• Bulletin of the Korean Space Science Society
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• 2000.10a
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• pp.75-75
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• 2000

No Abstract, See Full Text

• Korean Journal of Optics and Photonics
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• v.30 no.4
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• pp.142-145
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• 2019

Normally, a corner cube retroreflector (CCRR) sheet is used as a retroreflective mirror array (RRMA) in a volumetric display. Each CCRR unit reflects light in the retroreflective direction, which is parallel to the incident light, and it makes a blurred image, as it shifts the position of light within its dimensions. Adopting a "curved planar wall" and "parabolic focusing" (x-axis), a hybrid-t(transverse direction)-RRMA is proposed, to improve the image quality and brightness. The improvement of image contrast is achieved by tuning a "linear v-shaped groove" structure to a "parabolic v-shaped groove". Also, the system has been simplified and the brightness enhanced 4 times by removing the half mirror.

• Journal of the Optical Society of Korea
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• v.17 no.5
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• pp.371-375
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• 2013

To improve the utilization efficiency of solar energy, a new solar optical concentrating system composed of a parabolic reflector with a square cross-section, a hyperbolic reflector with a square cross-section and two converging convex lenses has been designed. The proposed method can simultaneously focus and shape sun light into a square pattern on the solar panel. In addition, the total reflection property of photonic crystal within the range of the visible sunlight spectrum has been analyzed. Finally, the relationship between solar concentrating multiples and the diameter of the primary mirror has been discussed.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.93-102
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• 2021

In this research, we present a natural lighting system with transmission distance of 30m and lighting efficiency of 35% (30m standard) for operating hours of 7h/day (based on clear sky). The system is composed of parabolic reflective mirror and modified light pipe that can secure more than 88% of light concentration efficiency. The light loss rate of newly designed light pipe transmission system is demonstrated to 0.8 %/m in the straight-line part and 2%/m in the curved part. Modified light pipe daylighting system shows better performance over fiber optic daylighting system in terms of transmission distance (1.5 times longer) and illuminance (3.05 times higher).

• Korean Journal of Optics and Photonics
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• v.4 no.1
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• pp.114-119
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• 1993

We constructed a laser-heated pedestal growth station using a 25 W $CO_2$ laser to grow various single crystal fibers. The LHPG system consists of the optical system which includes a reflaxicon, an elliptic mirror and a parabolic mirror with their centers drilled, and the translation system to move a source and a seed independently. To test the system, we pulled a few ruby fibers with diameter of 600 ${\mu}m$ and length of 2 cm, and studied characteristics of their photoluminescence.

• Solar Energy
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• v.1 no.1
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• pp.1-11
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• 1981

The electric generation system by solar energy was built which is composed of $10m^2$ reflector, parabolic mirror and the absorbers. The absorber(I) is a single iron pipe and the absorber (II) contains seven small iron pipes. The ratio of the area of the reflectors to that of the absorber is around 99.4-440. The absorber(II) is more efficient in power than (II) by 5.6 percent. The steam power efficiency of the absorber (II) is 25 percent in this experiments and 20 percent efficiency would be expected for 80.000 Kilowatts.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.816-819
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• 2005

This paper proposes a coordinate correction technique using the transformation of 3D parabolic coordinate function and BP(Back Propagation) neural network in order to solve space distortion problem caused by using catadioptric camera. Although Catadioptric camera can obtain omni-directional image at all directions of 360 degrees, it makes an image distorted because of an external form of lens itself. Accordingly, To obtain transformed ideal distance coordinate information from distorted image on 3 dimensional space, we use coordinate transformation function that uses coordinates of a focus at mirror in the shape of parabolic plane and another one which projected into the shape of parabolic from input image. An error of this course is modified by BP neural network algorithm.

• Journal of the Optical Society of Korea
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• v.20 no.2
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• pp.314-320
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• 2016

The glass thermal forming process provides a high volume, low cost approach to producing aspherical reflectors for x-ray optics. Thin glass sheets are shaped into mirror segments by replicating the mold shape at high temperature. Heating parameters in the glass thermal slumping process are crucial to improve surface quality of the formed glass. In this research, the heating process of a thermal slumping glass sheet on a concave parabolic mold was simulated with the finite-element method (FEM) to investigate the effects of heating rate and soaking temperature. Based on the optimized heating conditions, glass samples 0.5 mm thick were formed in a furnace with a steel concave parabolic mold. The figure errors of the formed glass were measured and discussed in detail. It was found that the formed glass was not fully slumped at the edges, and should be trimmed to achieve better surface deviation. The root-mean-square (RMS) deviation and peak-valley (PV) deviation between formed glass and mold along the axial direction were 2.3 μm and 4.7 μm respectively.

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.287-293
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• 2008

The collimator which makes a collimated beam, is an essential instrument for assembly and evaluation of telescopes. Recently, the Cassegrain type collimator has been widely used for its compact size as the focal length of high resolution cameras becomes longer. However, this kind of collimator has a disadvantage in that the secondary mirror is a heat source which can degrade the evaluation accuracy for an IR camera system. In this paper, we present the fabrication and measurement process for an off-axis parabolic mirror with the physical diameter pf 1 m, effective diameter 930 mm, and the focal length 6 m. After four months of works we obtained the final surface wave-front error of 30.4 nm rms ($\lambda$/138, ${\lambda}=4.2\;{\mu}m$), which is capable of evaluation of an IR camera as well as a visible camera.

• Publications of The Korean Astronomical Society
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• v.18 no.1
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• pp.87-95
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• 2003

FIMS (Far-ultraviolet IMaging Spectrograph) is the main payload of STSAT-1 satellite which was successfully launched on September 27, 2003. The optical system of FIMS consists of two sets of parabolic cylinder mirror, slit, ellipsoidal reflection grating, and baffle system. We designed two types of baffle system for the FIMS: FOV baffle and order baffle. FOV baffle in the mirror house controls the field of view, and the order baffle in the vacuum box blocks the rays reflected rays by different orders.