• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.443-448
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• 2003

A study on optimum design of the lightweight mirror of a satellite camera is presented. An optical surface deformation of the lightweight mirror, which is a principal component of the camera system, is an important factor affecting the optical performance of the whole camera system. In this study, optimum design of the lightweight mirror is presented. Total weight of the mirror to reduce the optical surface deformation and the launching cost is used as an objective function. Peak-to-valley value and natural frequency of the mirror are given as constraints to the optimization problem. The sensitivities of the objective function and constraint are calculated by a finite difference method. The optimization procedure is carried out by the commercial optimizer, DOT. As a verification of the optimum design of the mirror, two design examples are treated. In the real application example, the lightweight mirror with 600mm effective diameter is treated. The optimized results with various design variables, which are obtained by considering thickness limitations, are analyzed.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.12
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• pp.1111-1118
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• 2010

Combustion measurements based on optical techniques have recently become of major interest as tools not only for clarifying the combustion mechanism but also for validating the computational results for the combustion fields. In this study, the particle behavior in turbulent pulverized coal flame are investigated using advanced optical diagnostics. A laboratory-scale pulverized coal combustion burner is specially fabricated as open type in order to apply various optical measurement techniques. The detailed particle behavior is performed by LDV (laser Doppler velocimetry) and SDPA (shadow Doppler particle analyzer). It is observed that the particle mean diameter increase as the distance from burner increases, and this is found to be caused by the decrease of small particles' diameter and increase of large particles' diameter. This is because of result in the char reaction and the particle swelling due to devolatilization, respectively. The size-classified streamwise velocities of pulverized coal particles in the central region of the jet show the same magnitude, whereas those in the outer region are different depending on the particle size. The results show that the velocity and size-classified diameter of the pulverized coal particles in the flame can be measured well by SDPA.

• Design & Manufacturing
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• v.1 no.1
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• pp.7-11
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• 2007

The fabrication of precision optical components by deterministic CNC grinding is an area of great current interest. Replacement of the traditional, craftsman driven, optical fabrication process is essential to reduce costs and increase process flexibility and reliability. Moreover, CNC grinding is well suited to the fabrication of complex shapes such as aspheres, making it possible to design optical systems with fewer components and reduced weight. Current technology is capable of producing surfaces with less than 2 microns peak to valley error, 50 nm rms surface roughness, and less than 1 micron subsurface damage. Bound abrasive tools, in which the abrasive particles are fixed in a second (matrix) material, play an important part in achieving this performance. In this paper, the factors affecting the ultra-fine surface roughness and profile accuracy of machined surfaces of aspheric parts has been analyzed experimentally and theoretically and on ultra-precision aspheric grinding system and precise adjusting mechanism have been designed and manufactured. In the paper we report the results of experiments and modeling performed to examine the effects of machinability, occurring during grinding of optical surfaces, on the tool surface profile. Profiles of machined surface were measured by using SEM. In order to optimize grinding conditions of aspheric lens processing, we performed experiments by design of experiments.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.9
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• pp.6-12
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• 2011

In this paper, we propose a design method for a reliable and improved field-installable optical connectors(FIOC) which are needed for long-distance and low loss FTTH configuration. To this end, we optimize the angle of splicing between the inner fiber and the field fiber of the FIOC, so that the low loss connection of optical fibers is possible without using any angle alignment tools as well as angled cleavers. More precisely, we set the cutting angle of the inner filber and the field fiber to be $2^{\circ}$ by using an angled cleaver and $0^{\circ}{\sim}1^{\circ}$ by using a general fiber cutter, respectively. Splicing these two optical fibers without any further adjustment, we can keep the insertion loss within 0.3dB and the reflection loss within -60dB.

• Current Optics and Photonics
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• v.1 no.2
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• pp.132-137
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• 2017

To investigate the usefulness of optical coherence tomography (OCT) for imaging lymphedema, we directly compared it to other histological methods in a mouse model of lymphedema. We performed detailed imaging of the lymphedema lesion on a mouse tail. We imaged the mouse tail in vivo with OCT and created histopathological samples. We constructed a spectrometer-based OCT system using a fiber-optic Michelson interferometer. The light was directed to 50:50 couplers that split the light into reference and sample arms. Backscattered light from a reference mirror and the sample produced an interference fringe. An OCT image of the lymphedema model revealed an inflammatory reaction of the skin that was accompanied by edema, leading to an increase in the light attenuation in the dermal and subcutaneous layers. Similar to OCT image findings, histological biopsy showed an inflammatory response that involved edema, increased neutrophils in epidermis and subdermis, and lymphatic microvascular dilatation. Furthermore, the lymphedema model showed an increase in thickness of the dermis in both diagnostic studies. In the mouse tail model of lymphedema, OCT imaging showed very similar results to other histological examinations. OCT provides a quick and useful diagnostic imaging technique for lymphedema and is a valuable addition or complement to other noninvasive imaging tools.

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.294-301
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• 2008

We have performed modeling and simulations of optical characteristics for a cholesteric liquid crystal (CLC) color filter. Berreman's $4{\times}4$ matrix method was used for the calculation of reflectance spectra of the CLC color filter with respect to the incident angle. The results were employed as input parameters for a user-defined coating property of an illumination design software based on the ray-tracing method, LightTools. Color shift characteristics of a planar transmission-type CLC color filter were simulated using LightTools. The results were compared with the results obtained with Berreman's $4{\times}4$ matrix method. It was found that color shift characteristics of the CLC color filter could be simulated to a reasonable accuracy when the reflectance spectra with less than 5 degrees of incremental incidence-angle were used as the input data for the user-defined coating property of LightTools. We have simulated color shift characteristics of a reflection-type CLC color filter having hemi-spherical patterns. The simulation method reported in this paper has been found to be also used for a non-planar CLC color filter structure.

• Journal of Radiation Protection and Research
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• v.41 no.3
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• pp.282-285
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• 2016

Background: To optimize the photon transmission efficiency of light guides used in scintillation detectors, LightTools code, which can construct and track light, was used to analyze photon transmission effectiveness with respect to light guides thickness. Materials and Methods: This analysis was carried out using the commercial light guide, N-BK 7 Optical Glass by SCHOTT, as a model for this study. The luminous exitance characteristic of the LYSO scintillator was used to analyze the photon transmission effectiveness according to the thickness of the light guide. Results and Discussion: The results of the simulations showed the effectiveness of the photon transmission according to the thickness of the light guide, which was found to be distributed from 13.38% to 33.57%. In addition, the photon transmission efficiency was found to be the highest for light guides of 4 mm of thickness and a receiving angle of $49^{\circ}$. Conclusion: Through such simulations, it is confirmed that photon transmission efficiency depends on light guide thickness and subsequent changes in the internal angle of reflection. The aim is to produce an actual light guide based on these results and to evaluate its performance.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.264-265
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• 2005

In this paper the conceptual design and development of a compact vertical type soft x-ray microscope is described. This x-ray microscope operates in the water window wavelength region(2.3 ${\sim}$ 4.4nm), where natural contrast between carbon(protein) and oxygen(water) allows imaging of unstained biological material their natural, hydrated environment. Until now, operational x-ray microscopes are based on synchrotron radiation sources, which limit their accessibility. Many biologists would benefit from having the x-ray microscope as a tool among other tools in their own laboratory, For this purpose we introduced the compact vertical type soft X-ray microscope with 50 nm resolution for biomedical application. The compact vertical type soft x-ray microscope is based on a laser plasma x-ray source, doubled ellipsoidal condenser reflective optics, diffractive zone plate optics and MCP coupled with CCD to record an x-ray image.

• Current Optics and Photonics
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• v.1 no.6
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• pp.613-617
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• 2017

Due to optimal advances such as chromatic performance, durability, low power consumption, high efficiency, long-lifetime, and excellent environmental friendliness, white LEDs (WLEDs) are widely used in vehicle front lighting, backlighting, decorative lighting, street lighting, and even general lighting. In this paper, the remote packaging WLEDs (RP-WLEDs) with bi-layer red-emitting $Sr_2Si_5N_8:Eu^{2+}$ and yellow-emitting YAG:Ce phosphor was proposed and investigated. The simulation results based on the MATLAB software and the commercial software Light Tools indicated that the color rendering index (CRI) of bi-layer phosphor RP-WLEDs had a significant increase. The CRI had a considerable increase from 72 to 94. In conclusion, the results showed that bi-layer red-emitting $Sr_2Si_5N_8:Eu^{2+}$ and yellow-emitting YAG:Ce phosphor could be a prospective approach for manufacturing RP-WLEDs with enhanced optical properties.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.108-113
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• 2001

Recently, the mechanical structures applied to many industrial products, especially in electronic products, appear to be miniaturized and complicated. This trend makes it difficult to analyze the stress distribution of those mechanical structures and generates new challenges for precise measurement of strain. Therefore, generally most of those cases largely depend on the finite element analysis. But the development of optical metrology which has the capability of non-contact, full-field and precise measurement makes it possible to solve these measuring problems. Among the optical measurement techniques, the electronic speckle pattern interferometry (ESPI) has been developed and considered as one of the most useful tools for measuring displacement and deformation. But the shortage of recognition and difficulties of measurement have limited its industrial applications in spite of its excellent capabilities. Therefore in this study, in order to enhance the industrial application of ESPI, the measurement of in-plane displacement of mechanical structure with ESPI, which is applied to washing machine and cannot be measured by strain gauges, was performed. And the verification of validity of FEA results was also done.