• Publications of The Korean Astronomical Society
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• v.22 no.4
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• pp.201-209
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• 2007

We have preliminarily designed two infrared optical systems of the multi-purpose infrared camera system (MIRIS) which is the main payload of STSAT-3. Each optical system consists of a Cassegrain telescope, a field lens and a 1:1 re-imaging lens system that is essential for providing a cold stop. The Cassegrain telescope is identical for both of two infrared cameras, but the field correction lens and re-imaging lens system are different from each other because of different bands of wavelength. The effective aperture size is 100mm in diameter and the focal ratio is f/5. The total length of the optical system is 300mm and the position of the cold stop is 25mm from the detector focal plane. The RMS spot size is smaller than $40{\mu}m$ over the whole detector plane.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.322-323
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• 2015

Traditional rotation type large beacon was characterized by frequent failure, long repair time and high cost etc. These problems are caused by traditional light sources(metal halide lamps or tungsten halogen lamps). In order to solve these problems, IALA standards-based(efficiency and reliability) large LED beacon technologies are needed. we developed by applying a LED. The object of the this project, to design a reflective optics and the high power LED lighting engine module. And to develop a rotational speed control system for controlling flash pattern of beacon. As a result, to develop of LED beacon for landfall mark that distance to reach the light 20NM to 27NM.

• Current Optics and Photonics
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• v.1 no.5
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• pp.456-467
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• 2017

The benefits of network coding in all-optical multicast networks have been widely demonstrated. In this paper, we mainly discuss the multicast service efficiently provisioning problem in the network coding enabled elastic optical networks (EONs). Although most research on routing and spectrum allocation (RSA) has been widely studied in the elastic optical networks (EONs), rare research studies RSA for multicast in the network coding enabled EON, especially considering the time delay constraint. We propose an efficient heuristic algorithm, called Network Coding based Multicast Capable-Multipath Routing and Spectrum Allocation (NCMC-MRSA) to solve the multipath RSA for multicast services in the network coding enabled EON. The well-known layered graph approach is utilized for NCMC-MRSA, and two request ordering strategies are utilized for multiple multicast requests. From the simulation results, we observe that the proposed algorithm NCMC-MRSA performs more efficient spectrum utilization compared with the benchmark algorithms. NCMC-MRSA utilizing the spectrum request balancing (SRB) ordering strategy shows the most efficient spectrum utilization performance among other algorithms in most test networks. Note that we also observe that the efficiency of NCMC-MRSA shows more obvious than the benchmark algorithm in large networks. We also conduct the performance comparisons of two request ordering strategies for NCMC-MRSA. Besides, we also evaluate the impact of the number of the linkdisjoint parallel w paths on the spectrum utilization performance of the proposed algorithm NCMC-MRSA. It is interesting to find that the change of the parameter w in a certain range has a significant impact on the performance of NCMC-MRSA. As the parameter w increases to a certain value, the performances of NCMC-MRSA cannot be affected by the change of w any more.

• Current Optics and Photonics
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• v.1 no.5
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• pp.474-490
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• 2017

Since the recent slowdown in the smartphone market, studies for wearable devices are briskly being carried out to find new markets, such as virtual reality devices. In this paper, a head-mounted display (HMD) which provides expanded virtual images before human eyes by enlarging images of a small display was designed, and the tolerance analysis method for a focus-adjustable HMD based on afocal optical systems was studied. There are two types of HMDs: a see-through type that allows the user to view the surroundings, and a see-close type where the user can only view the display screen; the former is used in this study. While designing the system, we allowed a lens within the system to be shifted to adjust its focus from +1 to -4 D (diopters). The yield of the designed systems was calculated by taking the worst-case scenario of a uniform distribution into account. Additionally, a longitudinal aberration was used rather than MTF for the tolerance analysis with respect to system performance. The sensitivity of the designed system was calculated by assigning a certain tolerance, and the focus lens shift was calculated to adjust the image surface variations resulting from the tolerance. The smaller the tolerance, the more expensive the unit price of the products. Very small tolerances may even be impossible to fabricate. Considering this, the appropriate tolerance was assigned; the maximum shift of the focus lens in which the image surface can be adjusted was obtained to find the changes in aberration and a good yield.

• Current Optics and Photonics
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• v.2 no.3
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• pp.261-268
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• 2018

Stimulated polariton scattering (SPS) from the $A_1$ transverse optical (TO) modes of $BaTiO_3$ bulk crystal generating a terahertz (THz) wave with the noncollinear phase-matching (NPM) condition is theoretically investigated. To our best knowledge, this is the first report on THz wave generation from $BaTiO_3$ bulk crystal via SPS. Phase-matching (PM) characteristics in the NPM configuration are analyzed. Effective parametric gain lengths for the Stokes and THz waves in the NPM configuration are calculated. The effective parametric gain coefficient and absorption coefficient of the THz wave in $BaTiO_3$ are theoretically simulated. The THz phonon flux densities generated via SPS in $BaTiO_3$ are theoretically calculated by solving the coupled wave equations under the NPM condition. The PM characteristics and THz-wave parametric gain characteristics in $BaTiO_3$ are compared to those in $MgO:LiNbO_3$. The results of the analysis indicate that $BaTiO_3$ is an attractive optical crystal for efficient THz wave generation via SPS.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.402-409
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• 2018

This paper describes the plan and procedure of a development test and evaluation that will be performed to verify the performance and technology of multi-mission unmanned surface vehicles (MMUSVs). In order to verify the design requirement of MMUSVs, we designed and manufactured the common platform of MMUSVs, which have an overall length of8.4 m, a displacement of 3,100 kg, and a speed of more than35 kts. The platform is equipped with several sub-systems, including radar and an EOTS/IRS. The EOTS/IRS, along with the search radar, is used for effective detection, identification, and targeting. The core technologies of MMUSV for DT&E will be investigated. The common platform design technologies, remote operating and control system technologies, autonomous navigation technologies, and unmanned operational technology of sensors and equipment will be studied for the development of the MMUSV's core technologies. The system will be able to make precise observations and track targets both manually and automatically during day and night conditions. Currently, the verification tests for each of the technologies and for the integrated system are in the pipeline for DT&E, which will be performed next year. Also, software reliability and life tests will be performed.

• Journal of Navigation and Port Research
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• v.37 no.6
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• pp.587-595
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• 2013

Establishment and operation of Aids to Navigation in the process of port design, construction and management are crucial factor of maritime safety and collision prevention. According to the IMO SOLAS Chapter 5, regulation 13, the establishment and operation of maritime safety facilities are mandated for the competent authorities. The facilities of Aids to Navigations are moving to a concept of e-Navigation with state-of-the-art technology of radio navigation equipments such as AIS, DGPS and e-Loran from the traditional visual facilities (optics, shape), Although the autonomous maritime traffic system is a new trend, yet the traditional and conventional Aids to Navigation like lighthouses and beacons are still imperative for vessel's safe navigation. In this paper, for decision of service level of maritime traffic facilities to enhance the efficiency of visual navigation system management it was proposed the Aids to Navigation availability as an efficient management system incorporating the whole maritime traffic facilities under one management system. Comparison of foreign level of services and analysis of the theoretical background of them were analyzed and the proposed LOS was applied to Incheon area to evaluate the safety of navigation routes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2571-2578
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• 2014

In this paper, we propose a computational generation method of elemental images for time-multiplexed 3D integral imaging display based lens division. In the proposed method, we analyze the image formation between 3D object and elemental images based on ray optics. Based on the analyzed formation, we generate the elemental image set for time-multiplexed display. Positions of an object point picked up in proposed method is shifted for half size of lens divided from those in conventional method when generating elemental images. To show the usefulness of the proposed method, we carry out the preliminary experiments and present the results.

• Laser Solutions
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• v.6 no.3
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• pp.19-28
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• 2003

The manufacturing process for the microfluidic device can include sequential steps such as master fabrication, electroforming, and injection molding. The laser ablation, using masks, has been applied to the fabrication of channels in microfluidic devices. In this research, an excimer laser was used to engrave microscopic channels on the surface of PET (polyethylene terephthalate), which shows a high absorption ratio for an excimer laser beam with a wavelength of 248 m. When 50-${\mu}{\textrm}{m}$-wide rectangular microscopic channels are ablated with a 500 ${\times}$ 500 ${\mu}{\textrm}{m}$ square mask at a magnification ratio of 1/10, ditch-shaped defects were found in both corners. The measurement of laser beam intensity showed that a coherent image in the PET target caused such defects. Analysis based on the Fourier diffraction theory enabled the prediction of the coherent shape at the image surface as well as the diffraction beam shape between the mask and the image surface. It also showed that the diameter of the aperture had a dominant effect. The application of aperture with a diameter of less than 3 mm helped to eliminate such defects in the ablated rectangular microscopic channels on PET without such ditch-shaped defects.

• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1374-1377
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• 2018

We achieved 95% visibility in the Hong-Ou-Mandel interference experiment while we achieved only 56% visibility in a previous report. We used a 120 mW 405 nm single-mode continuous wave laser, a 5-mm-thick type-1 ${\beta}$-barium borate single crystal, standard Hong-Ou-Mandel interferometer optics, two avalanche photodiode single-photon counters, and a homemade coincidence counting unit. The photon collection unit was the key difference between the present study and the previous study. In the present experiment, we used single-mode optical fibers for photon collection, which suppressed accidental coincidence between-different mode photons by acting as a spatial filter because of its core size being much smaller than a multi-mode fiber.