• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.4
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• pp.448-452
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• 2004

The micromachined variable optical attenuator(VOA) was presented in the paper. The VOA has two single mode fiber(SMF) aligned with free space and symmetric parallel plate actuator with microshutter, which can control a amount of light by driving the actuator. In the paper, analysis on driving performances of the VOA was performed and can be reduced threshold voltage through the decreasing displacement actuating range. This paper presents a VOA that is fabricated using bosch deep silicon etching process with silicon on insulator(SOD wafer. The VOA consists of driving electrode, ground electrode, actuating microshutter, and mechanical stopper. In this VOA, actuating shutter is driven by electrostatic force and the threshold voltage is close to 28V, 46V come along with the spring width of 5${\mu}{\textrm}{m}$, 7${\mu}{\textrm}{m}$ respectively. Attenuation range is measured from 2.4㏈ to 16.7㏈.

• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.135-141
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• 2007

This paper describes the design technology for a third generation thermal imaging system, which is more compact than before, using a $320\times240$ mid-IR focal plane detector. The third generation non-scanning thermal imaging system was constructed as a compact thermal imaging module as a reconnaissance, surveillance and navigation sensor for helicopter and infantry vehicles in the $1980's\sim1990's$ and now, we designed a new compact infrared camera and studied a new type of non-uniformity correction lens fer this camera.

• Journal of The Korean Astronomical Society
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• v.34 no.2
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• pp.111-117
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• 2001

Recently, we have set up a new digital CCD camera system, MicroMax YHS-1300 manufactured by Roper Scientific for Ha observation by Solar Flare Telescope at Bohyunsan Optical Astronomy Observatory. It has a 12 bit dynamic range, a pixel number of 1300$\times$1030, a thermoelectric cooler, and an electric shutter. Its readout speed is about 3 frames per second and the dark current is about 0.05 e-/p/s at $-10^{\circ}C$. We have made a system performance test by confirming the system linearity, system gain, and system noise that its specification requires. We have also developed a data acquisition software which connects a digital camera con-troller to a PC and acquires H$\alpha$ images via Microsoft Visual C++ 6.0 under Windows 98. Comparisons of high quality H$\alpha$ images of AR 9169 and AR 9283 obtained from SOFT with the corresponding images from Learmonth Solar Observatory in Australia confirm that our H$\alpha$ digital observational system is performed properly. Finally, we present a set of H$\alpha$ images taken from a two ribbon flare occurred in AR 9283.

• Journal of the Korean Vacuum Society
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• v.18 no.6
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• pp.474-480
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• 2009

We have investigated optical properties of InAs quantum dots (QDs) grown on GaAs (100) substrate by molecular beam epitaxy, by means of photoluminescence (PL) and time-resolved PL spectroscopy. InAs QDs were grown by using In interruption growth technique, in which the In flux was periodically interrupted by a closed In shutter during InAs QDs growth. The shutter of In source was opened for 1 s and then closed for 0, 9, 19, 29, or 39 s. This growth sequence was repeated 30 times during QDs growth. For each sample, the total amount of In contributing to the growth was the same (30 s) but total growth time was varied during the InAs growth. As the In interruption time is increased from 0 to 19 s, the PL peak position of the QDs is red-shifted from 1096 to 1198 nm, and the PL intensity is increased. However, the PL peak is unchanged and the intensity is decreased as the In interruption time is increased further to 39 s. The PL decay times measured at the PL peak position for all the InAs QDs are independent on the QD growth conditions and showed about 1 ns. The red-shift of PL peak and the increase of PL intensity can be explained due to increased QD size and the enhancement in the migration of In atoms using In interruption technique. These results indicated that the size and shape of InAs QDs can be controlled by using In interruption growth technique. Thus the emission wavelength of the InAs QDs on GaAs substrate can also be controlled.

• Journal of computational fluids engineering
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• v.15 no.1
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• pp.24-30
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• 2010

A preliminary thermal analysis is performed for the optical payload system of a geostationary satellite. The optical payload considered in this paper is GOCI(Geostationary Ocean Color Imager) of COMS of Korea. The radiative and conductive thermal models are employed in order to predict thermal responses of the GOCI on the geostationary orbit. The results of this analysis are as follows: 1) the GOCI instrument thermal control is satisfactory to provide the temperatures for the GOCI performances, 2) the thermal control is defined and interfaces are validated, and 3) the entrance baffle temperature and shutter wheel motor gradient are found slightly out their specification, therefore further detailed analyses should be continued on these elements.

• Journal of Astronomy and Space Sciences
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• v.32 no.3
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• pp.229-235
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• 2015

We estimated the orbit of the Communication, Ocean and Meteorological Satellite (COMS), a Geostationary Earth Orbit (GEO) satellite, through data from actual optical observations using telescopes at the Sobaeksan Optical Astronomy Observatory (SOAO) of the Korea Astronomy and Space Science Institute (KASI), Optical Wide field Patrol (OWL) at KASI, and the Chungbuk National University Observatory (CNUO) from August 1, 2014, to January 13, 2015. The astrometric data of the satellite were extracted from the World Coordinate System (WCS) in the obtained images, and geometrically distorted errors were corrected. To handle the optically observed data, corrections were made for the observation time, light-travel time delay, shutter speed delay, and aberration. For final product, the sequential filter within the Orbit Determination Tool Kit (ODTK) was used for orbit estimation based on the results of optical observation. In addition, a comparative analysis was conducted between the precise orbit from the ephemeris of the COMS maintained by the satellite operator and the results of orbit estimation using optical observation. The orbits estimated in simulation agree with those estimated with actual optical observation data. The error in the results using optical observation data decreased with increasing number of observatories. Our results are useful for optimizing observation data for orbit estimation.

• Journal of Biomedical Engineering Research
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• v.19 no.5
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• pp.531-538
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• 1998

This paper represents the design of 3D endoscopic image processing system in order to Improve visualization and enhance the ability of the surgeon to perform delicate endoscopic surgery. The proposed 3D systems have four features of stereo endoscopic image processing The multiplexer give field seauential stereo for recording and for aligning cameras and viewing stereo with 3D monitor. Demultiplexing of the field sequential image which separates out the R and L images for dual TFT-LCD 3D monitor viewed with passive polarized glasses. separable processing of the left and right eye images, and design of TFT-LCD 3D monitor. The viewing angle, zone, and image quality of the Polarization-type Stereoscopic Display (SM500TFT-3D) system which we have developed using 15 Samsung TFT-1.CD with a screen resolution of 1024×768 pixels were measured and compared with those of Electric Shutter-type Stereoscopic Display system. The result of experiments shows that the Polarization-type Stereoscopic Display System using TFT-LCD has a wade viewing angle and zone which Is necessary fort multi-view and it has better image quality and stability of the optical performances than the Electric Shutter-type does.

• Korean Journal of Optics and Photonics
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• v.6 no.1
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• pp.26-32
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• 1995

A Kerr cell was utilized as an optical shutter to generate a shortened pulse and as an isolator between amplifiers in an iodine laser system. By rotating the polarization of incident laser pulse only during the timing window of high voltage applied to the Kerr cell, shortened pulses of 5 ns and 1 ns, corresponding to the difference in propagation time of two coaxial cables, were obtained. It was also noticed that more than one timing window of Kerr cell was produced with a long incident laser pulse from the oscillator. The measured transmittance of Kerr cell with respect to applied voltage was compared with the theoretical estimation using the electro-optic Kerr effect theory. Through the amplification of the shortened pulse in iodine amplifiers. a pulse of 0.5 GW(2 J in 4 ns) was obtained. ained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.5
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• pp.303-306
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• 2014

In this paper, by using a dual frequency liquid crystal material, we propose a liquid crystal device with a fast response characteristics. The dual frequency liquid crystal material has a positive dielectric anisotropy value at a low frequency. With a high frequency, the dielectric anisotropy becomes negative. Therefore, the relaxation process is governed by not only the elastic deformation, but also the dielectric interaction. The measured decay time and rise time were 0.88 ms and 0.33 ms, respectively.

• The Korean Journal of Ceramics
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• v.5 no.1
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• pp.50-54
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• 1999

$(Pb_xLa_{1-x}) (Zr_yTi_{1-y})O_3$ (PLZT) thin films with electrooptic effect are promising for the optical application such as display or light shutter. However, it is difficult to use inexpensive and transparent glass substrates because the conventional process for preparation of PLZT requires temperatures above $600^{\circ}C$. In order to deposit a perovskite PLZT thin films at low processing temperatures through alkoxide route, we have offered several seeding processes which reduce the activation energy for crystallization. In this study, we optimized the stacking structure of multilayered PLZT for obtaining single phase perovskite at lower temperatures. As a result, ferroelectric PLZT thin films with different compositions were successfully prepared at a temperature as low at $500^{\circ}C$.