• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.76-77
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• 2003

차세대 정보저장 기술중의 하나인 홀로그래픽 데이터 저장 기술은 빠른 데이터 접근속도와 기록 매질의 동일 위치에 수 천 페이지의 광정보를 중첩 기록할 수 있기 때문에 높은 저장용량을 갖는다. 이러한 홀로그래픽 데이터 저장을 위한 주요 구성으로 SLM(spatial light modulation)과 홀로그래픽 기록 매질을 들 수 있다. SLM은 전기적 신호를 광신호로 변조하기 위한 입력장치로 사용되며, 홀로그래픽 시스템에 사용되는 기록 매질은 고감도, 간단한 실시간 처리, 고회절효율, 기록 후 긴 안정성이 요구된다. (중략)

• Journal of the KSME
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• v.43 no.5
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• pp.66-73
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• 2003

이 글에서는 차세대 대용량 정보저장장치 중 중요한 역할이 기대되고 있는 홀로그래픽 데이터 스토리지의 기록.재생 원리 및 고밀도 기록을 가능하게 하는 핵심 기술인 데이터 다중화기법(Multiplexing Technique)에 대하여 알아 보고자 한다.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.5
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• pp.51-57
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• 2014

In this paper, we introduce the adaptive threshold detection scheme based on an evolutionary arithmetic algorithm for the M-ary holographic data storage(HDS) system. The genetic algorithm is a particular class of evolutionary arithmetic based on the process of biological evolution, which is a very promising technique for optimization problem and estimation applications. In this study, to improve the detection performance that is degraded by the HDS channel environment and the pixel misalignment, the threshold value was assumed to be a population set of the evolutionary algorithm. The proposed method can find an appropriate population set of bit threshold, which minimizes bit error rate(BER) as increased generation. For performance evaluation, we consider severe misalignment effect in the 4-ary holographic data storage system. Furthermore, we measure the BER performance and compare the proposed methods with the conventional threshold detection scheme, which verifies the superiority of the proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.809-814
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• 2012

We propose an adaptive threshold detector algorithm for multi-level holographic data storage based on the expectation-maximization (EM) method. In this paper, the signal intensities that are passed through the four-level holographic channel are modeled as a four Gaussian mixture with unknown DC offsets and the threshold levels are estimated based on the maximum likelihood criterion. We compare the bit error rate (BER) performance of the proposed algorithm with the non-adaptive threshold detection algorithm for various levels of DC offset and misalignments. Our proposed algorithm shows consistently acceptable performance when the DC offset variance is fixed or the misalignments are lower than 20%. When the DC offset varies with each page, the BER of the proposed method is acceptable when the misalignments are lower than 10% and DC offset variance is 0.001.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7C
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• pp.581-586
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• 2010

The holographic data storage system stores multiple data pages by multiplexing. But the inter-page interference(IPI) caused by multiplexing reduces the intensity of the hologram. The simulation of the holographic storage systems has to consider the IPI. Therefore, we introduce a channel modeling that takes care of inter-page interference in the holographic data storage system. We simulate the performance of PRML detection on the hologrpahic data storage system with IPI modeling.

• Broadcasting and Media Magazine
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• v.6 no.3
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• pp.26-39
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• 2001

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.5
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• pp.3-7
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• 2017

Holographic data storage system (HDSS) features short access times, high storage capacities, and fast transfer rates, since the data is recorded and read not by lines but by pages within a volume of holographic material. Burst error caused by physical impact on the high density storage system becomes very longer than that of conventional storage systems. This paper proposes an LDPC product code using two LDPC code to resolve burst error. When a total code rate is similar, the performance of two LDPC code having high code rate is better than that of one LDPC code having low code rate. Also, with error factors of two-dimensional intersysbol interference and misalignment, the proposed scheme can improve the performance in holographic data storage system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11C
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• pp.1037-1043
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• 2006

In this paper, we introduce a two-dimensional modulation code for holographic data storage systems(HDSS), which is a candidate for the next generation data storage system. The two-dimensional(2D) intersymbol interference(ISI) induces higher bit error rate(BER). The balanced number of zeros(dark) and ones(light) in each page reduces inter-page interference(IPI). The code rate is 519. Although the proposed code has higher code rate than other 2D code with rate 4/9, the BER performances of two codes are similar.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.42-43
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• 2005

Higher density in the holographic storage can be obtained by using shorter wavelength laser and higher numerical aperture (NA). In this paper, we adopted a blue laser diode with a wavelength of 405nm and high NA object lens. And the phase conjugation method is applied to prevent image distortion due to high NA. The performance of the system has been shown experimentally.

• Transactions of the Society of Information Storage Systems
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• v.7 no.1
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• pp.1-6
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• 2011

A control method for the angle servo of reference beam during reading recoded data images of a holographic data storage system is presented. The recording scheme with angle offset is adopted in order to verify the proposed angle servo. Using this recording scheme, the angle error signal is generated and we can implement the angle servo. Experiments have been performed on recording and reading data images to compensate Bragg angle mismatch.