• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.73-76
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• 2010

The issue of inspection and characterization of microstructures has emerged as a major consideration in design, fabrication, and detection of MEMS devices. However, the conventional measurement techniques, including scanning electron microscopy (SEM) imaging, atomic force microscopy (AFM) scanning, and mechanical surface profiler, require often destructive process or may be difficult to measure with a wafer scale. In this paper, we characterize the surface profiles of microstructures using an optical scanner based on a DVD pick-up module. Scanning images of the microstructures are successfully generated using the intensity of reflected light from different depths of the surface profiles, based on the focus error signal (FES) from photodiodes. It is shown that the proposed optical scanner can be used as an alternative measurement system with high performance and low cost, compared to conventional measurement techniques.

• Journal of Korea Multimedia Society
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• v.5 no.2
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• pp.215-221
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• 2002

In high speed optical disc devices, the vibration caused by unbalanced displacement leads the focus and tracking servo systems to be unstable, and increases the data search time. In this paper, we propose a new scheme to solve the unbalanced displacement problem. The proposed method detects the unbalanced rate by differential amplifying optical power received at photo diode and converts it into an electrical signal. controlling the speed of spindle motor, according to the detected unbalanced rate, makes it possible to improve the performance of tracking and data searching tasks. Also, we analyze the dynamic characteristics of focus and tracking servo systems in high speed mode and provide the firmware and hardware architecture that the proposed method can be installed as an add-on- module in the existing system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.386-389
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• 2003

Recent issues in Optical Disk Drive (ODD) are focused on small size. Blu-ray Disk (BD), using blue laser (405nm wavelength) and high NA (0.85) objective lens. can store 25Gbyte on a conventional 12cm optical disk. Small Form Factor Optical (SFFO) drive uses 3cm disk which can store 1.5Gbyte on a disk. This kind of Small Form Factot Optical (SFFO) drive correspond to PCMCIA type memory (Compact Flash or Micro Drive). Preferably, Optical Disk has relatively low cost of the storage media per Byte rather than PCMCIA type memory. To make Small Form Factor Optical (SFFO) drive. optical pickup and its component must be miniaturized. Miniaturization of the component needs new concept of Optical Pickup. This paper is focused on two main subjects. One is Objective Lens design which can be manufactured on a wafer, and the other is optical path design of the pickup which has 2mm thickness.

• Transactions of the Society of Information Storage Systems
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• v.2 no.1
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• pp.79-84
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• 2006

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 are 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.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.12
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• pp.109-119
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• 2002

In this paper, mechanism design of optical pickup actuator for fast access is proposed. This actuator is composed of moving magnet type actuator and moving coil type actuator for tracking and fine motion, respectively. Moving magnet type tracking actuator is configurated by two permanent magnets and four air-core solenoids. Additional damper by induced current in tracking actuator can reduce the transient vibration between the coarse seeking servo and fine seeking servo. Variable stiffness can be acquired by applying current to air-core solenoid simply. This actuator can achieve fast access by these additional damper and stiffness. Performance of this actuator is predicted through the FEM, simulation and simple experiment. Settling time for transient vibration is reduced to 14.7% according to simulation result.

• Transactions of the Society of Information Storage Systems
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• v.2 no.2
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• pp.117-122
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• 2006

A novel method to find interaction dynamics between focusing direction and tracking direction in an optical pick-up is proposed. and the decoupling control to reduce the interaction effect is discussed. First, the basic principle to detect dynamic interaction analysis using back electromotive force is introduced. Second, the interaction analysis between focusing and tracking direction of is analyzed for a commercial slim type optical pick-up. Finally. decoupling control process and its simulation results are shown.

• Journal of Korean Electronics
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• v.24 no.8
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• pp.26-27
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• 2004

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.762-769
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• 2003

본 연구에서는 적층형 압전소자를 이용하여 초소형 및 슬림형 광디스크 드라이브용 광픽업 구동기를 개발하였다. 최근에 휴대용 정보기기의 급격한 발달로 인해 다양한 형태의 초소형 정보저장기기가 사용되고 있으며 착탈식 형태의 초소형 광디스크를 사용하는 ODD가 개발 중에 있다. 적층 형태의 압전소자와 유연 힌지 형태의 변위 확대기구를 사용하여 구동기의 출력 힘과 허용 변위를 증가시키도록 설계하였다. 압전형 구동기의 동특성을 고려한 모델링과 이론적 해석을 통해 목표 변위와 성능을 만족하도록 설계 변수를 최적화하였고 이를 ANSYS를 이용한 해석과 비교하였다. 상용화된 적층형 압전소자를 이용한 prototype 올 제작하여 실험을 수행하였으며 이론적인 예상 값과 잘 일치함을 보였다. 이와 같은 이론적 해석과 실험 결과를 토대로 높이가 2.5mm이며 15V 에서 $\pm$400$\mu\textrm{m}$의 변위를 갖는 슬림형 및 초소형 ODD에 적합한 압전형 구동기를 설계하였다.

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

• Journal of KSNVE
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• v.10 no.2
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• pp.221-228
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• 2000

In this paper, analytical study is performed to reduce residual vibration in seeking mode of optical pick-up. The conditions for acceleration adn deceleration time in trapezoidal velocity profile to reduce residual vibration are derived for undamped vibration system. To verify the validity of conditiosn two example studies are carried out. Numerical and experimental implementations for flexible arm system attached to moving part show that residual vibration is effectively reduced by calculated velocity profile. In addition, simulation study for optical pick-up reveals that by changing natural frequency to resonance frequency the conditions derived assuming undamped system can be applied to obtain velocity profile for minimum residual energy in damped vibration system.