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Picometer Detection by Adaptive Holographic Interferometry
Published in Klaus D. Sattler, Fundamentals of PICOSCIENCE, 2013
Attempts to work around the phase problem in the x-ray crystallography community include (i) heavy-element substitution, (ii) direct methods, and (iii) anomalous scattering (Ladd and Palmer, 2003). Under very favorable conditions, iterative phase retrieval techniques can extract wavelength-limited images from nonperiodic x-ray (Miao et al., 1999; Abbey et al., 2008) and electron (Zuo et al., 2003) diffraction patterns. In these "coherent diffractive imaging" (CDI) techniques, a diffraction pattern is acquired from a specimen surrounded by an area of fixed phase-the "support." Repetitive Fourier transformations of diffraction data that include scattering from the support converge on a function that represents the amplitude and phase of the specimen and surroundings.
Chiral surface spin textures in Cu2OSeO3 unveiled by soft X-ray scattering in specular reflection geometry
Published in Science and Technology of Advanced Materials, 2022
V. Ukleev, C. Luo, R. Abrudan, A. Aqeel, C. H. Back, F. Radu
A sketch of the experimental geometry is shown in Figure 1(a). The XRMS experiment was carried out at the dipole beamline PM-3 [58] of the BESSY II synchrotron (Helmholtz-Zentrum Berlin, Germany) using the recently commissioned ALICE-II station dedicated to soft X-ray scattering and coherent diffraction imaging, an upgraded version of ALICE [59]. The main new capability of ALICE-II is that the chamber accommodates a large scattered angle for the two-dimensional (2D) charge coupled device (CCD) detector (up to = 144), as shown in Figure 1(b). This is achieved by choosing the entrance flange that meets the required reflected angle for the CCD. The CCD itself can be mounted at two different distances with respect to the sample, namely at 28 cm and at 80 cm, referred to as low-resolution and high-resolution options, respectively. Recent upgrade of the endstation includes motorized beamstop available for both experimental configurations. Practically, in the low-resolution setting, the CCD chip can accommodate a reciprocal space representing up to nm lateral structures at a resonant energy of Cu, and for all available scattering angles.
Median momentum reweighted amplitude flow for phase retrieval with arbitrary corruption
Published in Journal of Modern Optics, 2021
Zhang Quanbing, Liu Dequn, Hu Feihang, Li Aoya, Cheng Hong
It is well known that a great deal of the information available in an optical system resides in the phase; however, ordinary optical detectors cannot measure the phase due to the very high frequency of light [1]. Phase retrieval methods are able to recover the phase from available amplitude or intensity measurements and have proved very important in practice. This problem is prevalent in coherent diffraction imaging [2], X-ray crystallography [3], Fourier ptychography [4], and other areas [5–7].