• Proceedings of the KSME Conference
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• 2001.06e
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• pp.714-719
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• 2001

The Holographic Particle Velocimetry system can be a promising optical tool for the measurements of three dimensional particle velocities. In this research, the optical system for double pulse holographic recording and reconstruction of particle images was developed. Validation experiments for the developed system were conducted measuring the velocities of glass beads on a rotating disk. Uncertainty analysis was performed to identify the sources of all relevant errors and to evaluate their magnitude. The measurement results of distance between glass beads, size, and velocities of them using holographic method compared reasonalbly well with the known values within acceptable range of errors.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.793-796
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• 2010

The equalizer compensates a signal distorted by transmission lines and amplifying stages, so the signal can have uniform characteristics over all frequency range. The equalizer in ODD(Optical Disc Drive) improves the stability of the extracted clock from a received signal and the readability of an inserted disc by suppressing noise and ISI(Inter-Symbol Inference). The length of marks-spaces and track pitch on discs becomes shorter as the recording density of an optical media is higher, which causes noise and ISI. And, the sensitivity about the fluctuation of physical systems is higher as the optical devices become more complicate. This paper proposes a method to select the coefficient of built-in equalizer of ODD in order to maintain the quality of signals against noise and ISI caused by system fluctuation.

• Transactions of the Society of Information Storage Systems
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• v.7 no.2
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• pp.53-59
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• 2011

We have developed a compact and high-power mode-locked fiber laser for multilayered optical memory. Fiber lasers have the potential to be compact and stable light sources that can replace bulk solid-state lasers. To generate high-power pulses, we used stretched-pulse mode locking. The average power and pulse width of the output pulse from the fiber laser that we developed were 109 mW and 2.1 ps, respectively. The dispersion of the output pulse was compensated with an external single-mode fiber of 2.5 m length. The pulse was compressed from 2.1 ps to 93 fs by dispersion compensation. The fiber laser we have developed is possible to use as a light source of multilayered optical memory. We also present a fiber confocal microscope as an alignment-free readout system of multilayered optical memories. The fiber confocal microscope does not require fine pinhole position alignment because the fiber core is used as the point light source and the pinhole, and both of which are always located at the conjugated point. The configuration reduces the required accuracy of pinhole position alignment. With these techniques we can present an all-fiber recording and readout system for multilayered memories.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.3
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• pp.63-69
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• 1998

In this paper, a new input method is proposed to improve shift-invariant property of a photorefractive correlator andwe implemented real-time optical pattern recognition system using it. In the conventional photorefractive correlator, it is vrey difficult to satisfy the Bragg condition in the pattern recognition process. So, correlation peak is decreased heavily for the shift of input image. If a liquid crystal television(LCTV) without an anlyzer is used as input device, we can get the correlation result regardless of shift of input image because beam path is not changed during storage of holographic filter and correlation process. Also recording time of a holographic matched filter in photorefractive crystal is reduced and the correlation peak is increased because incident beam on the LCTV is transmitted completely. Therefore total optical efficiency is improved. We compared and analyzed the correlation results of proposed photorefractive correlator by computer simulation and optical experiment. We used a BaTiO$_{3}$ single crystal which has high diffraction efficiency in optical experiment.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.267-274
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• 2002

In this paper, the real-time color pattern recognition system is experimented by optical approach using the SLM(TH LCD) and a photorefractive material. In the implemented system, the character patterns to recognize are controlled of an SLM, and a 10mm thick LiNbO$_3$ crystal having high angular selectivity and photorefractive effect is used for recording materials. The shape and color informations of the red or green color patterns are excellently discriminated at independent positions by real-time processing, as the results obtained by proposed optical architecture.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.6
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• pp.1435-1440
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• 2010

This paper presents encrypted secret code recording system which can insert an unique manufacture ID code after complete disc process. First, we detect a memory block synchronizing signal which is SYNC. by using FPGA, then, design a recording pattern to write Multi Pulse. Finally, a method that any data is recorded in any place in any data area of optical disc by using a FPGA was proposed. Newly proposed method in this paper that any user records user data in protected data areas on digital video optical discs, can be very useful for effective software copy protection, and can be applicable to encrypted record on high density DVD in near future.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.124-127
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• 2005

Rewritable optical memory devices such as an CD-RW and DVD+RW are data storage media, which take advantage of the different optical properties in the amorphous and crystalline states of phase change materials. The switching property, structural transformation, transformation kinetics and chemical bindings of $Ge_xSb_{100-x}$($6{\le}x{\le}$34) were studied to investigate the feasibility of applying $Ge_xSb_{100-x}$ alloys in optical memory. The $Ge_xSb_{100-x}$ thin film was deposited by RF magnetron co-sputtering system and phase change characteristics were investigated by X-ray diffraction (XRD), static tester, inductively coupled plasma atomic emission spectrometer (ICP-AES) and atomic force microscopy (AEM). Optimum fiim composition of $Ge_xSb_{100-x}$ was studied and its minimum time fur laser induced crystallization and optical contrast fur phase transition was performed. These results might be correlated with the binding energies between Ge and Sb, and indicate that $Ge_xSb_{100-x}$ have an potential far optical memory applications.

• Transactions of the Society of Information Storage Systems
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• v.2 no.3
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• pp.163-168
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• 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
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• v.3 no.3
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• pp.123-125
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• 2007

We report the readout stability improvement results of super-resolution near field structure (Super-RENS) writeonce read-many (WORM) disk at a blue laser optical system. (Laser wavelength 405nm, numerical aperture 0.85) By using diffusion barrier structure (GeSbTe sandwiched by GeN) and high transition temperature recording material ($BaTiO_3$), material diffusion of phase change layer and recording mark degradation were greatly improved during high power (Pr=2.0mW) readout process up to $1{\times}10^5$ times.