HoloHDR: Multi-color Holograms Improve Dynamic Range

Holographic displays generate Three-Dimensional (3D) images by displaying single-color holograms time-sequentially, each lit by a single-color light source. However, representing each color one by one limits peak brightness and dynamic range in holographic displays. This paper introduces a new driving scheme, HoloHDR, for realizing higher dynamic range images in holographic displays. Unlike the conventional driving scheme, in HoloHDR, three light sources illuminate each displayed hologram simultaneously at various brightness levels. In this way, HoloHDR reconstructs a multiplanar three-dimensional target scene using consecutive multi-color holograms and persistence of vision. We co-optimize multi-color holograms and required brightness levels from each light source using a gradient descent-based optimizer with a combination of application-specific loss terms. We experimentally demonstrate that HoloHDR can increase the brightness levels in holographic displays up to three times with support for a broader dynamic range, unlocking new potentials for perceptual realism in holographic displays.Comment: 10 pages, 11 figure

Non-iterative phase hologram computation for low speckle holographic image projection

Phase-only spatial light modulators (SLMs) are widely used in holographic display applications, including holographic image projection (HIP). Most phase computer generated hologram (CGH) calculation algorithms have an iterative structure with a high computational load, and also are prone to speckle noise, as a result of the random phase terms applied on the desired images to mitigate the encoding noise. In this paper, we present a non-iterative algorithm, where simple Discrete Fourier Transform (DFT) relations are exploited to compute phase CGHs that exactly control half of the desired image samples (those on even - or odd - indexed rows - or columns) via a single Fast Fourier Transform (FFT) and trivial arithmetic operations. The encoding noise appearing on the uncontrolled half of the image samples is reduced by the application of structured, non-random initial phase terms so that speckle noise is also kept low. High quality reconstructions are obtained under temporal averaging of several SLM frames. Interlaced video within half of the addressable image area is readily deliverable without frame rate division. Our algorithm provides about 6X and 20X reduction in computational cost compared to IFTA and FIDOC algorithms, respectively. Simulations and experiments verify that the algorithm constitutes a promising option for real-time computation of phase CGHs

Supporting Acting Performances Through Mixed Reality and Virtual Environments

Motion capture actors need to deal with short preparation times and highly rely on their acting and imagination skills. To support these actors, we developed a mixed reality application that allows showing digital acting environments while performing and tested our prototype with 6 traditionally trained theatre and TV actors. As a result, these 6 actors indicated that our application supported them getting into the demanded acting moods with less unrequired emotions. The acting scenario was also better understood with less need of explanation than when just discussing the scenario, as commonly done in theatre acting

Dynamic Characterization of MEMS Scanners

A simple yet precise optical characterization technique for beam scanning devices is proposed. The method uses a single photodetector to measure various dynamic characteristics of scanning devices, including frequency, scan angle, scan phase, and the mechanical quality factor, given that the scan waveform is known. A quantitative performance analysis and a set of experimental characterization results are presented. Experimentally 0.007 % scan angle measurement accuracy is demonstrated and it is shown that it can be improved