菲涅耳衍射区和夫琅和费衍射区的动态部分相干光散斑场特性

Study on the properties of the dynamic partially coherent speckle in the Fresnel and Fraunhofer diffraction regions

研究了菲涅耳衍射区和夫琅和费衍射区动态部分相干光散斑的特性 .利用部分相干光互强度传播的理论 ,得出了在部分相干光照明时 ,由运动散射体产生的动态散斑光强时空交叉的自相关函数的一般形式 ,并由此得出了散斑沸腾和平移的一般规律 .通过适当选择光源和调整光路参数 ,在实验上得到了菲涅耳和夫琅和费衍射区的部分相干光散斑 ,对夫琅和费面上的动态部分相干光散斑的平移和沸腾现象进行了定性研究 ;采用光子计数及数据自动采集的方法 ,对部分相干光散斑随时间的演化及动态部分相干光散斑的沸腾进行了定量测量 .这些实验结果与理论结果相符合 .

We have studied the properties of the dynamic partially coherent speckles in the Fresnel and Fraunhofer diffraction regions. We use the theory of propagation of the mutual intensity in partially coherent light, and derive the general form of the spatio-temporal cross-correlation functions of the dynamic speckle intensities produced by a moving diffusing object. Based on these theoretical expressions, the characteristics of the movement and the boiling of the dynamic partially coherent speckles are discussed. By choosing the proper extended incoherent light source and by adjusting the parameters of the optical setup, we have observed experimentally the partially coherent speckle in the Fresnel and Fraunhofer diffraction regions. Then we study qualitatively the movement and the boiling of the speckles. Using techniques of photon counting and automatic data acquisition, we have measured the temporal evolution of the speckle intensity in the Fraunhofer plane as the object moves, and thus measured the cross-correlation of the speckles versus the temporal increment. The experimental data are in agreement with the theoretical results.