무안경식 3 차원 디스플레이와 투사형 디스플레이를 이용한 깊이 융합 디스플레이의 관찰 특성 향상

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 이병호.In this dissertation, various methods for enhancing the viewing characteristics of the depth-fused display are proposed with combination of projection-type displays or integral imaging display technologies. Depth-fused display (DFD) is one kind of the volumetric three-dimensional (3D) displays composed of multiple slices of depth images. With a proper weighting to the luminance of the images on the visual axis of the observer, it provides continuous change of the accommodation within the volume confined by the display layers. Because of its volumetric property depth-fused 3D images can provide very natural volumetric images, but the base images should be located on the exact positions on the viewing axis, which gives complete superimpose of the images. If this condition is not satisfied, the images are observed as two separated images instead of continuous volume. This viewing characteristic extremely restricts the viewing condition of the DFD resulting in the limited applications of DFDs. While increasing the number of layers can result in widening of the viewing angle and depth range by voxelizing the reconstructed 3D images, the required system complexity also increases along with the number of image layers. For solving this problem with a relatively simple configuration of the system, hybrid techniques are proposed for DFDs. The hybrid technique is the combination of DFD with other display technologies such as projection-type displays or autostereoscopic displays. The projection-type display can be combined with polarization-encoded depth method for projection of 3D information. Because the depth information is conveyed by polarization states, there is no degradation in spatial resolution or video frame in the reconstructed 3D images. The polarized depth images are partially selected at the stacked polarization selective screens according to the given depth states. As the screen does not require any active component for the reconstruction of images, projection part and reconstruction part can be totally separated. Also, the projection property enables the scalability of the reconstructed images like a conventional projection display, which can give immersive 3D experience by providing large 3D images. The separation of base images due to the off-axis observation can be compensated by shifting the base images along the viewers visual axis. It can be achieved by adopting multi-view techniques. While conventional multi-view displays provide different view images for different viewers positions, it can be used for showing shifted base images for DFD. As a result, multiple users can observe the depth-fused 3D images at the same time. Another hybrid method is the combination of floating method with DFD. Convex lens can optically translate the depth position of the object. Based on this principle, the optical gap between two base images can be extended beyond the physical dimension of the images. Employing the lens with a short focal length, the gap between the base images can be greatly reduced. For a practical implementation of the system, integral imaging method can be used because it is composed of array of lenses. The floated image can be located in front of the lens as well as behind the lens. Both cases result in the expansion of depth range beyond the physical gap of base images, but real-mode floating enables interactive application of the DFD. In addition to the expansion of depth range, the viewing angle of the hybrid system can be increased by employing tracking method. Viewer tracking method also enables dynamic parallax for the DFD with real-time update of base images along with the viewing direction of the tracked viewers. Each chapter of this dissertation explains the theoretical background of the proposed hybrid method and demonstrates the feasibility of the idea with experimental systems.Abstract i Contents iv List of Figures vi List of Tables xii Chapter 1 Introduction 1 1.1 Overview of three-dimensional displays 1 1.2 Motivation 7 1.3 Scope and organization 9 Chapter 2 Multi-layered depth-fused display with projection-type display 10 2.1 Introduction 10 2.2 Polarization-encoded depth information for depth-fused display 12 2.3 Visualization with passive scattering film 16 2.4 Summary 30 Chapter 3 Compact depth-fused display with enhanced depth and viewing angle 31 3.1 Introduction 31 3.2 Enhancement of viewing characteristics 34 3.2.1 Viewing angle enhancement using multi-view method 34 3.2.2 Depth enhancement using integral imaging 37 3.2.3 Depth and viewing angle enhancement 39 3.3 Implementation of experimental system with enhanced viewing parameters 44 3.4 Summary 51 Chapter 4 Real-mode depth-fused display with viewer tracking 52 4.1 Introduction 52 4.2 Viewer tracking method 55 4.2.1 Viewer-tracked depth-fused display 55 4.2.2 Viewer-tracked integral imaging for a depth-fused display 58 4.3 Implementation of viewer-tracked integral imaging 63 4.4 Summary 71 Chapter 5 Conclusion 72 Bibliography 74 초록 83Docto

High Performance Three-Dimensional Display Based on Polymer-Stabilized Blue Phase Liquid Crystal

Autostereoscopic 2D/3D (two-dimension/three-dimension) switchable display has been attracting great interest in research and practical applications for several years. Among different autostereoscopic solutions, direction-multiplexed 3D displays based on microlens array or parallax barrier are viewed as the most promising candidates, due to their compatibility with conventional 2D display technologies. These 2D/3D switchable display system designs rely on fast switching display panels and photonics devices, including adaptive focus microlens array and switchable slit array. Polymer-stabilized blue phase liquid crystal (PS-BPLC) material provides a possible solution to meet the aforementioned fast response time requirement. However, present display and photonic devices based on blue phase liquid crystals suffer from several drawbacks, such as low contrast ratio, relatively large hysteresis and short lifetime. In this dissertation, we investigate the material properties of PS-BPLC so as to improve the performance of PS-BPLC devices. Then we propose several PS-BPLC devices for the autostereoscopic 2D/3D switchable display system designs. In the first part we evaluate the optical rotatory power (ORP) of blue phase liquid crystal, which is proven to be the primary reason for causing the low contrast ratio of PS-BPLC display systems. Those material parameters affecting the ORP of PS-BPLC are investigated and an empirical equation is proposed to calculate the polarization rotation angle in a PS-BPLC cell. Then several optical compensation methods are proposed to compensate the impact of ORP and to improve the contrast ratio of a display system. The pros and cons of each solution are discussed accordingly. In the second part, we propose two adaptive focus microlens array structures and a high efficiency switchable slit array based on the PS-BPLC materials. By optimizing the design parameters, these devices can be applied to the 2D/3D switchable display systems. In the last section, we focus on another factor that affects the performance and lifetime of PS-BPLC devices and systems: the UV exposure condition. The impact of UV exposure wavelength, dosage, uniformity, and photo-initiator are investigated. We demonstrate that by optimizing the UV exposure condition, we can reduce the hysteresis of PS-BPLC and improve its long term stability

다시점 디스플레이와 핀홀 방식 집적영상에 기반한 3차원 디스플레이의 개선에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기공학부, 2012. 8. 이병호.최근 10년간, 디스플레이 시장은 미세 공정과 유기 및 무기 발광 소자의 발달로 인하여 급속도로 평판 디스플레이 시장으로 전환되었고, 보다 현실감 있는 영상을 재생하기 위한 노력을 통하여 2차원 고화질 영상의 시대에서 3차원 입체 영상의 시대로 전환되어 가고 있다. 이미 TV시장과 영화 시장에는 편광 방식의 안경을 이용한 3차원 디스플레이가 성공적으로 자리를 잡고 있으며, 이들을 활용한 컨텐츠 또한 지속적으로 제작되고 있다. 그러나 궁극적인 3차원 디스플레이를 향한 연구는 현재의 안경식 방식에서 안경을 착용하지 않으면서도 다시점의 3차원 영상을 관측할 수 있는 무안경식 3차원 디스플레이 방식으로 집중 되고 있다. 본 논문은 무안경식 3차원 디스플레이 방식 중 다시점 디스플레이와 핀홀형 집적영상에 기반을 둔 3차원 디스플레이의 개선에 관한 연구이다. 지금까지 연구된 다양한 3차원 디스플레이 방식 중, 패럴랙스 배리어, 렌티큘러와 같은 다시점 디스플레이와 집적영상은 가장 상용화에 가까운 무안경식 3차원 디스플레이 방식이다. 그러나 무안경식 3차원 디스플레이의 상용화를 위해서는 디스플레이 기술, 관찰자의 인지요인, 그리고 광학적 정보처리 기술의 세 가지 측면에서의 문제점들에 대한 논의가 필요하다. 이 논문은 무안경식 3차원 디스플레이 중, 다시점 디스플레이와 핀홀(pinhole)형 집적영상을 이 세 가지 측면에서 개선하는 연구에 대한 내용을 담고 있다. 먼저 디스플레이 기술적인 측면에서는, 전계발광소자(electroluminescent film) 혹은 평판 디스플레이에 배열된 컬러 필터를 이용하여 핀홀형 집적영상의 시야각, 해상도, 광선 집적도 그리고 2차원/3차원 변환을 개선하는 방법들을 제안한다. 먼저 깊이 표현 범위가 기본적으로 넓은 핀홀형 집적영상의 2차원/3차원 변환으로의 확장을 위하여 전계발광소자에 기반을 둔 새로운 광원 변환 기술을 제안한다. 전계발광소자는 기본적으로 자르거나 휘거나 혹은 구멍을 뚫어도 발광에 영향을 받지 않는 특성을 가지고 있어, 전계발광소자에 균일한 핀홀을 배열하여 기존의 핀홀형 집적영상으로 이용이 가능하다. 따라서 이를 이용하여, 2차원/3차원 변환이 가능한 집적영상을 설계할 수 있고, 구부리면서 발광 상태를 유지하는 특성을 이용하여 광시야각을 갖는 반원 형태의 3차원 디스플레이로 제작할 수 있다. 또한 360도 전체에서 관찰이 가능한 집적영상 기반의 3차원 디스플레이로 확장하여 제안한다. 그리고 현재 대중적으로 사용되는 액정 디스플레이상의 컬러 필터 층을 핀홀 배열과 빔 프로젝터를 이용하여 광선 집적도, 해상도 그리고 깊이 표현 범위를 확장한 핀홀형 집적영상으로 제안한다. 실제 액정 디스플레이상의 컬러 필터는 3가지 색으로 나뉘어져 있고, 이를 이용하여 각각 색 영역이 다른 핀홀 배열로 사용이 가능하다. 이와 함께 빔 프로젝터를 이용하여, 한 요소 영상의 영역이 기존의 방식에 비해 넓어지고 서로 침범할 수 있게 되어 해상도와 광선 집적도가 최대 3배 향상되는 것을 확인할 수 있다. 집적영상의 개선과 함께 디스플레이 측면에서의 개선에서는, 무안경식 3차원 디스플레이의 특성을 개선하기 위하여 다시점 디스플레이와 1차원 집적영상을 분석하고 융합하는 연구도 진행한다. 두 가지의 다른 무안경식 3차원 디스플레이 방식을 융합하기 위하여, light field를 이용한 공간-각도 분포 분석과 이의 주파수영역에서의 분석을 진행한다. 분석을 통해 얻어진 두 방식의 공간-각도 분포 특징을 이용하여 다시점 디스플레이와 1차원 집적영상을 시분할 및 부픽셀분할을 통해 한 디스플레이 상에서 구현하여, 보다 품질이 향상된 무안경식 3차원 디스플레이를 제안한다. 또 다른 무안경식 3차원 디스플레이의 과제는 관찰자의 인지 요소로, 본 논문에서는 다시점 디스플레이와 집적영상에서의 깊이 해상도 및 조절력 반응에 대한 연구를 진행한다. 먼저 다시점 디스플레이 상에서 3차원 디스플레이 자체의 해상도와 cardboard 효과에 의한 인지 깊이 해상도 변화를 살펴보기 위해, 다시점 디스플레이 기반의 3차원 방송 환경을 구축하고, 디스플레이 자체의 깊이 해상도 표현의 제한, 다시점 영상 합성 과정 중의 깊이 해상도 표현의 제한 그리고 cardboard 효과에 의한 깊이 해상도 제한을 수식적으로 분석하고, 관찰자를 대상으로 한 설문을 진행한다. 이를 통해, 다시점 3차원 디스플레이 방송 환경에서 3차원 영상을 위한 깊이정보의 해상도를 위한 기준을 제시한다. 또한 무안경식 3차원 디스플레이에서 수렴-조절의 충돌을 해결하기 위해 논의되고 있는 초다시점 조건과 집적영상의 상관관계를 밝히기 위하여, 집적영상에서 초다시점 조건을 만족하는 영역을 분석 및 시뮬레이션을 진행하고 이 영역 안과 밖에서 관찰자의 조절력을 측정한다. 이 과정을 통해, 집적영상에서 초다시점 조건과 관찰자의 조절력 변화와의 상관관계를 찾을 수 있다. 그리고 무안경식 3차원 디스플레이를 이용한 또 다른 과제인 광학적 정보 처리에서는, 요소영상과 다시점 영상을 이용한 깊이 추출과 3차원 영상의 재획득에 대한 연구를 진행한다. Optical flow에 기반을 둔 보다 정확한 깊이 추출 알고리즘을 이용하여 요소영상에서 추출한 부영상의 깊이를 추출하는 방법과 이의 응용에 대해 본 논문에서 설명한다. Optical flow에 기반을 둔 3차원 물체의 깊이 추출을 컴퓨터를 이용한 실사 3차원 영상의 재획득에 활용하는 경우, 집적영상의 본질적인 문제인 pseudoscopic 문제를 해결할 수 있다. 본 논문을 통한 무안경식 3차원 디스플레이의 디스플레이 기술, 관찰자의 인지요인, 그리고 광학적 정보처리 기술적인 측면에서의 개선 방법들은 추후 무안경식 3차원 디스플레이 시장의 확대와 가정용 TV시장으로의 진출에 크게 기여할 수 있을 것으로 보인다.This dissertation presents studies on improvement of three-dimensional (3D) displays based on multi-view display and pinhole-type integral imaging. Among various types of 3D displays, integral imaging and multi-view display such as parallax barrier and lenticular 3D display are almost commercialized autostereoscopic 3D display. For commercialization, autostereoscopic 3D display has three issues that are limitation of display technology, human factors related on human visual system and optical information processing technology. In this dissertation, the author will address the studies about the improvement methods for multi-view display and pinhole-type integral imaging in three issues. In the issue of display technology, the improvement methods of pinhole-type integral imaging using electroluminescent (EL) film and color filters on display panel are proposed to enhance the viewing angle, resolution, ray density and two-dimensional (2D)/3D convertibility. For large expressible depth range and 2D/3D convertibility in pinhole-type integral imaging, pinhole-type integral imaging is modified by new light source conversion layer based on EL film. The EL film has the advantage that it can operate continuously even when it is cut or punctured. Using this characteristic, the author generates an array of pinholes on an EL film to form a point light source array for reconstructing 3D images based on integral imaging. Taking advantage of the flexibility of EL films, a 2D/3D convertible integral imaging system with a wide viewing angle using a curved EL film is proposed which is extended to 360-degree viewable cylindrical 3D display system. For enhancement of ray density, resolution and expressible depth range in pinhole-type integral imaging, the system using color filter pinhole array on liquid crystal display panel with projection scheme is proposed. A color filter structure on liquid crystal display panel acts as pinhole array in integral imaging with separation of color channel. The use of color filter pinhole array and projection scheme can enlarge the region of one-elemental image and improve the resolution and ray density remarkably. In addition to the improvement of pinhole-type integral imaging, analysis and convergence of multi-view display and one-dimensional (1D) integral imaging are presented for improvement of characteristics in autostereoscopic display. For the convergence of two different autostereoscopic 3D display, multi-view display and integral imaging, light field analysis of spatio-angular distribution and its frequency domain analysis are performed. From the analysis, the convergence type of autostereoscopic 3D display based on multi-view display and 1D integral imaging is proposed by using time-multiplexing and sub-pixel multiplexing technique. On another issue in autostereoscopic 3D display, the depth resolution and accommodation response of human factors in multi-view display and integral imaging are researched. To find the effect of fundamental depth resolution and cardboard effect to the perceived depth resolution in multi-view display, the fundamental depth resolution and the cardboard effect from the synthesis process in the multi-view 3D TV broadcasting are analyzed and a subjective test is performed. In addition, the analysis and measurement of accommodation response of integral imaging with satisfying super multi-view display is performed to reveal the relation between the accommodation response of integral imaging and super multi-view condition. On the other issue of autostereoscopic 3D display, the optical information processing from elemental image and multi-view images in depth extraction and computational pickup method without pseudoscopic problem is presented. A more accurate depth extraction algorithm using optical flow from sub-images of elemental image is proposed and its applications are also presented in this dissertation.Abstract i Contents iv List of Figures ix List of Tables xvii Chapter 1 Introduction 1 1.1 Overview of autostereoscopic three-dimensional displays 1 1.2 Motivation of this dissertation 4 1.3 Scope and organization 7 Chapter 2 Enhancement of pinhole-type integral imaging using electroluminescent film and color filters on display panel 11 2.1 Integral imaging system using an electroluminescent film backlight for three-dimensional/two-dimensional convertibility and a curved structure 11 2.1.1 Introduction 11 2.1.2 Principles of 3D/2D convertible integral imaging using EL film 14 2.1.3 Experimental results 23 2.1.4 Conclusion 29 2.2 360-viewable cylindrical integral imaging system using a three-dimensionaltwo-dimensional switchable and flexible backlight 30 2.2.1 Introduction 30 2.2.2 Principles of the 360-degree viewable cylindrical integral imaging system 33 2.2.3 Analysis on the characteristic parameters and viewing zone of the 360-degree viewable cylindrical integral imaging system 36 2.2.4 Experiment 39 2.2.5 Conclusion 43 2.3 Integral imaging using color filter pinhole array on display panel 44 2.3.1 Introduction and motivation 44 2.3.2 Principles of proposed method 47 2.3.3 Experimental setup and results 54 2.3.4 Conclusion 60 Chapter 3 Analysis and convergence of multi-view display and one-dimensional integral imaging 62 3.1 Comparison of multi-view display and integral imaging 62 3.1.1 Principles of multi-view display and one-dimensional integral imaging 63 3.1.2 Principles of multi-view display and integral imaging in pickup methods 67 3.1.3 Analysis of multi-view display and integral imaging in light filed 73 3.2 Computational reacquisition of a real three-dimensional object for integral imaging without matching of pickup and display lens array 80 3.2.1 Introduction 80 3.2.2 Depth extraction and triangular mesh reconstruction from sub-images using optical flow 81 3.2.3 Conversion from point cloud to face texture information 83 3.2.4 Experimental result 85 3.2.5 Conclusion 87 3.3 Time-multiplexing and sub-pixel mapping of multi-view display and integral imaging 89 3.3.1 Design parameters of multi-view display and integral imaging 90 3.3.2 Convergence type of autostereoscopic display using time-multiplexing or sub-pixel mapping of multi-view display and one-dimensional integral imaging 91 3.3.3 Experimental result 94 Chapter 4 Perceived depth resolution and accommodation response of multi-view display and integral imaging 99 4.1 Effect of fundamental depth resolution and cardboard effect to perceived depth resolution on multi-view display 99 4.1.1 Introduction 100 4.1.2 Fundamental depth resolution from specification of slanted lenticular display 102 4.1.3 View synthesis parameters from specification of stereo pickup and multi-view display 105 4.1.4 Stereo pickup and multi-view synthesis of 3D object with varying depth resolution 109 4.1.5 Numerical comparison of synthesized view images in PSNR and NCC with varying depth resolution 113 4.1.6 Subjective test for limitation of perceived depth resolution in multi-view display 115 4.1.7 Conclusion 122 4.2 Effect of viewing region satisfying super multi-view condition in integral imaging 124 4.2.1 Introduction 124 4.2.2 Analysis of viewing region satisfying super multi-view condition in integral imaging 125 4.2.3 Expressible depth range and size of 3D object in integral imaging with super multi-view condition 128 4.2.4 Simulation 129 4.2.5 Accommodation response with super multi-view condition in integral imaging 131 4.2.6 Experimental result 132 4.2.7 Experimental result 136 Chapter 5 Conclusion 137 Bibliography 140 Appendix 148 한글 초록 149Docto

Adaptive micro-optical phase modulators based on liquid crystal technology

Mención Internacional en el título de doctorThis thesis began with the project “Advanced Devices of Liquid Crystal and Electroluminescent Organic Diodes. Hybrid Applications for 3D Vision” funded by the Spanish government. The goal of this project was the development of optical devices to achieve 3D vision in portable devices without glasses or external elements. In order to achieve the goals of this project, solutions based on liquid crystal are considered. Specifically, adaptive micro-optical phase modulators based on liquid crystal technology are researched in depth. The gradient of the refractive index varies spatially the phase delay experienced by an impinging wavefront of a light beam. By using this effect, any refractive optical element may be reproduced with the proper voltage gradient applied to the sample. This is the main operating principle of the micro-optical phase modulators proposed in this thesis. As original contribution of this thesis, a novel algorithm to solve the position of a nematic liquid crystal molecular director is proposed. Once the liquid crystal is completely characterized, the developing of a specific model to know the electro-optic response of the micro-optical phase modulators is also relevant. Another original contribution is a novel equivalent electric circuit for modeling liquid crystal microlenses. An interesting feature of the model is that it provides an analytical solution for microlenses with modal and hole-patterned electrode schemes, by using a simple software tool. The required driving scheme (modal or hole-patterned) can be predicted. These theories have been validated by experimental results. For more complex devices, the equations are solved by Finite Element Method. A new manufacturing protocol is proposed to make the first set of modal microlens arrays. As a first step simple devices (monopixel cells) are fabricated in order to do a complete study of the liquid crystal electro-optical behavior. The characterization of the liquid crystal electro-optical parameters is determinant in order to design more complex devices. Refractive index and permittivity are the most important features considered. These parameters have been characterized to validate the proposed theoretical modelling of the liquid crystal molecular position. These devices have required special fabrication processes as well as a special characterization set-up especially in terms of size resolution or arrangement complexity. A custom micropositioner is developed and control software is programmed in relation to these tasks. The software automates the characterization process giving directly measured results of: phase modulation, focal distance, thickness or aberrations. These results have made it possible to validate experimentally the proposed electrical modeling for micro-optical devices. Demonstration of the viability of the liquid crystal lenticular technology has been carried out for an autostereoscopic application. This scheme provides the observer with the option of changing between horizontal and vertical views through his portable autostereoscopic display. Finally, last research contributions of this work of thesis have taken advantage of the deep knowledge of the electro-optical properties of lenticular devices for autostereoscopic applications, to guide the design of refined micro-optical phase modulators. Adaptive axicons and optical vortices are specially emphasized because their relevance from both, the scientific and technological point of view.Esta tesis se inició con el proyecto de investigación “Dispositivos avanzados de cristal líquido y diodos orgánicos electroluminiscentes. Aplicaciones híbridas para visión 3D”, financiado por el gobierno español. El objetivo de este proyecto consistía en el desarrollo de dispositivos ópticos para lograr visión 3D en dispositivos portátiles sin necesidad de gafas o elementos externos. Con el fin de alcanzar los objetivos de este proyecto, se consideran soluciones basadas en cristal líquido. En concreto, moduladores adaptativos de fase micro-ópticos basados en tecnología de cristal líquido. El gradiente del índice de refracción varía espacialmente el retardo de fase experimentado por un frente de onda incidente. Mediante el uso de este efecto, cualquier elemento óptico refractivo puede ser reproducido mediante un gradiente de tensión adecuado aplicado a la muestra. Este es el principio de funcionamiento de los moduladores de fase micro-ópticos propuestos en esta tesis. Como aportación original de esta tesis, se propone un nuevo algoritmo para resolver el director molecular de un cristal líquido nemático. Una vez que el cristal líquido está completamente caracterizado, es necesario el desarrollo de un modelo específico para saber la respuesta electro-óptica de los moduladores de fase micro-ópticos. Otra contribución original, consiste en un circuito eléctrico equivalente para el modelado de microlentes de cristal líquido. Una característica interesante del modelo es que proporciona una solución analítica para microlentes con esquemas de electrodos modales y “hole patterned”. Se puede predecir la topología necesaria en función de los parámetros de construcción. Estas teorías han sido validadas por resultados experimentales. Para los dispositivos más complejos, las ecuaciones se resuelven por el método de elementos finitos. Se propone un nuevo protocolo de fabricación para hacer microlentes modales. Como primer paso se fabrican dispositivos sencillos (células monopixel) con el fin de hacer un estudio completo del comportamiento electro-óptico del cristal líquido. La caracterización de los parámetros electro-ópticos de cristal líquido es determinante para diseñar dispositivos más complejos. El índice de refracción y la permitividad son las características más importantes. Estos parámetros se han caracterizado para validar el modelo teórico de la posición molecular de cristal líquido. Estos dispositivos han requerido procesos de fabricación complejos, así como montajes de caracterización determinados. Se ha desarrollado un microposicionador y un software de control. El software automatiza el proceso de caracterización dando resultados de: modulación de fase, distancia focal, grosor o aberraciones. Estos resultados han permitido validar experimentalmente el modelado eléctrico propuesto para dispositivos micro-ópticos. La demostración de la viabilidad de la tecnología propuesta se ha llevado a cabo mediante un dispositivo autoestereoscópico. Este dispositivo ofrece al observador la opción de cambiar entre vistas horizontal y vertical a través de su pantalla autoestereoscópica portátil. Finalmente, los últimos aportes de investigación de este trabajo de tesis se han aprovechado del profundo conocimiento de las propiedades electro-ópticas de los dispositivos lenticulares para aplicaciones autoestereoscópicas. Se pueden destacar los axicones adaptativos y vórtices ópticos por su relevancia tanto desde el punto de vista científico como tecnológico.Este trabajo ha sido desarrollado en el marco de los proyectos TEC2009-13991-C02-01 financiado por el Ministerio de Ciencia e Innovación y FACTOTEM2 S2009/ESP-1781 financiado por la Comunidad de Madrid.Programa Oficial de Doctorado en Ingeniería Eléctrica, Electrónica y AutomáticaPresidente: Ignacio Raúl Matías Maestro.- Secretario: Antonia Isabel Pérez Garcilópez.- Vocal: Dimitrios C. Zografopoulo

Perceptually Optimized Visualization on Autostereoscopic 3D Displays

The family of displays, which aims to visualize a 3D scene with realistic depth, are known as "3D displays". Due to technical limitations and design decisions, such displays create visible distortions, which are interpreted by the human vision as artefacts. In absence of visual reference (e.g. the original scene is not available for comparison) one can improve the perceived quality of the representations by making the distortions less visible. This thesis proposes a number of signal processing techniques for decreasing the visibility of artefacts on 3D displays. The visual perception of depth is discussed, and the properties (depth cues) of a scene which the brain uses for assessing an image in 3D are identified. Following the physiology of vision, a taxonomy of 3D artefacts is proposed. The taxonomy classifies the artefacts based on their origin and on the way they are interpreted by the human visual system. The principles of operation of the most popular types of 3D displays are explained. Based on the display operation principles, 3D displays are modelled as a signal processing channel. The model is used to explain the process of introducing distortions. It also allows one to identify which optical properties of a display are most relevant to the creation of artefacts. A set of optical properties for dual-view and multiview 3D displays are identified, and a methodology for measuring them is introduced. The measurement methodology allows one to derive the angular visibility and crosstalk of each display element without the need for precision measurement equipment. Based on the measurements, a methodology for creating a quality profile of 3D displays is proposed. The quality profile can be either simulated using the angular brightness function or directly measured from a series of photographs. A comparative study introducing the measurement results on the visual quality and position of the sweet-spots of eleven 3D displays of different types is presented. Knowing the sweet-spot position and the quality profile allows for easy comparison between 3D displays. The shape and size of the passband allows depth and textures of a 3D content to be optimized for a given 3D display. Based on knowledge of 3D artefact visibility and an understanding of distortions introduced by 3D displays, a number of signal processing techniques for artefact mitigation are created. A methodology for creating anti-aliasing filters for 3D displays is proposed. For multiview displays, the methodology is extended towards so-called passband optimization which addresses Moiré, fixed-pattern-noise and ghosting artefacts, which are characteristic for such displays. Additionally, design of tuneable anti-aliasing filters is presented, along with a framework which allows the user to select the so-called 3d sharpness parameter according to his or her preferences. Finally, a set of real-time algorithms for view-point-based optimization are presented. These algorithms require active user-tracking, which is implemented as a combination of face and eye-tracking. Once the observer position is known, the image on a stereoscopic display is optimised for the derived observation angle and distance. For multiview displays, the combination of precise light re-direction and less-precise face-tracking is used for extending the head parallax. For some user-tracking algorithms, implementation details are given, regarding execution of the algorithm on a mobile device or on desktop computer with graphical accelerator

투명한 매질에서의 광 경로 분석을 이용한 집약적 3차원 디스플레이

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2017. 2. 이병호.본 박사학위 논문에서는 광학적으로 투명한 매질에서의 광 경로 분석을 바탕으로 집약적인 3차원 디스플레이 시스템을 구현하는 접근 방법에 대하여 논의한다. 3차원 영상 장치를 구성하는 요소와 시청자 사이의 물리적인 거리를 줄이는 것은 집약적인 3차원 디스플레이 시스템을 구현하는 직관적인 방법이다. 또한, 기존 시스템의 크기를 유지하면서 더 많은 양의 3차원 영상 정보를 표현하는 것 또한 집약적 3차원 디스플레이 시스템을 의미한다. 높은 대역폭과 작은 구조를 가진 집약적 3차원 디스플레이 시스템을 구현하기 위하여 다음의 두 가지 광학 현상을 이용한다. 등방성 물질에서의 전반사 특성과 이방성 물질에서의 복굴절 특성이다. 가시광 영역에서 빛을 투과시키는 두 매질의 고유 광학 특성을 기존의 3차원 디스플레이 시스템에 적용하기 위하여 광 경로 추적을 통하여 분석한다. 광 도파로의 전반사 특성은 집약적 다중 투사 3차원 디스플레이 시스템을 구현하기 위하여 사용한다. 투사 광학계의 영상 정보는 광 도파로로 입사, 내부에서 전반사를 통하여 진행하고, 이에 수평 투사 거리는 광 도파로의 두께로 제한된다. 다수의 전반사 이후 영상 정보는 광 도파로의 출사 면을 통해 빠져나가고, 렌즈에 의하여 최적 시청 지점에서 시점을 형성한다. 광 도파로 내부에서의 광 경로를 등가 모델을 통하여 조사하고, 이를 통해 다수의 투사 광학계로부터 생성된 다수의 시점 영상이 왜곡되는 것을 분석하고 보정한다. 10개의 시점을 제공하는 집약적 다중 투사 3차원 디스플레이 시스템을 통해 제안된 방법을 검증한다. 향상된 대역폭 특성을 가진 다중 투사 3차원 디스플레이와 다중 초점 헤드 마운트 디스플레이 구현을 위한 이방성 판을 이용한 편광 다중화 방법을 제안한다. 빛의 편광 상태, 이방성 판의 광축 방향에 따라 광 경로가 달라진다. 측면 방향으로의 광 경로 전환은 다중 투사 3차원 디스플레이 기술과 결합하여 시점을 측면 방향으로 두 배로 증가시킨다. 깊이 방향으로의 광 경로 전환은 헤드 마운트 디스플레이에서 다중 초점 기능을 구현한다. 광 경로 추적 시뮬레이션을 통해 이방성 판의 모양, 광축, 파장 등의 다양한 파라미터 변화에 따른 광 경로 전환을 분석한다. 각각의 기능에 맞도록 설계된 이방성 판과 편광 회전자를 실시간으로 결합하여, 다중 투사 3차원 디스플레이와 다중 초점 헤드 마운트 디스플레이의 대역폭이 2배 증가한다. 각 시스템에 대한 시작품을 제작하고, 제안된 방법을 실험적으로 검증한다. 본 논문에서는 광 도파로와 복굴절 물질을 이용하여 그 광 경로를 분석, 대형의 다중 투사 3차원 디스플레이 시스템과 개인 사용자의 헤드 마운트 디스플레이 시스템의 크기를 감소시키고, 표현 가능한 정보량을 증가시키는 방법을 제안한다. 광 도파로와 이방성 판은 기존의 3차원 디스플레이 시스템과 쉽게 결합이 가능하며, 제안된 방법은 향후 소형뿐만 아니라 중대형 3차원 디스플레이 시스템의 집약화에 기여할 수 있을 것으로 기대된다.This dissertation investigates approaches for realizing compact three-dimensional (3D) display systems based on optical path analysis in optically transparent medium. Reducing the physical distance between 3D display apparatuses and an observer is an intuitive method to realize compact 3D display systems. In addition, it is considered compact 3D display systems when they present more 3D data than conventional systems while preserving the size of the systems. For implementing compact 3D display systems with high bandwidth and minimized structure, two optical phenomena are investigated: one is the total internal reflection (TIR) in isotropic materials and the other is the double refraction in birefringent crystals. Both materials are optically transparent in visible range and ray tracing simulations for analyzing the optical path in the materials are performed to apply the unique optical phenomenon into conventional 3D display systems. An optical light-guide with the TIR is adopted to realize a compact multi-projection 3D display system. A projection image originated from the projection engine is incident on the optical light-guide and experiences multiple folds by the TIR. The horizontal projection distance of the system is effectively reduced as the thickness of the optical light-guide. After multiple folds, the projection image is emerged from the exit surface of the optical light-guide and collimated to form a viewing zone at the optimum viewing position. The optical path governed by the TIR is analyzed by adopting an equivalent model of the optical light-guide. Through the equivalent model, image distortion for multiple view images in the optical light-guide is evaluated and compensated. For verifying the feasibility of the proposed system, a ten-view multi-projection 3D display system with minimized projection distance is implemented. To improve the bandwidth of multi-projection 3D display systems and head-mounted display (HMD) systems, a polarization multiplexing technique with the birefringent plate is proposed. With the polarization state of the image and the direction of optic axis of the birefringent plate, the optical path of rays varies in the birefringent material. The optical path switching in the lateral direction is applied in the multi-projection system to duplicate the viewing zone in the lateral direction. Likewise, a multi-focal function in the HMD is realized by adopting the optical path switching in the longitudinal direction. For illuminating the detailed optical path switching and the image characteristic such as an astigmatism and a color dispersion in the birefringent material, ray tracing simulations with the change of optical structure, the optic axis, and wavelengths are performed. By combining the birefringent material and a polarization rotation device, the bandwidth of both the multi-projection 3D display and the HMD is doubled in real-time. Prototypes of both systems are implemented and the feasibility of the proposed systems is verified through experiments. In this dissertation, the optical phenomena of the TIR and the double refraction realize the compact 3D display systems: the multi-projection 3D display for public and the multi-focal HMD display for individual. The optical components of the optical light-guide and the birefringent plate can be easily combined with the conventional 3D display system and it is expected that the proposed method can contribute to the realization of future 3D display systems with compact size and high bandwidth.Chapter 1 Introduction 10 1.1 Overview of modern 3D display providing high quality 3D images 10 1.2 Motivation of this dissertation 15 1.3 Scope and organization 18 Chapter 2 Compact multi-projection 3D displays with optical path analysis of total internal reflection 20 2.1 Introduction 20 2.2 Principle of compact multi-projection 3D display system using optical light-guide 23 2.2.1 Multi-projection 3D display system 23 2.2.2 Optical light-guide for multi-projection 3D display system 26 2.2.3 Analysis on image characteristics of projection images in optical light-guide 34 2.2.4 Pre-distortion method for view image compensation 44 2.3 Implementation of prototype of multi-projection 3D display system with reduced projection distance 47 2.4 Summary and discussion 52 Chapter 3 Compact multi-projection 3D displays with optical path analysis of double refraction 53 3.1 Introduction 53 3.2 Principle of viewing zone duplication in multi-projection 3D display system 57 3.2.1 Polarization-dependent optical path switching in birefringent crystal 57 3.2.2 Analysis on image formation through birefringent plane-parallel plate 60 3.2.3 Full-color generation of dual projection 64 3.3 Implementation of prototype of viewing zone duplication of multi-projection 3D display system 68 3.3.1 Experimental setup for viewing zone duplication of multi-projection 3D display system 68 3.3.2 Luminance distribution measurement of viewing zone duplication of multi-projection 3D display system 74 3.4 Summary and discussion 79 Chapter 4 Compact multi-focal 3D HMDs with optical path analysis of double refraction 81 4.1 Introduction 81 4.2 Principle of multi-focal 3D HMD system 86 4.2.1 Multi-focal 3D HMD system using Savart plate 86 4.2.2 Astigmatism compensation by modified Savart plate 89 4.2.3 Analysis on lateral chromatic aberration of extraordinary plane 96 4.2.4 Additive type compressive light field display 101 4.3 Implementation of prototype of multi-focal 3D HMD system 104 4.4 Summary and discussion 112 Chapter 5 Conclusion 114 Bibliography 117 Appendix 129 초 록 130Docto

3D Pixel Mapping for LED Holoscpic 3D wall Display

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonIn recent years, 3D displays have been recognized as the ultimate dream of immersive display technology and there have been a great development immersive 3D technology including AR/VR and auto-stereoscopic 3D displays. Holoscopic 3D (H3D) system is one of the autostereoscopic 3D which is a true 3D imaging principle which mimics fly’s eye technique to capture and replay using a micro lens array which is an array of perspective lens of the same specification. LED wall display has shown a fast growth where LED digital displays are widely used in both in/outdoor for advertisement and entertainment. Ultra-big LED display monitor is an ideal hardware device to provide remarkable 3D viewing experience and fit numbers of viewers to perceive 3D effects at same time. However, compare with existing 3D technologies which successfully applied on LCD display monitor, LED display still suffers from resolution when applied pixel mapping method which uses number of 2D pixels to construct a 3D pixel. In this PhD research, an innovative 3D pixel mapping was explored and designed to enhance 3D viewing experience in horizontal direction of LED 3D Wall-size display. In particular, an innovative Holoscopic 3D imaging principle is used to design and prototype LED 3D Wall display of resolution enhancement. Compare with the classic 3D display method, this enhanced display method of LED display improved horizontal resolution double times without losing any viewpoints. The outcome research is promising as a good depth and motion parallax for medium to long distance viewing are achieved. In addition to the aforementioned, to improve the quality of rendered 3D images of LED display in omnidirectional directions, a distributed pixel mapping algorithm was designed to reduce the lens pitch three times to gain smoother motion parallax of rendered 3D images compare with traditional pixel mapping method in omnidirectional direction. Unfortunately, due to lack of high-resolution LED display monitor, this distributed pixel mapping method was eventually tested and evaluated on LCD display with 4K resolution

Head tracking two-image 3D television displays

The research covered in this thesis encompasses the design of novel 3D displays, a consideration of 3D television requirements and a survey of autostereoscopic methods is also presented. The principle of operation of simple 3D display prototypes is described, and design of the components of optical systems is considered. A description of an appropriate non-contact infrared head tracking method suitable for use with 3D television displays is also included. The thesis describes how the operating principle of the displays is based upon a twoimage system comprising a pair of images presented to the appropriate viewers' eyes. This is achieved by means of novel steering optics positioned behind a direct view liquid crystal display (LCD) that is controlled by a head position tracker. Within the work, two separate prototypes are described, both of which provide 3D to a single viewer who has limited movement. The thesis goes on to describe how these prototypes can be developed into a multiple-viewer display that is suitable for television use. A consideration of 3D television requirements is documented showing that glassesfree viewing (autostereoscopic), freedom of viewer movement and practical designs are important factors for 3D television displays. The displays are novel in design in several important aspects that comply with the requirements for 3D television. Firstly they do not require viewers to wear special glasses, secondly the displays allow viewers to move freely when viewing and finally the design of the displays is practical with a housing size similar to modem television sets and a cost that is not excessive. Surveys of other autostereoscopic methods included within the work suggest that no contemporary 3D display offers all of these important factors

Holoscopic 3D image depth estimation and segmentation techniques

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonToday’s 3D imaging techniques offer significant benefits over conventional 2D imaging techniques. The presence of natural depth information in the scene affords the observer an overall improved sense of reality and naturalness. A variety of systems attempting to reach this goal have been designed by many independent research groups, such as stereoscopic and auto-stereoscopic systems. Though the images displayed by such systems tend to cause eye strain, fatigue and headaches after prolonged viewing as users are required to focus on the screen plane/accommodation to converge their eyes to a point in space in a different plane/convergence. Holoscopy is a 3D technology that targets overcoming the above limitations of current 3D technology and was recently developed at Brunel University. This work is part W4.1 of the 3D VIVANT project that is funded by the EU under the ICT program and coordinated by Dr. Aman Aggoun at Brunel University, West London, UK. The objective of the work described in this thesis is to develop estimation and segmentation techniques that are capable of estimating precise 3D depth, and are applicable for holoscopic 3D imaging system. Particular emphasis is given to the task of automatic techniques i.e. favours algorithms with broad generalisation abilities, as no constraints are placed on the setting. Algorithms that provide invariance to most appearance based variation of objects in the scene (e.g. viewpoint changes, deformable objects, presence of noise and changes in lighting). Moreover, have the ability to estimate depth information from both types of holoscopic 3D images i.e. Unidirectional and Omni-directional which gives horizontal parallax and full parallax (vertical and horizontal), respectively. The main aim of this research is to develop 3D depth estimation and 3D image segmentation techniques with great precision. In particular, emphasis on automation of thresholding techniques and cues identifications for development of robust algorithms. A method for depth-through-disparity feature analysis has been built based on the existing correlation between the pixels at a one micro-lens pitch which has been exploited to extract the viewpoint images (VPIs). The corresponding displacement among the VPIs has been exploited to estimate the depth information map via setting and extracting reliable sets of local features. ii Feature-based-point and feature-based-edge are two novel automatic thresholding techniques for detecting and extracting features that have been used in this approach. These techniques offer a solution to the problem of setting and extracting reliable features automatically to improve the performance of the depth estimation related to the generalizations, speed and quality. Due to the resolution limitation of the extracted VPIs, obtaining an accurate 3D depth map is challenging. Therefore, sub-pixel shift and integration is a novel interpolation technique that has been used in this approach to generate super-resolution VPIs. By shift and integration of a set of up-sampled low resolution VPIs, the new information contained in each viewpoint is exploited to obtain a super resolution VPI. This produces a high resolution perspective VPI with wide Field Of View (FOV). This means that the holoscopic 3D image system can be converted into a multi-view 3D image pixel format. Both depth accuracy and a fast execution time have been achieved that improved the 3D depth map. For a 3D object to be recognized the related foreground regions and depth information map needs to be identified. Two novel unsupervised segmentation methods that generate interactive depth maps from single viewpoint segmentation were developed. Both techniques offer new improvements over the existing methods due to their simple use and being fully automatic; therefore, producing the 3D depth interactive map without human interaction. The final contribution is a performance evaluation, to provide an equitable measurement for the extent of the success of the proposed techniques for foreground object segmentation, 3D depth interactive map creation and the generation of 2D super-resolution viewpoint techniques. The no-reference image quality assessment metrics and their correlation with the human perception of quality are used with the help of human participants in a subjective manner