• Bulletin of the Korean Chemical Society
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• 제18권8호
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• pp.886-889
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• 1997

The crystal structure and optical properties of copper nanoparticles, prepared in fused silica by ion-implantation and subsequent heat-treatment, were characterized by X-ray, TEM, linear absorption, and degenerate four-wave mixing (DFWM) technique. The X-ray data show fcc lattice structure of the nanocrystals and their size was measured as 8-20 nanometer by high resolution TEM. Using DFWM, the third-order nonlinear optical coefficient of the Cu-SiO2 thin films was measured as 0.4-1.1×10-8 esu in the surface plasmon resonance absorption region (540-570 nm).

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.442-445
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• 2004

We report principles and results of design large FOV retinal display systems by software WinDEMOS and software for computer testing display systems TEDiS. We discuss results design head mounted and head up display. As combiner we are used volume interference recorded or synthetic HOE, and as the sours of the image high resolution transmitting or reflective liquid crystal matrixes on silicon (LCOS) or CRT.

• International Journal of Aeronautical and Space Sciences
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• 제17권1호
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• pp.37-44
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• 2016

Optical fiber temperature sensing systems have incomparable advantages over traditional electrical-cable-based monitoring systems. However, the fiber optic interrogators and sensors have often been rejected as a temperature monitoring technology in real-world industrial applications because of high cost and over-specification. This study proposes a multiplexed fiber optic temperature monitoring sensor system using an economical Optical Time-Domain Reflectometer (OTDR) and Hard-Polymer-Clad Fiber (HPCF). HPCF is a special optical fiber in which a hard polymer cladding made of fluoroacrylate acts as a protective coating for an inner silica core. An OTDR is an optical loss measurement system that provides optical loss and event distance measurement in real time. A temperature sensor array with the five sensor nodes at 10-m interval was economically and quickly made by locally stripping HPCF clad through photo-thermal and photo-chemical processes using a continuous/pulse hybrid-mode laser. The exposed cores created backscattering signals in the OTDR attenuation trace. It was demonstrated that the backscattering peaks were independently sensitive to temperature variation. Since the 1.5-mm-long exposed core showed a 5-m-wide backscattering peak, the OTDR with a spatial resolution of 40 mm allows for making a sensor node at every 5 m for independent multiplexing. The performance of the sensor node included an operating range of up to $120^{\circ}C$, a resolution of $0.59^{\circ}C$, and a temperature sensitivity of $-0.00967dB/^{\circ}C$. Temperature monitoring errors in the environment tests stood at $0.76^{\circ}C$ and $0.36^{\circ}C$ under the temperature variation of the unstrapped fiber region and the vibration of the sensor node. The small sensitivities to the environment and the economic feasibility of the highly multiplexed HPCF temperature monitoring sensor system will be important advantages for use as system-integrated temperature sensors.

• Journal of the Optical Society of Korea
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• 제17권1호
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• pp.91-96
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• 2013

We report a method for optical monitoring of tumors in an animal model using optical coherence tomography (OCT). In a spectral domain OCT system, a superluminescent diode light source with a full width of 66 nm at half maximum and peak wavelength of 950 nm was used to take images having an axial resolution of 6.8 ${\mu}m$. Cancer cells of PC-3 were cultured and inoculated into the hypodermis of auricle tissues in BALB/c nude mice. We observed tumor formation and growth at the injection region of cancer cells in vivo and obtained the images of tumor mass center and sparse circumferences. On the $5^{th}$ day from an inoculation of cancer cells, histological images of the tumor region using cross-sectional slicing and dye staining of specimens were taken in order to confirm the correlation with the high resolution OCT images. The OCT image of tumor mass compared with normal tissues was analyzed using its A-scan data so as to obtain a tissue attenuation rate which increases according to tumor growth.

• Journal of the Optical Society of Korea
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• 제4권1호
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• pp.48-53
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• 2000

In Optical Scanning Holography(OSH), 3-D holographic information of an object is generated by 2-D active optical scanning. The optical scanning beam can be a time-dependent Gaussian apodized Fresnel zone plate. In this technique, the holographic information manifests itself as an electric signal which can be sent to an electron-beam-addressed spatial light modulator for coherent image reconstruction. In this paper, we briefly review optical scanning holography and analyze the resolution achievable with the system. We also present mathmatical expressions of real and virtual images which are responsible for holographic image reconstruction. We then show the twin-image noise effect on the reconstruction in conjunction with the size of the Fresnel zone pattern through computer simulation.

• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.663-668
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• 2016

In single-photon-emission computed tomography (SPECT) with a pixelated semiconductor detector (PSD), not only pinhole collimators but also parallel-hole collimators are often used in preclinical nuclear-medicine imaging systems. The purpose of this study was to evaluate and compare pinhole and parallel-hole collimators in a PSD. For that purpose, we paired a PID 350 (Ajat Oy Ltd., Finland) CdTe PSD with each of the four collimators most frequently used in preclinical nuclear medicine: (1) a pinhole collimator, and (2) low-energy high-resolution (LEHR), (3) low-energy general-purpose (LEGP), and (4) low-energy high-sensitivity (LEHS) parallel-hole collimators. The sensitivity and spatial resolution of each collimator was evaluated using a point source and a hot-rod phantom. The highest sensitivity was achieved using LEHS, followed by LEGP, LEHR, and pinhole. Also, at a source-to-collimator distance of 2 cm, the spatial resolution was 1.63, 2.05, 2.79, and 3.45 mm using pinhole, LEHR, LEGP, and LEHS, respectively. The reconstructed hot-rod phantom images showed that the pinhole collimator and the LEHR parallel-hole collimator give a fine spatial resolution for preclinical SPECT with PSD. In conclusion, we successfully compared different types of collimators for a preclinical pixelated semiconductor SPECT system.

• 한국컴퓨터그래픽스학회논문지
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• 제13권4호
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• pp.7-12
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• 2007

최근들어 디지털 영상 기술의 발달로 많은 영화들이 디지털화되어 제작되고 있고, 이러한 디지털 영화를 직접 상영할 수 있는 디지털 시네마로의 전환이 빠르게 진행되고 있다. 하지만 아직 까지 디지털시네마에서 요구하는 2K이상의 고해상도를 지원하는 촬영 장비는 매우 고가이기 때문에 디지털 영화의 제작에 걸림돌이 되고 있다. 본 논문에서는 이러한 문제를 저가의 일반 비디오 카메라와 디지털 스틸 카메라의 조합을 통해 해결할 수 있는 방법을 제시한다. 즉, 비디오 카메라로 촬영한 저해상도 비디오 영상과 동시에 일정한 간격의 키프레임마다 함께 촬영된 고해상도 이미지들을 이용하여 새로운 고해상도 비디오 영상을 합성하는 것이다. 비디오 합성은 프레임 단위로 이루어지는데, 먼저 현재 프레임의 픽셀마다 대응되는 점의 위치를 앞뒤 키프레임들에서 찾는다. 대응점은 현재 프레임과 키프레임 간의 광흐름(optical flow)을 계산하여 찾게 된다. 대응점이 구해지면 키프레임의 고해상도 이미지에서 대응점 위치의 이미지 블럭을 가져와 현재 프레임의 해당 픽셀 위치에 복사한다. 만일 키프레임에서의 대응점을 찾을 수 없는 경우에는 현재 저해상도 비디오 프레임의 확대 이미지를 빈곳 채움에 이용하여 이미지를 완성한다. 본 연구의 결과는 고해상도 비디오 합성 외에 비사실적 비디오 렌더링 등과 같은 영상 효과의 구현에도 적용할 수 있다.

• 대한원격탐사학회지
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• 제33권5_1호
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• pp.607-615
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• 2017

본 연구에서는 동북아시아($15{\sim}55^{\circ}E$, $90{\sim}150^{\circ}N$) 영역에 대하여 극궤도 위성 Terra와 Aqua에 탑재된 Moderate Resolution Imaging Spectrometer (MODIS) 센서와 우리나라 정지궤도 위성인 통신해양기상위성(Communication, Ocean and Meteorological Satellite, COMS)에 탑재된 Meteorological Imager (MI) 센서에 의한 에어로졸 광학두께(AOT) 산출 결과와 지상의 Aerosol Robotic Network (AERONET) 관측 자료를 비교 분석하였다. 그 결과 MODIS와 MI에 의한 에어로졸 광학두께는 해양에서 비교적 잘 일치하였으나 구름 가장자리와 육지에서는 두 센서의 에어로졸 광학두께 차이가 크게 나타났다. 그 이유로서 MODIS는 가시 채널과 적외 채널을 혼용하는 반면 MI는 오직 가시채널 만 사용하기 때문에 구름 가장자리의 옅은 구름을 에어로졸로 인식할 수 있고 육지에서는 지표면 특성에 따라 MODIS와 MI에 의한 에어로졸 광학두께 산출 차이가 발생된다. 따라서 MI 에어로졸 광학두께는 구름 가장자리와 지표면 특성의 영향을 주는 지표면 반사도의 정확성 개선을 통해 에어로졸 광학두께 산출 결과를 개선할 수 있다고 사료된다.

• 한국광학회지
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• 제29권3호
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• pp.99-103
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• 2018

동적 광단층 탄성영상법은 광 결맞음 단층촬영법을 기반으로 하여 위상차에 의해 조직의 기계적 성질 중 하나인 탄성도를 측정하기 위한 기법이다. 광 결맞음 단층촬영법은 마이켈슨 간섭계를 기반으로 한 비침습적 고해상도 단면 촬영기법이다. 본 논문에서는 광단층 탄성영상법을 생체 조직에 적용하기 전에 실행가능성을 판단하고자 강도를 쉽게 구분할 수 있는 지우개, 스펀지, 샤프심으로 샘플을 제작하여 실험을 진행하였다. 샘플에 사인파의 일정한 진동자극을 가하기 위해 압전액추에이터를 샘플의 아래쪽에 위치시켰으며 위쪽에서 광 결맞음 단층촬영법으로 스캔하였다. 깊이마다 횡방향에 대한 변형속도를 힐버트 변환하여 포락선을 검출한 후 포락선의 높낮이를 색깔로 표현하여 이미지 상에서 샘플 내의 상대적인 강도를 비교할 수 있었다. 또한, 샘플단과 참조단 사이의 간섭을 이용하는 것보다 샘플단 내의 자기간섭을 이용할 경우 변형속도 계산에 있어 장점이 있음을 제시하였다.

• Current Optics and Photonics
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• 제7권1호
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• pp.38-46
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• 2023

Optical Fourier-domain reflectometry (OFDR) sensors have been widely used to measure distances with high resolution and speed in a noncontact state. In the electroplating process of a printed circuit board, it is critically important to monitor the copper-plating thickness, as small deviations can lead to defects, such as an open or short circuit. In this paper we employ a phase-based OFDR sensor for in situ relative distance sensing of a sample with nanometer-scale resolution, during electroplating. We also develop an optical-path difference (OPD)-regulated sensing probe that can maintain a preset distance from the sample. This function can markedly facilitate practical measurements in two aspects: Optimal distance setting for high signal-to-noise ratio OFDR sensing, and protection of a fragile probe tip via vertical evasion movement. In a sample with a centimeter-scale structure, a conventional OFDR sensor will probably either bump into the sample or practically out of the detection range of the sensing probe. To address this limitation, a novel OPD-regulated OFDR system is designed by combining the OFDR sensing probe and linear piezo motors with feedback-loop control. By using multiple OFDR sensors, it is possible to effectively monitor copper-plating thickness in situ and uniformize it at various positions.