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ERC

INTERFERE Report Summary

Project ID: 617779
Funded under: FP7-IDEAS-ERC
Country: Belgium

Mid-Term Report Summary - INTERFERE (Sparse Signal Coding for Interference-based Imaging Modalities)

In recent years, the domain of plenoptic imaging – for which holography is a key enabling modality – has known significant scientific and industrial evolutions. In this context, the ERC INTERFERE project stands on a matured vision of a future end-to-end holographic television system. Summarized, such systems are envisioned to use heterogeneous signal sources, originating from light field sensors and camera arrays, point cloud scanners, time-of-flight (TOF) cameras, holographic sensing devices (for miniature scenes), that are subsequently converted to a generic, sparse, holographic representation format, utilizing computer generated holography (CGH) techniques. From this holographic ‘information container’, a continuum of views can be extracted that serves as input for e.g. holographic head mounted display (HMD) devices or interactive holographic visualization tables. How to efficiently generate and represent this holographic information is a key question that is being addressed by INTERFERE. Research in the context as well as the associated dissemination actions have been steered along this vision.
INTERFERE delivered novel technologies and methodologies at microscopic and macroscopic scales. The research addressed the problem as a whole from capture, representation, transmission and final display of complex amplitude holograms. For example, a state-of-the-art CGH technique using point cloud data allows for very efficient hologram generation with accurate occlusion culling.This technique is input-sensitive in the sense that running time depends on the size of the point cloud light source and not on the definition of the computed hologram. Important advances on mathematical methods for processing complex amplitudes has been made. A novel modulo wavelet transform based on a fast lifting scheme processes phase data to allow for fast phase unwrapping in 4D profilometry. A new unitary transform models the diffraction between arbitrary (non-planar) surfaces: these transforms are reversible and therefore generalize Fresnelets to non-planar target spaces and hence are allowing for more efficient representations of deep holographic scenes.
Since today, no large consumer-rate holographic screens are technically feasible, many results of INTERFERE are more directly applicable at the microscopic scale. For example, a theoretically optical design of the distance from sample to the detector, in terms of assumed sparsity in the image reconstruction domain: hence, this design methodology provides guidelines for configuring a compressed sensing setup for holographic capturing. A novel phase-coded holography methodology for in-line holography has been designed, allowing zero-order free reconstructions with arbitrary reference beams. A state of the art holographic image codec has been implemented, based on packet and directional wavelet transforms. It provides excellent rate distortion performance for both microscale and macroscale holographic content.
Holograms are recordings of constructive and destructive light interference patterns and the signal is very different from natural imagery. Therefore, adapted quality assessment metrics and procedures had to be designed. A generalized objective quality metric based on sparse coding that is suitable for both classic and holographic image content provides similar performance to state of the art quality metrics. A novel prediction accuracy analysis uses the separation ratio for each partial quality estimator, which allows for accurately evaluating the response of quality metrics given certain stimuli. Subjective quality assessment procedures for holographic data which are based on alternative rendering modalities such as regular 2D displays and/or autostereoscopic light field displays allow for effective testing of the structural integrity of the information contained by the holograms.

Reported by

VRIJE UNIVERSITEIT BRUSSEL
Belgium
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