Technique for positioning hologram for balancing large data capacity with fast readout

Shimada, Kunio; Hosaka, Makoto; Yamazaki, Kazuyoshi; Shinsuke, Onoe; Ide, Tomohiro

doi:10.7567/jjap.56.09na04

Cited by 3 publications

(3 citation statements)

References 23 publications

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“…The optical parameters used in this study (summarized in Table 3) were determined experimentally. 30,31 For example, when f r ¼ 40 mm, f 0 ¼ 12.4 mm, and the relative position shift of the disc Δ defocus remains at 50 μm, we should move the NyA Δ defocus 0 ¼ 520 μm in the focal axis to ensure high readout quality.…”

Section: New Disc-positioning Mechanismmentioning

confidence: 99%

High-speed focus servo control system using Nyquist aperture mounted on a triaxial actuator for holographic disc drive system

2020

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We have developed a holographic data storage system using angular-multiplexing recording that has a large capacity of 2 TB and a data transfer rate of 1 Gbit∕s. To read a hologram recorded on a holographic disc at high speed, it is necessary to control the relative position shift between a hologram recorded on a disc and a readout optical system. However, in angularmultiplexing data storage systems, the optical system has no moving mechanism, unlike conventional optical discs such as Blu-ray Discs™. Therefore, it is difficult to control the disc position with high precision and to reduce the settling time of the positioning because the holographic disc has no physical structure for the position control mechanism to control the relative position shift. In the systems, a disc mounted on a disc stage is moved to a position where the signal-tonoise ratio of the reproduced hologram becomes the maximum value. Hence, we present a servo control system based on a shift of the Nyquist aperture using a real-time position error signal to control the disc position. In experiments, a positioning accuracy of AE15 μm and a settling time of 8.5 ms for our angular-multiplexing data storage system using a nonlinear parabolic focus position error signal have been observed. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: New Disc-positioning Mechanismmentioning

confidence: 99%

High-speed focus servo control system using Nyquist aperture mounted on a triaxial actuator for holographic disc drive system

2020

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“…Hologram memory is a promising candidate for this purpose because of the use of parallel data processing for recording and the reconstruction of page data at high densities [1][2][3]. Therefore, numerous related technologies have been studied for optical systems, including recording media [4][5][6][7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Modified Random Phase Masks with Phase Modulation Elements Exhibiting Gaussian Profiles Using Molecular Migration under Photopolymerization

et al. 2019

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Random phase masks are important technical elements for realizing holographic memory systems that enable high density recording. However, the broadly distributed Fourier spectrum often presents a problem because wide recording spots result in reduced total storage capacity for a recording medium. In the present study, we propose modified random phase masks with phase modulation elements exhibiting Gaussian profiles to suppress the spread of the recording spot and keep it in a narrow area, based on the reduction of the high-frequency components in a random phase pattern. We confirm the effectiveness of the proposed random phase mask using simulations of a computer-generated binary hologram. However, issues still remain in terms of the fabrication of random phase masks with Gaussian profiles. Therefore, we evaluate the feasibility of fabricating the proposed random phase mask using molecular diffusion under photopolymerization. The results confirm the feasibility of this approach over a relatively wide area for actual fabrication.

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“…Ide and Shimada et al developed a high-accuracy control method for holographic memory drives. 24,25) Recently, neural network learning has been studied to obtain higher SNRs even if there is noise in the reproduced data pages. 26,27) However, owing to the spatial filter for increasing the data recording density and the sampling of the reproduced data pages on the camera (which does not satisfy the sampling theorem) in the optical setup, the SNR decreases even if noise does not exist.…”

Section: Introductionmentioning

confidence: 99%

Applying digital filter to data pages before recording to increase signal-to-noise ratio in holographic memory

Muroi¹,

Katano²,

Kinoshita³

et al. 2018

Jpn. J. Appl. Phys.

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The spatial filter in the path of the signal and reconstructed beams and the sampling of reproduced data pages on a camera cause a nonuniform brightness distribution of bright symbols and degrade the signal-to-noise ratio (SNR). We thus applied a digital filter to data pages before recording to improve the reproduced data quality. The simulation results showed that a digital filter with coefficients of the neighboring horizontal and vertical taps from the center tap of −0.10 improved the brightness distribution of bright symbols and increased the SNR of the reproduced data. We experimentally investigated the effect of the digital filter in angle-multiplexed holograms. As a result, the SNR increased and the bit error rate decreased. We found that this method is effective for improving the reproduced data quality.

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Technique for positioning hologram for balancing large data capacity with fast readout

Cited by 3 publications

References 23 publications

High-speed focus servo control system using Nyquist aperture mounted on a triaxial actuator for holographic disc drive system

High-speed focus servo control system using Nyquist aperture mounted on a triaxial actuator for holographic disc drive system

Fabrication of Modified Random Phase Masks with Phase Modulation Elements Exhibiting Gaussian Profiles Using Molecular Migration under Photopolymerization

Applying digital filter to data pages before recording to increase signal-to-noise ratio in holographic memory

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