Intensity-only optical compressive imaging using a multiply scattering material and a double phase retrieval approach

In this paper, the problem of compressive imaging is addressed using natural randomization by means of a multiply scattering medium. To utilize the medium in this way, its corresponding transmission matrix must be estimated. To calibrate the imager, we use a digital micromirror device (DMD) as a simple, cheap, and high-resolution binary intensity modulator. We propose a phase retrieval algorithm which is well adapted to intensity-only measurements on the camera, and to the input binary intensity patterns, both to estimate the complex transmission matrix as well as image reconstruction. We demonstrate promising experimental results for the proposed algorithm using the MNIST dataset of handwritten digits as example images

Reference-less measurement of the transmission matrix of a highly scattering material using a DMD and phase retrieval techniques

This paper investigates experimental means of measuring the transmission matrix (TM) of a highly scattering medium, with the simplest optical setup. Spatial light modulation is performed by a digital micromirror device (DMD), allowing high rates and high pixel counts but only binary amplitude modulation. We used intensity measurement only, thus avoiding the need for a reference beam. Therefore, the phase of the TM has to be estimated through signal processing techniques of phase retrieval. Here, we compare four different phase retrieval principles on noisy experimental data. We validate our estimations of the TM on three criteria : quality of prediction, distribution of singular values, and quality of focusing. Results indicate that Bayesian phase retrieval algorithms with variational approaches provide a good tradeoff between the computational complexity and the precision of the estimates

Effect of Photonic Structures in Organic Light-Emitting Diodes – Light Extraction and Polarization Characteristics

Edited by Jai Sing

Primal-dual coding to probe light transport

We present primal-dual coding, a photography technique that enables direct fine-grain control over which light paths contribute to a photo. We achieve this by projecting a sequence of patterns onto the scene while the sensor is exposed to light. At the same time, a second sequence of patterns, derived from the first and applied in lockstep, modulates the light received at individual sensor pixels. We show that photography in this regime is equivalent to a matrix probing operation in which the elements of the scene's transport matrix are individually re-scaled and then mapped to the photo. This makes it possible to directly acquire photos in which specific light transport paths have been blocked, attenuated or enhanced. We show captured photos for several scenes with challenging light transport effects, including specular inter-reflections, caustics, diffuse inter-reflections and volumetric scattering. A key feature of primal-dual coding is that it operates almost exclusively in the optical domain: our results consist of directly-acquired, unprocessed RAW photos or differences between them.Alfred P. Sloan Foundation (Research Fellowship)United States. Defense Advanced Research Projects Agency (DARPA Young Faculty Award)Massachusetts Institute of Technology. Media Laboratory (Consortium Members

Construction and Calibration of Optically Efficient LCD-based Multi-Layer Light Field Displays

Near-term commercial multi-view displays currently employ ray-based 3D or 4D light field techniques. Conventional approaches to ray-based display typically include lens arrays or heuristic barrier patterns combined with integral interlaced views on a display screen such as an LCD panel. Recent work has placed an emphasis on the co-design of optics and image formation algorithms to achieve increased frame rates, brighter images, and wider fields-of-view using optimization-in-the-loop and novel arrangements of commodity LCD panels. In this paper we examine the construction and calibration methods of computational, multi-layer LCD light field displays. We present several experimental configurations that are simple to build and can be tuned to sufficient precision to achieve a research quality light field display. We also present an analysis of moiré interference in these displays, and guidelines for diffuser placement and display alignment to reduce the effects of moiré. We describe a technique using the moiré magnifier to fine-tune the alignment of the LCD layers

비등방성 광학 소자를 이용한 광 시야각 근안 디스플레이

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2019. 2. 이병호.Near-eye display is considered as a promising display technique to realize augmented reality by virtue of its high sense of immersion and user-friendly interface. Among the important performances of near-eye display, a field of view is the most crucial factor for providing a seamless and immersive experience for augmented reality. In this dissertation, a transmissive eyepiece is devised instead of a conventional reflective eyepiece and it is discussed how to widen the field of view without loss of additional system performance. In order to realize the transmissive eyepiece, the eyepiece should operate lens to virtual information and glass to real-world scene. Polarization multiplexing technique is used to implement the multi-functional optical element, and anisotropic optical elements are used as material for multi-functional optical element. To demonstrate the proposed idea, an index-matched anisotropic crystal lens has been presented that reacts differently depending on polarization. With the combination of isotropic material and anisotropic crystal, the index-matched anisotropic crystal lens can be the transmissive eyepiece and achieve the large field of view. Despite the large field of view by the index-matched anisotropic crystal lens, many problems including form factor still remain to be solved. In order to overcome the limitations of conventional optics, a metasurface is adopted to the augmented reality application. With a stunning optical performance of the metasurface, a see-through metasurface lens is proposed and designed for implementing wide field of view near-eye display. The proposed novel eyepieces are expected to be an initiative study not only improving the specification of the existing near-eye display but opening the way for a next generation near-eye display.근안 디스플레이는 높은 몰입감과 사용자 친화적인 인터페이스로 인해 증강 현실을 구현하는 가장 효과적인 기술로 최근 활발한 연구가 계속되고 있다. 이러한 근안 디스플레이의 중요한 성능 중 시야각은 매끄럽고 몰입감 있는 경험을 사용자에게 전해줌으로써 가장 중요한 광학적 평가지표 중에 하나이다. 본 논문에서는 기존의 반사형 아이피스 (eyepiece) 를 대신하는 투과형 아이피스를 제안한다. 이러한 투과형 아이피스를 구현하기 위해서는 외부 정보에 대해서는 투명한 유리와 같이 투과시키며, 동시에 가상 정보는 렌즈로 작동하여 먼 거리에 띄울 수 있는 광학소자를 개발하여야 한다. 이러한 투과형 아이피스를 구현하기 위해서 편광에 따라 다르게 반응하는 굴절률 정합 이방성 결정 렌즈 (index-matched anisotropic crystal lens) 를 제안하였다. 이방성 결정 구조 (anisotropic crystal)로 이루어진 렌즈와 이를 둘러싼 등방성 물질 (isotropic crytal) 로 이루어진 굴절률 정합 이방성 결정 렌즈는 편광에 따라 다르게 작동한다. 이러한 투과형 아이피스는 기존의 근안 디스플레이에 비해 넓은 시야각을 제공할 수 있지만 이방성 결정 구조의 낮은 굴절률 차이로 인해 시스템의 크기가 커지는 단점을 가지고 있다. 본 논문에서는 이러한 단점을 개선하기 위해 메타 표면을 증강 현실 디스플레이 분야에 적용하였다. 메타 표면의 기존 광학 소자를 능가하는 놀라운 광학 성능을 이용하여 넓은 시야각을 가지는 근안 디스플레이를 구현하기 위해 투명 메타 렌즈를 제안하였다. 편광에 따라 다르게 반응하는 투명 메타렌즈는 넓은 시야각과 경량화 시스템 구현이 가능하며 이를 입증하기 위해 투명 메타렌즈의 설계 방법 뿐 아니라 실제 구현을 통한 가능성을 입증하였다. 이러한 새로운 아이피스에 대한 개념은 기존의 근안 디스플레이의 사양 개선에 유용하게 사용될 뿐 아니라 차세대 근안 디스플레이를 위한 선도적인 역할을 할 것으로 기대된다.Abstract Contents List of Tables List of Figures Near-eye displays with wide field of view using anisotropic optical elements Chapter 1 Introduction 1.1 Near-eye displays for augmented reality 1.2 Optical performances of near-eye display 1.3 State-of-the-arts of near-eye display 1.4 Motivation and contribution of this dissertation Chapter 2 Transmissive eyepiece for wide field of view near-eye display 2.1 Transmissive eyepiece for near-eye display Chapter 3 Near-eye display using index-matched anisotropic crystal lens 3.1 Introduction 3.2 Index-matched anisotropic crystal lens 3.2.1 Principle of the index-matched anisotropic crystal lens 3.2.2 Aberration analysis of index-matched anisotropic crystal lens 3.2.3 Implementation 3.3 Near-eye displays using index-matched anisotropic crystal lens 3.3.1 Near-eye display using index-matched anisotropic crystal lens 3.3.2 Flat panel type near-eye display using IMACL 3.3.3 Polarization property of transparent screen 3.4 Conclusion Chapter 4 Near-eye display using metasurface lens 4.1 Introduction 4.2 See-through metasurface lens 4.2.1 Metasurface lens 4.3 Full-color near-eye display using metasurface lens 4.3.1 Full-color near-eye display using metasurface lens 4.3.2 Holographic near-eye display using metasurface lens for aberration compensation 4.4 Conclusion Chapter 5 Conclusion Bibliography AppendixDocto

Wide band frequency tracker performance and design of an all angle laser Doppler optical homodyne receiver, ground wind and wind tunnel measurements program, volume 2 Final report

Analysis and measurement of characteristics of wide band frequency trackers and design and fabrication of all angle laser Doppler velocimete

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

Aperture scanning Fourier ptychographic microscopy

Fourier ptychographic microscopy (FPM) is implemented through aperture scanning by an LCOS spatial light modulator at the back focal plane of the objective lens. This FPM configuration enables the capturing of the complex scattered field for a 3D sample both in the transmissive mode and the reflective mode. We further show that by combining with the compressive sensing theory, the reconstructed 2D complex scattered field can be used to recover the 3D sample scattering density. This implementation expands the scope of application for FPM and can be beneficial for areas such as tissue imaging and wafer inspection