• ETRI Journal
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• v.24 no.3
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• pp.205-210
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• 2002

This paper describes our high-density near-field optical recording using bent cantilever fiber probes installed in an atomic force microscope. We conducted a near-field reading of nano-scale hole patterns with a 100 nm spatial resolution and a 25 ${\mu}m$/s scan speed; this implies a capability of a data reading density of 60 Gb/$in^2$ with a 0.25 kbps data transfer rate. In addition, we investigated re-writable near-field recording on photochromic diarylethene films. We successfully recorded erasable memory bits having a minimum width of 600 nm in a writing time as short as 30ms. We found that using a cantilever probe simplifies the setup and operation of the near-field optical recording system and may offer multifunctional recording capabilities.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1256-1258
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• 1993

Optical data storage offer high density storage and archival storage capability. In this study, we selected the ablation mechanism-one of an irreversible recording system-using the antireflection trilayer(ART) structure. Optical recording medium is a $(Te_{86}Se_{14})_{50}Bi_{50}$ thin films. Actually, ART structure is fabricated and compared to monolayer structure. ART structure leads to the reduction of recording power as well as an increase in the effciency compared to the monolayer structure.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.128-129
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• 2002

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1C
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• pp.59-64
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• 2004

We propose a new RLL(run length limited) (2,7) PP(parity preserving) code with 4 RMTR(repeated minimum transition run) for optical recording. The proposed code has better characteristics in terms of density ratio, RMTR, DC(direct current) component suppression, BER(bit error rate) and system complexity than (2,1O) code that currently applied in storage systems and (1,7) PP code that highly recommended as the next generation optical recording system. Some characteristics of the code are described with several simulations. And the proposed code's superiorites in performance is illustrated as compared with the other codes.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.2
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• pp.101-109
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• 1998

In this paper, we implemented holographic optical memory systm which can store and reconstruct many images using new input and angular multiplexing method. In the new input method, phase infomation of input image is inputed in the recording material instead of brightness information. To do so, we represented the images, which captured with CCD camera or displayed on the computer monitor, on the liquid crystal television(LCTV) which removed polarizer/analyzer. Therefore, we can generate uniform input beam intensity regardless of the total brightness of input image, and apply the scheduled recording method. Also we can increase the intensity of input beam so reduce the recording time of input image. And reconstructedimage is acquired by transforming phase information into brightness information of image with analyzer. The incident angle of reference beam is acquired by Fourier transform of the binary phase hologram(BPH) which designed with SA algorithm on the LCTV. The proposed optical memory system is stable because the incident angle of the reference beam is controlled easy and electronically. We demonstreated optical experiment which store and reconstruct various type images in BaTiO$_{3}$ using proposed holographic memory system.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2008-2010
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• 2001

최근에 광 디스크 기기의 고배속화에 따라서 디스크의 재생 속도는 점차로 증가하고 있다. 이러한 경향에 따라 트랙킹 제어 루프에서 나타나는 디스크의 편심에 의한 외란의 영향은 더욱 커지게 되므로 기존의 선형 제어기만으로는 디스크의 편심량이 큰 경우에 고배속에서 원하는 트랙 추종 성능을 얻을 수가 없다. 본 논문에서는 이러한 문제점을 해결하기 위해서 반복 학습 제어 알고리즘과 드라이브 시스템의 액츄에이터의 주파수 응답 특성을 이용한 새로운 트랙 추종 제어 방법을 제안한다. 또한, 제안된 트랙 추종 제어 시스템의 제어 성능을 실험을 통하여 검증하여 본다.

• Journal of the Optical Society of Korea
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• v.4 no.1
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• pp.66-70
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• 2000

The main problem of image projection on a transmission type holographic screen is color sepa-ration. And it can be overcome by using a long narrow slit type diffuser as a source of the object beam when we record the screen. But that screen is not optimized and so needs changing several conditions. To set up the system many complicate things should be taken into accounted so it is very important to analyze the basic structure by simple concepts and calculations. We designed the system so that recording and projection axis coincide in one line and showed that the analysis of the system is very simple. We did it by a 1st order paraxial approximation calculation and it was good enough to describe the system. The photo-emulsion layer shrinks after processing of the hologram. It induced unsatisfactory color matching at the viewing zone. To overcome this effect, we pre-checked the shrinkage rate of an emulsion layer by experiments and modified the recording set up to compensate for the amount of shrinkage.

• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.34-41
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• 2005

We report some recent results in the rewritable Blu-ray Disc with enhanced overwrite cyclability by using the growth dominant eutectic based Ge(Sb70Te30)+Sb recording layer, GeN interface layer and write strategy optimization. We have developed phase-change optical media with appropriate write strategy for 36(i.e., 1X)-72Mbps(i.e., 2X) dual speed Blu-ray Disc system and fur the future high speed optical data storage. For recording layer, eutectic-based Ge(Sb70Te30)+Sb material was used and Sb/Te ratio and Ge content were optimized to obtain proper erasability and archival stability of recorded amorphous marks. The recording layer is wrapped up in GeN interface layers to obtain overwrite cyclability and higher crystallization speed. In addition, we designed appropriate write strategy so called Time-Shifted Multipulse (TSMP) write strategy where starting position of multipulse parts are shined from reference clock. With this write strategy, the jitter characteristics of the disc was improved and we found that leading edge jitter was improved much more than trailing edge jitter in 1X-2X speed recording. Finally, we investigated the higher speed feasibility of 144Mbps(i.e., 4X) by adopting some elemental doping to the eutectic based Ag-In-Sb-Te recording layer and structural optimization of constitution layers in Blu-ray Disc. In the paper, we report the effect of Sn addition for the feasibility of higher speed recording. The addition of Sn shows increases of the crystallization speed of phase change recording layer.

• Journal of Information Display
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• v.3 no.3
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• pp.12-16
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• 2002

We first review a real-time three-dimensional (3-D) holographic recording technique called optical scanning holography (OSH) and discuss holographic reconstruction using spatial light modulators (SLMs). We then present how the overall system can be used for 3-D holographic television (TV) display with a wide-angle view of a 3-D image, and address some of the issues encountered. Finally, we suggest some techniques to alleviate the issues encountered in such a 3-D holographic TV system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9C
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• pp.871-876
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• 2005

In this paper, we propose an improved partial response maximum likelihood (PRML) detection scheme that has an adaptive equalizer and can be applied in the asymmetric optical recording system with high-density. We confirmed that the proposed PRML detector improves detection performance. In addition, we implemented the detector by Verilog HDL. The adaptive equalizer is composed of tap coefficient updating unit using LMS algorithn and FIR filter. FIR filter is implemented by the transposed direct form architecture for high speed operation. Viterbi detector is implemented by the register exchange method.