相干调制X光成像技术研究

We plan to develop a new type of single-shot "lensless" imaging technique called coherent modulation imaging (CMI). The technique is based on solving the phase problem well-known in the physics in reconstructing the exit-wave of a sample. A spatial phase modulator is introduced downstream of the sample which helps to remove the ambiguous solutions of the phase problem and thus results in fast convergence. The existence of ambiguous solutions has been a long-time challenge which would cause the phasing algorithm stagnates and fails. The CMI method is suitable for any kind of samples including extended samples, or complex-valued samples for which the current single-shot methods are difficult to apply. There is only one measurement needed in CMI, making it particularly suitable for the investigation of ultra-fast sample dynamics. The spatial resolution is only limited by the wavelength of radiation, the angular size of recorded data, and the sample damage. The underlying mathematical mechanism of this scheme will be studied and experiments in transmission, reflection, as well as Bragg geometry, will be implemented. The technique is expected to have broad applications in materials science and biology science among others.

发展一种新型的相干X光显微成像技术。该技术通过算法求解物理学中的相位问题从而重构出光通过物体后的波前分布。通过在样品后引入波前调制解决了长期困扰相位恢复成像研究中的解不唯一带来的算法不收敛问题。该技术可同时获得样品损耗及准确定量的样品相位信息。适用于各种物体包括延展型物体和同时具有复杂损耗及相位变化的物体。只需要单次测量适合快速动态过程研究。空间分辨率仅受限于辐射源波长和记录数据的数值孔径。将研究该方法的数学机理，并在透射，反射和布拉格反射等不同实验几何上实现该方法。发展的技术在材料科学，生物学上具有极大的应用前景。

以叠层扫描成像为代表的相干衍射成像技术在过去的20年获得了巨大的进步，已经成为各大同步辐射光源成像线站的一个主流技术。 然而叠层成像技术需要对样品进行多次测量不适合动态过程的研究。 申请人提出的相干调制成像（CMI）技术具有和叠层类似的算法收敛性能。作为单次成像技术，CMI特别适合瞬态过程成像。 本项目旨在完善和扩展相干调制成像技术。.主要的研究内容包括：近场实验几何，低相干性的影响，调制器函数的自动获得，单次谱（多波长）成像；布拉格实验几何BCMI；位置矫正算法；相干调制成像和叠层成像混合技术； 这些研究内容都获得了明确的进展。为在低相干光源（电镜）和强脉冲光源（自由电子激光器）上实现该技术铺平了道路。为实现大动态范围表面测量和单次谱学成像提供了新的有特色的方法。 发表了14篇文章， 第一标注10篇；申请了3项发明专利，其中1个为PCT专利申请。

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