London Centre for Nanotechnology, University College London, London WC1E 6BT, UK.
Research Complex at Harwell, Harwell Campus, Didcot OX11 0FA, UK.
Nat Commun. 2016 Nov 18;7:13367. doi: 10.1038/ncomms13367.
Phase retrieval is a long-standing problem in imaging when only the intensity of the wavefield can be recorded. Coherent diffraction imaging is a lensless technique that uses iterative algorithms to recover amplitude and phase contrast images from diffraction intensity data. For general samples, phase retrieval from a single-diffraction pattern has been an algorithmic and experimental challenge. Here we report a method of phase retrieval that uses a known modulation of the sample exit wave. This coherent modulation imaging method removes inherent ambiguities of coherent diffraction imaging and uses a reliable, rapidly converging iterative algorithm involving three planes. It works for extended samples, does not require tight support for convergence and relaxes dynamic range requirements on the detector. Coherent modulation imaging provides a robust method for imaging in materials and biological science, while its single-shot capability will benefit the investigation of dynamical processes with pulsed sources, such as X-ray free-electron lasers.
相位恢复是一种在仅能记录波场强度的情况下进行成像的长期存在的问题。相干衍射成像是一种无透镜技术，它使用迭代算法从衍射强度数据中恢复幅度和相位对比图像。对于一般的样品，从单个衍射图案中进行相位恢复一直是算法和实验上的挑战。在这里，我们报告了一种使用样品出射波的已知调制进行相位恢复的方法。这种相干调制成像方法消除了相干衍射成像的固有模糊性，并使用了一种可靠的、快速收敛的涉及三个平面的迭代算法。它适用于扩展的样品，不需要严格的收敛支撑，并且放宽了对探测器的动态范围要求。相干调制成像为材料和生物科学中的成像提供了一种稳健的方法，而其单次拍摄能力将有利于利用脉冲源（如 X 射线自由电子激光器）研究动态过程。
