• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.129-133
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• 2005

Data storage related with writing and retrieving requires high storage capacity, fast transfer rate and less access time. Today any data storage system cannot satisfy these conditions, however holographic data storage system can perform faster data transfer rate because it is a page oriented memory system using volume hologram in writing and retrieving data. System can be constructed without mechanical actuating part therefore fast data transfer rate and high storage capacity about $1Tb/cm^3$ can be realized. In this paper, to reduce errors of binary data stored in holographic data storage system, a new method for bit error reduction is suggested. First, find cluster centers using subtractive clustering algorithm then reduce intensities of pixels around cluster centers and fuzzy rules. Therefore, By using this error reduction method following results are obtained ; the effect of Inter Pixel Interference noise is decreased and the intensity profile of data page becomes uniform therefore the better data storage system can be constructed.

• Transactions of the Society of Information Storage Systems
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• v.7 no.1
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• pp.19-24
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• 2011

Holographic Data Storage System, one of the next generation data storage devices, is a 2-dimensional page oriented memory system using volume holograms in writing and retrieving process. Recently photopolymer with disc type substrate was selected as a media for the Holographic Data Storage System. The disc tilt occurs when the media rotates and the external disturbance applies. The disc tilt causes the change of the angle between the reference beam and the media, the data cannot be retrieved with the right angle or other data page is retrieved. The tilt is generated in a 2-axis direction (tangential, radial). The tangential tilt direction is the same with the multiplexing plane, while the radial tilt direction is a perpendicular to the multiplexing plane. In this research we propose 2-axis tilt angle servo system. The tilt errors are measured by using external photo detector and the additional red laser. Then the tangential direction tilt is compensated by using the galvano mirror. Also the radial direction tilt is compensated by the rotating prism between the relay lens in the reference field. Finally we confirm the compensation results through the Signal to Noise Ratio(SNR) and Bit Error Rate(BER).

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.921-924
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• 1999

By controlling the pixels of a liquid crystal display (LCD) electronically, we fabricated a real-time moving window on a LCD, through which light passes. Using the moving window and hi-focusing lens, we suggested a non-mechanical spatio-angular multiplexed holographic memory system and demonstrated its feasibility through optical experiments. The principle of the proposed method and optical experimental results are also presented.

• Journal of the Optical Society of Korea
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• v.8 no.1
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• pp.21-28
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• 2004

When femtosecond laser pulses are focused inside the bulk of transparent materials, the intensity in the focal volume becomes high enough to produce permanent structural modifications. This technique has been applied to fabricate three-dimensional photonic structures such as optical memory, waveguides, gratings, and couplers inside a wide variety of transparent materials. In this paper, we review the fabrication of optical elements in glasses with femtosecond laser pulses, including the fabrication of waveguides, couplers, Bragg gratings, zone plates, holographic memory, and micro holes.

• Proceedings of the Optical Society of Korea Conference
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• 2004.07a
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• pp.260-261
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• 2004

• Proceedings of the Optical Society of Korea Conference
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• 1998.08a
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• pp.98-99
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• 1998

In this paper, an acousto-optic defiector9ADO) is used to perform the angular multiplexing without moving parts. The error-correction coding techniques was used to achive low bit-error rates in the experiment. A part of Lena image(64*64) encoded by Reed-Solomon codes were stored and retrieved.

• Transactions of the Society of Information Storage Systems
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• v.1 no.2
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• pp.155-160
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• 2005

In this paper, the channel decoder promising reliable data retrieving in noisy holographic channel has been developed for holographic WORM(write once read many) system. It covers various DSP(digital signal processing) blocks, such as align mark detector, adaptive channel equalizer, modulation decoder and ECC(error correction code) decoder. The specific schemes of DSP are designed to reduce the effect of noises in holographic WORM(H-WORM) system, particularly in prototype of DAEWOO electronics(DEPROTO). For real time data retrieving, the channel decoder is redesigned for FPGA(field programmable gate array) based hardware, where DSP blocks calculate in parallel sense with memory buffers between blocks and controllers for driving peripherals of FPGA. As an input source of the experiments, MPEG2 TS(transport stream) data was used and recorded to DEPROTO system. During retrieving, the CCD(charge coupled device), capturing device of DEPROTO, detects retrieved images and transmits signals of them to the FPGA of hardware channel decoder. Finally, the output data stream of the channel decoder was transferred to the MPEG decoding board for monitoring video signals. The experimental results showed the error corrected BER(bit error rate) of less than $10^{-9}$, from the raw BER of DEPROTO, about $10^{-3}$. With the developed hardware channel decoder, the real-time video demonstration was possible during the experiments. The operating clock of the FPGA was 60 MHz, of which speed was capable of decoding up to 120 mega channel bits per sec.

• 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.

• Journal of the Optical Society of Korea
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• v.18 no.6
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• pp.698-705
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• 2014

We propose a new development for calculating a computer-generated hologram (CGH) through the use of multiple general-purpose graphics processing units (GPGPUs). For optimization of the implementation, CGH parallelization, object point tiling, memory selection for object point, hologram tiling, CGMA (compute to global memory access) ratio by block size, and memory mapping were considered. The proposed CGH was equipped with a digital holographic video system consisting of a camera system for capturing images (object points) and CPU/GPGPU software (S/W) for various image processing activities. The proposed system can generate about 37 full HD holograms per second using about 6K object points.