920 research outputs found

    Dense Reconstruction of Transparent Objects by Altering Incident Light Paths Through Refraction

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    Capturing and Reconstructing the Appearance of Complex {3D} Scenes

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    In this thesis, we present our research on new acquisition methods for reflectance properties of real-world objects. Specifically, we first show a method for acquiring spatially varying densities in volumes of translucent, gaseous material with just a single image. This makes the method applicable to constantly changing phenomena like smoke without the use of high-speed camera equipment. Furthermore, we investigated how two well known techniques -- synthetic aperture confocal imaging and algorithmic descattering -- can be combined to help looking through a translucent medium like fog or murky water. We show that the depth at which we can still see an object embedded in the scattering medium is increased. In a related publication, we show how polarization and descattering based on phase-shifting can be combined for efficient 3D~scanning of translucent objects. Normally, subsurface scattering hinders the range estimation by offsetting the peak intensity beneath the surface away from the point of incidence. With our method, the subsurface scattering is reduced to a minimum and therefore reliable 3D~scanning is made possible. Finally, we present a system which recovers surface geometry, reflectance properties of opaque objects, and prevailing lighting conditions at the time of image capture from just a small number of input photographs. While there exist previous approaches to recover reflectance properties, our system is the first to work on images taken under almost arbitrary, changing lighting conditions. This enables us to use images we took from a community photo collection website

    ํˆฌ๋ช…ํ•œ ๋งค์งˆ์—์„œ์˜ ๊ด‘ ๊ฒฝ๋กœ ๋ถ„์„์„ ์ด์šฉํ•œ ์ง‘์•ฝ์  3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ)-- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ์ „๊ธฐยท์ปดํ“จํ„ฐ๊ณตํ•™๋ถ€, 2017. 2. ์ด๋ณ‘ํ˜ธ.๋ณธ ๋ฐ•์‚ฌํ•™์œ„ ๋…ผ๋ฌธ์—์„œ๋Š” ๊ด‘ํ•™์ ์œผ๋กœ ํˆฌ๋ช…ํ•œ ๋งค์งˆ์—์„œ์˜ ๊ด‘ ๊ฒฝ๋กœ ๋ถ„์„์„ ๋ฐ”ํƒ•์œผ๋กœ ์ง‘์•ฝ์ ์ธ 3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด ์‹œ์Šคํ…œ์„ ๊ตฌํ˜„ํ•˜๋Š” ์ ‘๊ทผ ๋ฐฉ๋ฒ•์— ๋Œ€ํ•˜์—ฌ ๋…ผ์˜ํ•œ๋‹ค. 3์ฐจ์› ์˜์ƒ ์žฅ์น˜๋ฅผ ๊ตฌ์„ฑํ•˜๋Š” ์š”์†Œ์™€ ์‹œ์ฒญ์ž ์‚ฌ์ด์˜ ๋ฌผ๋ฆฌ์ ์ธ ๊ฑฐ๋ฆฌ๋ฅผ ์ค„์ด๋Š” ๊ฒƒ์€ ์ง‘์•ฝ์ ์ธ 3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด ์‹œ์Šคํ…œ์„ ๊ตฌํ˜„ํ•˜๋Š” ์ง๊ด€์ ์ธ ๋ฐฉ๋ฒ•์ด๋‹ค. ๋˜ํ•œ, ๊ธฐ์กด ์‹œ์Šคํ…œ์˜ ํฌ๊ธฐ๋ฅผ ์œ ์ง€ํ•˜๋ฉด์„œ ๋” ๋งŽ์€ ์–‘์˜ 3์ฐจ์› ์˜์ƒ ์ •๋ณด๋ฅผ ํ‘œํ˜„ํ•˜๋Š” ๊ฒƒ ๋˜ํ•œ ์ง‘์•ฝ์  3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด ์‹œ์Šคํ…œ์„ ์˜๋ฏธํ•œ๋‹ค. ๋†’์€ ๋Œ€์—ญํญ๊ณผ ์ž‘์€ ๊ตฌ์กฐ๋ฅผ ๊ฐ€์ง„ ์ง‘์•ฝ์  3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด ์‹œ์Šคํ…œ์„ ๊ตฌํ˜„ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋‹ค์Œ์˜ ๋‘ ๊ฐ€์ง€ ๊ด‘ํ•™ ํ˜„์ƒ์„ ์ด์šฉํ•œ๋‹ค. ๋“ฑ๋ฐฉ์„ฑ ๋ฌผ์งˆ์—์„œ์˜ ์ „๋ฐ˜์‚ฌ ํŠน์„ฑ๊ณผ ์ด๋ฐฉ์„ฑ ๋ฌผ์งˆ์—์„œ์˜ ๋ณต๊ตด์ ˆ ํŠน์„ฑ์ด๋‹ค. ๊ฐ€์‹œ๊ด‘ ์˜์—ญ์—์„œ ๋น›์„ ํˆฌ๊ณผ์‹œํ‚ค๋Š” ๋‘ ๋งค์งˆ์˜ ๊ณ ์œ  ๊ด‘ํ•™ ํŠน์„ฑ์„ ๊ธฐ์กด์˜ 3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด ์‹œ์Šคํ…œ์— ์ ์šฉํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๊ด‘ ๊ฒฝ๋กœ ์ถ”์ ์„ ํ†ตํ•˜์—ฌ ๋ถ„์„ํ•œ๋‹ค. ๊ด‘ ๋„ํŒŒ๋กœ์˜ ์ „๋ฐ˜์‚ฌ ํŠน์„ฑ์€ ์ง‘์•ฝ์  ๋‹ค์ค‘ ํˆฌ์‚ฌ 3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด ์‹œ์Šคํ…œ์„ ๊ตฌํ˜„ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์‚ฌ์šฉํ•œ๋‹ค. ํˆฌ์‚ฌ ๊ด‘ํ•™๊ณ„์˜ ์˜์ƒ ์ •๋ณด๋Š” ๊ด‘ ๋„ํŒŒ๋กœ๋กœ ์ž…์‚ฌ, ๋‚ด๋ถ€์—์„œ ์ „๋ฐ˜์‚ฌ๋ฅผ ํ†ตํ•˜์—ฌ ์ง„ํ–‰ํ•˜๊ณ , ์ด์— ์ˆ˜ํ‰ ํˆฌ์‚ฌ ๊ฑฐ๋ฆฌ๋Š” ๊ด‘ ๋„ํŒŒ๋กœ์˜ ๋‘๊ป˜๋กœ ์ œํ•œ๋œ๋‹ค. ๋‹ค์ˆ˜์˜ ์ „๋ฐ˜์‚ฌ ์ดํ›„ ์˜์ƒ ์ •๋ณด๋Š” ๊ด‘ ๋„ํŒŒ๋กœ์˜ ์ถœ์‚ฌ ๋ฉด์„ ํ†ตํ•ด ๋น ์ ธ๋‚˜๊ฐ€๊ณ , ๋ Œ์ฆˆ์— ์˜ํ•˜์—ฌ ์ตœ์  ์‹œ์ฒญ ์ง€์ ์—์„œ ์‹œ์ ์„ ํ˜•์„ฑํ•œ๋‹ค. ๊ด‘ ๋„ํŒŒ๋กœ ๋‚ด๋ถ€์—์„œ์˜ ๊ด‘ ๊ฒฝ๋กœ๋ฅผ ๋“ฑ๊ฐ€ ๋ชจ๋ธ์„ ํ†ตํ•˜์—ฌ ์กฐ์‚ฌํ•˜๊ณ , ์ด๋ฅผ ํ†ตํ•ด ๋‹ค์ˆ˜์˜ ํˆฌ์‚ฌ ๊ด‘ํ•™๊ณ„๋กœ๋ถ€ํ„ฐ ์ƒ์„ฑ๋œ ๋‹ค์ˆ˜์˜ ์‹œ์  ์˜์ƒ์ด ์™œ๊ณก๋˜๋Š” ๊ฒƒ์„ ๋ถ„์„ํ•˜๊ณ  ๋ณด์ •ํ•œ๋‹ค. 10๊ฐœ์˜ ์‹œ์ ์„ ์ œ๊ณตํ•˜๋Š” ์ง‘์•ฝ์  ๋‹ค์ค‘ ํˆฌ์‚ฌ 3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด ์‹œ์Šคํ…œ์„ ํ†ตํ•ด ์ œ์•ˆ๋œ ๋ฐฉ๋ฒ•์„ ๊ฒ€์ฆํ•œ๋‹ค. ํ–ฅ์ƒ๋œ ๋Œ€์—ญํญ ํŠน์„ฑ์„ ๊ฐ€์ง„ ๋‹ค์ค‘ ํˆฌ์‚ฌ 3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด์™€ ๋‹ค์ค‘ ์ดˆ์  ํ—ค๋“œ ๋งˆ์šดํŠธ ๋””์Šคํ”Œ๋ ˆ์ด ๊ตฌํ˜„์„ ์œ„ํ•œ ์ด๋ฐฉ์„ฑ ํŒ์„ ์ด์šฉํ•œ ํŽธ๊ด‘ ๋‹ค์ค‘ํ™” ๋ฐฉ๋ฒ•์„ ์ œ์•ˆํ•œ๋‹ค. ๋น›์˜ ํŽธ๊ด‘ ์ƒํƒœ, ์ด๋ฐฉ์„ฑ ํŒ์˜ ๊ด‘์ถ• ๋ฐฉํ–ฅ์— ๋”ฐ๋ผ ๊ด‘ ๊ฒฝ๋กœ๊ฐ€ ๋‹ฌ๋ผ์ง„๋‹ค. ์ธก๋ฉด ๋ฐฉํ–ฅ์œผ๋กœ์˜ ๊ด‘ ๊ฒฝ๋กœ ์ „ํ™˜์€ ๋‹ค์ค‘ ํˆฌ์‚ฌ 3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด ๊ธฐ์ˆ ๊ณผ ๊ฒฐํ•ฉํ•˜์—ฌ ์‹œ์ ์„ ์ธก๋ฉด ๋ฐฉํ–ฅ์œผ๋กœ ๋‘ ๋ฐฐ๋กœ ์ฆ๊ฐ€์‹œํ‚จ๋‹ค. ๊นŠ์ด ๋ฐฉํ–ฅ์œผ๋กœ์˜ ๊ด‘ ๊ฒฝ๋กœ ์ „ํ™˜์€ ํ—ค๋“œ ๋งˆ์šดํŠธ ๋””์Šคํ”Œ๋ ˆ์ด์—์„œ ๋‹ค์ค‘ ์ดˆ์  ๊ธฐ๋Šฅ์„ ๊ตฌํ˜„ํ•œ๋‹ค. ๊ด‘ ๊ฒฝ๋กœ ์ถ”์  ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ํ†ตํ•ด ์ด๋ฐฉ์„ฑ ํŒ์˜ ๋ชจ์–‘, ๊ด‘์ถ•, ํŒŒ์žฅ ๋“ฑ์˜ ๋‹ค์–‘ํ•œ ํŒŒ๋ผ๋ฏธํ„ฐ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ๊ด‘ ๊ฒฝ๋กœ ์ „ํ™˜์„ ๋ถ„์„ํ•œ๋‹ค. ๊ฐ๊ฐ์˜ ๊ธฐ๋Šฅ์— ๋งž๋„๋ก ์„ค๊ณ„๋œ ์ด๋ฐฉ์„ฑ ํŒ๊ณผ ํŽธ๊ด‘ ํšŒ์ „์ž๋ฅผ ์‹ค์‹œ๊ฐ„์œผ๋กœ ๊ฒฐํ•ฉํ•˜์—ฌ, ๋‹ค์ค‘ ํˆฌ์‚ฌ 3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด์™€ ๋‹ค์ค‘ ์ดˆ์  ํ—ค๋“œ ๋งˆ์šดํŠธ ๋””์Šคํ”Œ๋ ˆ์ด์˜ ๋Œ€์—ญํญ์ด 2๋ฐฐ ์ฆ๊ฐ€ํ•œ๋‹ค. ๊ฐ ์‹œ์Šคํ…œ์— ๋Œ€ํ•œ ์‹œ์ž‘ํ’ˆ์„ ์ œ์ž‘ํ•˜๊ณ , ์ œ์•ˆ๋œ ๋ฐฉ๋ฒ•์„ ์‹คํ—˜์ ์œผ๋กœ ๊ฒ€์ฆํ•œ๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ๊ด‘ ๋„ํŒŒ๋กœ์™€ ๋ณต๊ตด์ ˆ ๋ฌผ์งˆ์„ ์ด์šฉํ•˜์—ฌ ๊ทธ ๊ด‘ ๊ฒฝ๋กœ๋ฅผ ๋ถ„์„, ๋Œ€ํ˜•์˜ ๋‹ค์ค‘ ํˆฌ์‚ฌ 3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด ์‹œ์Šคํ…œ๊ณผ ๊ฐœ์ธ ์‚ฌ์šฉ์ž์˜ ํ—ค๋“œ ๋งˆ์šดํŠธ ๋””์Šคํ”Œ๋ ˆ์ด ์‹œ์Šคํ…œ์˜ ํฌ๊ธฐ๋ฅผ ๊ฐ์†Œ์‹œํ‚ค๊ณ , ํ‘œํ˜„ ๊ฐ€๋Šฅํ•œ ์ •๋ณด๋Ÿ‰์„ ์ฆ๊ฐ€์‹œํ‚ค๋Š” ๋ฐฉ๋ฒ•์„ ์ œ์•ˆํ•œ๋‹ค. ๊ด‘ ๋„ํŒŒ๋กœ์™€ ์ด๋ฐฉ์„ฑ ํŒ์€ ๊ธฐ์กด์˜ 3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด ์‹œ์Šคํ…œ๊ณผ ์‰ฝ๊ฒŒ ๊ฒฐํ•ฉ์ด ๊ฐ€๋Šฅํ•˜๋ฉฐ, ์ œ์•ˆ๋œ ๋ฐฉ๋ฒ•์€ ํ–ฅํ›„ ์†Œํ˜•๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ์ค‘๋Œ€ํ˜• 3์ฐจ์› ๋””์Šคํ”Œ๋ ˆ์ด ์‹œ์Šคํ…œ์˜ ์ง‘์•ฝํ™”์— ๊ธฐ์—ฌํ•  ์ˆ˜ ์žˆ์„ ๊ฒƒ์œผ๋กœ ๊ธฐ๋Œ€๋œ๋‹ค.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 ์ดˆ ๋ก 130Docto

    Reconsidering light transport : acquisition and display of real-world reflectance and geometry

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    In this thesis, we cover three scenarios that violate common simplifying assumptions about the nature of light transport. We begin with the first ingredient to any รงD rendering: a geometry model. Most รงD scanners require the object-of-interest to show diffuse refectance. The further a material deviates from the Lambertian model, the more likely these setups are to produce corrupted results. By placing a traditional laser scanning setup in a participating (in particular, fuorescent) medium, we have built a light sheet scanner that delivers robust results for a wide range of materials, including glass. Further investigating the phenomenon of fluorescence, we notice that, despite its ubiquity, it has received moderate attention in computer graphics. In particular, to date no datadriven reflectance models of fluorescent materials have been available. To describe the wavelength-shifling reflectance of fluorescent materials, we define the bispectral bidirectional reflectance and reradiation distribution function (BRRDF), for which we introduce an image-based measurement setup as well as an efficient acquisition scheme. Finally, we envision a computer display that showsmaterials instead of colours, and present a prototypical device that can exhibit anisotropic reflectance distributions similar to common models in computer graphics.In der Computergraphik und Computervision ist es unerlรคsslich, vereinfachende Annahmen รผber die Ausbreitung von Licht zumachen. In dieser Dissertation stellen wir drei Fรคlle vor, in denen diese nicht zutreffen. So wird die dreidimensionale Geometrie von Gegenstรคnden oft mit Hilfe von Laserscannern vermessen und dabei davon ausgegangen, dass ihre Oberflรคche diffus reflektiert. Dies ist bei den meisten Materialien jedoch nicht gegeben, so dass die Ergebnisse oft fehlerhaft sind. Indem wir das Objekt in einem fluoreszierenden Medium einbetten, kann ein klassischer CD-Scanner-Aufbau so modifiziert werden, dass er verlรคssliche Geometriedaten fรผr Objekte aus verschiedensten Materialien liefert, einschlieรŸlich Glas. Auch die akkurate Nachbildung des Aussehens von Materialien ist wichtig fรผr die photorealistische Bildsynthese. Wieder interessieren wir uns fรผr Fluoreszenz, diesmal allerdings fรผr ihr charakteristisches Erscheinungsbild, das in der Computergraphik bislang kaum Beachtung gefunden hat. Wir stellen einen bildbasierten Aufbau vor, mit dem die winkel- und wellenlรคngenabhรคngige Reflektanz fluoreszierender Oberflรคchen ausgemessen werden kann, und eine Strategie, um solche Messungen effizient abzuwickeln. SchlieรŸlich befassen wir uns mit der Idee, nicht nur Farben dynamisch anzuzeigen, sondern auch Materialien und ihr je nach Lichteinfall und Blickwinkel unterschiedliches Aussehen. Einer generellen Beschreibung des Problems folgt die konkrete Umsetzung in Formzweier Prototypen, die verschiedene Reflektanzverteilungen auf einer Oberflรคche darstellen kรถnnen

    DEVELOPING ELECTROMAGNETIC AND PHOTONIC DEVICES BY USING ARTIFICIAL DIELECTRIC MATERIALS

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    Transformation-Optics (TO) is a new theoretical tool that allows for designing advanced electromagnetic and photonic devices. TO theory often prescribes material parameters for transformed media that cannot be found in nature. Metamaterials (MMs) were initially used for realization of TO-based devices. However, conventional MMs possess noticeable losses caused by their metallic parts that prevents their utilization in optical range. Alternatively, photonic crystals (PhCs) formed from arrays of low-loss all-dielectric elements can be good substitutes for building TO-prescribed devices. Metasurfaces (MSs) comprised from 2D arrays of dielectric resonators (DRs) have been found as other promising candidates for realizing flat and efficient devices. In our work, we explored incorporation of all-dielectric artificial media in invisibility cloaks, representing the most exciting TO application, wave collimators, and MSs. We studied associated electromagnetic and photonic phenomena and solved engineering problems met at the development of device prototypes. We designed and used anisotropic PhCs composed of rectangular lattice dielectric rod arrays to build up a cylindrical cloak medium realizing prescriptions of TO (Chapter 2). We also formed another cylindrical invisibility cloak by utilizing the self-collimation phenomenon in PhCs without considering TO prescriptions for turning the wave in the cloak medium (Chapter 3). Furthermore, we designed a wave collimator by employing high-anisotropic rectangular lattice dielectric rod arrays with unidirectional near-zero refractive indices (Chapter 4). Then, we studied the resonance and scattering responses of MSs composed of dielectric disks, while altering the periodicity of MSs. Our results demonstrated that periodicity of arrays has significant influence on defining the responses of MSs. (Chapter 5). Increasing lattice constants of dielectric MSs provided us with an opportunity to investigate interactions between lattice resonances (LRs) and dipolar electric and magnetic resonances that affected characteristics of MSs (Chapter 6). We analyzed the formation of Fano responses and wave interference processes in dense MSs to reveal the nature of electromagnetically induced transparency (EIT) that was detected at the frequency of electric dipolar resonance. (Chapter 7)

    Design and evaluation of a full-sensitivity tilt scanning interferometry system for displacement field tomography and profilometry

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    This thesis reports the investigation and further development of a tilt scanning interferometry system for surface profilometry and sub-surface tomographic applications. A new 3D full sensitivity interferometry system extends the work carried out on a previous prototype that was capable of measuring displacement along one lateral plus the axial component. Depth-resolved imaging is achieved by the acquisition of a sequence of 2D interferograms whilst the illumination beam undergoes a constant rate of tilt and full sensitivity displacement is achieved by performing scans from multiple illumination directions. The comparison of phase volumes from two successive series of scans enables 3D displacement fields to be determined. The working principle that describes the technique is presented, covering the reconstruction of a depth-resolved sample from the detected intensity distribution. The system performance is studied, including measurement repeatability and factors that affect the depth resolution and depth range. Depth resolution is fundamentally limited by the range of the illumination tilting angle and the new system design enables a larger range. However, the resolution is degraded by a frequency chirp that appears in the temporal interference signal when a large tilting range is scanned. It is shown through a numerical simulation that the chirp depends on the curvature of the illumination wavefront and also on the position of the pivot axis of the illumination beam. Data processing methods are proposed to overcome these limitations and their effects are illustrated with experimental measurements of opaque surfaces and a weakly scattering phantom with internal features. Displacement measurements involving a controlled rigid body rotation and tilt of a weakly scattering phantom were completed to validate the expected deformations. Both in-plane and out-of-plane components were measured

    ACM Transactions on Graphics

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    Additive manufacturing has recently seen drastic improvements in resolution, making it now possible to fabricate features at scales of hundreds or even dozens of nanometers, which previously required very expensive lithographic methods. As a result, additive manufacturing now seems poised for optical applications, including those relevant to computer graphics, such as material design, as well as display and imaging applications. In this work, we explore the use of additive manufacturing for generating structural colors, where the structures are designed using a fabrication-aware optimization process. This requires a combination of full-wave simulation, a feasible parameterization of the design space, and a tailored optimization procedure. Many of these components should be re-usable for the design of other optical structures at this scale. We show initial results of material samples fabricated based on our designs. While these suffer from the prototype character of state-of-the-art fabrication hardware, we believe they clearly demonstrate the potential of additive nanofabrication for structural colors and other graphics applications

    Nondestructive evaluation of 3d printed, extruded, and natural polymer structures using terahertz spectroscopy and imaging

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    Terahertz (THz) spectroscopy and imaging are considered for the nondestructive evaluation (NDE) of various three-dimensional (3D) printed, extruded, and natural polymer structures. THz radiation is the prime candidate for many NDE challenges due to the added benefits of safety, increased contrast and depth resolution, and optical characteristic visualization when compared to other techniques. THz imaging, using a wide bandwidth pulse-based system, can evaluate the external and internal structure of most nonconductive and nonpolar materials without any permanent effects. NDE images can be created based on THz pulse attributes or a materialโ€™s spectroscopic characteristics such as refractive index, attenuation coefficient, or the level birefringence present within. The evaluation processes for polyethylene gas pipes and amber specimens lack efficient and accurate NDE techniques while 3D printed polymer structures currently have no standardized NDE methods. The primary focus of this research is to determine and evaluate the use of THz spectroscopy and imaging as a NDE technique for a variety of polymers extruded mechanically and naturally. Results indicate the refractive indices, attenuation coefficients, and level of birefringence of several 3D printing filaments including copolyester (CPE), nylon, polycarbonate (PC), polylactic acid (PLA), and polypropylene (PP) may change depending on the printing parameters. THz spectroscopy is used to measure relative permittivity of printed ceramic samples with various sintering temperatures. THz imaging proves to be a successful method to diagnose print head misalignment in ceramic nanoparticle jetting printing processes. Proper diagnosis of surface level defects on polyethylene (PE) gas pipelines is achieved along with preliminary joint fault imaging and 3D visualization by creating an interactive detailed map of surface level defects. THz NDE imaging, combined with tailored refractive index matching materials, can construct tomographic images and 3D reconstructions of multi-million-year-old amber. Visual and THz birefringence images are created to determine stress direction within extruded PE and amber. These results suggest that THz spectroscopy and imaging have multiple confirmed uses in the NDE of polymer structures, both mechanically and naturally fabricated

    Computational Light Transport for Forward and Inverse Problems.

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    El transporte de luz computacional comprende todas las tรฉcnicas usadas para calcular el flujo de luz en una escena virtual. Su uso es ubicuo en distintas aplicaciones, desde entretenimiento y publicidad, hasta diseรฑo de producto, ingenierรญa y arquitectura, incluyendo el generar datos validados para tรฉcnicas basadas en imagen por ordenador. Sin embargo, simular el transporte de luz de manera precisa es un proceso costoso. Como consecuencia, hay que establecer un balance entre la fidelidad de la simulaciรณn fรญsica y su coste computacional. Por ejemplo, es comรบn asumir รณptica geomรฉtrica o una velocidad de propagaciรณn de la luz infinita, o simplificar los modelos de reflectancia ignorando ciertos fenรณmenos. En esta tesis introducimos varias contribuciones a la simulaciรณn del transporte de luz, dirigidas tanto a mejorar la eficiencia del cรกlculo de la misma, como a expandir el rango de sus aplicaciones prรกcticas. Prestamos especial atenciรณn a remover la asunciรณn de una velocidad de propagaciรณn infinita, generalizando el transporte de luz a su estado transitorio. Respecto a la mejora de eficiencia, presentamos un mรฉtodo para calcular el flujo de luz que incide directamente desde luminarias en un sistema de generaciรณn de imรกgenes por Monte Carlo, reduciendo significativamente la variancia de las imรกgenes resultantes usando el mismo tiempo de ejecuciรณn. Asimismo, introducimos una tรฉcnica basada en estimaciรณn de densidad en el estado transitorio, que permite reusar mejor las muestras temporales en un medio parcipativo. En el dominio de las aplicaciones, tambiรฉn introducimos dos nuevos usos del transporte de luz: Un modelo para simular un tipo especial de pigmentos gonicromรกticos que exhiben apariencia perlescente, con el objetivo de proveer una forma de ediciรณn intuitiva para manufactura, y una tรฉcnica de imagen sin lรญnea de visiรณn directa usando informaciรณn del tiempo de vuelo de la luz, construida sobre un modelo de propagaciรณn de la luz basado en ondas.<br /
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