• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.848-851
• /
• 2007

Recently, as the demand of the information storage devices with large storage capacity such as BD(Blu-ray Disk) and HDTV(high-definition television) is increased, the optical storage devices are also required to have fast data transfer rate and large storage capacity. To satisfy these requirements, the actuator for optical disk drive should have high flexible mode frequencies for system stability. In this paper, we suggested a moving magnet type actuator having high flexible mode frequency. However, the moving magnet type actuator does not have sufficient driving sensitivities due to the weight of its moving part. To improve driving sensitivities, we designed the model with the closed electromagnetic circuit for tracking direction. In addition, driving sensitivities and flexible mode frequencies were improved by using DOE(Design of Experiments) for magnetic circuit and modifying the lens holder. Consequently, it is confirmed that the designed model is satisfied with the desired specifications.

• Transactions of the Society of Information Storage Systems
• /
• v.1 no.2
• /
• pp.182-187
• /
• 2005

A large area micro mirror is an optical element that functions as changing an optical path by reflection in integrated optical system. We fabricated the large area silicon mirror by anisotropic etching using MEMS for implementation of integrated optical pickup. In this work, we report the optimum conditions to better fabricate and design, greatly improve mirror surface quality. To obtain mirror surface of $45^{\circ},\;9.74^{\circ}$ off-axis silicon wafer from (100) plane was used in etching condition of $80^{\circ}C$ with 40wt.% KOH solution. After wet etching, polishing process by MR fluid was applied to mirror surface for reduction of roughness. In the next step, after polymer coating on the polished Si wafer, the Si mirror was fabricated by UV curing using a trapezoid bar-type way structure. Finally, we obtained peak to valley roughness about 50 nm in large area of $mm^2$ and it is applicable to optical pickup using blu-ray wavelength as well as infrared wavelength.

• Transactions of the Society of Information Storage Systems
• /
• v.10 no.1
• /
• pp.7-13
• /
• 2014

The Blu-ray Disc Recordable(BD-R) is one of strong candidates for archival application among optical media formats, because of its large capability. However, the well-defined accelerated aging test conditions and evaluation criteria have not yet been fully confirmed for BD-R. In this study, the data stability and degradation aspect of BD-R were analyzed by the random-symbol error rate(R-SER) measurement after the accelerated aging test. And a reasonable test condition of accelerated aging for BD-R and the appropriate evaluation criterion using R-SER measurement were discussed.

• 정보저장시스템학회:학술대회논문집
• /
• 2005.10a
• /
• pp.154-159
• /
• 2005

The next generation of optical storage systems requires higher numerical aperture (NA) objective lenses and shorter wavelength laser in order to improve the unit areal density. A blu-ray technology satisfies a miniaturization and a high capacity which are the requirements of the portable device. In this paper, we analyze the optical performance of hybrid micro lens and do active alignment. The hybrid micro lens is manufactured by using a wafer based fabrication technology. Optical components of hybrid micro lens are evaluated. The measurement of the optical power, the spot size and the wavefront error awe performed to evaluate the hybrid micro lens with NA 0.85. Using the measured data, we estimate if the performance of hybrid micro lens corresponds to the designed performance. After the performance of hybrid micro lens is evaluated, the integrated optical pickup and the hybrid micro lens are assembled by active alignment using UV curing and the optical performance of SFFOP is satisfied with BD specifications.

• Proceedings of the Optical Society of Korea Conference
• /
• 2004.02a
• /
• pp.248-251
• /
• 2004

근접장 초해상 기술 중 대표적인 Super-RENS (Super Resolution Near Field Structure) 기술을 이용하여 25GB 용량의 BD(Blu-ray Disc) 다음 세대로 예상되는 100 ${\sim}$ 200 GB 용량의 Media 및 기록 재생 기기를 개발하고자 한다. 현재까지 이 기술의 어려움이었던 Stability 특성은 10만회 재생 내구성을 확인하엿고 CNR (신호 대 잡음 비) 특성은 50 nm 미세 마크에 대하여 40 dB의 특성을 확보 하였다. 이 특성은 대략 75 GB에 대응하는 것으로 BD System을 그대로 사용하면서 달성한 세계 최고의 기록 밀도로 평가된다. 향후 과제는 Jitter. Error Rate등 실제 신호 특성의 확보로서, 이의 확보를 통하여 기술의 상품화 가능성이 확인될 것이다.

• Transactions of the Society of Information Storage Systems
• /
• v.2 no.3
• /
• pp.163-168
• /
• 2006

Small form factor optical pickup (SFFOP) corresponding to BD specifications is strongly proposed for the next-generation portable storage device. In order to generate SFFOP, small sized optical pickup has been fabricated. We have developed a small sited optical pickup that is called the integrated optical pickup (IOP). The fabrication method of this system is mainly dependant on the use of the wafer based micro fabrication technology, which has been used in MEMS process such as photolithography, reactive ion etching, wafer bonding, and packaging process. This approach has the merits for mass production and high assembling accuracy. In this study, to generate the small sized optical pickup for high recording capacity, IOP corresponding to BD specifications has been designed and developed, including three main parts, 1) design, fabrication and evaluation of objective lens unit, 2) design and fabrication of IOP and 3) evaluation process of FES and TES.

• Transactions of the Society of Information Storage Systems
• /
• v.3 no.1
• /
• pp.23-27
• /
• 2007

Blu-ray disc 이후의 차세대 고밀도 광 기록 기술로 주목받는 홀로그래픽 데이터 스토리지 시스템을 설계, 제작하고 기록 재생 test 를 수행하였다. 시스템은 각도 다중화법을 채택하였고, 파장 405nm, NA 0.55 신호광 Fourier 변환 렌즈로 미디어에 defocus 하여 기록하였다. 1 page 용량은 raw bit 로 0.74Mbit 이고, SLM 과 CCD 의 over-sampling 비율은 1:1.5 가 되도록 구성하였다. 얻어진 raw 이미지는 위치 및 distortion 보상등의 신호처리 후, 70page 다중화 조건에서 bER $1{\times}10-2$ 수준으로 재생해 낼 수 있었다. 온도 변화에 의한 신호 열화를 보상하기 위해 External Cavity Tunable Blue LD 를 개발하여 온도 변화 $10^{\circ}C$까지 보상 가능함을 확인하였다.

• Transactions of the Society of Information Storage Systems
• /
• v.11 no.2
• /
• pp.31-35
• /
• 2015

The Blu-ray Disc Recordable-Triple Layer (BD-R TL) media is considered as one of strong candidates for archival application among optical media formats, due to its large capacity. However, the long-term stability and degradation aspect have not been fully understood yet for BD-R TL media. Thus, the BD-R TL media were recorded at full tracks and analyzed by the random-symbol error rate (R-SER) measurement at different recording layers and recording positions after the accelerated aging test to understand its long-term stability. Finally, the general degradation aspect of BD-R TL media was discussed to improve the long-term stability.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.294-295
• /
• 2007

80년대 초에 개발된 CD(Compact Disc) Disc는 지난 27여 년간 급속한 발전을 하였다. 95년에 DVD가 발표되면서 영화 Title제작이 되어 우리는 안방에서 고화질의 DVD를 감상할 수 있었다. CD-R(Recordable) 로부터 시작된 기록 기술은 CD-RW를 거쳐 DVD-Recordable, DVD-ReWritable 및 DVD-RAM, Light Scribe등 거쳐 BD(Blu-Ray) 기술에 까지 이르게 되었다. 광 Disc 기술은 3가지 분야로 나눌 수 있다. 안정된 제어를 위한 Servo 기술, Mechanical 기술, PC와communication 할 수 있는 Interface 기술 등으로 나눌 수 있다. Servo 제어 기술은 다음과 같이 4가지 분야로 구성되어 있다. Focus Servo, Tracking Servo, Sled Servo, Spindle Servo. Disc 회전을 제어를 담당하고 있는 Spindle Servo Block에서는 Hall Sensor를 이용하여 Disc의 회전을 Count하여 Feedback 하였다. 그러나 갈수록 심화 되고 있는 가격 경쟁 상황에서 Hall Sensor를 대체하여 회전수를 Conut하는 방법이 필요 하였다. BEMF(역기전력)을 이용한 Zero Crossing 방법이 이를 대체 하였지만, Motor의 전기적인 특성 편차 등에 안정된 control이 안되어서, Motor를 관리하는 방법으로 진행되어 왔다. 이것은 생산 Loss로 이어져서 Hall Sensorless의 장점을 훼손하게 되었다..본 논문에서는 이러한 Sensorless Type Spindle Motor의 문제점에 대해 Common 단자를 이용하여 안정된 제어 방법을 제안 한다. less Type의 문제점인 초기 기동 문제를 Common 단자를 이용하여 안정되게 Spindle motor를 Control 하는 방법에 대해 연구 하고자 한다.

• Proceedings of the KIEE Conference
• /
• 2003.11c
• /
• pp.735-739
• /
• 2003

This paper presents a direct seek control algorithm for swing-arm type dual stage servo system that consists of a coarse actuator and a fine actuator. The proposed scheme is to design a control system that attenuates the effect of dynamic coupling between the two actuators so that the seek operation can be performed in a single-shot with stability. In an optical drive system with dual stage servo mechanism, the effect of dynamic coupling between the two actuators needs to be handled during the coarse seek operation due to its inherent structure. In an extreme case, the two actuators can collide each other, which leads to critical degradation of the seek performance. To handle this problem, our proposed control scheme is to generate the drive signals such that the two actuators behave as if they are a single fixed body. To this end, a feedforward controller and two feedback controllers are designed that enable the current drive system perform wide range of track seek. Simulation results are provided to show the validity and feasibility of our proposed algorithm.