• Journal of the Korean Society of Visualization
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• v.2 no.1
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• pp.52-56
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• 2004

Several visualization techniques of laser diagnostics are presented for combustion phenomena, including Mie scattering for flow, Rayleigh and Raman scattering spectroscopy for major species, laser-induced fluorescence for minor species, and laser-induced incandescence for soot. These techniques have been applied to understand the various combustion phenomena more clearly, including buoyancy-dominant flow system, diffusion flam oscillation, laminar and turbulent lifted flames, flame propagation along a vortex ring, and soot zone characteristics. The usefulness of laser diagnostics on a better understanding of physical mechanism is demonstrated.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2001.05a
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• pp.114-118
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• 2001

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.236-246
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• 2004

Artificial carious lesions in various depths were observed with visual examination using light transillumination, bite-wing radiography, laser fluorescence, and dye-enhanced laser fluorescence to determine the reproducibility, correlation of each diagnostic method, diagnostic sensitivity and diagnostic specificity. And optical densities according to demineralized times were measured whether laser fluorescence could be used as a quantitative diagnostic method. The following results were obtained whether laser fluorescence could be used for diagnosis of initial proximal caries. 1. Tau-c values of visual examination was 0.08 which showed lowest reproducibility and those of bite-wing radiography, laser fluorescence, dye-enhanced laser fluorescence were 0.60, 0.48, and 0.64, respectively which showed relatively high reproducibility. 2. The correlation between demineralization time and each examination was the highest in dye-enhanced laser fluorescence$({\gamma}=0.51)$ followed by laser fluorescence$({\gamma}=0.43)$, bite-wing radiograph$({\gamma}=0.35)$, and visual examination$({\gamma}=0.33)$. Dye-enhanced laser fluorescence and laser fluorescence showed significant correlation with demineralization time. 3. The sensitivity of laser fluorescence and dye-enhanced laser fluorescence for diagnosing approximal caries based on bite-wing radiography were 67%, 100% and those of specificity were 57%, 11% which showed diagnostic specificity was relatively lower than sensitivity. 4. The difference in optical density(DFR) between sound teeth and carious lesions according to lesion depth was high with dye-enhanced laser fluorescence compared with laser fluorescence. DFR measured with laser fluorescence according to changes in lesion depth was statistically significant but was not statistically significant with dye-enhanced laser fluorescence. Based on these results, laser fluorescence and dye-enhanced laser fluorescence have comparable diagnostic power as bite-wing radiography in early diagnosis of proximal caries.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.1-9
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• 2003

To evaluate the quantitative nature of laser fluorescence(LF) and dye-enhanced laser fluorescence(DELF) on early enamel caries, artificial caries were induced on the bovine enamels and argon laser was irradiated on the surfaces of lesions. Fluorescence radiance from enamel specimen was recorded with CCD camera which was connected to PC image analyzing system. The difference of fluorescence of radiance(DFR) between the carious and the sound enamel in each sample of the LF and the DELF groups were measured by image analyzing program. The DFR of lesion surfaces measured with laser fluorescence and lesion depths were evaluated and the results are as follows: The caries lesions were discriminated from sound enamels by the darkness with LF and by the brightness with DELF. The DELF was more sensitive than the LF at the earlier stage of demineralization.

• Magazine of the Korea Institute for Structural Maintenance and Inspection
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• v.18 no.1
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• pp.27-36
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• 2014

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.184-184
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• 2016

플라즈마에 레이저 빛을 입사한 후 CCD 소자로 획득한 영상은 검고 밝은 픽셀로 이루어지며 이를 플라즈마 스펙클 패턴이라 정의한다. 그림 1은 $NH_3$ 플라즈마에서 획득한 스펙클 패턴을 보이고 있다 [1]. 광학에서 스펙클 패턴은 빛의 산란을 이용해 정의하고 있지만 최근의 연구에서 이 같은 정의가 잘 못되어졌음이 보고된 바 있다 [2]. 스펙클 패턴은 입사된 빛 물질과 빛 물질 에너지를 흡수하는 표면 플라즈몬 캐리어 (surface plasmon carriers-SPC)가 함께 공존하는 전자계 에너지 필드라고 정의된 바 있다 [2]. 플라즈마 스펙클 패턴은 진공이 SPC와 같은 음의 물질과 입자로 채워져 있다는 가정에 기초하고 있다 [1]. 새로이 정의된 스펙클 패턴은 전하가 없는 photon 모델과는 달리 빛이 양의 전하를 가지고 있다는 사실에 기초한 것이며, 이는 최근의 빛 물질 수집과 관련한 실험적 연구 [3], 빛 물질의 화학적 원소 분석 [4], 빛 물질의 양의 입자성 [5]에 근거를 두고 있다. 빛 물질은 그림 2 [6] 에서와 같이 물 방울을 태양 또는 레이저 빛에 노출시켜 용이하게 수집할 수 있다 [3-6]. 플라즈마 스펙클 패턴에서 픽셀합 분포함수 (pixel sum distribution function-PSDF)을 구할 수 있으며, PSDF에서 추출한 정보는 optical emission spectroscopy, langmuir probe로 수집한 데이터와 매우 유사한 경향성을 보였다 [1, 6]. 이는 스펙클 패턴이 플라즈마의 광학적 전기적 정보를 저장하고 있음을 의미한다. 본 발표에서는 새로운 플라즈마 진단 방식으로서의 스펙클 이미징 시스템, 동작원리, 물리적 기초, 그리고 응용사례 등을 살펴본다.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.1
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• pp.169-179
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• 2000

The purpose of this study is to develop the system which convert the optical difference of teeth texture between intact enamel and incipient caries lesion into shade difference by laser fluorescence and to develop new and simple caries activity test using laser fluorescence. The experimental design of this study consists of three parts. In first part, a new method for the in vitro assessment of changes in initial enamel caries lesion of Bovine teeth using laser fluorescence is tested. In second part, in vivo assessment undertaken. Number of teeth which showed incipient carious lesion on buccal surface examined by laser fluorescence was compared with the caries activity test of $Cariescreen^{(R)}$ test and other oral environmental test of dDfFtT. In third part, new caries activity test measured by laser fluorescence was developed on the basis of above results and evaluated the sensitivity, specificity, and diagnostic power. Optical density measured by laser fluorescence was increased as increasing the depth of incipient carious lesion and showed high correlation$(\gamma=0.7015)$ with lesion depth. Optical density showed direct proportion to lesion depth. Linear equation was obtained between the optical density and the lesion depth by regression analysis. The result of caries activity test with laser fluorescence showed high correlation with those of $Cariescreen^{(R)}$ test and dDfFtT examination. Caries activity test with laser fluorescence showed 48% of sensitivity, 52% of specificity, and 45% of diagnostic power on the basis of dDfFtT examination, and also showed 48% of sensitivity, 51% of specificity, and 36% of diagnostic power on the basis of $Cariescreen^{(R)}$ test. In regard above result, caries activity test with laser fluorescence considered to be reliable for caries activity test compared with other oral environmental test. and it was also considered to be practical because it would be simple, inexpensive, and time saving method.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.182-182
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• 2015

레이저 홀로그램을 이용하여 $N_2$ 플라즈마를 진단하였다. 홀로그램 이미지에서 추출한 데이터는 optical emission spectroscopy와 langmuir probe로 측정한 데이터와 매우 유사한 경향성을 보였다. 이는 홀로그램 센서가 플라즈마의 전기 광학적 입자 정보를 제공할 수 있음을 의미한다. 홀로그램 안에 이 같은 정보가 저장될 수 있는 원리는 빛을 구성하는 양의 전하를 가지는 입자와 진공을 채우고 있는 음의 입자가 함께 형성하는 전자기적 에너지 필드의 형성에 있음을 밝힌다. 이러한 원리에 기초해서 그간 개발된 센서들을 소개한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.166-173
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• 2014

A noncontact nondestructive testing (NDT) method is proposed to detect the damage of pipeline structures and to identify the location of the damage. To achieve this goal, a scanning laser source actuation technique is utilized to generate a guided wave and scans a specific area to find damage location more precisely. The ND: YAG pulsed laser is used to generate Lamb wave and a piezoelectric sensor is installed to measure the structural responses. The measured responses are analyzed using three dimensional Fourier transformation (3DFT). The damage-sensitive features are extracted by wavenumber filtering based on the 3D FT. Then, flaw imaging techniques of a pipeline structures is conducted using the damage-sensitive features. Finally, the pipes with notches are investigated to verify the effectiveness and the robustness of the proposed NDT approach.

• Progress in Medical Physics
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• v.6 no.1
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• pp.19-37
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• 1995

The use of lasers in medicine has opened up entirely new fields of therapy and diagnosis. The process in biotechnical applications of laser is basically different from traditional one in other technical field because of critical account to the human body. This paper surveys the principle of biomedical applications as well as possible future developments in laser medicine. In particular, the following subjects are extensively presented : 1) laser-tissue interaction, 2) therapeutic, and diagnostic technique, 3) laser op tical fiber for medicine, and 4) laser safety.