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PhD Defense


Mr Tobias Birnbaum - VUB-ETRO [Email]


For wave phenomena, the holographic principle describes how, based upon light
propagation laws and a recording of the amplitude and the phase of a wave
front in one place – called a hologram – a wave front in another place can be
obtained. The holographic principle can be applied to, among others any
electro-magnetic wave. It has great impact on applications such as holographic
microscopy, interferometry and non-destructive testing.
Applied to visible light, holograms allow seamless observation of 3D content
without any distortions or adversary effects such as mismatching visual cues. At
sufficient space-frequency bandwidths, holograms become optically
indistinguishable from reality and can be refocused at observation time. When
those high-quality holograms became digitally accessible due to advances in
processing power in recent years, manipulation, duplication, and computergeneration from purely synthetic content became feasible. Applied to
macroscopic content, the most
promising applications include preservation of cultural treasures, art,
entertainment, educational purposes, medical imaging, surgical assistance, big
data visualizations, and computer aided design.
However, digital holograms can only convey as much information because of
their large space-frequency bandwidths resulting in resolutions of several
gigapixel. Thus compression becomes a necessity, especially for dynamic
content. As holograms of visible light are based on the interference of diffracted
coherent light, they look similar to the patterns visible on the surface of a pond,
after throwing a hand full of pebbles into. In a numerical hologram, typically,
each point in the scene influences every point in the hologram. Both facts
together render signal
characteristics of holograms conceptually very different from regular images
and videos, and thus novel strategies to compress dynamic holograms need to
be investigated.
This PhD thesis consists of several aspects necessary to design such strategies
as well as a first proposition of a holographic video codec suitable for multipleindependently objects. Most contributions exploit heavily the concepts of spatial
frequency (number of lines per unit length) and optical phase-space (also
known as space-frequency or time-frequency domain). The novel contributions
include: compression of static Fourier holograms based on wave atoms
refinement of a STFT based static compresion scheme suited for all DH types a
segmentation of
holograms corresponding to scenes of multiple independently moving objects
and resulting from it, a generic holographic motion compensation scheme for
such scenes. From the latter an inter-frame compression strategy is derived and
a generic video compression scheme is proposed. Further contributions concern,
various contributions to subjective quality assessment of digital holograms a
newly proposed versatile similarity measure for complex numbers and studies
on speckle denoising of the back-propagated wave fields with the objective to
find lowcomplexity algorithms with acceptable visual performance.


Short CV

Diploma in applied mathematics, TU Bergakademie Freiberg, 2016


Date: 31.03.2022

Time: 16:00

Location: Room D.2.01 Building D

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