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lüll Phase recovery and lensless imaging by iterative methods in optical, X-ray and electron diffraction Spence JC; Weierstall U; Howells MPhilos Trans A Math Phys Eng Sci 2002[May]; 360 (1794): 875-95Thomas Young's quantitative analysis of interference effects provided the confidence needed to revive the wave theory of light, and firmly established the concept of phase in optics. Phase plays a similarly fundamental role in matter-wave interferometry, for which the field-emission electron microscope provides ideal instrumentation. The wave-particle duality is vividly demonstrated by experimental 'Young's fringes' using coherent electron beams under conditions in which the flight time is less than the time between particle emission. A brief historical review is given of electron interferometry and holography, including the Aharonov-Bohm effect and the electron Sagnac interferometer. The simultaneous development of phase-contrast imaging at subnanometre spatial resolution has greatly deepened our understanding of atomic processes in biology, materials science and condensed-matter physics, while electron holography has become a routine tool for the mapping of electrostatic and magnetic fields in materials on a nanometre scale. The encoding of phase information in scattered farfield intensities is discussed, and non-interferometric, non-crystallographic methods for phase retrieval are reviewed in relationship to electron holography. Examples of phase measurement and diffraction-limited imaging using the hybrid input-output iterative algorithm are given, including simulations for soft X-ray imaging, and new experimental results for coherent electron and visible-light scattering. Image reconstruction is demonstrated from experimental electron and visible-light Fraunhofer diffraction patterns. The prospects this provides for lensless imaging using particles for which no lenses exist (such as neutrons, condensates, coherent atom beams and X-rays) are discussed. These new interactions can be expected to provide new information, perhaps, for example, in biology, with the advantage of less damage to samples.|*Algorithms[MESH]|Holography/instrumentation/methods[MESH]|Humans[MESH]|Image Enhancement/instrumentation/*methods[MESH]|Lenses[MESH]|Microscopy, Electron/instrumentation/*methods[MESH]|Microscopy, Interference/instrumentation/*methods[MESH]|Phantoms, Imaging[MESH]|X-Ray Diffraction/instrumentation/*methods[MESH] |