論文 - 最田　裕介

Binary computer-generated-hologram-based holographic data storage

Naru Yoneda, Yusuke Saita, Takanori Nomura

Applied Optics ( OPTICAL SOC AMER )  58 ( 12 ) 3083 - 3090   2019年04月  [査読有り]

　概要を見る

Conventional computer-generated-hologram-based holographic data storage (CGH-HDS) needs to use a multilevel modulatable spatial light modulator (SLM). A binary SLM usually has a higher refresh rate than a multilevel one, and it enables HDS to increase the data transfer rate. To increase the data transfer rate by using a binary SLM, the introduction of a binary CGH is proposed. In general, a binary CGH degrades the image quality of reconstructed intensity distribution and emphasizes high spatial frequency components of datapages. In the proposed method, reconstructed intensity distributions that satisfy image quality as datapages can be obtained with low-pass filtering with an aperture at a plane of a recording medium. The optimum size of an aperture is numerically evaluated. The proposed method is experimentally verified. Moreover, the proposed method can achieve single and multiplexed recording of three datapages by a spherical reference beam with a binary CGH. (C) 2019 Optical Society of America

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Transport-of-intensity holographic data storage based on a computer-generated hologram

Naru Yoneda, Yusuke Saita, Koshi Komuro, Teruyoshi Nobukawa, Takanori Nomura

Applied Optics ( OPTICAL SOC AMER )  57 ( 30 ) 8836 - 8840   2018年10月  [査読有り]

　概要を見る

To increase the recording density of computer-generated-hologram (CGH)-based holographic data storage, a phase data page reconstruction method by the transport of intensity equation (TIE) is proposed. The TIE generally requires a scanning image sensor because the phase retrieval process needs at least two defocused intensity distributions. Although the TIE is applied, the proposed method enables detection of the distributions simultaneously by utilizing an extra conjugate component reconstructed from the CGH. Experimental results show that the proposed method allows reconstructing of a phase data page without any additional elements, which keeps the optical setup simple and low cost. (C) 2018 Optical Society of America

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Three-dimensional shift multiplexed recording in coaxial holographic data storage with virtual varifocal lens

Yusuke Saita, Masahiro Karaike, Takanori Nomura

Optics InfoBase Conference Papers ( OSA - The Optical Society )  2018   2018年

　概要を見る

Holographic data storage (HDS) is one of attractive solutions for archiving huge number of data produced all over the world. A coaxial system in HDS has some advantages of simple setup, tolerance to vibrations, and so on. In a coaxial system, the two-dimensional (2D) shift multiplexing is achieved by lateral medium shifts corresponding to disk rotation. Also, the multi-layer recording with a kinoform varifocal lens has also been proposed, which is based on adding a defocus phase distribution to signal and reference patterns displayed on a spatial light modulator (SLM) [1]. In this paper, we propose the three-dimensional (3D) shift multiplexing combining these multiplexed schemes and the criteria to determine the appropriate recording condition. The proposed method confirms the feasibility of improving the recoring density in coaxial HDS.

Computer-generated-hologram-based holographic data storage using a transport of intensity equation

Naru Yoneda, Yusuke Saita, Koshi Komuro, Teruyoshi Nobukawa, Takanori Nomura

Optics InfoBase Conference Papers   Part F125-OPJ 2018   2018年

　概要を見る

Utilization of phase information can increase the recording density of holographic data storage. In this paper, a transport of intensity equation is introduced to computer-generated-hologram-based holographic data storage, which can obtain the phase datapage while keeping an optical setup simple and compact. Moreover, two defocused intensity distributions for the transport of intensity equation can be simultaneously obtained by using a conjugate beam from the computer-generated hologram.

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Large dynamic range wavefront sensing using Shack-Hartmann wavefront sensor based on pattern correlations

Saita Yusuke, Nomura Takanori

OPTICAL DESIGN AND TESTING VIII ( SPIE-INT SOC OPTICAL ENGINEERING )  10815   2018年  [査読有り]

　概要を見る

Wavefront sensing techniques are mainly needed in an adaptive optics system for high resolution imaging. One of them is a Shack-Hartmann method which is composed of very simple structure. Although the method is widely utilized, it also has the limitation for the measurable magnitude of wavefront aberrations. To overcome the problem, the improved Shack-Hartmann method for larger aberrated wavefronts has been proposed. In this paper, the principle of the proposed method and the numerical evaluation of the performance of the proposed method are presented.

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マイクロドットレンズの視力とコントラスト感度に対する影響

井手 武, 塩谷俊介, 久松良輔, 大林知央, 神田寛行, 伊東一良, 野村孝徳, 最田裕介, 戸田郁子, 坪田一男, 不二門尚

あたらしい眼科 ( メディカル葵出版 )  33 ( 9 ) 1376 - 1380   2016年09月  [査読有り]

Shack-Hartmann wavefront sensor with large dynamic range by adaptive spot search method

Hironobu Shinto, Yusuke Saita, Takanori Nomura

APPLIED OPTICS ( OPTICAL SOC AMER )  55 ( 20 ) 5413 - 5418   2016年07月  [査読有り]

　概要を見る

A Shack-Hartmann wavefront sensor (SHWFS) that consists of a microlens array and an image sensor has been used to measure the wavefront aberrations of human eyes. However, a conventional SHWFS has finite dynamic range depending on the diameter of the each microlens. The dynamic range cannot be easily expanded without a decrease of the spatial resolution. In this study, an adaptive spot search method to expand the dynamic range of an SHWFS is proposed. In the proposed method, spots are searched with the help of their approximate displacements measured with low spatial resolution and large dynamic range. By the proposed method, a wavefront can be correctly measured even if the spot is beyond the detection area. The adaptive spot search method is realized by using the special microlens array that generates both spots and discriminable patterns. The proposed method enables expanding the dynamic range of an SHWFS with a single shot and short processing time. The performance of the proposed method is compared with that of a conventional SHWFS by optical experiments. Furthermore, the dynamic range of the proposed method is quantitatively evaluated by numerical simulations. (C) 2016 Optical Society of America

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Improvement of Image Quality of 3D Display by Using Optimized Binary Phase Modulation and Intensity Accumulation

Kazunobu Masuda, Yusuke Saita, Ryusuke Toritani, Peng Xia, Kouichi Nitta, Osamu Matoba

JOURNAL OF DISPLAY TECHNOLOGY ( IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC )  12 ( 5 ) 472 - 477   2016年05月  [査読有り]

　概要を見る

To improve the reconstructed image quality in a 3D display system using binary phase modulator, we propose two successive methods that are a modified iterative Fresnel algorithm for designing the binary phase pattern and the intensity addition for the speckle reduction. Numerical and experimental results show the effectiveness of the proposed methods by increasing the number of iteration for optimizing the binary phase distribution and the number of intensity addition.

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Improvement of image quality of three-dimensional display using a binary phase distribution

Kazunobu Masuda, Yusuke Saita, Ryusuke Toritani, Peng Xia, Kouichi Nitta, Osamu Matoba

Proceedings of the International Display Workshops ( International Display Workshops )  2   1230 - 1233   2015年

　概要を見る

A method to improve the quality of the reconstructed 3D image by using a binary phase distribution is presented. The proposed method consists of two sub-methods that are the optimization of binary phase distribution by modified Fresnel ping-pong algorithm and temporally average of the speckle patterns. The results are presented.

Expansion of dynamic range in Shack-Hartmann wavefront sensor using dual microlens array

Hironobu Shinto, Yusuke Saita, Takanori Nomura

BIOPHOTONICS JAPAN 2015 ( SPIE-INT SOC OPTICAL ENGINEERING )  9792   2015年  [査読有り]

　概要を見る

A Shack-Hartmann wavefront sensor (SHWFS) which consists of a microlens array and an image sensor has been used to measure the wavefront aberrations in various fields owing to its advantages such as simple configuration. However, a conventional SHWFS has the finite dynamic range. The dynamic range cannot be expanded without sacrificing the spatial resolution and the sensitivity in a conventional SHWFS. In this study, the SHWFS using a dual microlens array to solve the problem is proposed. In the proposed method, an astigmatic microlens is arranged at the center of a group of 2 x 2 spherical microlenses. A pattern image including spots and linear patterns is obtained at the focal plane by the dual microlens array. The pattern image can be separated into two images as if two microlens array with different diameter were used by discriminating spots from linear patterns with the pattern matching technique. The proposed method enables to expand the dynamic range of an SHWFS by using the separated two images. The performance of the proposed method is confirmed by the numerical simulation for measuring a spherical wave.

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Wavefront Measurement with Large Dynamic Range Using Holographic Shack-Hartmann Wavefront Sensor

Yusuke Saita, Hironobu Shinto, Takanori Nomura

2015 14TH WORKSHOP ON INFORMATION OPTICS (WIO) ( IEEE )    2015年  [査読有り]

　概要を見る

The proposed holographic Shack-Hartmann wavefront sensor can measure a wavefront aberration with large dynamic range. It is realized by introducing a holographic optical element and pattern matching technique. To confirm the flexibility of the sensor, measurements of the wavefronts with various aberrations are numerically demonstrated.

Expansion of dynamic range in Shack-Hartmann wavefront sensor using dual microlens array

Hironobu Shinto, Yusuke Saita, Takanori Nomura

Progress in Biomedical Optics and Imaging - Proceedings of SPIE ( SPIE )  9792   2015年  [査読有り]

　概要を見る

A Shack-Hartmann wavefront sensor (SHWFS) which consists of a microlens array and an image sensor has been used to measure the wavefront aberrations in various fields owing to its advantages such as simple configuration. However, a conventional SHWFS has the finite dynamic range. The dynamic range cannot be expanded without sacrificing the spatial resolution and the sensitivity in a conventional SHWFS. In this study, the SHWFS using a dual microlens array to solve the problem is proposed. In the proposed method, an astigmatic microlens is arranged at the center of a group of 2 x 2 spherical microlenses. A pattern image including spots and linear patterns is obtained at the focal plane by the dual microlens array. The pattern image can be separated into two images as if two microlens array with different diameter were used by discriminating spots from linear patterns with the pattern matching technique. The proposed method enables to expand the dynamic range of an SHWFS by using the separated two images. The performance of the proposed method is confirmed by the numerical simulation for measuring a spherical wave.

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Holographic Shack–Hartmann wavefront sensor based on the correlation peak displacement detection method for wavefront sensing with large dynamic range

Yusuke Saita, Hironobu Shinto, Takanori Nomura (担当区分： 筆頭著者,　責任著者 )

Optica ( OSA - The Optical Society )  2 ( 5 ) 411 - 415   2015年  [査読有り]

　概要を見る

A method to expand the dynamic range for a Shack–Hartmann wavefront sensor (SHWFS) is proposed. An SHWFS consists of a microlens array and an image sensor, and it has been widely used to measure the wavefront aberration of a lightwave in various fields. However, a very large aberrated wave cannot be correctly measured due to the finite dynamic range that depends on the diameter of each microlens. The proposed method enables an SHWFS to measure wavefronts with larger aberrations by applying holography and pattern matching technologies. For measurement of a spherical wave, the proposed method is compared with a conventional one by numerical simulations and optical experiments. Their results confirm the performance of the proposed method.

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Design method of input phase mask to improve light use efficiency and reconstructed image quality for holographic memory

Yusuke Saita, Takanori Nomura (担当区分： 筆頭著者,　責任著者 )

Applied Optics   53 ( 19 ) 4136 - 4140   2014年06月  [査読有り]

Design of reference pattern and input phase mask for coaxial holographic memory

Yusuke Saita, Takanori Nomura, Eiji Nitanai, Takuhisa Numata (担当区分： 筆頭著者 )

Japanese Journal of Applied Physics   50 ( 9 ) 09ME03   2011年09月  [査読有り]

　概要を見る

Design methods of a reference pattern and an input phase mask for a coaxial holographic memory are described. By the proposed method, it is expected that the useless consumption of the dynamic range of a recording medium will decrease, and the light efficiency and the interference efficiency between the signal beam and the reference beam will be improved. A reference pattern and an input phase mask are designed by a simulated annealing. The performance of the proposed design method is confirmed by numerical simulations and optical experiments. Furthermore, the holographic memory system using both the designed reference pattern and the designed input phase mask is also confirmed by numerical simulations and optical experiments. © 2011 The Japan Society of Applied Physics.

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