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Near-eye holographic displays are the holy grail of wear-on 3D display devices because they are intended to project realistic wide-angle virtual scenes with parameters matching human vision. One of the key features of a realistic perspective is the ability to move freely around the virtual scene. This can be achieved by addressing the display with wide-angle computer-generated holograms (CGHs) that enable continuous viewpoint change. However, to the best of our knowledge there is no technique able to generate these types of content. Thus, in this work we propose an accurate and non-paraxial hologram update method for wide-angle CGHs that supports continuous viewpoint change around the scene. This method is based on the assumption that with a small change in perspective, two consecutive holograms share overlapping data. This enables reusing the corresponding part of the information from the previous view, eliminating the need to generate an entirely new hologram. Holographic information for the next viewpoint is calculated in two steps: first, a tool approximating the Angular Spectrum Propagation is proposed to generate the hologram data from previous viewpoint; and second, the efficient Phase Added Stereogram algorithm is utilized for generating the missing hologram content. This methodology offers fast and accurate calculations at the same time. Numerical and optical experiments are carried out to support the results of the proposed method. [ABSTRACT FROM AUTHOR]

Featured Application: Visually interpretable phase space representations can aid the development of new methodologies in digital holography in general and can be evaluated for any digital hologram. Concrete applications presented in the paper are: coarse scene depth estimation, scene analysis, and digital hologram (processing) artifact analysis. Digital holograms are a prime example for signals, which are best understood in phase space—the joint space of spatial coordinates and spatial frequencies. Many characteristics, as well as optical operations can be visualized therein with so called phase space representations (PSRs). However, literature relies often only on symbolic PSRs or on, in practice, visually insufficient PSRs like the Wigner–Ville representation. In this tutorial-style paper, we will showcase the S-method, which is both a PSR that can be calculated directly from any given signal, and that allows for a clear visual interpretation. We will highlight the power of space-frequency analysis in digital holography, explain why this specific PSR is recommended, discuss a broad range of basic operations, and briefly overview several interesting practical questions in digital holography. Data Set: www.erc-interfere.eu Data Set License: CC-BY-NC-SA [ABSTRACT FROM AUTHOR]

A novel approach for color holographic 3D displays employing several liquid crystal based spatial light modulators (SLM) is presented. A multicolor reconstruction is introduced into circular monochrome display architecture with horizontal-only-parallax through the use of space-division method (SDM). In the SDM active area of an SLM is divided into three regions generating the RGB component images by using color spatial filter composed of a three glass stripes that are attached to the front of each SLM. Relatively low complexity level of SDM enables to upgrade a horizontal-only-parallax monochrome display to a color one at the expense of image resolution. There is no reduction of remaining key performance parameters, i.e., image dimensions, refresh frame rate, and viewing angle are preserved with no increase of SLM number. In this paper, practical aspects of color imaging implementation, including filter mask design and hardware calibration, are considered. Developed procedures focus on major three effects, i.e., spectral calibration of response of highly dispersive SLM phase, spatial calibration of filter mask and numerical alignment of RGB imaging volumes. The presented experimental results of static and dynamic 3D reconstructions of computer generated holograms validate the performance of calibration procedures and the high color imaging quality of the display. [ABSTRACT FROM PUBLISHER]

Optical Diffraction Tomography is a technique for retrieving a 3-dimensional refractive index distribution from phase objects without destroying the structure of the samples. In the article we discuss the selection and implementation of full and limited angle version of tomographic reconstruction processes together with the analysis of different methods for gathering projections. We present two efficient implementations of full and limited angle tomographic systems including total processing paths and providing the examplary results of 3-D refractive index determination measurements of biological samples. [ABSTRACT FROM AUTHOR]

Abstract: A rapid autofocusing technique is a fundamental element for a vast range of applications of digital holography. In this paper we propose a new autofocusing method that permits to detect a tilted optimal focus plane. The method is based on estimation of focusing condition of the optical field by evaluating the sharpness in its amplitude distribution. The developed algorithm is fully automated. It consists of two major steps, first the rotation axis is localized from the map of local sharpness and then the angular orientation of the image plane is derived by maximizing the focus of optical fields reconstructed in many subsequent tilted planes. In our study six image sharpness quantification methods are investigated and the numerical propagation between inclined planes is performed with an efficient band limited angular spectrum algorithm. The utility of the proposed method for autofocusing to a tilted image plane is experimentally confirmed in a digital holographic microscopy setup by carrying out a successful reconstruction of holograms of the exemplary amplitude (the 1951 USAF positive target) and phase (a matrix of microlenses) objects. [Copyright &y& Elsevier]

Objective quality assessment of digital holograms has proven to be a challenging task. While prediction of perceptual quality of the recorded 3D content from the holographic wavefield is an open problem; perceptual quality assessment from content after rendering, requires a time-consuming rendering step and a multitude of possible viewports. In this research, we use 96 Fourier holograms of the recently released HoloDB database to evaluate the performance of well-known and state-of-the-art image quality metrics on digital holograms. We compare the reference holograms with their distorted versions: (i) before rendering on the real and imaginary parts of the quantized complex-wavefield, (ii) after converting Fourier to Fresnel holograms, (iii) after rendering, on the quantized amplitude of the reconstructed data, and (iv) after subsequently removing speckle noise using a Wiener filter. For every experimental track, the quality metric predictions are compared to the Mean Opinion Scores (MOS) gathered on a 2D screen, light field display and a holographic display. Additionally, a statistical analysis of the results and a discussion on the performance of the metrics are presented. The tests demonstrate that while for each test track a few quality metrics present a highly correlated performance compared to the multiple sets of available MOS, none of them demonstrates a consistently high-performance across all four test-tracks. • Analysis of the predicted visual quality by the objective quality metrics operating on the hologram plane. • 3D Benchmarking the tested quality prediction methods on numerically reconstructed holograms. • Investigating quality prediction of rendered holograms after speckle denoising. • Assessing the impact of the hologram type, Fresnel or Fourier, on the prediction performance. • General guidelines for deployment of currently available IQMs on holographic content. [ABSTRACT FROM AUTHOR]