简便快速的纳米分辨中能X射线成像相位提取方法

Synchrotron radiation based full-field x-ray microscopy has significant applications in materials and cell imaging thanks to its non-destructive nanometer-resolution 3D imaging ability. As an important tool, however, conventional soft x-ray microscopy has a quite limited focal depth, therefore is inappropriate for imaging cells larger than 5 um. Another important tool, hard x-ray microscopy, does have a rather large focal depth, but inevitably accompanied with very low image contrast due to the high penetration power of hard x-rays to biological specimens. Recently, a novel x-ray microscopy technique has been suggested with both an acceptable large focal depth as well as a high contrast to biological specimens, using Zernike phase contrast mechanism with intermidiate enery x-rays. This NSFC proposal aims at solving the phase retrieval problem possibly existed in intermediate enery x-ray Zernike microscopy by introducing the idea of Nomarski differential interferential microscopy, therefore offers an improved differential phase contrast imaging method. Compared with conventional x-ray Zernike phase contrast method and other existing quantitative phase retrieval methods, the suggested method can retrieve accurate phase and absorption information in a single shot, therefore provides better data for 3D tomography reconstruction of large cells. The goal of this proposal is: offering a quantitative 3D observation tool to various scientific researches with advantages of nanometer-resolution and high accuracy.

同步辐射X射线全场显微术能够对样品进行无损、三维、纳米分辨的成像，在材料、生命科学等领域、特别是完整细胞显微术方面有重要应用。但是传统软X射线显微术的焦深有限，不适用于直径大于5微米的细胞；另一方面，硬X射线显微术虽然焦深大，但是因其穿透力太强而对生物样品的成像衬度非常低。新近提出的中能X射线泽尼克显微术很好地弥补了两者的不足，能够对几十微米大小的细胞进行高衬度显微成像。本课题拟针对中能泽尼克相衬显微术中存在的相位提取问题，通过引入Nomarski微分干涉的思想，提出基于X射线双频光栅的微分干涉相衬成像方案。相比于传统的泽尼克相衬方案和其他定量相衬方案，本方案能够更为简便、快速地获取相位与吸收信息，进而为大细胞的折射率三维重建提供准确的数据。本课题的研究将为国内众多学科领域、特别是生命科学，提供更为方便准确的纳米形貌表征手段。

同步辐射X射线全场显微术能够对样品进行无损、三维、纳米分辨的成像，在材料、生命科学等领域、特别是完整细胞显微术方面有重要应用。但是传统的泽尼克相衬显微术中存在的相位与吸收信息混迭的问题。课题通过引入Nomarski微分干涉的思想，提出基于X射线双频光栅的微分干涉相衬成像方案。相比于传统的泽尼克相衬方案和其他定量相衬方案，本课题方案能够更为简便、快速地获取相位与吸收信息，进而为大细胞的折射率三维重建提供准确的数据。经过课题的研究，针对同步辐射TXM平台设计的微分相位提取方案能够高效准确地分离吸收的影响，为折射率CT重建提供正确的图像信息。根据计算，在理想pi/2相位双频光栅的情况下，±1级衍射像的强度效率合计超过1/2；对于5.4keV能量下的Ni双频光栅，理论效率也能够达到30%。而这种方法的一大优点是：若探测器横向尺寸达到普通探测器的三倍，则完全可以免除任何步进操作一次性获取所有信息（现阶段实验只能通过移动探测器来等效大尺寸探测器）。本方法相对于其它TXM平台定量相移提取方案，具有兼容性高、采集简便快速的特点，有望在未来的X射线纳米成像线站中作为传统Zernike方案的有益补充。