Atomic Layer Deposition of Chemical Passivation Layers and High Performance Anti-Reflection Coatings on Back-Illuminated Detectors

A back-illuminated silicon photodetector has a layer of Al2O3 deposited on a silicon oxide surface that receives electromagnetic radiation to be detected. The Al2O3 layer has an antireflection coating deposited thereon. The Al2O3 layer provides a chemically resistant separation layer between the silicon oxide surface and the antireflection coating. The Al2O3 layer is thin enough that it is optically innocuous. Under deep ultraviolet radiation, the silicon oxide layer and the antireflection coating do not interact chemically. In one embodiment, the silicon photodetector has a delta-doped layer near (within a few nanometers of) the silicon oxide surface. The Al2O3 layer is expected to provide similar protection for doped layers fabricated using other methods, such as MBE, ion implantation and CVD deposition

Electrically Addressable Hybrid Architectures of Zinc Oxide Nanowires Grown on Aligned Carbon Nanotubes

The fabrication and characterization of hybrid architectures of ZnO nanowires (ZNWs) grown on organized carbon nanotubes (CNTs), by a two-step chemical vapor deposition (CVD) process involving CNT growth from a hydrocarbon source followed by ZNW growth using a Zn metal source, is reported. The ZNWs grow uniformly and radially from individual CNTs and CNT bundles, and the aligned morphology of the CNTs is not disturbed by the ZNW growth process. The nucleation and growth of ZnO crystals on CNTs are analyzed in relation to the classical vapor–solid mechanism. Importantly, the CNTs make uniform and distributed electrical contact to the ZNWs, with up to a 1000-fold yield advantage over conventional ZNW growth on a flat substrate. Hybrid ZNW/CNT sheets are fabricated by scalable CVD, rolling, and printing methods; and their electrical properties, which are governed by transport through the anisotropic CNT network, are characterized. Functional interaction between the ZNWs and CNTs is demonstrated by photoconductive behavior and photocurrent generation of the hybrid material under UV illumination. There is significant future opportunity to extend these processing methods to fabricate other functional oxides on CNTs, and to build devices that harness the attractive properties of ZNWs and CNTs with high volumetric efficiency over large areas.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77980/1/2470_ftp.pd

Ultrasound-mediated Optical Imaging and Focusing in Scattering Media

Because of its non-ionizing and molecular sensing nature, light has been an attractive tool in biomedicine. Scanning an optical focus allows not only high-resolution imaging but also manipulation and therapy. However, due to multiple photon scattering events, conventional optical focusing using an ordinary lens is limited to shallow depths of one transport mean free path (lt\u27), which corresponds to approximately 1 mm in human tissue. To overcome this limitation, ultrasonic modulation (or encoding) of diffuse light inside scattering media has enabled us to develop both deep-tissue optical imaging and focusing techniques, namely, ultrasound-modulated optical tomography (UOT) and time-reversed ultrasonically encoded (TRUE) optical focusing. While UOT measures the power of the encoded light to obtain an image, TRUE focusing generates a time-reversed (or phase-conjugated) copy of the encoded light, using a phase-conjugate mirror to focus light inside scattering media beyond 1 lt\u27. However, despite extensive progress in both UOT and TRUE focusing, the low signal-to-noise ratio in encoded-light detection remains a challenge to meeting both the speed and depth requirements for in vivo applications. This dissertation describes technological advancements of both UOT and TRUE focusing, in terms of their signal detection sensitivities, operational depths, and operational speeds. The first part of this dissertation describes sensitivity improvements of encoded-light detection in UOT, achieved by using a large area (∼5 cm × 5 cm) photorefractive polymer. The photorefractive polymer allowed us to improve the detection etendue by more than 10 times that of previous detection schemes. It has enabled us to resolve absorbing objects embedded inside diffused media thicker than 80 lt\u27, using moderate light power and short ultrasound pulses. The second part of this dissertation describes energy enhancement and fluorescent excitation using TRUE focusing in turbid media, using photorefractive materials as the phase-conjugate mirrors. By using a large-area photorefractive polymer as the phase-conjugate mirror, we boosted the focused optical energy by ~40 times over the output of a previously used photorefractive Bi12SiO20 crystal. Furthermore, using both a photorefractive polymer and a Bi12SiO20 crystal as the phase-conjugate mirrors, we show direct visualization and dynamic control of TRUE focus, and demonstrate fluorescence imaging in a thick turbid medium. The last part of this dissertation describes improvements in the scanning speed of a TRUE focus, using digital phase-conjugate mirrors in both transmission and reflection modes. By employing a multiplex recording of ultrasonically encoded wavefronts in transmission mode, we have accelerated the generation of multiple TRUE foci, using frequency sweeping of both ultrasound and light. With this technique, we obtained a 2-D image of a fluorescent target centered inside a turbid sample having a thickness of 2.4 lt\u27. Also, by gradually moving the focal position in reflection mode, we show that the TRUE focal intensity is improved, and can be continuously scanned to image fluorescent targets in a shorter time

특징 혼합 네트워크를 이용한 영상 정합 기법과 고 명암비 영상법 및 비디오 고 해상화에서의 응용

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2020. 8. 조남익.This dissertation presents a deep end-to-end network for high dynamic range (HDR) imaging of dynamic scenes with background and foreground motions. Generating an HDR image from a sequence of multi-exposure images is a challenging process when the images have misalignments by being taken in a dynamic situation. Hence, recent methods first align the multi-exposure images to the reference by using patch matching, optical flow, homography transformation, or attention module before the merging. In this dissertation, a deep network that synthesizes the aligned images as a result of blending the information from multi-exposure images is proposed, because explicitly aligning photos with different exposures is inherently a difficult problem. Specifically, the proposed network generates under/over-exposure images that are structurally aligned to the reference, by blending all the information from the dynamic multi-exposure images. The primary idea is that blending two images in the deep-feature-domain is effective for synthesizing multi-exposure images that are structurally aligned to the reference, resulting in better-aligned images than the pixel-domain blending or geometric transformation methods. Specifically, the proposed alignment network consists of a two-way encoder for extracting features from two images separately, several convolution layers for blending deep features, and a decoder for constructing the aligned images. The proposed network is shown to generate the aligned images with a wide range of exposure differences very well and thus can be effectively used for the HDR imaging of dynamic scenes. Moreover, by adding a simple merging network after the alignment network and training the overall system end-to-end, a performance gain compared to the recent state-of-the-art methods is obtained. This dissertation also presents a deep end-to-end network for video super-resolution (VSR) of frames with motions. To reconstruct an HR frame from a sequence of adjacent frames is a challenging process when the images have misalignments. Hence, recent methods first align the adjacent frames to the reference by using optical flow or adding spatial transformer network (STN). In this dissertation, a deep network that synthesizes the aligned frames as a result of blending the information from adjacent frames is proposed, because explicitly aligning frames is inherently a difficult problem. Specifically, the proposed network generates adjacent frames that are structurally aligned to the reference, by blending all the information from the neighbor frames. The primary idea is that blending two images in the deep-feature-domain is effective for synthesizing frames that are structurally aligned to the reference, resulting in better-aligned images than the pixel-domain blending or geometric transformation methods. Specifically, the proposed alignment network consists of a two-way encoder for extracting features from two images separately, several convolution layers for blending deep features, and a decoder for constructing the aligned images. The proposed network is shown to generate the aligned frames very well and thus can be effectively used for the VSR. Moreover, by adding a simple reconstruction network after the alignment network and training the overall system end-to-end, A performance gain compared to the recent state-of-the-art methods is obtained. In addition to each HDR imaging and VSR network, this dissertation presents a deep end-to-end network for joint HDR-SR of dynamic scenes with background and foreground motions. The proposed HDR imaging and VSR networks enhace the dynamic range and the resolution of images, respectively. However, they can be enhanced simultaneously by a single network. In this dissertation, the network which has same structure of the proposed VSR network is proposed. The network is shown to reconstruct the final results which have higher dynamic range and resolution. It is compared with several methods designed with existing HDR imaging and VSR networks, and shows both qualitatively and quantitatively better results.본 학위논문은 배경 및 전경의 움직임이 있는 상황에서 고 명암비 영상법을 위한 딥 러닝 네트워크를 제안한다. 움직임이 있는 상황에서 촬영된 노출이 다른 여러 영 상들을 이용하여 고 명암비 영상을 생성하는 것은 매우 어려운 작업이다. 그렇기 때문에, 최근에 제안된 방법들은 이미지들을 합성하기 전에 패치 매칭, 옵티컬 플로우, 호모그래피 변환 등을 이용하여 그 이미지들을 먼저 정렬한다. 실제로 노출 정도가 다른 여러 이미지들을 정렬하는 것은 아주 어려운 작업이기 때문에, 이 논문에서는 여러 이미지들로부터 얻은 정보를 섞어서 정렬된 이미지를 합성하는 네트워크를 제안한다. 특히, 제안하는 네트워크는 더 밝게 혹은 어둡게 촬영된 이미지들을 중간 밝기로 촬영된 이미지를 기준으로 정렬한다. 주요한 아이디어는 정렬된 이미지를 합성할 때 특징 도메인에서 합성하는 것이며, 이는 픽셀 도메인에서 합성하거나 기하학적 변환을 이용할 때 보다 더 좋은 정렬 결과를 갖는다. 특히, 제안하는 정렬 네트워크는 두 갈래의 인코더와 컨볼루션 레이어들 그리고 디코더로 이루어져 있다. 인코더들은 두 입력 이미지로부터 특징을 추출하고, 컨볼루션 레이어들이 이 특징들을 섞는다. 마지막으로 디코더에서 정렬된 이미지를 생성한다. 제안하는 네트워크는 고 명암비 영상법에서 사용될 수 있도록 노출 정도가 크게 차이나는 영상에서도 잘 작동한다. 게다가, 간단한 병합 네트워크를 추가하고 전체 네트워크들을 한 번에 학습함으로서, 최근에 제안된 방법들 보다 더 좋은 성능을 갖는다. 또한, 본 학위논문은 동영상 내 프레임들을 이용하는 비디오 고 해상화 방법을 위한 딥 러닝 네트워크를 제안한다. 동영상 내 인접한 프레임들 사이에는 움직임이 존재하기 때문에, 이들을 이용하여 고 해상도의 프레임을 합성하는 것은 아주 어려운 작업이다. 따라서, 최근에 제안된 방법들은 이 인접한 프레임들을 정렬하기 위해 옵티컬 플로우를 계산하거나 STN을 추가한다. 움직임이 존재하는 프레임들을 정렬하는 것은 어려운 과정이기 때문에, 이 논문에서는 인접한 프레임들로부터 얻은 정보를 섞어서 정렬된 프레임을 합성하는 네트워크를 제안한다. 특히, 제안하는 네트워크는 이웃한 프레임들을 목표 프레임을 기준으로 정렬한다. 마찬가지로 주요 아이디어는 정렬된 프레임을 합성할 때 특징 도메인에서 합성하는 것이다. 이는 픽셀 도메인에서 합성하거나 기하학적 변환을 이용할 때 보다 더 좋은 정렬 결과를 갖는다. 특히, 제안하는 정렬 네트워크는 두 갈래의 인코더와 컨볼루션 레이어들 그리고 디코더로 이루어져 있다. 인코더들은 두 입력 프레임으로부터 특징을 추출하고, 컨볼루션 레이어들이 이 특징들을 섞는다. 마지막으로 디코더에서 정렬된 프레임을 생성한다. 제안하는 네트워크는 인접한 프레임들을 잘 정렬하며, 비디오 고 해상화에 효과적으로 사용될 수 있다. 게다가 병합 네트워크를 추가하고 전체 네트워크들을 한 번에 학습함으로서, 최근에 제안된 여러 방법들 보다 더 좋은 성능을 갖는다. 고 명암비 영상법과 비디오 고 해상화에 더하여, 본 학위논문은 명암비와 해상도를 한 번에 향상시키는 딥 네트워크를 제안한다. 앞에서 제안된 두 네트워크들은 각각 명암비와 해상도를 향상시킨다. 하지만, 그들은 하나의 네트워크를 통해 한 번에 향상될 수 있다. 이 논문에서는 비디오 고해상화를 위해 제안한 네트워크와 같은 구조의 네트워크를 이용하며, 더 높은 명암비와 해상도를 갖는 최종 결과를 생성해낼 수 있다. 이 방법은 기존의 고 명암비 영상법과 비디오 고해상화를 위한 네트워크들을 조합하는 것 보다 정성적으로 그리고 정량적으로 더 좋은 결과를 만들어 낸다.1 Introduction 1 2 Related Work 7 2.1 High Dynamic Range Imaging 7 2.1.1 Rejecting Regions with Motions 7 2.1.2 Alignment Before Merging 8 2.1.3 Patch-based Reconstruction 9 2.1.4 Deep-learning-based Methods 9 2.1.5 Single-Image HDRI 10 2.2 Video Super-resolution 11 2.2.1 Deep Single Image Super-resolution 11 2.2.2 Deep Video Super-resolution 12 3 High Dynamic Range Imaging 13 3.1 Motivation 13 3.2 Proposed Method 14 3.2.1 Overall Pipeline 14 3.2.2 Alignment Network 15 3.2.3 Merging Network 19 3.2.4 Integrated HDR imaging network 20 3.3 Datasets 21 3.3.1 Kalantari Dataset and Ground Truth Aligned Images 21 3.3.2 Preprocessing 21 3.3.3 Patch Generation 22 3.4 Experimental Results 23 3.4.1 Evaluation Metrics 23 3.4.2 Ablation Studies 23 3.4.3 Comparisons with State-of-the-Art Methods 25 3.4.4 Application to the Case of More Numbers of Exposures 29 3.4.5 Pre-processing for other HDR imaging methods 32 4 Video Super-resolution 36 4.1 Motivation 36 4.2 Proposed Method 37 4.2.1 Overall Pipeline 37 4.2.2 Alignment Network 38 4.2.3 Reconstruction Network 40 4.2.4 Integrated VSR network 42 4.3 Experimental Results 42 4.3.1 Dataset 42 4.3.2 Ablation Study 42 4.3.3 Capability of DSBN for alignment 44 4.3.4 Comparisons with State-of-the-Art Methods 45 5 Joint HDR and SR 51 5.1 Proposed Method 51 5.1.1 Feature Blending Network 51 5.1.2 Joint HDR-SR Network 51 5.1.3 Existing VSR Network 52 5.1.4 Existing HDR Network 53 5.2 Experimental Results 53 6 Conclusion 58 Abstract (In Korean) 71Docto

Gradient metasurfaces: a review of fundamentals and applications

In the wake of intense research on metamaterials the two-dimensional analogue, known as metasurfaces, has attracted progressively increasing attention in recent years due to the ease of fabrication and smaller insertion losses, while enabling an unprecedented control over spatial distributions of transmitted and reflected optical fields. Metasurfaces represent optically thin planar arrays of resonant subwavelength elements that can be arranged in a strictly or quasi periodic fashion, or even in an aperiodic manner, depending on targeted optical wavefronts to be molded with their help. This paper reviews a broad subclass of metasurfaces, viz. gradient metasurfaces, which are devised to exhibit spatially varying optical responses resulting in spatially varying amplitudes, phases and polarizations of scattered fields. Starting with introducing the concept of gradient metasurfaces, we present classification of different metasurfaces from the viewpoint of their responses, differentiating electrical-dipole, geometric, reflective and Huygens' metasurfaces. The fundamental building blocks essential for the realization of metasurfaces are then discussed in order to elucidate the underlying physics of various physical realizations of both plasmonic and purely dielectric metasurfaces. We then overview the main applications of gradient metasurfaces, including waveplates, flat lenses, spiral phase plates, broadband absorbers, color printing, holograms, polarimeters and surface wave couplers. The review is terminated with a short section on recently developed nonlinear metasurfaces, followed by the outlook presenting our view on possible future developments and perspectives for future applications.Comment: Accepted for publication in Reports on Progress in Physic

Toward commercial realisation of whole field interferometric analysis

The objective of this work was to produce an instrument which could undertake wholefield inspection and displacement measurement utilising a non-contacting technology. The instrument has been designed to permit operation by engineers not necessarily familiar with the underlying technology and produce results in a meaningful form. Of the possible techniques considered Holographic Interferometry was originally identified as meeting these objectives. Experimental work undertaken 'provides' data which confirms the potential of the technique for solving problems but also highlights some difficulties. In order to perform a complete three dimensional displacement analysis a number of holographic views must be recorded. Considerable effort is required to extract quantitative data from the holograms. Error analysis of the experimental arrangement has highlighted a number of practical restrictions which lead to data uncertainties. Qualitative analysis of engineering components using Holographic Interferometry has been successfully undertaken and results in useful analytical data which is used in three different engineering design programmes. Unfortunately, attempts to quantify the data to provide strain values relies upon double differentiation of the fringe field, a process that is highly sensitive to fringe position errors. In spite of this, these experiments provided the confidence that optical interferometry is able to produce data of suitable displacement sensitivity, with results acceptable to other engineers.....

Using light to control and investigate cell biology

It is no surprise that light plays an important role in life. With the development of modern technologies, light has also proven to be a powerful tool for the interrogation of molecular and cellular biology. Beyond its use in microscopic applications, light has emerged as an attractive modulator of cellular function. Within the last two decades, scientists have begun to harness the power of light and light-sensitive moieties to synthetically alter molecular processes in living cells. In combination with more conventional experimental techniques, this approach has allowed for the precise elucidation of many biological mechanisms that underpin development and disease. Here, I report on recent advances in optobiological techniques and their application in cell biology. I also include a novel study on the optogenetic delineation of growth factor signaling in neuronal development. Finally, I report on the spectroscopic analysis of fluorescent nanoparticles with potential biological utility

Deformable Beamsplitters: Enhancing Perception with Wide Field of View, Varifocal Augmented Reality Displays

An augmented reality head-mounted display with full environmental awareness could present data in new ways and provide a new type of experience, allowing seamless transitions between real life and virtual content. However, creating a light-weight, optical see-through display providing both focus support and wide field of view remains a challenge. This dissertation describes a new dynamic optical element, the deformable beamsplitter, and its applications for wide field of view, varifocal, augmented reality displays. Deformable beamsplitters combine a traditional deformable membrane mirror and a beamsplitter into a single element, allowing reflected light to be manipulated by the deforming membrane mirror, while transmitted light remains unchanged. This research enables both single element optical design and correct focus while maintaining a wide field of view, as demonstrated by the description and analysis of two prototype hardware display systems which incorporate deformable beamsplitters. As a user changes the depth of their gaze when looking through these displays, the focus of virtual content can quickly be altered to match the real world by simply modulating air pressure in a chamber behind the deformable beamsplitter; thus ameliorating vergence–accommodation conflict. Two user studies verify the display prototypes’ capabilities and show the potential of the display in enhancing human performance at quickly perceiving visual stimuli. This work shows that near-eye displays built with deformable beamsplitters allow for simple optical designs that enable wide field of view and comfortable viewing experiences with the potential to enhance user perception.Doctor of Philosoph

Advanced Stereoscopy towards On-Machine Surface Metrology and Inspection

With the goal of inventing an integral on-machine integral 3D machine vision inspection system, which monitors the parts quality and extract required patterns or structures during the manufacturing process using low-cost hardware and in a high-speed mode, this dissertation discussed the newly developed strobe-stereoscopy (SS) technique for in- motion targets examination. Stereoscopy is utilized for 3D reconstruction from recorded image pairs based on the triangulation of the display pixels, test target, and cameras. Stroboscopy is introduced to lock the moving target at different locations by frequency matching between the light source and the controlled motor. Fluorescent fluid was introduced and implemented to the SS system for high-gloss reflective surface inspection. Stereoscopy technique is limited on the diffused surface because of the sensitivity to illumination dispersion, fluorescent strobe-stereoscopy (FSS) technique overcomes the limitation to polished surface inspection and is applied to step- by-step fabrication process monitoring thus complete the metrology-in-loop for the automated production. The surface filtering-based image selection and extraction approach (ISE) is created for quick pattern extraction from the freeform base structure, which was integrated into the built hardware configuration. In this dissertation, the performance of inspection systems has been analyzed and validated with comprehensive experiment results. Potential and future work of the proposed technique was included as well