• Journal of the Optical Society of Korea
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• v.20 no.4
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• pp.481-487
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• 2016

This study presents a new optical system for a combiner-type head-up display (HUD) with a cylindrical lens as an asymmetrical aberration corrector, instead of a freeform mirror. In the initial design process based on off-axial aberration analysis, we obtain an off-axis two-mirror system corrected for linear astigmatism and spherical aberration by adding a conic secondary mirror to an off-axis paraboloidal mirror. Thus, since the starting optical system for an HUD is corrected for dominant aberrations, it enables us to balance the residual asymmetrical aberrations with a simple optical surface such as a cylinder, not a complex freeform surface. From this design process, an optical system for an HUD having good performance is finally obtained. The size of the virtual image is 10 inches at 2 meters away from a combiner, and the area of the eye box is 130×50 mm².

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.2
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• pp.103-108
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• 2005

Loading/Unloading task in the real industry is performed by crane, but most of the loading/unloading task with the weight of 5kg∼30kg is done by human workers and this kind of work causes industrial disaster of workers. Therefore it is necessary to develop low cost loading/unloading manipulator system to prevent this kind of industrial accidents. This paper is concerned with the design and fabrication of 2 axis pneumatic manipulators using on/off solenoid valves and accurate position control without respect to the external load and low damping in the pneumatic rotary actuator. To overcome the change of external load, switching of control parameter using LVQNN (Learning Vector Quantization Neural Network) is newly applied, which estimates the external loads in the pneumatic cylinder. As an underlying controller, a state feedback controller using position, velocity and acceleration is applied to the switching control system. The effectiveness of the proposed control algorithms are demonstrated through experiments of pneumatic cylinder with various loads.

• The Bulletin of The Korean Astronomical Society
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• v.25 no.2
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• pp.75-75
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• 2000

• 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

• Journal of Astronomy and Space Sciences
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• v.18 no.3
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• pp.239-248
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• 2001

Far-ultraviolet IMaging Spectrograph (FIMS) is the main payload of the first Korean scientific satellite, KAISTSAT-4, which will be launched in 2002. Among the optical parts, parabolic cylinder mirror does not have any heritage from previous astronomical missions, so the manufacturing and testing process itself is a challenging issue. We describe the method of manufacturing and measuring of the off-axis parabolic cylinder mirror and our initial experiments to establish the entire manufacturing process. Using the method, the profile error can meet the specification of $lambda$ per cm which is closely related with the astronomical performances. In case of the surface roughness, temperature controlled pitch polishing reduces $R_{q}$ under 1 nm implying that scattering in the entire spectral range of FIMS is less than 2% of the incident UV light.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.10
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• pp.1619-1625
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• 1997

This paper concerns a 2-axis PR type pneumatic manipulator system translating in vertical and rotating in horizontal directions. A simplified linear model is mathematically formulated similar to the pneumatic acturators in dynamic responses in order to devise an appropriate position control scheme. A PD controller preceding the on/off solenoid valve turns out not only economical but also effective in reducing rise time and amplitude of limit cycles, if its control gains are determined on the basis of frequency response. And, additional implementation of symmetric or asymmetric deadband at the PD controller output greatly helps minimize valve opening numbers, positional error, and undesirable direction-dependent property due to the gravitational load. Such a control concept is synthesized through numerical simulations and next applied to the experimental set-up, featuring enhanced positional servo characteristics.

• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.65-70
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• 2004

An imaging spectrograph concept optimized for extended far-ultraviolet emission sources is presented. Although the design was originally developed for FIMS aboard the first Korean science satellite STSAT-l launched on September 27, 2003, no rigorous theoretical background of the spectrograph design has been published. The spectrograph design employs an off-axis parabolic cylinder mirror in front of a slit that guides lights to a diffraction grating. The concave grating provides moderate spatial resolution over a large field of view. This mapping capability is absent in most astronomical instruments but is crucial to the understanding of the nature of a variety of astrophysical phenomena. The aberration theory presented in this paper can be extended to holographic gratings in order to improve the spatial as well as the spectral resolutions.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.86-87
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• 2001

Far-ultraviolet IMaging Spectrograph(이하 FIMS)는 2002년에 발사 예정인 과학위성 1호의 주 탑재체이며, 은하 주변에 분포한 고온의 가스에서 방출되는 자외선 영역 (short wavelength band ： 900-1150 $\AA$, long wavelength band ： 1335-1750$\AA$)의 방출선을 약 2$\AA$의 분광 분해능으로 관측하는 천문학적 목표를 가지고 있다 일반적인 망원경을 사용하는 대신 제한된 위성의 크기 내에서, 넓은 지역에 퍼져 있는 가스의 분포와 특성을 관측하는데 적합하도록, 그림 1과 같이 비축 포물 원통 반사경과 타원형의 substrate를 가진 회절 에돌이발 (grating)의 사용을 고안하였다. (중략)

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.3
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• pp.83-87
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• 2007

This study was classified and compared astigmatism's refractional abnormal degrees with visual acuity state of full correction which turned on axises of only 5 degree, 10 degree, and 15 degree. Subjects of this study were 57 college students (114 eyes) who had neither eye diseases nor binocular abnormality, were from their twenties to fifties, with myopia. It appeared that 30.8% of subjects who had astigmatism wore glasses with wrong axis of astigmatism. After accurate correction of the visual acuity and degrees of astigmatism, when we moved to corrected axises at 5 degree, 10 degree, 15 degree, failure of visual acuity with one line or more were 56.1%, 84.2%, 93.8%, respectively. When we comapre the completely-corrected visual acuity with the visual acuity with dricted axes, the bigger the width of visual acuity's weakness was the bigger the drifted angle. The change of normal visual acuity according to drifting angle of corrected axises of astigmatism, when we compared with full correction, appeared 0.94 in 5 degree, 0.87 in 10 degree, and 0.79 in 15 degree. Drift of 5 degree from fully corrected axis, corresponded to difference of visual acuity about one line, drift of 10 degree to 1.8 line difference of visual acuity, and drift of 15 degree about to 2.6 line difference. Through this study, we were sure that, in the case of drifting away from the right axis of astigmatism, it lead to visual weakness and asthenopia. Therefore we darely advise that optometrists should make mistake of axis least by confirming accucacy of corrected axis after despensing of spectacles of astigmatism.