• Korean Journal of Optics and Photonics
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• v.13 no.1
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• pp.1-8
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• 2002

Optical payloads for earth-observation satellites become bigger as the required resolution becomes finer. For example, the diameter of the primary mirror of IKONOS, which has ground sampling distances of 1m/4m in panchromatic/multi spectral bands, is about 700mm. As the size of optical payload becomes bigger, the light-weighting of the mirrors becomes more significant. This paper presents the FEM results of the following four mirror types of 300 m diameter under gravity release and temperature changes: flat back mirror, single arch mirror, double arch mirror, and honeycomb sandwich mirror. Furthermore, this paper extends the FEM results to larger mirrors up to the diameter of 1m based on a general scaling law and Valenete\`s equation.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.519-524
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• 2013

Purpose: This study relates to the development of dot-sight device, whose length is reduced, with a prism beam splitter. Methods: We developed a new dot-sight device whose length was reduced by eliminating the optical axis tilt of the doublet reflector to reduce the occurrence of the parallax and by redesigning the doublet reflector to use a prism beam splitter. Results: We could develop the new type dot-sight device having a prism beam splitter and the dot reticle generator and the doublet reflector, of which optical axises showed a T-letter type with the optical axis of the observer's eye. Conclusions: In this study, we designed and developed a new type dot sight employing a prism beam splitter that could be able to further enhance the accuracy of the fire in comparison with the traditional dot sight, thereby reducing the overall optical length of system. The new designed dot sight was able to be reduced 2.2 times on the overall optical length, and could be improved more than three times on the accuracy of shooting in the horizontal direction, than the traditional dot sight.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.142-147
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• 2004

Satellite laser ranging (SLR), which is the most accurate geodetic method for precise orbit determination of artificial satellites, will be used to determine the precise orbit of STSAT2. This paper will present the development of a Laser Reflector Array (LRA) of STSAT2. Currently one LRA was designed, analyzed, manufactured, optically tested and assembled.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.252-259
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• 1993

A holosymmetric four-mirror system with unit magnification is designed for use in the micro-lithography using a deep ultraviolet wavelength of $0.248 {\mu}m$(KrF excimer laser line). In the holosymmetric system all orders of coma and distortion are zero. By applying this principle to the 4-spherical mirror system, we have obtained only one exact solution for the unit magnification holosymmetric four-spherical mirror system with all zero third order aberrations. For correction of the residual higher order aberrations of the system, aspherization is introduced keeping the holosymmetric properties. We have obtained near diffraction-limited performance for the wavelength of 0.248 pm within N.A. of 0.33 and image field diameter of 7.6 mm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.5
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• pp.445-454
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• 2015

In this paper, we propose an optimal design method for a dual reflector antenna(DRA) using the Genetic algorithm. In order to reduce the computational burden during the optimal design, we exploit the iterative physical optics(IPO) to calculate the surface current distribution at each reflector antenna. To improve the accuracy, we consider the shadow effect by the structure and the coupling effect by the multi-reflection based on the iterative MFIE(Magnetic Field Integral Equation). To reduce the number of design variables and generate a smooth surface, we use the Bezier function with the control points, which become the design variables in this paper. We adopt the HPBW(Half Power Beam Width), the FNBW(First Null Beam Width), and the SLL(Side Lobe Level) as the objective or cost functions. To verify the results, we compare them with the those of the commercial tool.

• Bulletin of the Korean Space Science Society
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• 2003.05b
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• pp.38-38
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• 2003

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.1
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• pp.39-46
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• 1993

In this paper, an offset paraboloidal reflector antenna satisfied efficiency of over 60% and sidelobe envelope line of 29-25$log\theta$ was designed and manufactured for Ku-band VSAT(Very Small Aperture Terminal) antenna. The radiation patterns of experimental antenna were computed by applying the series expansion method using the Zernike polynomials. The measured patterns are in good agreement with the computed results. The Gain, efficiency, and sidelobe envelop line fairly well satisfy the design specifications except first sidelobe level.

• Korean Journal of Optics and Photonics
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• v.24 no.3
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• pp.111-119
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• 2013

A large aspheric mirror is a key component for large astronomical telescopes and high resolution satellite cameras. Since it is large and has an aspheric form, it is much more difficult to fabricate it compared to the similar size of spherical mirror. Especially, the opto-mechanical design and analysis is critical to reduce the deformation of mirror surface due to the external forces such as gravity or temperature change, as the mirror size is larger and lightweighting ratio is increased. The design requirements for the mirror are different depending on the particular ground and space applications because the environmental conditions are changed. In this paper, we explain the opto-mechanical design and analysis for ground and space applications that are among the most difficult to achieve among several technologies related to development of the large aspheric mirror.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.1
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• pp.122-132
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• 1999

In this paper, a shaped small-size ADE(Axially Displaced Ellipse) reflector antenna of 30 cm in diameter operating from 37 to 40 GHz was designed. The experimental antenna was manufactured, and the radiation characteristics evaluated. In the procedure of antenna design, aperture field distribution was assumed to uniform + parabolic distribution. And the variations of beam width, aperture efficiency, and sidelobe level as functions of aperture field distributions were investigated, and these results presented to be used in antenna design. The measured gain and sidelobe level of experimental antenna were found 39.9 dBi(efficiency : 61.9%) and -18.8 dB for 40 GHz. These values show good agreement in design goal of efficiency more than 60% and sidelobe level less than -20 dB.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.71.2-71.2
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• 2013

1 m 천체망원경에 대한 초기 광기계 구조해석이 진행되었다. 3개의 반사경으로 구성되는 광학계는 Richey-Cretien 방식으로써 두 개의 Nasmyth 초점을 제공하고, 초점비는 F/8이다. 결정된 반사경 마운트 방법에 의해 반사경면의 표면 RMS(Root Mean Square) 변형량은 모두 20 nm보다 작다. 전체 구조물에 대한 구조해석을 수행하기 위해 솔리드, 쉘, 빔 요소 등으로 구성된 정밀유한요소 모델이 NX 소프트웨어로 설계되었다. 전체 구조물은 첫 번째 고유모드는 68 Hz에서 병진모드가 발생했다. 중력에 대해서는 최대 응력이 18.2 MPa로써 미비하였고, 전체 최대 변위는 50.3 ${\mu}m$ 로써 계산되었다. 이 변위값은 광학설계 소프트웨어에 재입력되어 광학계의 성능이 재분석 될 것이다.