• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.6
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• pp.459-464
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• 2013

In this paper, we introduce a modulation code design problem where best selection of two-dimensional codewords are determined to reduce two-dimensional (2D) intersymbol interference (ISI) and interpage interference (IPI). Codeword selection problem is formulated as a quadratic integer programming model that minimizes intra- and inter-symbol differences subject to uniform symbol usage and minimal Hamming distance violations. Second integer programming model detects the occurrence of isolated pixel pattern in the selected codewords. The proposed models are applied to 4-level and 2-level 6/8 codes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.479-480
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• 2005

The Analog data is impossible to perfect reconstruct original data at a hologram data storage because of noise such as cross talk. So it is necessary that data can be stored by digital signal unavoidably. Therefore this work deals with experiments from this point of view through writing & reading of digital data. We stored 256bit digital data at one point on As-Ge-Se-S chalcogenide thin film and we reconstruct original data of 100% through the specified algorithm such as the histogram equalization, the interactive correction, etc. This result shows that the data is able to reconstruct under relative low diffraction efficiency. As the result, we expect the possibility of chalcogenide thin film for HDDS as the analysis of the effective resolution refer to reconstruction rate and diffraction efficiency.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.11
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• pp.9-14
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• 2016

In the holographic data storage system, the data can be stored more than one bit per pixel and the storage capacity and transmission rate can be increased. In this paper, we proposed a sparse-ON pixel 4/6 balanced-modulation code that the code rate is 1.33 (bit/pixel) with uniform page density. Even though the performance of the proposed sparse-ON pixel 4/6 balanced-code is similar to 2/3 and 6/9 modulation codes, it can increase the storage capacity more than these modulation codes and also store more pages in a volume by reducing the rate of ON pixels to mitigate IPI (inter-page interference).

• Macromolecular Research
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• v.13 no.6
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• pp.477-482
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• 2005

Photopolymers are attractive materials for holographic 3-D data storage because of their high photosensitivity and large refractive index modulation. We synthesized the six-armed dendrimer for fabricating the new photopolymer. It was prepared using the initiating mixture of hexaarylbiimidazole (HABI), mercapto-benzoxazole (MOBZ), and 2,6-bis(4-diethylaminobenzylidene)cyclopentanone (DEAW), which is sensitive to 514 nm wavelength. The holographic gratings were fabricated successfully in these photopolymer samples by conventional optical interference method. We investigated the effect of dendrimer, either as a binder or as a plasticizer in the cellulose acetate butyrate (CAB), on the diffraction behavior. The addition of only 1 wt$\%$ of dendrimer-I into the CAB significantly increased the diffraction efficiency. The sample doped with dendrimer showed around 80-83$\%$ of the diffraction efficiency.

• The KIPS Transactions:PartC
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• v.9C no.2
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• pp.173-180
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• 2002

Smartcard is highlighted as infrastructure that has an excellent security for executing functions such as user authentication, access control, information storage and control, and its market is expanding rapidly. But possibilities of forgery and alteration by hacking are increasing as well. This Paper makes cut off of Smartcard forgery and alteration that use angular multiplexing and private key multiplexing hologram on holographic security Encryption, and proposes system capable verfication of forgery and alteration impossible on existing smartrard by adopting smartcard chip and holographic memory chip.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5A
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• pp.688-695
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• 2000

We present a multi-view autostereoscopic display system based on volume holographic storage technique. In this proposed system, the interference pattern of spatial multiplexed plane reference and angular multiplexed plane object beams are recorded into a photorefractive crystal, which plays a role of guiding object beams of multi-view images into the desired persfective directions. For reconstruction, object beams containing the desired multi-view image information, which satisfy Bragg matching condition, are illuminated in the time-division multiplexed manner onto the crystal. Then multiple stereoscopic images are Projected to the display plane for autostereoscopic 3D viewing.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.134-138
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• 2005

The crosstalk noise of thick holographic photopolymer is studied. Three different experiments, (1) reading area dependency (2) post-exposure effect (3) effect of later recorded holograms on earlier recorded holograms, have been accomplished and a tendency of crosstalk noises has been found for each case. The larger reading area, the higher crosstalk noises fur the later recorded holograms. Before the post-exposure the crosstalk noises are higher in the earlier recorded holograms, but after the post-exposure the crosstalk noises we higher in the later recorded holograms. The crosstalk noises of the earlier recorded holograms become higher as more holograms are recorded by multiplexing. To explain the tendency of crosstalk noises of these experiments, we suggest a model considering the anisotropic shrinkage of the photopolymer According to the model. the shrinkage is more dominant at the center of the recorded region than the edge of that. After the post-exposure, however, the amount of shrinkage becomes the same far the whole recorded region. The results of all three experiments are well explained by this model.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.58-59
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• 2001

최근 홀로그래픽 데이터 저장 국제 워크샵(International Workshop on Holographic Data Storage)에서 발표된 자료에 따르면 광메모리 데모 시스템들의 저장 용량이 100MB~150GB에 달하고 있으며, page당 용량은 1백만 비트(1000$\times$1000 bits)이상, 데이터 전송 속도는 1Gbit/sec에 이르고 있다. 반면에 현재까지는 상용화 단계의 시스템은 발표되지 않고 있다. 본 논문에서는 이들 시스템과 성능 차이는 많이 나지만 그 동안의 광굴절 결정의 특성 실험결과와 각각의 광학 시스템의 연구 결과들을 토대로 디지털 데이터를 기록하고 재생할 수 있는 초기 자동화된 데모 시스템을 구현하였다. (중략)

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.12
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• pp.92-98
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• 1998

In this paper, we implemented an angularly multiplexed volume holographic memory system using an AOD that is controlled electronically, with rapid access time(10$mutextrm{s}$) and accurate repeatability of the reference beam. First we designed an AOD-based angular multiplexing system without the frequency compensation of the object beam, and magnified the deflection angle of AOD through the combination of lens so that we increased the storage capacity up to six times. Finally fifty-one images were stored experimentally in a photorefractive material of 1㎤ Fe:LiNbO$_3$.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.3
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• pp.63-69
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• 2001

Holographic transmission gratings were performed by an Ar-laser( ${\lambda}$=514nm) intensity, the ratio fo LC contents to the surfactant. The addition of the surfactant to the LC and pre-polymer systems causes the droplet to maintain the ideal size at the high fraction(over 40wt%) of the LC contents that induce the films to be fabricated with high diffraction efficiency than that of no surfactant series. The image of these films was examined using a charge coupled device (CCD). We also studied the angular selectivity plots which support the important role in the multiplexer channel (MUX). Eventually, we showed the reconstructive optical image recorded in this transmission mode of HPDLCs.