• 정보저장시스템학회논문집
• /
• 제7권1호
• /
• pp.19-24
• /
• 2011

Holographic Data Storage System, one of the next generation data storage devices, is a 2-dimensional page oriented memory system using volume holograms in writing and retrieving process. Recently photopolymer with disc type substrate was selected as a media for the Holographic Data Storage System. The disc tilt occurs when the media rotates and the external disturbance applies. The disc tilt causes the change of the angle between the reference beam and the media, the data cannot be retrieved with the right angle or other data page is retrieved. The tilt is generated in a 2-axis direction (tangential, radial). The tangential tilt direction is the same with the multiplexing plane, while the radial tilt direction is a perpendicular to the multiplexing plane. In this research we propose 2-axis tilt angle servo system. The tilt errors are measured by using external photo detector and the additional red laser. Then the tangential direction tilt is compensated by using the galvano mirror. Also the radial direction tilt is compensated by the rotating prism between the relay lens in the reference field. Finally we confirm the compensation results through the Signal to Noise Ratio(SNR) and Bit Error Rate(BER).

• 한국인터넷방송통신학회논문지
• /
• 제17권1호
• /
• pp.199-206
• /
• 2017

환경 잡음은 음성인식 시스템의 성능을 떨어뜨릴 수 있다. 이 논문은 인식 시스템이 잡음에 강인하도록 만들기 위하여, 켑스트럼에 기초한 특징 보상을 수행하는 과정을 제시한다. 이 방법은 부가적인 잡음의 영향을 제거하기 위한 직접적인 스펙트럼 기울기 보상에 기초를 둔다. 잡음 보상 방법은 로그 전력 스펙트럼의 스펙트럼 기울기 계산에 의하여 캡스트럼 영역에서 동작한다. 스펙트럼 보상은 SNR에 의존하는 켑스트럼 평균 보상 방법과 함께 사용된다. 백색 가우스 잡음, 지하철 잡음 및 자동차 잡음에 있는 조건에서, 실험 결과는 제안한 보상 방법이 여러 SNR에서 인식률을 상당히 개선한다는 것을 보여준다.

• Journal of Astronomy and Space Sciences
• /
• 제40권4호
• /
• pp.237-245
• /
• 2023

Laser communication has been considered as a novel method for earth observation satellites with generation of high data volume. It offers faster data transmission speeds compared to conventional radio frequency (RF) communication due to the short wavelength and narrow beam divergence. However, laser beams are refracted due to atmospheric turbulence between the ground and the satellite. Refracted laser beams, upon reaching the receiver, result in angle-of-arrival (AoA) fluctuation, inducing image dancing and wavefront distortion. These phenomena hinder signal acquisition and lead to signal loss in the course of laser communication. So, precise alignment between the transmitter and receiver is essential to guarantee effective and reliable laser communication, which is achieved by pointing, acquisition, and tracking (PAT) system. In this study, we simulate the effectiveness of tip/tilt compensation for more efficient laser communication in the satellite-ground downlink. By compensating for low-order terms using tip/tilt mirror, we verify the alleviation of AoA fluctuations under both weak and strong atmospheric turbulence conditions. And the performance of tip/tilt correction is analyzed in terms of the AoA fluctuation and collected power on the detector.

• Journal of the Optical Society of Korea
• /
• 제13권4호
• /
• pp.451-455
• /
• 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.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 추계학술대회논문집
• /
• pp.782-787
• /
• 2002

In optical disk drives (ODD), the demands of high data density and high speed have been increasing rapidly to achieve high data capacity and data transfer rate. The short wavelength laser, High NA objective lens, and high track following performance are needed to raise data density and data rate. For high-performance actuator, the improvement of linearity and acceleration become more important. Also, 3-axis actuator for active tilt compensation is introduced to overcome the decrease in disk tilt tolerance which is induced by short wavelength laser. In this paper, a hybrid type 3-axis actuator is presented and a new yoke structure, which can reduce the interaction between yoke and moving magnet, is designed to keep the efficiency of magnetic circuit. Experimental results show the validity of the yoke in the hybrid type actuator.

• Journal of Advanced Marine Engineering and Technology
• /
• 제37권2호
• /
• pp.192-198
• /
• 2013

본 논문은 2축 구조를 가진 안정화 지향성 Pan-Tilt 시스템을 개발하기 위한 기초연구로서 2축 Pan-Tilt와 Pan-Tilt 구동 하드웨어 보드를 제작하고 표적 추적을 위한 제어기를 설계하는 내용이다. Pan-Tilt 시스템을 6 자유도 선박운동 시뮬레이터에 탑재하여 테스트 환경을 구축하고 RCGA를 이용하여 Pan-Tilt의 모델 매개변수를 추정한 다음, 추정된 모델과 RCGA에 기초하여 시뮬레이션과 실험을 수행함으로써 2 자유도 PID 제어기 동조의 유효성을 검토한다.

• 한국광학회지
• /
• 제14권1호
• /
• pp.12-16
• /
• 2003

$0^{\circ}C$에서 5$0^{\circ}C$까지 온도를 변화시켜 가며 100 GHz의 채널 간격으로 L-band 40채널을 운용했을 때, 온도에 따른 L-band EDFA의 출력 스펙트럼 변화와 이득 변동폭을 측정하였다. 이득 포화 영역에서의 이득의 변화로 인한 출력 스펙트럼의 변화는 온도에 따른 출력 스펙트럼의 변화와 상반되는 점을 이용하여 1단과 2단 사이에 삽입한 가변 감쇄기를 조절하여 온도에 따른 이득 변동을 보상하였다. 그 결과, $0^{\circ}C$에서 최대 3 dB까지 차이를 보이던 이득 변동 폭은 가변 감쇄기를 이용한 온도 보상으로 1 dB 이내로 줄어듦을 볼 수 있었다.

• 전자공학회논문지
• /
• 제52권5호
• /
• pp.190-196
• /
• 2015

본 논문은 항법장치 위치보정을 위해 칼만필터를 적용한 GPS/INS융합의 다중보정방법을 제안한다. 연구에서는 관성항법장치를 구현하기 위해 9축 항법장치로 보정알고리즘을 적용하여 위치오차를 감소시킨 방법을 적용했다. 일반적으로 GPS/INS는 위치정보를 얻어낼 수 있지만 위치정보를 구하는 과정에서 오차 또한 더불어 커지게 되기에 이를 보정하기 위한 강인한 오차 보정 알고리즘이 필요하다. 본 논문에서는 9축 관성센서(mpu-9150)의 외란에 대한 강인성 향상을 위해 가속도계 보정 알고리즘을 사용하여 tilt보정을 수행했으며, 제어 대상체의 정확한 방위를 파악할 수 있도록 Yaw각 재정의 알고리즘을 적용하였다. 최종적으로 GPS/INS와 칼만 필터를 함께 결합한 통합시스템을 구현하였다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 추계학술대회논문집
• /
• pp.226-233
• /
• 2003

There are many researches going on to develop the information storage devices using Blue-ray disc and DVD as a demand for high-density information storage devices is highly increasing. This high-density information storage device requires a short-wave laser and objective lens of high numerical aperture set in fer its operation. And, that brings out rapid decrease of tilt tolerance. Therefore, it is necessary that an actuator should control tilt motions to get a stable signal. In this paper, a new mathematical form of 3-D.O.F coupled model is formulated and magnetic circuit in constraints is most effectively designed with the use of the moving coil type actuator in higher sensitivity. Further, this paper presents a tilt coil whose rotational center point is put on that of the lens through the variation of tilt coil and proposes a 3-axis actuator with high sensitivity improved in its dynamic property through its structure analysis.

• 정보저장시스템학회논문집
• /
• 제3권4호
• /
• pp.191-195
• /
• 2007

The optical disc drive has used a high NA objective lens and a shorter wavelength laser diode for high recording density. But high NA and shorter wavelength cause several margins to become short. Focusing and tracking servo has to be more accurate and active tilt compensation mechanism is also needed for coma aberration compensation. In this paper, we proposed 3-axis moving magnet type actuator. For 3-DOF motion, moving coil actuator has to be equipped with 6 wires for supplying 3 independent signals. However, moving magnet type actuator doesn't need to change the configuration of wires because coils are in stator. So, we added a tilt mechanism to the 2-axis moving magnet actuator which is designed in previous research. Addition of the tilt mechanism cuts down the focus sensitivity. So, maximization the tilting sensitivity and securing the focusing sensitivity are objectivities of this research. DOE (design of experiments) procedures of electromagnetic circuit are performed for parameter study and the optimization is also performed to maximize the tilt sensitivity. And then the final design is suggested and its performance is verified by FE simulation.