• Journal of Institute of Control, Robotics and Systems
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• v.17 no.9
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• pp.947-953
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• 2011

Radome aberration error causes degradation of miss distance as well as stability of high maneuver missile system with RF seeker. A study about radome compensation method is important in this kind of missile system design. Several kinds of methods showed good compensation performance in their paper. Proposed adaptive Particle filter estimates line of sight rate excluding the radome induced error. This paper shows effectiveness of adaptive Particle filter as compensation method of radome aberration error. Robust performance of this filter depends on external aiding measurement, target acceleration. Tuning of system error covariance can make this filter unsensitive against the error of target acceleration information. This paper demonstrates practical usage of adaptive Particle filter for reducing miss distance and increasing stability against disturbance of radome aberration error through performance analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.346-350
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• 2004

In Blu-ray(BD) optical system, as a short laser wavelength of laser diode and thin cover layer thickness of' disc, the proper adjustment of spherical aberration should be performed. Considering thin cover layer' thickness and tolerance variation of disc in BD optical system, spherical aberration in BD format is mort: serious than CDㆍDVD format Especially, in dual-layer disc, to compensate the aberration at each layer, optical component should be moved finely in the way of optical path. In this study, 1 -axis moving actuator was introduced as the method of compensating the spherical aberration, and the mechanism of the system was described. Finally, its effect on optical system will be mentioned.

• Journal of the Optical Society of Korea
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• v.13 no.4
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• pp.451-455
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• 2009

We present a numerical procedure that compensates for tilt phase aberration in in-line digital holography by computing the period of interference patterns in the reconstructed phase image. This method enables the reconstruction of correct and accurate phase information, even if strong tilt aberrations exist. Example applications of tilt aberration compensation are shown for a tilted plate, a micro-lens array, and a thin film transistor. This method is convenient because it uses only one hologram and no hardware to minimize the tilt aberration.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.4 no.2
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• pp.182-186
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• 2004

This paper describes an advanced compensation for non-linear functions designed to remove steering aberrations from phased array antennas. This system alters the steering command applied to the antenna in a way that the appropriate angle commands are given to the array steering software for the antenna to point to the desired position instead of squinting. Artificial neural networks are used to develop the inverse function necessary to correct the aberration. Also a straightforward antenna steering function is implemented with neural networks for the 9-term polynomials of forward steering function. In all cases the aberration is removed resulting in small RMS angular errors across the operational angle space when the actual antenna position is compared with the desired position. The use of neural network model provides a method of producing a non-linear system that can correct antenna performance and demonstrates the feasibility of generating an inverse steering algorithm.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.5
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• pp.519-525
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• 2011

High-resolution earth-observing satellites acquire substantial amount of geospatial images. In addition to high image quality, high-resolution satellite images (HRSI) provide unprecedented direct georegistration accuracy, which have been enabled by accurate orbit determination technology. Direct georegistration is carried out by relating the determined position and attitude of camera to the ground target, i.e., projecting an image point to the earth ellipsoid using the collinearity equation. However, the apparent position of ground target is displaced due to the atmosphere and satellite velocity causing significant georegistration bias. In other words, optic ray from the earth surface to satellite cameras at 400~900km altitude refracts due to the thick atmosphere which is called atmospheric refraction. Velocity aberration is caused by high traveling speed of earth-observing satellites, approximately 7.7 km/s, relative to the earth surface. These effects should be compensated for accurate direct georegistration of HRSI. Therefore, this study presents the equation and the compensation procedure of atmospheric refraction and velocity aberration. Then, the effects are simulated at different image acquisition geometry to present how much bias is introduced. Finally, these effects are evaluated for Quickbird and WorldView-1 based on the physical sensor model.

• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.80-81
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• 2005

• Transactions of the Society of Information Storage Systems
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• v.8 no.1
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• pp.11-15
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• 2012

In this paper, we experimentally investigated compensation method of the mechanical errors for the micro holographic storage. The aim of this research was overcome of disc tilt and spherical aberration problems. The proposed method was performed by using glass plate and zoom optics.

• Journal of the Optical Society of Korea
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• v.19 no.1
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• pp.45-54
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• 2015

In this study, a novel parallel wavefront correction system architecture is proposed, and a model-based tabu search (MBTS) algorithm is introduced for this new system to compensate wavefront aberration caused by atmospheric turbulence in a free-space optical (FSO) communication system. The algorithm flowchart is presented, and a simple hypothetical design for the parallel correction system with multiple adaptive optical (AO) subsystems is given. The simulated performance of MBTS for an AO-FSO system is analyzed. The results indicate that the proposed algorithm offers better performance in wavefront aberration compensation, coupling efficiency, and convergence speed than a stochastic parallel gradient descent (SPGD) algorithm.

• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.42-47
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• 2005

We developed an optical pickup system which is used fer Blu-ray Disc. A liquid crystal element was used to make compensation for spherical aberration. Spherical aberration is a difficult problem in the optical pickup system for Blu-ray Disc. To reduce the effects of wavelength variation from the laser source, we designed a diffraction optical element. We took a measurement of all of the parts used to make a pickup system and validated the performance of each part. Then, we made a performance test fur the optical pickup system which we developed for Blu-ray Disc and the results were satisfactory.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.151-152
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• 2005

Blu-ray 디스크에서는 NA=0.85 의 높은 개구수를 채용함으로써 디스크 보호층의 두께 변동에 따른 구면수차 발생량이 매우 커지는 문제가 발생하게 된다. 따라서 디스크 두께 공차 $3{\mu}m$에서 Blu-ray 시스템의 수차 발생 허용수준을 초과한다. 그리고 Multi-layer 디스크의 경우 각 층의 간격이 $25{\mu}m$ 정도의 간격을 두고 배치되어 있어 기록층 사이에서 발생하는 구면수차의 보정이 필요하며, 종래의 기술은 보상범위가 $3{\mu}m$로 한정되어 사용이 불가능하며 또한 대물렌즈 조립공차가 엄격히 관리되어야 하는 문제점을 안고 있었다. 본 연구에서는 액정렌즈에 의한 구면수차 보정으로 이러한 문제점들을 해결하고자 하였다. 액정렌즈는 오목렌즈 액정소자와 볼록렌즈 액정소자로 구성되며 픽업 광학계 내에 조합하여 설계함으로써 Multi-layer 디스크의 두께 변동에 따라 발생하는 구면수차를 보정하고 대물렌즈 조립공차 문제를 해결할 수 있다.