Publication Details



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 multiple independently 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 low complexity algorithms with acceptable visual performance.