Scattering Optical Elements: Stand-Alone Optical Elements Exploiting Multiple Light Scattering

Park, Jongchan,Cho, Joong-Yeon,Park, Chunghyun,Lee, KyeoReh,Lee, Heon,Cho, Yong-Hoon,Park, YongKeun American Chemical Society 2016 ACS NANO Vol.10 No.7

<P>Optical design and fabrication techniques are crucial for making optical elements. From conventional lenses to diffractive optical elements and to recent metasurfaces, various types of optical elements have been proposed to manipulate light where optical materials are fabricated into desired structures. Here, we propose a scattering optical element (SOE) that exploits multiple light scattering and wavefront shaping. Instead of fabricating optical materials, the SOE consists of a disordered medium and a photopolymer-based wavefront recorder, with shapes impinging on light on demand. With the proposed stand-alone SOEs, we experimentally demonstrate control of various properties of light, including intensity, polarization, spectral frequency, and near field. Due to the tremendous freedom brought about by disordered media, the proposed approach will provide unexplored routes to manipulate arbitrary optical fields in stand-alone optical elements.</P>

Shape from focus based on 3D structure tensor using optical microscopy

Mahmood, Muhammad T.,Lee, Ik H. John WileySons, Inc. 2020 Microscopy research and technique Vol.83 No.1

<P><B>Abstract</B></P><P>Shape from focus (SFF) is a widely used passive optical method for 3D shape reconstruction. In SFF, a focus measure, which is used to estimate the relative focus level, plays a critical role in depth estimation. In this article, we present a new focus measure for accurate 3D shape estimation in optical microscopy based on the analysis of 3D structure tensor. First, the 3D tensors are computed from the input image sequence for each pixel. Then, each tensor is decomposed into point, curve, and surface tensors by decomposing tensors into eigenvalues and eigenvectors. Finally, the surfaceness is used to measure the quality of sharpness. The proposed focus measure provides accurate focus values and better resistance against noise. The proposed measure is evaluated by conducting experiments using image sequences of simulated and microscopic real objects. The comparative analysis demonstrates the effectiveness of the proposed focus measure in recovering 3D shape.</P>

Effects of Hair Colors on the Optical Illusion of Body Types

( Eun Ji Li ),( Boo Ja Shim ) 한국패션비즈니스학회 2003 패션 비즈니스 Vol.7 No.3

The purpose of this study is to determine affects of hair colors on physical shapes and images through field survey and experimental research. For the purpose, this researcher surveyed 230 female college students residing in Busan about their dyed hair colors, and selected the subjects for the study. Then the researcher an experimental research on the subjects by suing test stimuli. Results of the study can be described as follows: Experiment of the Optical Illusion of Physical Shapes. For all items measured for the experiment, except four ones, if was found that hair colors provided significant efforts of optical illusion factor analysis, included horizontality, outlines of the body and face, a horizontal line of the shoulder, the length, verticality and a horizontal line of the face. According to hair colors, black made the body look slimmer and the face look apparent. White made the body height look low, the outline of the face look clear and the neck or shoulder look fleshed. Female college students whose hair color was orange looked unclear in the body silhouette, bright in the face and broad in the hip and shoulder. Other students whose hair color was red, attracting the line of vision upward most strongly, looked fleshed in the upper body and broad in the face. Finally, blue made the face look dark.

간접 반사형 LED 조명기구의 반사판 형태에 따른 배광형태 및 조명환경 변화 분석

김유신(Yu-Sin Kim),최안섭(An-Seop Choi) 한국조명·전기설비학회 2011 조명·전기설비학회논문지 Vol.25 No.1

Development of high efficiency and eco-friendly LED source has been progressed continuously. Also, by nation’s regulations, public institutions have changed existing luminaires to LED luminaires. However, there are several differences between existing luminaires and the intensity distribution of general planar LED luminaires. In case of changing existing luminaires to LED luminaires, by such differences, there are inefficiencies both quality aspect and energy aspect in luminous environment. Therefore, this study aims to conduct a study on the changes of intensity distribution and luminous environment by reflector shapes in indirect reflected LED luminaires with software for optical design of a luminaire (Photopia 2.0) and lighting design of a space (ReluxPro). This study shows the changes of intensity distribution and luminous environment of indirect reflected LED luminaires and indirect fluorescent lamp luminaires by reflector shapes.

분포형 광섬유센서와 변형률 모드를 이용한 구조물의 손상탐지기법

이종원(Lee Jong-Won) 대한건축학회 2011 大韓建築學會論文集 : 構造系 Vol.27 No.2

A damage detection method using natural frequency and strain mode shape calculated from dynamic strain date obtained by distributed fiber optic sensor is presented. An analytical model for cracked beam is used to calculate the natural frequency and strain mode shape for damaged beam, and damage location and severity are estimated based on neural network technique using the measured natural frequency and strain mode shape. An experimental study was carried out on a cracked cantilever beam to verify the present method for damage identification. The cracks were inflicted on the beam and free vibration tests were performed for the dynamic strain data from the distributed fiber optic sensor. The damage estimation was carried out and it has been found that the identified damage locations and severities agree reasonably well with the inflicted damages on the structure.

분포형 광섬유센서와 변형률 모드를 이용한 구조물의 손상탐지기법

이종원,Lee, Jong-Won 대한건축학회 2011 대한건축학회논문집 Vol.27 No.2

A damage detection method using natural frequency and strain mode shape calculated from dynamic strain date obtained by distributed fiber optic sensor is presented. An analytical model for cracked beam is used to calculate the natural frequency and strain mode shape for damaged beam, and damage location and severity are estimated based on neural network technique using the measured natural frequency and strain mode shape. An experimental study was carried out on a cracked cantilever beam to verify the present method for damage identification. The cracks were inflicted on the beam and free vibration tests were performed for the dynamic strain data from the distributed fiber optic sensor. The damage estimation was carried out and it has been found that the identified damage locations and severities agree reasonably well with the inflicted damages on the structure.

Simultaneous interferometric measurement of the absolute thickness and surface shape of a transparent plate using wavelength tuning Fourier analysis and phase shifting

Kim, Yangjin,Hibino, Kenichi,Kizaki, Toru,Sugita, Naohiko,Mitsuishi, Mamoru Elsevier 2017 Precision engineering Vol.48 No.-

<P><B>Abstract</B></P> <P>The absolute optical thickness and surface shape of optical devices are considered as the fundamental characteristics when designing optical equipment. The thickness and surface shape should be measured simultaneously to reduce cost. In this research, the absolute optical thickness and surface shape of a 6–mm-thick fused silica transparent plate of diameter 100mm was measured simultaneously by a three-surface Fizeau interferometer. A measurement method combining the wavelength tuning Fourier and phase shifting technique was proposed. The absolute optical thickness that corresponds to the group refractive index was determined by wavelength tuning Fourier analysis. At the beginning and end of the wavelength tuning, the fractional phases of the interference fringes were measured by the phase shifting technique and optical thickness deviations with respect to the ordinary refractive index and surface shape were determined. These two kinds of optical thicknesses were synthesized using the Sellmeier equation for the refractive index of fused silica glass, and the least square fitting method was used to determine the final absolute optical thickness distribution. The experimental results indicate that the all the measurement uncertainties for the absolute optical thickness and surface shape were approximately 3nm and 35nm, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The absolute optical thickness and surface shape of a transparent plate were measured simultaneously using wavelength tuning. </LI> <LI> Two kinds of signal from interferogram were separated in the frequency domain using 4<I>N</I> − 3 phase shifting algorithm. </LI> <LI> 4<I>N</I> − 3 algorithm was used for compensating the phase shift errors and coupling errors. </LI> <LI> Two kinds of optical thicknesses were synthesized using Sellmeier equation and least square fitting. </LI> </UL> </P>

ASM-LK Optical Flow 기반 최적 얼굴정서 특징분석 기법

고광은(Kwang-Eun Ko),박승민(Seung-Min Park),박준형(Junheong Park),심귀보(Kwee-Bo Sim) 한국지능시스템학회 2011 한국지능시스템학회논문지 Vol.21 No.4

얼굴영상에서 나타나는 정서특징을 분석하기 위하여 본 논문에서는 Active Shape Model (ASM)과 Lucas-Kanade (LK) optical flow 기법을 기반으로 하는 특징검출 및 분석방법을 제안한다. Facial Action Coding System에 근거하여 묘사된 정서적 특징을 고려하여, 특징이 분포하는 영역에 위치한 다수의 landmark로 shape 모델을 구성하고 모델에서 각 Landmark를 중심으로 하는 움직임 벡터 윈도우 내부의 픽셀에 대한 LK 기법을 통해 optical flow 벡터를 추출한다. 추출된 움직임 벡터의 방향성 조합에 근거하여 얼굴정서특징을 shape 모델로 표현할 수 있으며, 베이지안 분류기라는 확률 기반 추론기법을 기반으로 정서적 상태에 대한 추정할 수 있다. 또한, 정서특징분석과정의 연산 효율성과 정확성 향상을 도모하기 위하여 common spatial pattern (CSP) 분석기법을 적용하여 정서상태 별로 상관성이 높은 특징만으로 구성된 최적 정서특징을 추출한다. In this paper, we propose an Active Shape Model (ASM) and Lucas-Kanade (LK) optical flow-based feature extraction and analysis method for analyzing the emotional features from facial images. Considering the facial emotion feature regions are described by Facial Action Coding System, we construct the feature-related shape models based on the combination of landmarks and extract the LK optical flow vectors at each landmarks based on the centre pixels of motion vector window. The facial emotion features are modelled by the combination of the optical flow vectors and the emotional states of facial image can be estimated by the probabilistic estimation technique, such as Bayesian classifier. Also, we extract the optimal emotional features that are considered the high correlation between feature points and emotional states by using common spatial pattern (CSP) analysis in order to improvise the operational efficiency and accuracy of emotional feature extraction process.

Tunable Diffractive Optical Element Tailored by Shape Memory Epoxy for Temperature-targeted Micro-optics

D. K. Kyeong(경도경),J. Lee(이지훈),M. K. Kwak(곽문규) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월

As Diffractive Optical Elements (DOEs) have emerged as an interesting research area in the past decades, there is enormous interest to overcome intrinsic limitations of DOEs such as shape tunability. Since substantial time- and cost-consuming process are required to change the existing structure, applying shape memory polymers (SMPs) to microstructures is essential for realizing tunable micro -optics. The feasibility was already verified by previous research but correlation of image recovery with temperature is still unknown. In this work, we show that the morphing temperature of far-field diffraction patterns can be easily tailored by changing Neopentyl glycol diglycidyl ether (NGDE) molar ratio in shape memory epoxy. To measure the correlation of image recovery ratio and temperature simultaneously, open-source machine learning based image quality metrics are used with temperature sensor. We found that image morphing temperature is closely related with the presence of temporarily formed microstructures. Thus, specific temperature-targeted microoptics can be suggested by demonstrating the relationship between morphing temperature and material composition.

Recent advances in optical imaging through deep tissue: Imaging probes and techniques

윤석찬,Seo Young Cheon,Sangjun Park,Donghyun Lee,Yeeun Lee,Seokyoung Han,Moonseok Kim,구희범 한국생체재료학회 2022 생체재료학회지 Vol.26 No.4

Optical imaging has been essential for scientific observations to date, however its biomedical applications has been restricted due to its poor penetration through tissues. In living tissue, signal attenuation and limited imaging depth caused by the wave distortion occur because of scattering and absorption of light by various molecules including hemoglobin, pigments, and water. To overcome this, methodologies have been proposed in the various fields, which can be mainly categorized into two stategies: developing new imaging probes and optical techniques. For example, imaging probes with long wavelength like NIR-II region are advantageous in tissue penetration. Bioluminescence and chemiluminescence can generate light without excitation, minimizing background signals. Afterglow imaging also has high a signal-to-background ratio because excitation light is off during imaging. Methodologies of adaptive optics (AO) and studies of complex media have been established and have produced various techniques such as direct wavefront sensing to rapidly measure and correct the wave distortion and indirect wavefront sensing involving modal and zonal methods to correct complex aberrations. Matrix-based approaches have been used to correct the high-order optical modes by numerical post-processing without any hardware feedback. These newly developed imaging probes and optical techniques enable successful optical imaging through deep tissue. In this review, we discuss recent advances for multi-scale optical imaging within deep tissue, which can provide reseachers multi-disciplinary understanding and broad perspectives in diverse fields including biophotonics for the purpose of translational medicine and convergence science.