Load-balancing multi-LCD light field display

The spatio-angular resolution of a light field (LF) display is a crucial factor for delivering adequate spatial image quality and eliciting an accommodation response. Previous studies have modelled retinal image formation with an LF display and evaluated whether accommodation would be evoked correctly. The models were mostly based on ray-tracing and a schematic eye model, which pose computational complexity and inaccurately represent the human eye population's behaviour. We propose an efficient wave-optics-based framework to model the human eye and a general LF display. With the model, we simulated the retinal point spread function (PSF) of a point rendered by an LF display at various depths to characterise the retinal image quality. Additionally, accommodation responses to the rendered point were estimated by computing the visual Strehl ratio based on the optical transfer function (VSOTF) from the PSFs. We assumed an ideal LF display that had an infinite spatial resolution and was free from optical aberrations in the simulation. We tested points rendered at 0-4 dioptres of depths having angular resolutions of up to 4x4 viewpoints within a pupil. The simulation predicted small and constant accommodation errors, which contradict the findings of previous studies. An evaluation of the optical resolution on the retina suggested a trade-off between the maximum achievable resolution and the depth range of a rendered point where in-focus resolution is kept high. The proposed framework can be used to evaluate the upper bound of the optical performance of an LF display for realistically aberrated eyes, which may help to find an optimal spatio-angular resolution required to render a high quality 3D scene.

When employing the light field method with standard lens array and the holographic functional screen (HFS) to realize the tabletop three-dimensional (3D) display, the viewing area of the reconstructed 3D images is right above the screen. As the observers sit around the table, the generated viewpoints in the middle of the viewing area are wasteful. Here, a 360-degree viewable light-field display system is demonstrated, which can present 3D images to multiple viewers in ring-shaped viewing range. The proposed display system consists of the HFS, the aspheric conical lens array, a 27-inch LCD with the resolution of 3840×2160, the LEDs array and the Fresnel lens array. By designing the aspheric conical lens, the light rays emitting from the elemental images forms the viewpoints in a ring-type arrangement. And the corresponding coding method is given. Compared with the light field display with standard lens array, the viewpoint density is increased and the aliasing phenomenon is reduced. In the experiment, the tabletop light-field display based on aspheric conical lens array can present high quality 360-degree viewable 3D image with the right perception and occlusion.

This chapter discusses the topic of emerging light field displays from a signal processing perspective. Light field displays are defined as devices which deliver continuous parallax along with the focus and binocular visual cues acting together in rivalry-free manner. In order to ensure such functionality, one has to deal with the light field, conceptualized by the plenoptic function and its adequate parametrization, sampling and reconstruction. The light field basics and the corresponding display technologies are overviewed in order to address the fundamental problems of analyzing light field displays as signal processing channels, and of capturing and representing light field visual content for driving such displays. Spectral analysis of multidimensional sampling operators is utilized to profile the displays in question, and modern sparsification approaches are employed to develop methods for high-quality light field reconstruction and rendering.

In this paper, we present an improved light field display method with wider view range. In our system, two stacked transparent LCDs are used for glasses-free light field display. They modulate the uniform backlight which enters the observer's eyes to approximate the desired light field. The patterns displayed on the LCDs are optimized according to the target light field using an algorithm based on nonnegative matrix factorization (NMF). In order to achieve wider view range and reduce the computational complexity of the pattern optimization, we utilize a small number of sampling views of the light field. To properly choose the subset of the sampling views, a stochastic sampling algorithm is adopted. The effectiveness of the proposed method is demonstrated by the experimental results, and similar light field display results can be generated with reduced sampling views.

Light-field optics is different from conventional image-focusing optics, in which we discuss how correctly an image plane is transferred onto another plane through an optical system. This light-field optics does not deal with an “image” on a plane but conditions of rays in 3D space, instead. As conditions of rays in 3D space represent real 3D scene or 3D objects, 3D object is expressed on 2D plane as encoded data in light-field optics and these recorded data can be decoded back to 3D images reversibly. These exchangeable processes are represented by the relation of light-field camera and light-field display; a 3D image is recorded on 2D plane by a light-field camera, as it is, and is reconstructed from the recorded data by a light-field display. Recorded data on 2D plane by a light-field camera is not a formed image but encoded data. Therefore in light-field optics an optical system is free from limit of optical conjugate. Display plane can be put on any place, for example. Small flat displays can be set on the plane of spectacles instead of lenses and you can see an image through the optical system. It is a thin HMD. An e-book free from reading glasses might be realized in the same way. There are many applications of light-field optics as well as 3D recording and displaying system. I will report theorem of this light field optics and its applications we have made

The discrete nature of multiprojector light field displays results in aliasing when rendering scene points at depths outside the supported depth of field causing visual discomfort. We propose an efficient on-the-fly content-aware real-time depth retargeting algorithm for live 3D light field video to increase the quality of visual perception on a cluster-driven multiprojector light field display. The proposed algorithm is embedded in an end-to-end real-time system capable of capturing and reconstructing light field from multiple calibrated cameras on a full horizontal parallax light field display. By automatically detecting salient regions of a scene, we solve an optimization to derive a non-linear operator to fit the whole scene within the comfortable viewing range of the light field display. We evaluate the effectiveness of our approach on synthetic and real world scenes.

We propose a bifocal computational near eye light field display (bifocal computational display) and structure parameters determination scheme (SPDS) for bifocal computational display that achieves greater depth of field (DOF), high resolution, accommodation and compact form factor. Using a liquid varifocal lens, two single-focal computational light fields are superimposed to reconstruct a virtual object's light field by time multiplex and avoid the limitation on high refresh rate. By minimizing the deviation between reconstructed light field and original light field, we propose a determination framework to determine the structure parameters of bifocal computational light field display. When applied to different objective to SPDS, it can achieve high average resolution or uniform resolution display over scene depth range. To analyze the advantages and limitation of our proposed method, we have conducted simulations and constructed a simple prototype which comprises a liquid varifocal lens, dual-layer LCDs and a uniform backlight. The results of simulation and experiments with our method show that the proposed system can achieve expected performance well. Owing to the excellent performance of our system, we motivate bifocal computational display and SPDS to contribute to a daily-use and commercial virtual reality display.

In this research, a subjective evaluation was conducted to compare the impressions of facial expressions presented by a light field display using the near virtual-image mode and a two-dimensional (2D) display. The goal is to investigate if a real-size three-dimensional image of a human face presented by the light field display has a larger influence on emotions and presents more lifelike face expressions than those presented by the 2D display. The impressions of using the light field display and the 2D display were compared using eight assessment criteria. The constantly changing facial emotions were exhibited on a flat-panel light field display with a screen size of 31.5 in. and a viewing-zone angle of 43.8°. The evaluation results showed that the light-field image had significantly higher evaluation values than the 2D image on the evaluation terms like "sense of affinity," "feeling like touching," "stereoscopic sensation," "fatigue," and "sense of being."

Light field displays offer glasses-free 3D visualization, as observers do not need any viewing device to see the content in 3D. The angular resolution of such displays not only determines the achievable smoothness of the parallax effect, but also shapes the valid viewing area of light field visualization; higher angular resolutions support greater viewing distances. Therefore, the binocular disparity of a light field display with a given angular resolution lessens, fades away as the viewing distance increases, and the once true 3D visualization slowly becomes perceptually equivalent to a common 2D projection. However, as the current use case scenarios of light field technology define relatively close observations, this topic is rather under-investigated. In this paper, we address the binocular disparity of projection-based light field displays. The results of objective and subjective studies are presented, in which multiple viewing distances were used to evaluate binocular disparity. Beyond the separate models, the paper analyzes the correlations between them and discusses potential applications for future use cases.

Three-dimensional light field fusion display system and coding scheme for extending depth of field

We introduce our light field display simulation software that simulates the image observed by a viewer looking at a full parallax light field display. The simulation software uses the display parameters, viewer location and orientation, viewer pupil size and focus location to simulate the image observed by the viewer. This software has been used in simulating full parallax light field displays of various geometry and complexities as well as image processing and full parallax light field compression algorithms. The simulation results follow the real world observations very closely.

This paper introduces novel methods to add new material properties to a light field display, using computationally designed and fabricated pinholes. Most of the surface materials commonly used for LCDs are limited to smooth, transparent materials, such as glass or plastic. In conventional studies, a pinhole-based parallax barrier is employed in the design light field displays. We redefine these method to transform a non-transparent and non-smooth material, such as wood or stone, into a light field display. In this paper, we report on the fabrication process for the pinhole display, and evaluate the relationship between the pinhole and the optical characteristics of fabricated materials. We also report interactive applications including mirror-based light field displays Infinite AR. It realize to change the indicate that depending on viewpoints. We propose the wood display and the stone display as some porpose. We demonstrated a plate fabricated with 100--200 μm m diameter pinholes.

When rendering light field images for a light field display, there is an issue of image quality. To address this issue, we employ the bilinear interpolation for image processing and conduct quantitative data analysis by using Peak Signal‐to‐Noise Ratio (PSNR) and Structural Similarity Index (SSIM) [1].

A new type of laser system, known as a digital laser, was proposed in 2013. Many well-known laser beams with known analytical forms have been successfully generated in digital lasers. However, for a light field that does not have an analytical form, such as a multi-point light field or a light field with an arbitrary lateral distribution, how to generate such a light field from a digital laser has not been explored. The goal of this study was to experimentally explore how to generate an on-demand lateral laser field in a digital laser. In this study, a multi-point Gaussian laser beam was successfully generated in a digital laser by both controlling the range of the laser gain and the modulation of the phase boundary of the end of the cavity. This study then generated laser beams with an on-demand lateral field distribution by generating a superimposed multi-point laser field in a digital laser. Examples of triangles, rectangles, and letter T-shaped light fields produced by digital lasers were experimentally demonstrated. In summary, this study experimentally showed that a laser beam with an on-demand lateral field distribution could be generated in a digital laser by generating a superimposed multi-point laser field in a digital laser, in which a laser gain region covering the entire intra-cavity multi-point light field and the projected SLM (spatial light modulator) modulation function adopting a mimic amplitude mask are both used.

With the development of light-field acquisition technology from two-dimensional (2-D) to three-dimensional (3-D) sensors, point clouds are currently being used in the 3-D reconstruction of light-field imaging. The computational requirements of point cloud processing decrease the efficiency of 3-D object recognition in a light field reconstruction. An optimization strategy is proposed to improve the efficiency of object feature recognition in a 3-D light field reconstruction. The proposed method involves a normal estimation, uniform keypoint sampling, random Monte Carlo sampling, signature of histograms of orientations descriptor extraction, k -dimensional tree matching, and geometric consistency clustering estimation. During the experiments, all scenarios corresponding to each model are tested, 2711 times in three virtual and real international standard databases (i.e., Kinect, Mian, and Clutter). The experimental results indicate that the efficiency of the proposed method is improved by 9.26% on an average with the same accurate recognition rate of 84.67%.