• 천문학회보
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• 제36권2호
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• pp.87.1-87.1
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• 2011

Since early 90's, the solar X-ray telescopes such as Yohkoh SXT and Hinode XRT have observed coronal magnetic structures on the Sun's surface in the range of about $40'{\times}40'$ field-of-view (FOV) covering the full solar disk. Thus it has been stressed by the scientists that the optical structure of solar telescopes should be designed with care for improving the uniformity over a wide FOV. There would be, however, no unique solution in designing the optical system of a telescope for overcoming perfectly the problem of off-axis response variation. As a consequence, the correction of optical imperfectness of telescopes has become an important calibration step that should be performed beforehand when the observed images are to be used for photometric purposes. In particular, a special care should be taken when performing the temperature analysis with thin and thick filters for flaring activities observed at the periphery of the full FOV. From the analyses of both pre-launch calibration and in-flight observation data, the optical characteristics for describing the performance of solar X-ray telescopes, especially in view of their energy dependence, will be introduced and discussed in our presentation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.393-398
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• 2004

The near-field scanning micro scope (NSOM) technique is in the spotlight as the next generation storage device. Many different types of read/write mechanism for NSOM have been introduced in the literature. In order for a near-field probe to be successfully implemented in the system, a suitable slider and suspension are needed to be properly designed. The optical slider is designed considering near-filed optics and probe array. The suspension generally supports slider performance, and tracking servo capacity in HDD. Moreover, the suspension for optical slider also should meet the optical characteristics, and is also required to satisfy shock performances for the mobility for the actuator. In this study, the optical slider and the suspension fer near-field probe array are designed and analyzed.

• 정보저장시스템학회논문집
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• 제1권1호
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• pp.93-98
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• 2005

Rewritable optical disk is one of the essential data storage media in these days, which takes advantage of the different optical properties in the amorphous and crystalline states of phase change materials. As well known, data transfer rate is one of the most important parameter of the phase change optical disks, which is mostly limited by the crystallization speed of recording media. Therefore, we doped Sn/Bi to $Ge_2Sb_2Te_5$ alloy in order to improve the crystallization speed and investigated the dependence of phase change characteristics on Sn/Bi doping concentration. The Sn/Bi doped $Ge_2Sb_2Te_5$ thin film was deposited by RF magnetron co-sputtering system and phase change characteristics were investigated by X-ray diffraction (XRD), static tester, UV-visible spectrophotometer, electron probe microanalysis (EPMA), inductively coupled plasma mass spectrometer (ICP-MS) and atomic force microscopy (AFM). Optimum doping concentration of Bi and Sn were 5${\~}$6 at.$\%$ and the minimum time for crystallization was below than 20 ns. This improvement is correlated with the simple crystalline structure of Sn/Bi doped $Ge_2Sb_2Te_5$ and the reduced activation barrier arising from Sn/Bi doping. The results indicate that Sn/Bi might play an important role in the transformation kinetics of phase change materials..

• 한국광학회지
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• 제6권2호
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• pp.101-107
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• 1995

본 연구에서는 CFAP(Combined Filter of Amplitude and Phase)형태의 진폭과 위상이 변조된 Bessel beam의 회절 특성을 조사하기 위해 무수차 광학계와 구면수차가 포함된 광학계 각각에 대한 defocus에 따른 강도와 중심 스폿의 반경 변화, 그리고 Optical Transfer Function(OTF) 변화를 Bessel beam의 마디 수를 증가시키면서 계산하였다. Bessel beam은 구면수차를 포함한 광학계에서의 최대 강도 값과 최대 강도 점에서의 OFT값이 무수차 광학계의 경우보다 크게 나타나는 구면수차 보정효과를 보였으며 특히 구면수차가 3.lambda. 포함된 광학계에서의 OTF 값은 Clear aperture의 경우보다 높은 OTF값을 보였다. 또한 defocus에 따른 중심 스폿의 반경은 Airy disk의 반경보다 훨씬 작게 나타나는 영역이 있음을 알 수 있었으며 이러한 결과들은 고집적 반도체 소자 제작을 비롯한 고밀도 광 기록 장치에 이용 가능할 것이다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.648-649
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• 2012

• 정보저장시스템학회논문집
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• 제2권1호
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• pp.43-49
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• 2006

Fractal/angle multiplexing is a $LiNBO_3$ crystal using a X-Y Galvano mirror, and the random access concept in fractal/angle multiplexing are discussed in this paper. First, the brief introduction of the designed holographic digital data storage system is presented. Then, the average access time concept for the storage system is newly defined, and the comparison of the average access time between the holographic storage and a conventional optical disk is performed. Second, the basic simulation and experiment to find the X-Y Galvano mirror dynamics are conducted. From this analysis, we find that the average access time in our HDDS which has 6 degree scan angle is about 5 msec. This result is very high performance when it compared with the average access time of a conventional optical disk. Finally, some recording results using fractal/angle multiplexing are presented, then, the relationship between bit error rate and angle mismatch for the each multiplexing are discussed.

• 융합신호처리학회논문지
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• 제11권1호
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• pp.32-40
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• 2010

확장된 네이보어-제르니케 방법을 이용하여 광학계의 동공함수(pupil function)를 추산하는 알고리즘을 제안한다. 동공함수로부터 광학계가 가진 파면수차를 복원하고 아울러 동공에 비추어지는 빛의 밝기분포를 분석할 수 있다. 이 방법은 브루-레이 광픽업의 생산현장에 적용하여 실시간으로 광학계의 수차를 복원할 수 있다. 아울러 이 방법이 여러 다른 광학계에 널리 이용될 수 있음을 다양하게 수차를 부여해서 생성한 데이터를 분석하여 검증하였다. 초점영역의 빔 데이터로부터 동공함수를 얻는 역변환의 여러 방법 중에서 수차이론에 근거한 기존의 네이보어-제르니케 방법을 최근에 네덜란드 연구진이 개량한 확장된 네이보어-제르니케(extended Nijboer-Zernike: ENZ) 방법을 제안하였다. ENZ 방법은 초점영역의 3차원 빔 데이터로부터 해석적인 접근을 통하여 동공의 제르니케 계수를 효율적으로 계산해 낸다. 그러나 이 방법에서는 개구수(NA)가 큰 경우에는 근사적인 접근을 하도록 되어 있다. 본 연구에서는 보다 일반적인 상황에서 적용할 수 있는 수치해석 알고리즘을 개발하고, 이를 GUI 환경에서 운용할 수 있는 윈도 기반의 프로그램을 작성하여 생성한 빔 데이터에 적용하여 이 알고리즘의 유효성을 검증하여 13개의 복소 수차인자 $\beta_n^m$이 모든 요소가 0.7까지 분석을 하였고, 아울러 광픽업의 3D 빔 데이터를 실측해서 간섭계로 측정한 데이터와 R=0.98 정도의 상관관계를 가지는 것을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.2263-2265
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• 2000

본 연구에서는 광 픽업의 소형, 경량 제작을 위해 MEMS 기술을 이용하여 planar micro optics 방법으로 광 픽업을 구성하는 micro lens, actuator, beamsplitter 등을 설계, 제작하고 집적화한 픽업헤드를 구성하여 그 특성을 분석하였다. 특성분석 결과 disk에 focusing 되는 beam의 형상은 circle type의 비교적 양호한 결과를 얻을 수 있었고 beam spot size는 약 22$\mu m$로 실제 system에서 요구되는 0.9$\mu m$이내의 beam spot size에 비해 약 25배 가량 큰 beam spot size를 얻을 수 있었다.

• 한국소음진동공학회논문집
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• 제20권3호
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• pp.279-286
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• 2010

In this paper, we provide a robust track-following controller design method for the stable coarse seek control. Due to the inaccurate velocity control during a coarse seek, the shake of fine actuator is generated and thus a gain-up track-following control is required to complete stably the coarse seek. To this end, a loop gain adjustment algorithm is introduced to estimate accurately the shake of fine actuator. A weighting function can be properly selected from a minimum tracking gain-up open-loop gain, calculated from the estimated shake quantity of fine actuator. A robust tracking gain-up controller is designed by considering a robust $H_{\infty}$ control problem using the weighting function. The proposed design method is applied to the coarse seek control system of an optical rewritable drive and is evaluated through the experimental results.

• 대한전자공학회논문지
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• 제25권5호
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• pp.566-571
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• 1988

Laser scanning system using a hologram is simpler in optical system, lower in cost than using a polygon. In this paper, a thick hologram is fabricated for the underfilled transmission disk type with a merit of wabble insensitivity to vibration. High diffraction efficiency over 50% is obtained using silver halide recording material. The two-dimensional scan pattern with 13 scan-line is made by 7-facet hologon and mirror system. This system can be practically applied to POS(Point of Sale) bar-code symbol reader.