取决于粒子的散射截面和粒子数密度。互相关法测得的相关时间不受布朗运动的影响，其倒数与散射介质的流速成正比。提出了一种适用于致密胶体介质的速度测量新技术。少

The aim of the project is to reveal the statistical properties of laser light scattered by highly disordered media in motion and to develop new techniques for extracting information about the structure and motion of multiple scattering objects.(1)Dynamic light scattering from multiple diffusers : The temporal properties of light scattered by a cascade of moving random phase screens were studied theoretically under the Fresnel diffraction approximation. It was shown that the scattered light detected through an imaginig system exhibits some important features which cannot be observed in the light detected in the free-space propagation geometry.(2)Dynamic light scattering from particulate media : Dynamic light scattering from flowing particle suspensions was investigated experimentally, changing the volume density of particles from the single scattering regime to the multiple scattering one. Experiments revealed the intimate relationships between the scattering volume formed inside the sa … More mple and the temporal behavior of scattered light in the multiple scattering regime. In addition, it was found that the sensitivities of the intensity fluctuations of light to diffusive and colletive motions of the particles can be changed by controlling the numerical aperture of the imaging system used for detection.(3)Spectral-correlation measurements of multiply-scattered light : The cross-correlations of scattered light intensities with different wavelengths were measured using concentrated flowing microspheres undergoing Brownian motion. It was shown that the correlation coefficient of intensity fluctuations is mainly dependent both on the scattering cross section of each particle and the number density of the particles. The correlation time measured by the cross-correlation method was found to be unaffected by the Brownian motion, its reciprocal values being proportional to the flowing velocity of the scattering medium. A new technique for velocity measurement was proposed which is applicable to dense colloidal media. Less