• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1695-1700
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• 2011

In this paper, we introduce the network infrastructure in an advanced emu test line in Deabul. New technology has been applied to advanced EMU(DMU, integrated broadcasting system, black box and etc). In order to efficient and safely test of new developed train, failure, operation, status of test line and weather information should be monitored in real time. We has implemented a wireless and optical network infrastructure for reliability and scalability. The wireless communication capability between a car and ground is 20Mbps and back-hole network has 50Mbps of the communication performance. The network between test tracks and control office was established in the optical network. That can improve communication reliability.

• Transactions of the Society of Information Storage Systems
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• v.4 no.1
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• pp.19-22
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• 2008

For the assembly and evaluation of solid immersion lens (SIL) optical head which is the key component of SIL based near field recording (NFR) technology, we modify the Twyman-Green interferometer. Super-hemisphere SIL optical head for the surface recording is assembled and evaluated by the modified Twyman-Green interferometer. In order to verify the optical performance of the assembled SIL optical head, we compare the measured results of the SIL optical head with the simulation ones. Finally, we show the feasibility of applying the assembled SIL optical head to near field recording system by the experiment of the dynamic gap control based on test bed.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.75.2-76
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• 2021

MESSIER is a science satellite project to observe the Low Surface Brightness (LSB) sky at UV and optical wavelengths. The wide-field, optical system of MESSIER is optimized minimizing optical aberrations through the use of a Linear Astigmatism Free - Three Mirror System (LAF-TMS) combined with freeform mirrors. One of the key factors in observations of the LSB is the shape and spatial variability of the Point Spread Function (PSF) produced by scatterings and diffraction effects within the optical system and beyond (baffle). To assess the various factors affecting the PSF in this design, we use PhoSim, the Photon simulator, which is a fast photon Monte Carlo code designed to include all these effects, and also atmospheric effects (for ground-based telescopes) and phenomena occurring inside of the sensor. PhoSim provides very realistic simulations results and is suitable for simulations of very weak signals. Before the application to the MESSIER optics system, PhoSim had not been validated for confocal off-axis reflective optics (LAF-TMS). As a verification study for the LAF-TMS design, we apply Phosim sequentially. First, we use a single parabolic mirror system and compare the PSF results of the central field with the results from Zemax, CODE V, and the theoretical Airy pattern. We then test a confocal off-axis Cassegrain system and check PhoSim through cross-validation with CODE V. At the same time, we describe the shapes of the freeform mirrors with XY and Zernike polynomials. Finally, we will analyze the LAF-TMS design for the MESSIER optical system.

• Transactions of the Society of Information Storage Systems
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• v.3 no.3
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• pp.135-138
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• 2007

Using a Shack-Hartmann sensor and sub-wavelength sized pinhole point source, we develope an optical testing system that measures the wavefront error of high numerical aperture and small sized optical components. The subwavelength sized pinhole generates perfect spherical waves with large diffraction angle and this makes possible to test high numerical aperture optics. The Shack-Hartmann sensor reconstructs the wavefront and calculates the aberrations. We make a home-made reference plane wave source which generates nearly perfect plane waves and the calibration with this plane source gives the overall uncertainty of the optical testing system 0.010 $\lambda$ rms.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1514-1517
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• 2005

In recent years, as the demands of VBNS(Very high speed Backbone Network Service) and VDSL(Very high-data rate Digital Subscriber Line) increase, the development of kernel parts of optical communication such as PLC(Planar Light Circuit), Coupler, WDM elements increase. The alignment and the attachment technology are very important to fabricate the optical elements for communication. In this paper, the mechanism of rotational stage are studied. with the three different method and the results of them are applied to the design of the system. The performance test of resolution and travel is performed.

• KCI Concrete Journal
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• v.11 no.3
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• pp.109-114
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• 1999

Recently the interest in the safety assessment of civil infrastructures has increased. As bridge structures become large-scale, it is necessary to monitor and maintain the safety of large bridges, which requires smart systems that can make long-term monitoring a reality . Civil engineers have applied monitoring systems to several bridges, such as the New Haeng-Ju Bridge and Riverside Urban Highway Bridge, but these applications have some problems with the sensors for long-term measurement, setup techniques for the bridge monitoring system and the assessment of measured data. In the present study, an optical fiber sensor smart system was tested and confirmed in laboratory tests on the concrete members. By Attaching optical fiber sensors to the structural parts of the Sung-San Bridge, the bridge load test was measured. These smart concrete structure systems can be applied to bridges and the load capacity of the bridge can assessed.

• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.103-108
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• 2013

The operation of a Doppler wind LIDAR in a mobile environment is very sensitive to shocks and vibrations, which can cause critical failures such as misalignment of the optical path and damage to optical components. To be able to stabilize the LIDAR and to perform wind field measurements in motion, a shock absorption and vibration isolation system was designed and implemented. The performance of the vehicle-mounted Doppler wind LIDAR was tested in motion, first in a circular test route with a diameter of about 30 m and later in regular expressway traffic. The vibration isolation efficiency of the system was found to be higher than 82% in the main vibration area and shock dynamic deflection was smaller than maximal deflection of the isolator. The stability of the laser locking frequency in the same mobile environment before and after the vibration isolation system installation was also found to be greatly improved. The reliability of the vibration isolation system was confirmed by good results of the analysis of the LIDAR data, in particular the plane position indicator of the line of sight velocity and the wind profile.

• Fire Science and Engineering
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• v.30 no.2
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• pp.27-34
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• 2016

This paper studies a fire detection system using an optical fiber linear detector which can minimize damage from a fire by the most adaptable even in poor environmental conditions such as a tunnel or utility-pipe conduit vulnerable to fire. Using a strand of optical fiber, temperature can be displayed in intervals of meters and a fire can be detected remotely from a distance of several kilometers. Thanks to its strengths such as high reliability and long life, it is widely applied in harsh environments in the overseas. Therefore demands are expected to grow greatly in Korea as well. However, all optical signal drive and analysis module except for the optical fiber linear detector, tend to rely on import. Firstly this study deduced the location and the method of processing signals measuring temperature by using the optical fiber linear detector in order to develop a technology for a domestic model of fire detection system. Secondly this study designed and manufactured the optical analysis test module, and then we checked its performance.

• Publications of The Korean Astronomical Society
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• v.20 no.1 s.24
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• pp.143-149
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• 2005

KASI (Korea Astronomy and Space Science Institute) is developing the near-infrared camera system named KASINICS (KASI Near-Infrared Camera System) which will be installed at the 60cm f/13.5 Ritchey-Chretien telescope of the Sobaeksan Optical Astronomy Observatory (SOAO). The camera system is optimized for JHKL bands and has a 6 arcmin FOV. The optical system consists of two spherical mirrors and a 8-position filter wheel. With the exception for the dewar window, all optical elements are cooled inside cryogenic dewar. Since the Offner system is adopted to prevent thermal noises from outside of the telescope primary mirror, the secondary mirror of the Offner system acts as a cold Lyot stop. The optical performance does not change by temperature variations because the Aluminum mirrors contract and expand homogeneously with its mount. We finished the design and fabrication of the optical parts and are now aligning the optical system. We plan to have a test observation on 2006 January.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.94-100
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• 2016

A novel optical design for high resolution, large field of view (FOV) and multispectral remote sensing is presented. An f/7.3 Korsch and two f/17.9 Cook three-mirror optical systems are integrated by sharing the primary and secondary mirrors, bias of the FOV, decentering of the apertures and reasonable structure arrangement. The aperture stop of the Korsch system is located on the primary mirror, while those of the Cook systems are on the exit pupils. High resolution image with spectral coverage from visible to near-infrared (NIR) can be acquired through the Korsch system with a focal length of 14 m, while wide-field imaging is accomplished by the two Cook systems whose focal lengths are both 13.24 m. The full FOV is 4°×0.13°, a coverage width of 34.9 km at the altitude of 500 km can then be acquired by push-broom imaging. To facilitate controlling the stray light, the intermediate images and the real exit pupils are spatially available. After optimization, a near diffraction-limited performance and a compact optical package are achieved. The sharing of the on-axis primary and secondary mirrors reduces the cost of fabrication, test, and manufacture effectively. Besides, the two tertiary mirrors of the Cook systems possess the same parameters, further cutting down the cost.