672 research outputs found
Shedding Light on Diatom Photonics by means of Digital Holography
Diatoms are among the dominant phytoplankters in the worl's ocean, and their
external silica investments, resembling artificial photonics crystal, are
expected to play an active role in light manipulation. Digital holography
allowed studying the interaction with light of Coscinodiscus wailesii cell wall
reconstructing the light confinement inside the cell cytoplasm, condition that
is hardly accessible via standard microscopy. The full characterization of the
propagated beam, in terms of quantitative phase and intensity, removed a
long-standing ambiguity about the origin of the light. The data were discussed
in the light of living cell behavior in response to their environment
When holography meets coherent diffraction imaging
Modern imaging techniques at the molecular scale rely on utilizing novel
coherent light sources like X-ray free electron lasers for the ultimate goal of
visualizing such objects as individual biomolecules rather than crystals. Here,
unlike in the case of crystals where structures can be solved by model building
and phase refinement, the phase distribution of the wave scattered by an
individual molecule must directly be recovered. There are two well-known
solutions to the phase problem: holography and coherent diffraction imaging
(CDI). Both techniques have their pros and cons. In holography, the
reconstruction of the scattered complex-valued object wave is directly provided
by a well-defined reference wave that must cover the entire detector area which
often is an experimental challenge. CDI provides the highest possible, only
wavelength limited, resolution, but the phase recovery is an iterative process
which requires some pre-defined information about the object and whose outcome
is not always uniquely-defined. Moreover, the diffraction patterns must be
recorded under oversampling conditions, a pre-requisite to be able to solve the
phase problem. Here, we report how holography and CDI can be merged into one
superior technique: holographic coherent diffraction imaging (HCDI). An inline
hologram can be recorded by employing a modified CDI experimental scheme. We
demonstrate that the amplitude of the Fourier transform of an inline hologram
is related to the complex-valued visibility, thus providing information on
both, the amplitude and the phase of the scattered wave in the plane of the
diffraction pattern. With the phase information available, the condition of
oversampling the diffraction patterns can be relaxed, and the phase problem can
be solved in a fast and unambiguous manner.Comment: 22 pages, 7 figure
Phase Retrieval via Matrix Completion
This paper develops a novel framework for phase retrieval, a problem which
arises in X-ray crystallography, diffraction imaging, astronomical imaging and
many other applications. Our approach combines multiple structured
illuminations together with ideas from convex programming to recover the phase
from intensity measurements, typically from the modulus of the diffracted wave.
We demonstrate empirically that any complex-valued object can be recovered from
the knowledge of the magnitude of just a few diffracted patterns by solving a
simple convex optimization problem inspired by the recent literature on matrix
completion. More importantly, we also demonstrate that our noise-aware
algorithms are stable in the sense that the reconstruction degrades gracefully
as the signal-to-noise ratio decreases. Finally, we introduce some theory
showing that one can design very simple structured illumination patterns such
that three diffracted figures uniquely determine the phase of the object we
wish to recover
Isotropic-Resolution Tomographic Diffractive Microscopy
International audienceMicroscopy techniques based on recording of the optical field diffracted by the specimen, in amplitude and phase, like Digital Holographic Microscopy (DHM) have been a growing research topic in recent years. Tomographic acquisitions are possible if one is able to record information, while controlling variations of the specimen illumination. Classical approaches consider either illumination variation, simple to implement, but suffering fro the classical "missing cone" problem, or sample rotation, delivering images with quasi-isotropic, but lower resolution. We have developed an original-, combined tomographic diffractive microscope setup, making use of specimen rotation as well as illumination rotation, which is able to deliver images with an almost isotropic resolution better than 200 nm
Roadmap on structured light
Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized.Peer ReviewedPostprint (published version
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