• Structural Monitoring and Maintenance
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• v.1 no.2
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• pp.173-182
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• 2014

We describe the application of a distributed optical fiber sensor based on stimulated Brillouin scattering, as an integrated system for safety monitoring of railway infrastructures. The strain distribution was measured statically and dynamically along 60 meters of rail track, as well as along a 3-m stone arch bridge. We show that, gluing an optical fiber along the rail track, traffic monitoring can be performed in order to identify the train passage over the instrumented sector and determine its running conditions. Furthermore, dynamic and static strain measurements on a rail bridge are reported, aimed to detect potential structural defects. The results indicate that distributed sensing technology represents a valuable tool in railway traffic and safety monitoring.

• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.424-430
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• 2010

In coherent anti-Stokes Raman scattering (CARS) microscopy reported until now, conventional microscope objectives are used, so that they are limited for introduction into a living body. Gradient-index (GRIN) rod lenses might be a solution for miniaturized microscope objectives for in-vivo CARS microscopy. However, due to the inherent large amount of chromatic aberration, GRIN rod lenses cannot be utilized for this purpose. CARS imaging catheter, composed of miniaturized microscope objective and fiber bundle, can be introduced into a living body for minimally invasive diagnosis. In order to design the catheter, we have to first investigate design requirements. And then, the optical design is processed with design strategies and intensive computing power to achieve the design requirements. We report the miniaturized objective lens system with diffraction-limited performance and completely corrected chromatic aberrations for an in-vivo CARS imaging catheter.

• Journal of ILASS-Korea
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• v.7 no.3
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• pp.31-37
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• 2002

In previous study, diesel-methanol stratified injection system is manufactured and applied to a D.I. diesel engine in order to realize combustion improvement using methanol, which is oxygenated fuel with large latent heat. We know that NOx and soot is reduced by stratified injection of diesel fuel-methanol. Therefore, in the present study, combustion diagnosis using optical measurement is tried to make clear effect of methanol on simultaneous reduction of NOx and soot. Two-color method is used to measure flame temperature and KL value, which is approximately proportional to the soot consentration along the optical path. Laser induced scattering method was used to measure distribution of soot at two dimensional area. Also, it is compared exhaust characteristics of NOx and soot with results of optical measurement.

• Journal of the Optical Society of Korea
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• v.9 no.2
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• pp.39-44
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• 2005

Unlike for the bound states, several different boundary conditions are used for the continuum states above the barrier in semiconductor quantum wells. We employed three boundary conditions, infinite potential barrier boundary condition, periodic boundary condition and scattering boundary condition, and calculated the local number of states, wavefunctions and optical matrix elements for the symmetric and asymmetric quantum wells. We discussed how these quantities are related in the three boundary conditions. We argue that the scattering boundary condition has several advantages over the other two cases. These results would be useful in understanding quantum well lasers and detectors involving continuum states.

• Journal of the Korean Applied Science and Technology
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• v.29 no.3
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• pp.473-479
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• 2012

The influences of scatterer and absorber in turbid material by light scattering were interpreted for the scattered intensity and wavelength. The molecular properties have been studied by Monte Carlo simulation in resin of New Austria Tunnel Method. It has been found that the effects of optical properties in scattering media could be investigated by the optical parameters(${\mu}_s$, ${\mu}_a$, ${\mu}_t$). Monte Carlo Simulation method for modelling of light transport in the civil engineering and construction field was applied. The results using a phantom were discussed that the distance from source to detector is closer, and scattering intensity is stronger with those obtained through Monte Carlo Simulation. It may also aid in designing the best model for coatings and corrosion for the durability of metal constructions.

• Ocean and Polar Research
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• v.26 no.2
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• pp.133-143
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• 2004

For the purpose of understanding the cloud scattering effect of UV radiation at King Sejong station In West Antarctica, we analyzed the data measured by UV-Biometer at surface and compared its result with solar radiation model. The parameterization of UV radiation by cloud ice crystal was applied to solar radiation model and the sensitivity of this model for the variation of ice crystal was tested. The cloud optical thickness was calculated by using this solar radiation model. It was compared the result from calculation with CERES satellite data. In solar radiation model, the UV radiation was less scattered with increase of ice crystal size in cloud and this scattering effect was more important to UV-A radiation than Erythemal UV-B radiation. But scattering effects by altitude of cloud was not serious. The calculated cloud optical thicknesses in Erythemal UV-B and UV-A region were compared with CERES satellite data and the result by UV-A was more accurate than Erythemal UV-B region.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.1
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• pp.97-109
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• 2007

Vertical distribution and optical properties of atmospheric aerosols above the Korean peninsula are quite important to estimate effects of aerosol on atmospheric environment and regional radiative forcing. For the first time in Korea, vertical microphysical properties of atmospheric aerosol obtained by inversion algorithm were analyzed based on optical data of multi-wavelength Raman lidar system developed by the Advanced Environmental Monitoring Research Center (ADEMRC), Gwangju Institute Science and Technology (GIST). Data collected on 14 June 2004 at Gwangju ($35.10^{\circ}N,\;126.53^{\circ}E$) and 27 May 2005 at Anmyeon island ($36.32^{\circ}N,\;126.19^{\circ}E$) were used as raw optical data for inversion algorithm. Siberian forest fire smoke and local originated haze were observed above and within the height of PBL, respectively on 14 June 2004 according to NOAA/Hysplit backstrajectory analysis. The inversion of lidar optical data resulted in particle effective radii around $0.31{\sim}0.33{\mu}m$, single scattering albedo between $0.964{\sim}0.977$ at 532 nm in PBL and effective radii of $0.27{\mu}m$ and single scattering albedo between $0.923{\sim}0.924$ above PBL. In the case on 27 May 2005, biomass burning from east China was a main source of aerosol plume. The inversion results of the data on 27 May 2005 were found to be particle effective radii between $0.23{\sim}0.24{\mu}m$, single scattering albedo around $0.924{\sim}0.929$ at 532 nm. Additionally, the inversion values were well matched with those of Sun/sky radiometer in measurement period.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.298-301
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• 2007

Vertical distribution and optical properties of atmospheric aerosols above the Korean peninsula are quite important to estimate effects of aerosol on atmospheric environment and regional radiative forcing. For the first time in Korea, vertical microphysical properties of atmospheric aerosol obtained by inversion algorithm were analyzed based on optical data of multi-wavelength Raman lidar system developed by the Advanced Environmental Monitoring Research Center (ADEMRC), Gwangju Institute Science and Technology (GIST). Data collected on 14 June 2004 at Gwangju ($35.10^{\circ}N$, $126.53^{\circ}E$) and 27 May 2005 at Anmyeon island ($36.32^{\circ}N$, $126.19^{\circ}E$) were used as raw optical data for inversion algorithm. Siberian forest fire smoke and local originated haze were observed above and within the height of PBL, respectively on 14 June 2004 according to NOAA/Hysplit backstrajectory analysis. The inversion of lidar optical data resulted in particle effective radii around 0.32 ${\mu}m$, single scattering albedo between 0.97 at 532 nm in PBL and effective radii of 0.27 ${\mu}m$ and single scattering albedo of 0.92 above PBL. In the case on 27 May 2005, biomass burning from east China was a main source of aerosol plume. The inversion results of the data on 27 May 2005 were found to be particle effective radii between 0.24 ${\mu}m$, single scattering albedo around 0.91 at 532 nm. Additionally, the inversion values were well matched with those of Sun/sky radiometer in measurement period.

• Transactions on Electrical and Electronic Materials
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• v.13 no.6
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• pp.310-316
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• 2012

A new method for early caries diagnosis was proposed and tested through a home-made optical examination system that used quantitative light fluorescence (QLF) and digital imaging fiber optic transillumination (FOTI) (DIFOTI), with light sources across a wide spectral range, from 350 nm to 1,000 nm. The front-illuminated infrared light scattering image (FIR) showed similar diagnostic abilities to that of DIFOTI. The FIR method was invented based on the observation that caries lesions lose the high transmittance and low scattering properties of benign enamel tissue. There are various methods for the early diagnosis of caries, such as visual examination, exploration, X-ray radiography, QLF, FOTI, and infrared fluorescence (diagnodent). Among them, methods based on optical properties are regarded as having the most potential. A comparative study was performed between the FOTI, QLF, diagnodent, optical coherence tomography, and FIR scattering image methods, using 20 extracted teeth samples with early caries. A scale of lesion measurement based on optical image contrast was proposed. The statistical analysis showed a significant correlation between the DIFOTI and FIR methods (r = 0.35, p < 0.05). However, the QLF and diagnodent methods showed little association with FIR images, as they have different detection principles as compared with FIR. Tomographic images obtained by OCT, using 1,330 nm super luminescent LED as a gold standard of tooth structure, verified that the FOTI and FIR results correctly represented the lack of homogeneity in dental tissue. The newly proposed FIR method attained similar diagnostic results to those of FOTI, but with an easier approach.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.334-335
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• 2005