• 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.

• Nuclear Engineering and Technology
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• v.48 no.2
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• pp.482-494
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• 2016

The Feshbache-Kermane-Koonin (FKK) multi-step direct (MSD) theory of pre-equilibrium reactions has been used to compute the single-step cross-sections for some (p,${\alpha}$) reactions using the knock-on and pick-up reaction mechanisms at two incident proton energies. For the knock-on mechanism, the reaction was assumed to have taken place by the direct ejection of a preformed alpha cluster in a shell-model state of the target. But the reaction was assumed to have taken place by the pick-up of a preformed triton cluster (also bound in a shell-model state of the target core) by the incident proton for the pick-up mechanism. The Yukawa forms of potential were used for the proton-alpha (for the knock-on process) and proton-triton (for the pick-up process) interaction and several parameter sets for the proton and alpha-particle optical potentials. The calculated cross-sections for both mechanisms gave satisfactory fits to the experimental data. Furthermore, it has been shown that some combinations of the calculated distorted wave Born approximation cross-sections for the two reaction mechanisms in the FKK MSD theory are able to give better fits to the experimental data, especially in terms of range of agreement. In addition, the theory has been observed to be valid over a wider range of energy.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.189-193
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• 1997

Aspheric pick-up lenses are increasingly used in consumer products such as computer and multimedia, as their mass production has become possible owing to the injection molding process. However still much work needs to be done for more effective manufacture of aspheric lenses, one area of which is the in-line inspection of produced lenses. In this paper, we present a lateral-shearing interferometer that has specially been designed to have a high immunity to external vibration and atmospheric disturbance. The interferometer comprises four prisms. They are directly attached to each other using an immersion oil so that relative sliding motions between the prisms are allowed. Their relative displacement can readily generate necessary lateral-shearing and phase-shifting to determine the wavefront of the beam collimated by the lens under inspection. A special phase-measuring algorithm of arbitrary-bucket is adopted to compensate the phase-shifting error caused by the thickness reduction in the immersion oil. Zernike polynomial fitting has done for determinating quantitative aberration of aspheric pick-up lenses. The interferometer built in this work is robust to external mechanical vibration and atmospheric disturbance so that experimental results show that it has a repeatability of less than λ/100.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.1009-1012
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• 1999

Recently, there is a strong need of DVD (Digital Versatile Disk) system of high density. high speed, and high accuracy System performances mostly depend on not only optical system, but also servo technology to drive it. Therefore, we investigate main technology concerned with optical pick-up unit based on 4.7GB DVD-RAM and analyzes technology of optical and servo systems that are required for high density high speed and high accuracy from the viewpoint of control. And then, we design a linear controller based on specification of 4.7GB DVD-RAM that is commercially available now. We analyze the dynamic characteristics of optical system that is coupled with control system and verify effect on performance indices of servo due to Parameter variation of pick-up by simulation. Finally, we will propose controller design specifications and provide direction of technical development for servo system and problems coupled with high capacity for 15GB level in the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.378-380
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• 2002

There has been lower the tilt margin by the increase of coma aberration due to the reduction of wave-length and the increase of numerical aperture for high density recording. The RF signal degradation is increased as the decrease of tilt margin. To compensate the tilt margin, the optical pick-up actuator for high-speed CD/DVD re-writable system should be able to drive the radial-tilt motion. We announce that the 3-axis drive actuator for high-speed CD/DVD rewritable system. And what was more, the DC/AC sensitivities of this actuator are suitable fur the low-speed playability, the high-speed readability and the high-speed rewritability.

• Proceedings of the KIEE Conference
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• 2000.07c
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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.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.47-50
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• 2005

In this study, micro mirror array for small form factor optical pick-up was replicated by micro UV-molding. First, mold for micro mirror array was fabricated using micromachining. Also, to analyze the characteristics of the surface quality, flatness of replicated mirror surface were measured by white light scanning inteferometry system. The results show that the micro mirror array with a sufficient surface quality can be obtained by polymer replication process.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.2
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• pp.32-41
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• 1999

The design method that the structure of double actuators of read-only or read-writable DVD optical pick-up of high density can be compact into the structure of one actuator, is proposed. The designed actuator has the structure of the shaft sliding type in which the moving part can be rotated about the shaft accord to a used optical disc and an objective lens can be switched, and is suspended with magnetic spring. In this actuator, Coulomb's friction is used as damping force and the moving part is designed by finite element method so that the second natural vibration mode can not occur within the servo band. The mock-up of the actuator designed in this paper is made, and its dynamic characteristics is measured and estimated.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.1
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• pp.94-100
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• 1988

To improve the switching time of active optical bistable devices, we propose an active optical bistable device that consists of a diode laser, a transistor, and a photodetector. By implementing the proposed device we realize the optical bistable device with a 5 nanosecond switching time. This is the fastest switching time among the hybrid type optical bistable devices. It is also experimentally demonstrated that the proposed device may be used in an optical disc pick up.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.12
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• pp.1997-2003
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• 2003

Recently, there have been many researches and developments in optical disc drive by high density of track and high access speed. Therefore, the optical pick-up should guarantee highly accurate dynamic characteristics for the wide bandwidth in order to cope with this trend. These demands for optical pick-up actuator can be solved by improvements of lens-holder through the following methods. The first way is the analysis of the sensitivity matrix of design variables for vibration modes after appropriate design parameters are selected like shapes and local dimensions of a lens-holder. The second way is the optimization of design variables by calculating sequential linear programming after the problem of extending bandwidth are converted to problem of minimizing adequate objective function. In the result, modified FE model is obtained through several iterations by finite difference scheme(FDS). While results of the first way show better convergence of the target frequency, the second result shows better reduction of mass increase.