Dissertations / Theses on the topic 'Light-field displays'

One of the key issues in conventional stereoscopic displays is the well-known vergence-accommodation conflict problem due to the lack of the ability to render correct focus cues for 3D scenes. Recently several light field display methods have been explored to reconstruct a true 3D scene by sampling either the projections of the 3D scene at different depths or the directions of the light rays apparently emitted by the 3D scene and viewed from different eye positions. These methods are potentially capable of rendering correct or nearly correct focus cues and addressing the vergence-accommodation conflict problem. In this paper, we describe a generalized framework to model the image formation process of the existing light-field display methods and present a systematic method to simulate and characterize the retinal image and the accommodation response rendered by a light field display. We further employ this framework to investigate the trade-offs and guidelines for an optimal 3D light field display design. Our method is based on quantitatively evaluating the modulation transfer functions of the perceived retinal image of a light field display by accounting for the ocular factors of the human visual system. (C) 2017 Optical Society of America

Esta tese descreve métodos interativos para estimar e compensar erros de refração (NETRA) e opacidades ópticas (CATRA) em sistemas de imageamento usando telas de campos de luz programáveis, de alta resolução e alto contraste. Os novos métodos para oftalmologia computacional descritos aqui podem avaliar câmeras e olhos se o usuário do sistema estiver consciente do modelo de interação. A solução combina elementos ópticos baratos, interfaces interativas e reconstrução computacional. Uma tela de campos de luz, posicionada perto do olho, cria objetos virtuais em profundidades pré-definidas através de várias seções do olho. Via esta plataforma, cria-se uma nova gama de aplicações interativas que é extremamente sensível a aberrações ópticas. A capacidade de focar em um objeto virtual, alinhar padrões exibidos na tela e detectar suas variações de forma e brilho permite ao sistema estimar a função de propagação de ponto de luz para o olho e a acomodação da lente. Enquanto os sistemas convencionais requerem formação especializada, dispositivos caros, procedimentos de segurança sensíveis e normalmente não são móveis, esta tese simplifica o mecanismo, colocando o paciente no centro do teste. Ao final, a resposta do usuário calcula a condição de refração em termos de poderes esférico e cilíndrico, o eixo de astigmatismo, o poder de acomodação da lente e mapas para a opacidade, atenuação, contraste e função de espalhamento de um ponto de luz. O objetivo é permitir que o público em geral opere um sistema de iluminação portátil e obtenha uma compreensão de suas próprias condições visuais. Esta tese apresenta projetos ópticos para software e hardware para oftalmologia computacional. Avaliações com usuários e com câmeras com lentes modificadas são realizadas. Os dados compilados são usados para reconstruir visão afetada do indivíduo, oferecendo uma nova abordagem para capturar informações para o rastreio, diagnóstico e análises clínicas de anomalias visuais.
This thesis proposes light-field pre-warping methods for measuring and compensating for optical aberrations in focal imaging systems. Interactive methods estimate refractive conditions (NETRA) and model lens opacities (CATRA) of interaction-aware eyes and cameras using cost-efficient hardware apps for high-resolution screens. Tailored displays use stereo-viewing hardware to compensate for the measured visual aberrations and display in-focus information that avoids the need of corrective eyeglasses. A light-field display, positioned very close to the eye, creates virtual objects in a wide range of predefined depths through different sectors of the eye’s aperture. This platform creates a new range of interactivity that is extremely sensitive to spatially-distributed optical aberrations. The ability to focus on virtual objects, interactively align displayed patterns, and detect variations in shape and brightness allows the estimation of the eye’s point spread function and its lens’ accommodation range. While conventional systems require specialized training, costly devices, strict security procedures, and are usually not mobile, this thesis simplifies the mechanism by putting the human subject in the loop. Captured data is transformed into refractive conditions in terms of spherical and cylindrical powers, axis of astigmatism, focal range and aperture maps for opacity, attenuation, contrast and sub-aperture point-spread functions. These optical widgets carefully designed to interactive interfaces plus computational analysis and reconstruction establish the field of computational ophthalmology. The overall goal is to allow a general audience to operate portable light-field displays to gain a meaningful understanding of their own visual conditions. Ubiquitous, updated, and accurate diagnostic records can make private and public displays show information in a resolution that goes beyond the viewer’s visual acuity. The new display technology is able to compensate for refractive errors and avoid light-scattering paths. Tailored Displays free the viewer from needing wearable optical corrections when looking at it, expanding the notion of glasses-free multi-focus displays to add individual variabilities. This thesis includes proof-of-concept designs for ophthalmatic devices and tailored displays. User evaluations and validations with modified camera optics are performed. Capturing the daily variabilities of an individual’s sensory system is expected to unleash a new era of high-quality tailored consumer devices.

碩士
國立交通大學
光電工程研究所
107
As the development of the technology, the requirements of the display are increasing such as the higher resolution or purer color display. Take stereoscopy for example, in 2009, a movie called Avatar reached a box office record that was difficult to break in history, and its success relied on its breakthrough in 3D movies. Since then, people have invested in the development of stereoscopic display, and the technology of virtual reality (VR) and augmented reality AR come out. AR and VR can make the observer feel the virtual scenes really exist. In addition, AR and VR can not only be used in entertainment, but also be used in many industries such as manufacture, military, education, and medicine. Take AR for example, some AR head-mounted displays (HMDs) are produced by multinationals, like Google Glass or Hololens form Microsoft. However, there still have some issues need to be overcome. Traditional 3D displays generate 3D images by binocular disparity, and these 3D images can have a great depth effect. But, the observer will feel uncomfortable and have visual fatigue due to the mismatch between accommodation and convergence (A.C. conflict). Generally, current AR HMD products need another optical component to guide the panel light to the observer. Therefore, these AR HMDs cannot reach a high field of view (FOV), because of the low using efficiency of the light, and some geometric limitations. The good thing is that some researches about light field technology were proposed. The light field technology can record the intensity and angular information of the light. In addition, we can emit the recorded image and be deflected by the microlens array to reconstruct the light field image. The advantages of the light filed system are that it can provide a monocular focus cue, and the structure can remain compact and lightweight. In our research, a light field HMD structure is proposed. This structure can use twisted nematic (TN) cell and polarizers to control the polarization of incident light and displays the background image and light field image respectively. Then, using the time-multiplexing method by fast switching the voltage on the TN cell to get the AR image. Moreover, because the current transparent high-resolution panel is not mature, we have also proposed an architecture and software simulation to verify the feasibility of the original proposed light field near-eye display.

碩士
國立交通大學
照明與能源光電研究所
107
Nowadays, many researchers dedicate to developing 3D display technology to produce more natural images from displays. Also, glass-free 3D displays are developed and regarded as the next-generation 3D display technology due to the convenience of no glass-wearing necessary. However, there remain some issues of the traditional multi-view display. The most critical one is the visual fatigue caused by the accommodation-convergence conflict after continuously watching the multi-view display. To solve this issue, we design a one-dimensional light field structure. The lens pitch is set as 150 μm and the lens orientation is slanted -54.8 degrees to provide 12-view images on display panel. 　　In this thesis, we utilize the lenticular high-resistance (Hi-R) LC lens array for 2D/3D switchable light field display with compact structure, easy driven method and low driving voltage. In order to obtain an ideal lens with high optical performance, the sheet resistance of Hi-R layer and the ratio of lens aperture to cell gap have been considered. Both would affect the electric field distribution connected to the LC layer. For LC lens array of lens aperture 148 µm and cell gap 15 µm, we apply the proper Hi-R sheet resistance 10 to the power of 8 Ω/sq and then the focusing ability can be maintained superior as the focal length reaches the experimental required value. With analysis of these characteristics of lenticular Hi-R LC lens array, a high image performance 2D/3D switchable light field display is achieved.

碩士
國立臺灣大學
光電工程學研究所
104
Recently, auto-stereoscopic displays are the popular topics. There are many fields which use the auto-stereoscopic display technique. Light field displays are the most important topic in the auto-stereoscopic displays, and the systems require several design modifications to achieve the multi view characteristic of stereoscopic image. In the Master Thesis, we design a laser projection light field 3D display combined with the MEMS laser projectors and light field 3D display. The low cost and scalable system include the advantages of the laser projector and wide view angle. We use the two different diffuser screen and corresponding parameters to build two different systems. We also use the software to simulate two systems and compare the image results with the image results of our real system, and observe how the diffusion angle of the screen affect the image results. The crosstalk value of our system are measured and we compare the results with the other auto-stereoscopic display, and our systems have the better image quality of the crosstalk. We use the subjectivity experiment to define the perceptual depth of human, and we compared the two results with the real condition. The image people saw in the system with smaller are closer to the real object, and we design the experiment to find out how two system offer motion parallax by the number of sub-image. And we estimate how the image close to the full motion parallax when we promote the diffusion angle of screen. In the future research, we can displace the planar diffuser with the curved diffuser and there would be some advantages for curved screen. Or the laser speckle is another research in the laser display field. Fatigue is one of the research topics in the stereoscopic display.

碩士
國立交通大學
光電工程研究所
105
In this high tech generation, virtual spaces for commercial and personal usage are now gradually affecting our daily lives through the connection with internet platform, like shopping, cloud, video conference, online games, and so on. Nowadays, there are more and more research and products that trying to build the bridge between real life and virtual space. Therefore, the idea of virtual reality and augmented reality is the outcome of connecting real world and virtual concepts. So far, whether immersing in the virtual world or moving the virtual image to the real word, head-mounted display has being continuously innovated. The next generation of head-mounted display should be light, equipped with wide viewing angle, high resolution, instant 3D image, and more comfortable user experience. In fact, these are the issues head mounted displays now encounter. Therefore, in this thesis, we proposed a new type of near eye display which apply light filed technology to achieve the features of light and simple structure and comfortable for wearing. We used Sony 0.7” OLED as the display in our research and designed the parameters for the system as well as discussed about how the different parameters would affect the imaging quality. We first proposed a thick lens ray tracing algorithm to correct the ray-tracing error of elemental image in traditional pinhole ray-tracing algorithm so as to enhance imaging quality and available to be applied in real situation. In the meantime, a freeform micro-lens array was designed to solve the blurry image issue at large field of view. We then did the analysis on imaging quality and field of view, etc. The results show that compared with the conventional system using spherical micro-lens array, the effective field of view in our system is 4.5 times larger under the premise that the highest theoretical resolution is not reduced. We successfully designed a lighter head mounted display compared with the conventional one and improved the blurry image issue in large field of view in conventional light field display. We also did the tolerance analysis to evaluate the probability of production. In the future, we wish to apply light field head mounted display to more areas such as education, medical training, entertainment, commercial and etc.

碩士
國立臺灣大學
光電工程學研究所
106
As an emerging 3D display system, when compared to other auto-stereoscopic displays, light field display can not only provide the continuous motion parallax, but also the delicate horizontal parallax, so it has become one of the research hotspots. However, there are problems that affect the image quality such as the distortion of the image caused by the oblique projection and uneven brightness due to the viewing angle of the receiver, and the arrangement of projectors for the multi-projector-type horizontal light field displays. In this paper, we first analyze the causes of image distortion, and then propose a method, which corrects the image by adjusting the imaging positions of the image sources, to achieve the purpose of optimizing the image quality. C++ is used to implement the proposed algorithm, and the optimized image sources are applied to the actual system for projection. The experimental results show that the corrected image has a significant improvement compared with the uncorrected one. In addition, we have proposed a deformation metric algorithm for quantifying and comparing the projection results for the corrected and uncorrected images. Finally, a brightness equalization algorithm with the corresponding realization program is proposed, to enhance the brightness uniformity of the system.

碩士
國立臺灣大學
光電工程學研究所
106
As an emerging 3D display system, when compared with other auto-stereoscopic displays, light field display provides continuous motion parallax, and also a delicate horizontal parallax. As such, it has become one of the research hotspots. In this thesis, the screen of the original multi-projector light-field display system changed from the conventional planar screen to a convex screen, so a new parameter (radius of curvature) will be discussed in the system. Then, the relationship between the radius of curvature and the horizontal scattering angle of the screen, the distance between the projectors and screen, the viewing distance between the viewer and screen, and the angle between the projector and projector are discussed. The overall system is re-evaluated to determine the optimal values for the parameters, the best configuration and the best design of the viewing area. The performance is compared with a conventional planar light-field display system. In the simulation analysis, we used an optical simulation software 〖LightTools〗^TM to simulate different parameters. The simulated image is analyzed, and the result is used to change the shape variables and determine the best display system design. In the analysis of the prototype, a 3D printed frame is used to bend the display at desired curvatures to construct the apparatus for the purpose of experimental verification of the simulation. The comparison between the simulated image and actual image are discussed. Finally, both the planar and convex display systems are summarized to illustrate the advantages and disadvantages of this convex light field display system. In the last section, we used the luminance measurement to measure the brightness of the planar and convex display systems. We designed a set of evaluation methods to analyze the brightness difference between the two display systems using simulation and experimental measurements. The brightness of the convex display was found to be higher than that of the planar display. In the simulation, the brightness of the display is increased by 5.25%. In the experimental verification, the brightness is increased by 6.84%. In both the simulations and experimental measurements, the image performance for the convex light-field display is better when compared with that of the previous planar display

碩士
國立交通大學
光電工程研究所
106
Recently, with the development of high resolution flat panel display, virtual reality and augment reality head-mounted displays acquire significant improvements. This kind of 3D displays, which we also called stereoscope, provides an immersive 3D image with flexible 3D interaction, performing well in the application of movies, entertainments, and multimedia. However, the visual fatigue issue caused by accommodation-convergence conflict seriously decrease the usage time of head-mounted display. Although light field techniques could efficiently eliminate this problem, the characteristic of low resolution still bring another issue in the system. Therefore, we proposed a new type of virtual reality head-mounted display called light field / stereoscopic hybrid head-mounted display to rapidly switch the low resolution light field image and high resolution 2D image by time-multiplexing method. This system generates images by two modes. In light field mode, light field technique adopted to solve visual fatigue issue provides natural depth information for human eyes. In stereoscopic mode, we compensate the resolution of light field virtual image by high resolution 2D virtual image. After human visual persistence, observers would able to see an enhanced resolution 3D image with exact depth information.

碩士
國立交通大學
光電工程研究所
106
As the progress of technology, the display is no longer a flat panel display. Near-eye display (NED) with augmented reality (AR) and virtual reality (VR) can give users different novel experience from the flat panel display. It is believed that it will be widely applied in many fields, such as entertainment, education, and medicine, etc. Most NEDs use binocular parallax method to create 3D images. Binocular parallax method, also called stereoscopic method, separates 3D image into right eye and left eye image, which contain different angle information of the same object. After receiving two images into user’s right eye and left eye respectively, users will have depth perception automatically through the binocular fusion in the human brain. However, this method suffers from the accommodation-convergence conflict (A.C. conflict). In addition, bulky devices lead people to uncomfortable feeling. To solve these problems, light field near-eye display (LFNED) was proposed in 2013. The advantages of LFNED not only reduces thickness but addresses the A.C. conflict. LFNED using a micro-lens array has been developed to achieve thin structure and solve the problem of A.C. conflict, but the disadvantages are low spatial resolution and low field of view (FOV). Compare to current commercial stereoscopic VR products, the spatial resolution of LFNED is much smaller than the stereoscopic VR products. In this paper, we proposed a time-multiplexed component with birefringent plate and twisted nematic liquid crystal plate (TN plate) to achieve shifting image with one-half of pixel size. In application, proposed device could easily combine with LFNED or other VR system using flat panel displays. The results show that the resolution was enhanced from original resolution to 1.4x resolution. Moreover, it can reduce screen-door effect and rasterized effect to get smoother image. Since the spatial resolution is enhanced, we believed our method can make users get better immersive experience in LFNED system.

碩士
國立交通大學
光電工程研究所
107
Over the past decades, display technology has been developing rapidly. 3D display technology is a hot and novel topic in the field of display technology. Nowadays, convention 3D display based on binocular disparity has been commercialized. However, this type of 3D displays has the issue of accommodation-convergence conflict so it easily induces visual fatigue and dizziness. Therefore, to solve this issue, adopting the technique of light field to produce true 3D image has been widely studied in recent years. But, the resolution of the image will be sacrificed for displaying light field image. Accordingly, to meet the demand of users, switchable 2D/3D display and even partially 2D/3D display are required. In this thesis, the switchable liquid crystal micro-lens array (LCMLA) is used to realize a new type of display called partially 2D / hybrid light field display. At first, the proper LCMLA is designed for light field display. Then, the methods based on the frequency dependency of Hi-R LCMLA are proposed to improve its decenter issue and disclination line effect as well as optimize the device. Then, Hi-R LCMLA is combined with a fast response polarization rotator to switch partially light field 3D mode and high-resolution 2D mode rapidly. In addition, the display panel will alternatively present the processed images based on the determined 2D and 3D region. Finally, the user can perceive a partially 2D/3D image with the truly reconstructed 3D scene as well as the compensated resolution due to visual persistence.

This Thesis aims at studying and developing efficient solutions for light field coding. In this regard, this Thesis proposes a light field coding solution based on the High Efficiency Video Coding (HEVC) standard and using a non-local spatial prediction scheme, named selfsimilarity compensated prediction. This solution is able to exploit the inherent correlations of this new type of content to achieve high rate-distortion performance, without requiring any explicit knowledge of the particular optical acquisition setup used when acquiring the content. In addition to this, aiming at allowing faster deployment of light field applications and services in the consumer market, a scalable light field coding solution that provides backward compatibility with legacy display devices (e.g., 2D, 3D stereo, and 3D multiview) is also proposed in this Thesis. The proposed display scalable solution makes use of an efficient inter-layer prediction scheme that when combined with the self-similarity compensated prediction is able to achieve, in most of the cases, better rate-distortion performance than the non-scalable HEVC solution. Finally, to support the richer and flexible interaction functionalities that arise in light field imaging applications, this Thesis also proposes a novel scalability concept, named Field of View (FOV) scalability, as well as a FOV scalable coding solution. The FOV scalability supports progressively richer interaction functionalities in each higher layer by hierarchically organizing the light field angular information. Moreover, two novel inter-layer coding solutions are also proposed so as to achieve high rate-distortion performance in enhancement layer coding.
Esta Tese visa estudar e desenvolver soluções eficientes para a codificação do campo de luz. Especificamente, esta Tese propõe uma solução de codificação do campo de luz que se baseia na norma HEVC (High Efficiency Video Coding) e que utiliza um método de predição espacial não-local aqui designada como predição compensada da autossemelhança. A solução proposta é capaz de explorar as correlações inerentes ao conteúdo de campo de luz e, desta forma, obter um alto desempenho em termos de débito-distorção sem que seja necessário conhecer os pormenores do sistema ótico utilizado na aquisição do conteúdo. Adicionalmente, com o intuito de possibilitar uma difusão mais rápida de serviços e aplicações de campo de luz no mercado de consumo, esta Tese também propõe uma solução escalável de codificação do campo de luz de forma a garantir a compatibilidade com os dispositivos de visualização convencionais (por exemplo, 2D, 3D estereoscópico e 3D multivista). A solução escalável proposta assenta na utilização de um método eficiente de predição entre camadas que quando combinado com a predição compensada da autossemelhança consegue atingir, na maioria dos casos, um melhor desempenho em termos de débitodistorção que a solução não-escalável do HEVC. Finalmente, para garantir o suporte das poderosas funcionalidades de interação que surgem em aplicações de campo de luz, esta Tese propõe um novo conceito de escalabilidade chamado escalabilidade de campo de visão, assim como uma solução de codificação de campo de luz que suporta este novo tipo de escalabilidade. A escalabilidade de campo de visão possibilita organizar hierarquicamente a informação angular do campo de luz de forma a suportar, progressivamente, funcionalidades de interação mais ricas em cada camada superior. Para alcançar um alto desempenho em termos de débito-distorção na codificação das camadas superiores, dois novos métodos de predição entre camadas são também propostos.

碩士
國立交通大學
光電工程研究所
105
With the explosive development and improvement of technology, 3D displays have been used in different applications. For examples: movie、advertisement、exhibition and so on. In daily life. Also, these 3D displays use 3D glasses to achieve 3D effect. Even in medical field also has 3D displays applications. However, 3D displays have some issues which result in the unpopularity of 3D display in daily life. One main issue is visual fatigue which may cause by accommodation- convergence conflict (A.C. conflict), especially in stereoscopic 3D displays. Although there are many technologies can solve this issue ex: holography, volumetric 3D display, light field and so on. These technologies still have defects, such as small viewing angle, too large, resolution sacrificed. In this thesis, a new type display called Hybrid Display was proposed. In Hybrid Display, observers can see the full resolution image with depth information by fast switching 3D image mode and full resolution 2D image mode and merged by visual persistence. Therefore, Hybrid Display not only can solve A.C. conflict by using light field technology but also compensate the resolution of light field 3D image. Liquid crystal micro-lens array and Twisted Nematic devices were taken and played an important role in switching two modes in hybrid display.

碩士
國立臺灣大學
光電工程學研究所
102
A 3D light field display system requires several design modifications to achieve the multi-view characteristic of a 360&;#730; 3D image. While certain light field display utilized a high frame rate projector&;not;&;not; or many micro projectors to achieve the modifications, they also drastically increased the cost of the system. This thesis discusses the use of an optical simulation software to analyze different parameters in a light field display. First, different system configurations can affect the displayed image quality. Improving the geometric structure of the reflective screen can also decrease the frame rate requirement of the system. Since images projected and reflected from a tilted screen can result in image distortion, this thesis focuses on the analyses of different parameters to correct the distortion while maintaining the original dimensions of the 3D image. Optical simulation software further allows studies of sub-images within a light field display and the viewing angle of the system. Varying the diffusion angles of the reflective screen can correct blurred image and non-uniform brightness within the image. In addition, the receiver distance can help to quantify the amount of image distortion. This research formulates a quantitative method that can be used as an indicator for determining the quality of sub-image realignment and other image properties. Future studies can incorporate optical components into the system to further decrease the need for high frame rate projector. Multi-disciplinary cooperation, such as utilizing a tracking device to achieve real-time image correction by using previous image distortion data.