• Korean Journal of Optics and Photonics
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• v.7 no.2
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• pp.157-161
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• 1996

A simple laser Doppler velocimeter(LDV) using a $CO_2$ laser with its self-mixing effect has been developed. We measured the laser power which was modulated by Doppler frequency, when monochromatic laser light was focused to a moving target. The Doppler-shifted frequency was controlled by changing rotating speed of the turntable or the cosine of the angle between the direction of the laser beam and that of the rotating velocity.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.2
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• pp.22-27
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• 2011

Rain sensor detecting the presence of rain outside windshield glass of automobile by receiving scattered light from rain drops is proposed. Rain sensor using windshield glass as light waveguide required precision optical apparatus to inject light signal into windshield glass, and it was susceptible to outside shock and vibration, resulting malfunction, which altered optical coupling ratio. Proposed rain sensor, which detected scattered light from rain drops outside optical waveguide, did not require optical components because it did not need to inject light signal into light waveguide. This was advantageous because the sensor was less effected by shock and vibration. Fabricated rain sensor using scattered light outside waveguide responded not only to rain drops but also mist particles under simulated rain conditions using spraying nozzle, thus it showed prospects as rain sensor for automobile application.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.200-201
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• 2003

광섬유 OTDR 센서는 전자기 잡음이 없으며 원거리 가시 및 다중화가 가능한 유망한 센서이다. 광섬유 내부를 진행하는 빛은 광섬유의 밀도 변화에 따라 미소한 광산란이 연속적으로 발생하게 되는데 이러한 광산란을 레일리 (Rayleigh) 광산란이라고 한다. OTDR 센서는 펄스광을 광섬유에 입사한후 되돌아오는 레일리 산란광을 측정하면서 임의의 위치에 주어지는 외란의 영향을 후방 산란광의 감소로 알아내는 센서이다. 광섬유 OTDR 센서에 관련한 연구는 다음과 같다. (중략)

• Korean Journal of Optics and Photonics
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• v.25 no.4
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• pp.193-199
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• 2014

The net effect of the emitter orientation, Mie scatters, and pillow lenses on the outcoupling efficiency (OCE) of a bottom-emitting OLED having an internal photonic crystal layer was investigated by a combined optical simulation based on the finite-difference time-domain method (FDTD) and the ray-tracing technique. The simulation showed that when the emitter orientation was horizontal with respect to the OLED surface, the OCE could be increased by 54% when a photonic crystal layer was employed, while it could be improved by 86% under optimized conditions of Mie scatters and pillow lenses applied to the glass substrate. The peculiar intensity distribution of the OLED, caused by the periodic lattice structure of the photonic crystal layer, could be ameliorated by inserting Mie scatters into the glass substrate. This study suggests that conventional outcoupling structures combined with control of the emitter orientation could improve the OCE substantially.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1844-1846
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• 2001

광섬유는 저손실, 광대역의 전송특성을 가지며 세경(細徑), 경량등 많은 장점을 가지고 있지만 동케이블과 같이 파단점, 불연속점등의 장해점 탐색에 대한 어려움이 있다. 이러한 문제점을 해결하기 위하여 OTDR(Optical Time Domain Reflectometer)은 고감도, 고정도의 광센싱 기술, 극초단 광펄스 레이다 기술, 광다중화 센서 네트웍기술, 실시간 광신호처리 기술 등 정밀 광계측 및 신호처리기술을 적용하여 설치된 광섬유의 손실 정도를 측정하는 시스템으로 광섬유에 입사된 광의 산란 가운데 Rayleigh 산란에 의해서 생기는 후방산란광을 관측하여 광파이버의 파단점 탐색 및 손실측정이 가능하다. 최근 대부분의 유선통신망은 광섬유를 이용한 광통신방식으로 이루어지고 있으며 이러한 광섬유의 고장점을 찾기 위한 방법은 OTDR방식이 유일하다고 할 수 있다. 본 논문은 Rayleigh 후방산란에 의한 광학적 특성을 규명하고 이러한 특성을 이용하여 이용한 광섬유 유지보수용 계측시스템을 설계, 제작하고 실험한 결과에 대하여 설명하고 고찰하였다. 측정거리를 40Km까지 측정하도록 하였으며, 모니터상에서의 거리 분해능은 5m정도를 가지며 1310nm의 파장을 사용하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.80-80
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• 2008

바이오 센서 응용 연구에 많이 사용되는 금(Au) 나노 입자를 이용한 국소 표면 플라즈몬 공명(Localized Surface Plasmon Resonance, LSPR)에 의한 산란광을 검출하는데 주로 이용되는 암시야(dark field) 현미경 검출 방식에 관한 전산모사를 통하여 입사광의 입사 방식에 따른 산란광 세기를 정량적으로 분석하였다. 전산모사 기법으로는 국소 표면 플라즈몬 공명의 동역학적인 현상을 모사할 수 있는 유한차분시간영역(Finite Difference Time Domain, FDTD) 기법을 이용하였는데, 이러한 기법이 암시야 현미경 전산 모사에 유효함을 우선적으로 검증하였다. 암시야 현미경 검출 방식의 모사에서 입사 광원의 반사 입사 방식과 투과 입사 방식을 비교하였고, 각각의 방식에 서 입사광의 입사각에 따른 산랑광 세기를 계산하였다. 이러한 전산모사를 통하여 프리즘을 통한 내부 전반사(Total Internal Reflection, TIR) 방식에서 입사 광원의 임계각 근처에서 많이 발생하는 에바네슨트 장(evanescent field)을 결합하는 경우 산란광 세기가 증가함을 관찰하였고, 이러한 세기의 변화를 프레넬(Fresnel) 방정식에 의해 계산된 에바네슨트 장의 세기 분포와 비교 분석하였다.

• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.337-344
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• 1995

We have detected the resonant stimulated Raman scattering signal when the Q-switched Nd:YAG laser beam are incident on the $35~62{\mu}m$ sized water droplet as pump beam. The signals appeared as uniformly spaced peaks and the intervals between peaks become narrow as the droplet size increases. Also we have confirmed the morphology dependent resonances (MDR's) characteristic of the stimulated Raman scattering signal when the water droplet becomes nearly spherical shape after two water droplets are coupled to a droplet. The error in the measured intervals between MDR's of same mode order is about 5%.out 5%.

• Korean Journal of Optics and Photonics
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• v.16 no.6
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• pp.560-564
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• 2005

We used the polarized light scattering spectroscopy(PLSS) to get selectively the particle size information on a surface in optically diffuse material, and we analyzed the experimental results by Mie scattering theory. We found that the PLSS was the proper method fer getting the surface information in optically diffuse material. This method is able to be used in biotechlology area for diagnostics.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.3
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• pp.119-128
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• 2014

This paper presents a new method for improving the quality of images corrupted by an external source that generates an attenuation and scattering of light like dust, water droplets and fog. Conventional defog methods typically encounter a distortion such that the restored image has low contrast and oversaturation of color in some regions because of the mis-estimated airlight and wrong media transmission. Therefore, in order to mitigate these problems, we propose a robust airlight selection method and local saturation evaluation method for estimating media transmission. The proposed method addresses the wrong media transmission and over-saturation problems caused by the mis-estimated airlight and thereby improves the restored image quality. The results of relevant experiments of the proposed method against conventional ones confirm the improved accuracy of atmospheric light estimation and the quality of restored images with regard to objective and subjective performance measures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.35-41
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• 2010

In this paper, surface roughness has been experimentally identified using laser scattering images. The parameters and optical deflected rays of laser scattering are investigated on laser scattering system, and then their optimum parameters on grinding surfaces are selected using design of experiment. The application of the optimum parameters results in featured laser scattering images, in which the mean of vertical scattering distributions is regarded as a feature. It is shown that the feature of laser scattering distributions is linearly increased according to grinding surface roughness and so the information can be used as important factor for the measurement and evaluation of various surface roughness. In the future, the performance of the proposed laser scattering method will be evaluated using AFM.