相干性对PIE成像方法的影响

分析了相干性对PIE（Ptychographic Iterative Engine）成像技术的影响,指出光源相干性不理想将会引起再现结果中各个频谱分量强度相对于其真实值发生相对变化,而且这种变化随着相干系数的降低而逐步增大.由于实际再现结果是很多可能再现像的线性组合,因而往往包含很多的噪声或细节扭曲,同时当物体衍射能力较弱而零级衍射很强的情况下,高阶衍射间的干涉可以忽略,所得的再现结果相对于原始物体有明显的相位对比度弱化,但由于衍射场仅仅发生强度的减弱而相位并未改变,所以再现像仍然可以较好地反应物体的真实结构信息.

Influence of the partial coherence to the PIE imaging method

The influence of the coherency of the illumination to the PIE （Ptychographic Iterative Engine） imaging method is theoretically investigated and verified by computer simulation. It was pointed out that the partial coherency of the illumination will introduce some changes in the intensity of the spatial components in the reconstruction with PIE, This kind of change always becomes remarkable with the decreasing coherency of the illumination. The final reconstruction of the PIE is the linear combination of all the possibilities and thus always includes noise or distortions Furthermore, when the sample is weak enough, the high order diffractions will be much weak than the zero-order diffraction, and their interference between each other is negligible. The phase contract of the reconstruction can be obviously weak than that of the real object. However, since phase of the diffractions keeps unchanged while their strength is reduced, the reconstruction of partial coherence can still indicate the real structure of the object well.