• Journal of Radiation Protection and Research
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• v.34 no.1
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• pp.25-30
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• 2009

Micro-columnar CsI(Tl) is the most popular scintillator material which is used for many indirect digital X-ray imaging detectors. The light scattering at the surface of micro-columnar CsI(Tl) scintillator was studied to find the correlation between the surface roughness and the resultant image resolution of indirect X-ray imaging detectors. Using a commercially available optical simulation program, Light Tools, MTF (Modulation Transfer Function) curves of the CsI(Tl) film thermally evaporated on glass substrate with different thickness were calculated and compared with the experimental estimation of MTF values by the edge X-ray image method and CCD camera. It was found that the standard deviation value of Gaussian scattering model which is determined by the surface roughness of micro-columns could certainly change the MTF value of image sensors. This model and calculation methodology will be beneficial to estimate the overall performance of indirect X-ray imaging system with CsI(Tl) scintillator film for optimum design depending on its application.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.1
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• pp.11-17
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• 2004

We tried to design and manufacture a night scope which is used in the leisure sports field. The whole system consists of an IR light source part, an objective lens part, an intensifier tube part and an eye_piece lens part. We designed an objective lens part to the infinite object imaging optical-system with 80mm focal-length, 40mm effective-aperture and 14mm image-field-size of which the chromatic aberration is reduced by using materials of BK7 and FD4. The resolution of this system is about 25lines/mm at the 40% MTF value criterion. The eye_piece lens is adopted goods to be used commercially to save cost of production. The design technique which gets in this development will be utilized greatly in good developments of the dot, the sight and the day/night riflescope system at the hereafter.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.1
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• pp.148-156
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• 2007

This paper explains stocker system that is operated in the long distance and linear area. The power system of stocker system uses Contactless Power Supply(CPS) to reduce problems of particle generation. The circuit configuration of CPS is simplified than the conventional ones, and the prototype is designed for commercial product. To transfer output data(information) from crane(secondary vehicle system) of the CPS to Primary system optical modem and TMS320F243(DSP, TI) are used between primary and secondary. power system are used, and the output voltage is controlled by operating frequency modulation. This paper is applied to stocker system controlled as one to one communication between the moving part(secondary system) and fixed part(primary system) of crane using optical modem. The study makes one to multi communication between fixed part and moving part for the purpose of multi crane operation of stocker system and must be done in the future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.310-311
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• 2008

We have studied electro-optical characteristics of fringe-field switching (FFS) mode with high $d{\Delta}n$ according to the electrode position. In this device, the fringe-electric field drives the LCs to rotate so that the dielectric torque is electrode-positional dependent, which results in electrode-position dependency in the LC's rotating angle. We confirmed polarization microscope image and chromaticity diagram at the different electrode position with LC that have high $d{\Delta}n$. Since the FFS mode is influenced by horizontal and vertical electric field, the FFS mode modulates light using both phase retardation and polarization rotation effect, which had already been verified with previous studies. However, from another point of view, tight modulation of FFS mode has been demonstrated by performing experiment and calculated simulation at the high $d{\Delta}n$ LC cell.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.9 s.351
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• pp.158-164
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• 2006

Mobile operators will face many challenges both economically and technically, as WLAN evolve through a bewildering number of different standards during the coming years. Potentially this will require several upgrades to the mobile infrastructure. A new approach for addressing these challenges is evaluated in this paper. It is based on a radio over fiber (RoF) technology that uses electro-absorption modulator (EAM) and optical single sideband (OSSB) modulation technique and it promises to provide solutions that will be transparent to changes in protocols and frequency of operation as well as reducing radio access infrastructure costs. This paper describes the development of prototype RoF system based on the 60GHz band CATV transport distribution system with EAM and the possibility of radio over fiber technology for use in the broadband convergence network (BcN) wireless access infrastructure.

• Korean Journal of Optics and Photonics
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• v.20 no.2
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• pp.76-80
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• 2009

Finger-print recognition is achieved by comparing an input finger-print image with the stored images in the computer, and finally by determining agreement or disagreement. Encryption and decryption are necessary in the finger-print recognition process. In these process CGH (Computer Generated Hologram) is used, and finger-print images reconstructed from the CGHs are compared. In this paper, two methods of recognition are used, one is to compare the finger-print images of each other reconstructed from their CGHs and the other is to compare the CGHs to each other directly, to analyze the differences of finger-print recognition capability between these two methods. Experimental results show that the capability of finger-print recognition for comparing the CGHs of the two is about 150 times higher than in case of comparing the reconstructed finger-print images. Especially the changes of characteristics according to modulation types of CGH are analyzed.

• Korean Journal of Materials Research
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• v.23 no.4
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• pp.215-218
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• 2013

Vanadium dioxide ($VO_2$) is an attractive material for smart window applications where the transmittance of light can be automatically modulated from a transparent state to an opaque state at the critical temperature of ${\sim}68^{\circ}C$. Meanwhile, F : $SnO_2$ (F-doped $SnO_2$, FTO) glass is a transparent conductive oxide material that is widely used in solar-energy-related applications because of its excellent optical and electrical properties. Relatively high transmittance and low emissivity have been obtained for FTO-coated glasses. Tunable transmittance corresponding to ambient temperature and low emissivity can be expected from $VO_2$ films deposited onto FTO glasses. In this study, FTO glasses were applied for the deposition of $VO_2$ thin films by pulsed DC magnetron sputtering. $VO_2$ thin films were also deposited on a Pyrex substrate for comparison. To decrease the phase transition temperature of $VO_2$, tungsten-doped $VO_2$ films were also deposited onto FTO glasses. The visible transmittance of $VO_2$/FTO was higher than that of $VO_2$/pyrex due to the increased crystallinity of the $VO_2$ thin film deposited on FTO and decreased interface reflection. Although the solar transmittance modulation of $VO_2$/FTO was lower than that of $VO_2$/pyrex, room temperature solar transmittance of $VO_2$/FTO was lower than that of $VO_2$/pyrex, which is advantageous for reflecting solar heat energy in summer.

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.339-344
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• 2001

We propose a method to represent binary data by modulating both the intensity and the phase of uniform plane waves with a twisted-nematic liquid crystal display for holographic digital data storage especially in a disk-shaped recording medium. As far as intensity modulation is concerned, our method is not different from the conventional method, because binary bit values 0 and 1 are represented by the dark (off) and lit (on) states of the liquid crystal display pixels, respectively (or vice versa). With our method, however, the on pixels are also controlled so that the beams passing through them can have one of two different phase delays. If the difference of the two phase delays is close to 180 degrees, we can reduce the dc component of the data image and thus improve the beam intensity uniformity at the holographic recording plane when Fourier plane holograms are recorded. The feasibility of our method is experimentally demonstrated. rated.

• Korean Journal of Materials Research
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• v.9 no.11
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• pp.1144-1147
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• 1999

The effect of the heat treatment on electrochromic properties of $\textrm{MoO}_3$ thin films is investigated by studing optical modulation, optical density, response time, and cyclic voltammetry. From the results of XRD analysis, heat-treated at $450^{\circ}C$ in air for 1 hour Moo3 thin films are found to be crystalline while as-deposited and heat- treated at low temperature ($\leq\;300^{\circ}C$) film are amorphous. The electrochromic devices using as-deposited $\textrm{MoO}_3$ films exhibit good electrochromic properties compared to those using the heat treated $\textrm{MoO}_3$ films. It has shown that the heat-treatment affected the reversible color change and the electrochromic properties of $\textrm{MoO}_3$ films.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1234-1242
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• 2004

In this paper, the characteristics of compensation for interferenced mid-channel signal by neighbor channels through four-wave mixing (FWM) process dominantly is investigated as a function of channel input power, fiber dispersion coefficient and transmission length in WDM system with equally spaced channels. The compensation method used in this research is mid-span spectral inversion(MSSI). The highly nonlinear dispersion shifted fiber (HNL-DSF) is used as a nonlinear medium of optical phase conjugator (OPC) in order to compensate wideband WDM signals. First, we confirmed that the effect of FWM on channel interference is gradually reduced as fiber dispersion coefficient becomes gradually smaller, independent of signal format. And, we confirmed that RZ is better than NRZ as a modulation format for transmitting high power channel with allowable reception quality. But realization of flexible WDM systems regardless of channel number variation is possible by using NRZ rather than RZ format.