Holographic imaging modalities are gaining increasing interest in various application domains ranging from microscopy to high-end autostereoscopic displays. While much effort has been spent on the development of the optics, photonics and micro/nano-electronics that enable the design of holographic capturing and visualization devices, relatively few research effort has been targeted towards the underlying signal processing. One significant challenge relates to the fact that the data volumes needed in support of this kind of holographic applications is rapidly increasing: for visualization devices, and in particular holographic displays, unprecedented resolutions are desired resulting in huge bandwidth requirements on both the communication channels and internal computing and data channels. An additional challenge relates to the fact that we are handling an interference-based modality being complex amplitude based in nature. Both challenges lead to the fact that for example classic data representations and coding solutions fail to handle holographic data in an effective way. This paper attempts to provide some insights that enable to alleviate or a least reduce these bottlenecks and sketch an avenue for the development of efficient source coding solutions. Moreover, it will also outline the efforts the JPEG committee is undertaking in the context of the JPEG Pleno standardization programme to roll out a path for data interoperability of holographic solutions.
Holograms, either optically acquired or simulated numerically from 3D datasets, such as point clouds, have
special rendering requirements for display. Evaluating the quality of hologram generation techniques is not
straightforward, since high-quality holographic display technologies are still immature, In this paper we present
a framework for three-dimensional rendering of colour computer-generated holograms (CGHs) acquired from
point-clouds, on high-end light field displays. This allows for the rendering of holographic content with horizontal
parallax and wide viewing angle. We deploy prior work, namely a fast CGH method that inherently handles
occlusion problems to acquire high quality colour holograms from point clouds. Our experiments showed that
rendering holograms with the proposed framework provides 3D effect with depth disparity and horizontal-only
with wide viewing angle. Therefore, it allows for the evaluation of CGH techniques regarding functional properties
such as depth cues and efficient occlusion handling.
Digital holography is mainly used today for metrology and microscopic imaging and is emerging as an important potential technology for future holographic television. To generate the holographic content, computer-generated holography (CGH) techniques convert geometric descriptions of a 3D scene content. To model different surface types, an accurate model of light propagation has to be considered, including for example, specular and diffuse reflection. In previous work, we proposed a fast CGH method for point cloud data using multiple wavefront recording planes, look-up tables (LUTs) and occlusion processing. This work extends our method to account for diffuse reflections, enabling rendering of deep 3D scenes in high resolution with wide viewing angle support. This is achieved by modifying the spectral response of the light propagation kernels contained by the look-up tables. However, holograms encoding diffuse reflective surfaces depict significant amounts of speckle noise, a problem inherent to holography. Hence, techniques to improve the reduce speckle noise are evaluated in this paper. Moreover, we propose as well a technique to suppress the aperture diffraction during numerical, viewdependent rendering by apodizing the hologram. Results are compared visually and in terms of their respective computational efficiency. The experiments show that by modelling diffuse reflection in the LUTs, a more realistic yet computationally efficient framework for generating high-resolution CGH is achieved.
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