• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.274-280
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• 2002

This paper addresses the vibration mode shape measurement technique utilizing a Continuous Scanning Laser Doppler Vibrometer (CSLDV). The continuous scanning capability is added to the conventional discrete Laser Doppler Vibrometer by reflecting the laser beams on the surface of the object using two oscillating mirrors. The bow scanning resulted from the proposed scanning method is eliminated by feedback control. The velocity output signal from the CSLDV is modulated to give the spatial velocity distribution in terms of coefficients which are obtained from the Fast Fourier Transformation of the time dependent velocity signal. Using the Chebyshev series form, the analysis of the vibration mode shape techniques for straight Bine scanning and 2 dimensional scanning are presented and discussed. The performance of the proposed SLDV is presented using the experimental results of the vibration mode shape of a plate

• Journal of the Optical Society of Korea
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• 제5권1호
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• pp.5-8
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• 2001

In this work, we studied the effect of chirped grating on optical bistability in λ/4-shifted semiconductor distributed-feedback(DFB) devices, such as an etalon with nonlinear mirrors, a λ/4-shifted DFB waveguide and aλ/4-shifted DFB laser amplifier. We found that chirped DFB devices exhibit bistable switching at a lower input power.OCIS code : 050.2770, 190.1450, 190.5970, 230.0230.

• 한국의류학회지
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• 제26권11호
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• pp.1649-1659
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• 2002

It is anticipated that, in the 21st century, aesthetic sense will be altered radically with the introduction of new value systems and ethical standards. At the beginning of the 21st century, new aesthetic senses and identities have already emerged and exerted influence to the society, arts and fashion trends. The purpose of this study is to analyze the aesthetic characteristic of the transitional period of the 21st century. This study employed the qualitative analysis and the main aesthetic characteristics of the 21st transitional period were found as hybrid, technicism, neo-retro, new naturalism, and multi-nationalism. The transitional fashion in the 21s1 century mirrors the post-modern trends with diversity and indeterminacy as the basis of changes. It is expected that this pattern will continue to extend persistent and dominant influence to the future fashion industry. In the subsequent study, quantitative analysis wi]1 be conducted to verify the aesthetic characteristics analyzed in this study.

• 센서학회지
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• 제20권1호
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• pp.53-57
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• 2011

We developed a small methane detection system because methane gas is used in many areas and is dangerous. The developed system consisted of LD(Laser Diode) tuned a wavelength of $1.65\;{\mu}m$, two mirrors to collect a laser beam, photo detector. It could detect methane gas at a long range and its sensitivity was 1.98 V/$CH_4%$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.594-596
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• 2000

The best simulation condition for the fiber collimator that uses ball lenses was investigated. This kind of fiber collimator can be used in a Micro-Optical-Cross-Connects(MOXC). MOXC is composed of collimating ball lenses, micro mirrors and single-mode fibers. In order to design a MOXC, it is very important to calculate beam path, beam radius, divergence angle that determines the insertion loss of the MOXC. Since the beam profile from the fiber facet is not exact Gaussian profile, it was found that the simulation condition in which beam waist exists on the fiber facet, ignoring Numerical Aperture(NA), gives best agreement with the experimental results. Beam radii were measured with conventional knife edge method.

• 대한전자공학회논문지
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• 제25권9호
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• pp.1108-1114
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• 1988

Usng the P.Yeh's analytic method, we derive the condition for oscillation of a linear phase conjugate oscillator which consists of photorefractive medium and two conventional mirrors. From this general oscillation condition, we obtain the threshold oscillation conditon of a single phase conjugate resonator and the self-oscillation condition of photorefractive medium, then in special case (phase shift =90\ulcorner: no external dc electric field), oscillation conditions of the linear phase conjugate oscillator for any cavity length are derived. The results indicate that, unlike in a phase conjugate oscillator with Kerr-like medium, oscillation cannot occur at special cavity length for given couplinyg strengths.

• 한국태양에너지학회 논문집
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• 제22권2호
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• pp.49-59
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• 2002

Recently, due to high rise building by rapid urbanization, the spaces incapable of being penetrated by sunlight into interior is increasing. So, sunlighting systems are important means to be able to get sunlight into indoors and to make sure of sunshine awareness. This study aims to evaluate lighting performance of sunlighting mirror systems. As results. these are very useful for the increase of an average illuminance of indoors and the penetration of sunlight. Especially, the second reflecting mirrors can be applied to spaces lack of sunlight. And these sunlighting systems developed in the present study is validated physical and psychological performance to both building and people.

• 통합자연과학논문집
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• 제2권3호
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• pp.211-214
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• 2009

A new porous silicon (PSi) microcavity sensor for the detection of volatile organic compounds (VOCs) was developed. PSi microcavity sensor exhibiting unique reflectivity was successfully obtained by an electrochemical etching of silicon wafer. When PSi was fabricated into a structure consisting of two high reflectivity muktilayer mirrors separated by an active layer, a microcavity was formed. This PSi microcavity is very sensitive structures. Reflection spectrum of PSi microcavity indicated that the full-width at half-maximum (FWHM) was of 10 nm and much narrower than that of fluorescent organic molecules or quantum dot. The detection of volatile organic compounds (VOCs) using PSi microcavity was achieved. When the vapor of VOCs condensed in the nanopores, the refractive indices of entire particle increased. When PSi microcavity was exposed to acetone, ether, and toluene, PSi microcavity in reflectivity was red shifted by 28 nm, 33 nm, and 20 nm for 2 sec, respectively.

• 한국광학회지
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• 제8권6호
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• pp.456-460
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• 1997

링 레이저 공진기를 광학적으로 정렬하는 방법은 여러 가지가 있지만, 투과광 스펙트럼 측정법(cavity transmission spectrum control)은 측정이 매우 간단하고 공진기의 손실을 측정하면서 동시에 정렬을 할 수 있는 장점이 있다. 투과광 스펙트럼 측정법을 이용한 공진기의 광학적 정렬 장치를 구성하여, 레이저 자이로스코프에 사용할 링형 공진기에 모두 네 개의 반사경을 정렬 부착시켰으며, 동시에 정렬한 공진기의 내부 손실 값을 측정했다. 그 결과 최소 내부 손실은 0.98%였으며, 네 개의 반사경에 대한 총 반사 계수는 99.02%로 계산된다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제7권3호
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• pp.183-195
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• 2007

MEMS technology is proven to be an enabling technology to realize many components for optical networking applications. Due to its widespread applications, VOA has been one of the most attractive MEMS based key devices in optical communication market. Micromachined shutters and refractive mirrors on top of silicon substrate or on the device layer of SOI (Silicon-on-insulator) substrate are the approaches trapped tremendous research activities, because such approaches enable easier alignment and assembly works. These groups of devices are known as the planar VOAs, or two-dimensional (2-D) VOAs. In this review article, we conduct the comprehensively literature survey with respect to MEMS based planar VOA devices. Apparently MEMS VOA technology is still evolving into a mature technology. MEMS VOA technology is not only the cornerstone to support the future optical communication technology, but the best example for understanding the evolution of optical MEMS technology.