研究者詳細 - 野村　孝徳

論文 - 野村　孝徳

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Correlation-Based Multiplexing of Complex Amplitude Data Pages in a Holographic Storage System Using Digital Holographic Techniques

Teruyoshi Nobukawa, Takanori Nomura (担当区分：最終著者 )

POLYMERS ( MDPI AG ) 9 ( 8 ) 2017年08月 [査読有り]

Holographic recording media can store the amplitude and the phase, or the complex amplitude, of a beam on the basis of holography. Owing to this characteristic, digital data can be encoded onto the complex amplitude of a signal beam in holographic data storage. However, most of conventional holographic storage systems encode digital data onto the amplitude alone because there are difficulties for modulating and detecting the phase. To solve the difficulties, a holographic storage system using digital holographic techniques has been proposed. With the help of digital holographic techniques, it is possible to modulate and detect the complex amplitude of a signal beam. Moreover, the proposed system can modulate the complex amplitude of a reference beam. In this paper, by making use of the capability, a correlation-based multiplexing with uncorrelated reference beams is demonstrated in the proposed system. Multiple holograms can be recorded in the same volume of a recording medium with no need for mechanical movements. Experimental results show that the proposed system with a correlation-based multiplexing can improve the storage capacity and can utilize the full potential of a recording medium without crosstalk noise stem from the optical setup.

Generalized sequential four-step phase-shifting color digital holography

Takanori Nomura, Kazuma Shinomura (担当区分：筆頭著者,　責任著者 )

APPLIED OPTICS ( OPTICAL SOC AMER ) 56 ( 24 ) 6851 - 6854 2017年08月 [査読有り]

A generalized sequential four-step phase-shifting color digital holography is proposed. As an arbitrary phase-shift quantity is independent from wavelengths, it can be used for four-step phase-shifting color digital holography. Furthermore, no constraint on the phase-shifting quantities or statistical property on the hologram is required in the proposed method. Experimental results using a reflective object are shown to confirm the proposed phase-shifting digital holography. (C) 2017 Optical Society of America

Spatially incoherent Fourier digital holography by four-step phase-shifting rotational shearing interferometer and its image quality

Kaho Watanabe, Takanori Nomura (担当区分：最終著者 )

OPTICAL REVIEW ( OPTICAL SOC JAPAN ) 24 ( 3 ) 351 - 360 2017年06月 [査読有り]

Spatially incoherent Fourier digital holography using a rotational shearing interferometer for four-step phase-shifting method is proposed. The previous incoherent Fourier holography using a rotational shearing interferometer [Watanabe and Nomura (Appl. Opt. 54: A18, 2015)] employs the two-step phase-shifting method in the vertical and horizontal polarizations. The reconstructed image contains a large bias term. This paper proposes introduction of two kinds of wave plates in one path of a rotational shearing interferometer for a four-step phase-shifting method. A Fourier hologram is obtained from the four recorded holograms for eliminating the bias term and the twin image. The numerical simulation and the optical experiment demonstrate improvement of the image quality of reconstructed image by the twin image and bias level reduction. Furthermore, the effect of the size of an image sensor on the image quality in rotational shearing interferometer is also investigated by the numerical simulations.

Multimodal Imaging Based on Digital Holography

Osamu Matoba, Xiangyu Quan, Peng Xia, Yasuhiro Awatsuji, Takanori Nomura

Proceedings of the IEEE ( IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC ) 105 ( 5 ) 906 - 923 2017年05月 [査読有り]

© 2017 IEEE. Digital holography provides a method of the 3-D recording and numerical reconstruction by a simple optical system and a computer. Quantitative measurement and numerical refocusing are major characteristics. So far, many physical parameters such as amplitude, phase, polarization, fluorescence, and spectra can be obtained independently. Recently, multimodal imaging that can obtain simultaneously two or more physical parameters by combining digital holographic microscope and other optical microscopes such as a fluorescence optical microscope and a Raman scattering microscope has emerged. In this review, physical parametric imaging techniques based on digital holography are presented and then these techniques are enhanced to develop multimodal imaging based on digital holography.

Shift multiplexing with a spherical wave in holographic data storage based on a computer-generated hologram

Teruyoshi Nobukawa, Takanori Nomura (担当区分：最終著者 )

APPLIED OPTICS ( OPTICAL SOC AMER ) 56 ( 13 ) F31 - F36 2017年05月 [査読有り]

A holographic data storage system based on a computer-generated hologram (CGH) is simple and compact because a hologram of a data page is recorded through an imaging system without an additional optical path for a reference beam. In this paper, to improve the recording density of the holographic data storage based on a CGH, a shift multiplexing method using a spherical wave is proposed. A data page to be stored and a spherical wave are simultaneously reconstructed from a single CGH. This allows shift multiplexing by displacing a recording medium. Experimental results show that the proposed method can improve shift selectivity and enables us to implement shift multiplexing. (C) 2017 Optical Society of America

Digital super-resolution holographic data storage based on Hermitian symmetry for achieving high areal density

Teruyoshi Nobukawa, Takanori Nomura (担当区分：最終著者 )

OPTICS EXPRESS ( OPTICAL SOC AMER ) 25 ( 2 ) 1326 - 1338 2017年01月 [査読有り]

Digital super-resolution holographic data storage based on Hermitian symmetry is proposed to store digital data in a tiny area of a medium. In general, reducing a recording area with an aperture leads to the improvement in the storage capacity of holographic data storage. Conventional holographic data storage systems however have a limitation in reducing a recording area. This limitation is called a Nyquist size. Unlike the conventional systems, our proposed system can overcome the limitation with the help of a digital holographic technique and digital signal processing. Experimental result shows that the proposed system can record and retrieve a hologram in a smaller area than the Nyquist size on the basis of Hermitian symmetry. (C) 2016 Optical Society of America

Spatially incoherent Fourier digital holography

Takanori Nomura, Kaho Watanabe

Proceedings of SPIE - The International Society for Optical Engineering ( SPIE ) 10219 2017年

The possibility of incoherent digital holography has been widely studied because it is free from coherent light sources. Here spatially incoherent Fourier digital holography is described. The incoherent hologram is obtained by a rotational shearing interferometer. The hologram obtained by the interferometer is a cosine transform of a spatially incoherent object. After describing the principle of a rotational shearing interferometer, methods to obtain Fourier transform of an object presented.

Phase object mapping based on a complex amplitude measurement by transport of intensity equation

Koshi Komuro, Takanori Nomura

Optics InfoBase Conference Papers ( OSA - The Optical Society ) 2017 2017年

Coaxial polarization holographic data recording on a polarization-sensitive medium

Teruyoshi Nobukawa, Takashi Fukuda, Daisuke Barada, Takanori Nomura (担当区分：最終著者 )

OPTICS LETTERS ( OPTICAL SOC AMER ) 41 ( 21 ) 4919 - 4922 2016年11月 [査読有り]

A coaxial polarization holographic data recording is proposed, and a proof-of-principle experiment is demonstrated for the first time, to the best of our knowledge. A proposed recording system allows us to record and retrieve a volume polarization hologram using a simple optical setup, as compared with conventional polarization holographic data storage systems. By using the proposed system, the data pages encoded on horizontal and vertical linearly polarized beams were simultaneously recorded, and each data page was successfully retrieved without any error. Moreover, the effectiveness of a random phase mask was experimentally and quantitatively confirmed in polarization holographic data storage. (C) 2016 Optical Society of America

Multilevel recording of complex amplitude data pages in a holographic data storage system using digital holography

Teruyoshi Nobukawa, Takanori Nomura (担当区分：最終著者 )

OPTICS EXPRESS ( OPTICAL SOC AMER ) 24 ( 18 ) 21001 - 21011 2016年09月 [査読有り]

A holographic data storage system using digital holography is proposed to record and retrieve multilevel complex amplitude data pages. Digital holographic techniques are capable of modulating and detecting complex amplitude distribution using current electronic devices. These techniques allow the development of a simple, compact, and stable holographic storage system that mainly consists of a single phase-only spatial light modulator and an image sensor. As a proof-of-principle experiment, complex amplitude data pages with binary amplitude and four-level phase are recorded and retrieved. Experimental results show the feasibility of the proposed holographic data storage system. (C) 2016 Optical Society of America

Fast Hologram Pattern Generation by Adaptive Point-Spread Spherical Wave Synthesis

Yutaka Mori, Takanori Nomura (担当区分：最終著者 )

JOURNAL OF DISPLAY TECHNOLOGY ( IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC ) 12 ( 8 ) 815 - 821 2016年08月 [査読有り]

We propose an adaptive point-spread spherical wave synthesis method based on the point-source hologram technique for fast hologram pattern generation. The calculation time of the hologram generation is reduced by decreasing the number of reconstructed point sources composing an object. A larger point source is reconstructed in the area where an object can be partially expressed by low resolution. The point-spread is adjusted corresponding to the spatial frequency of an object. The effectiveness of the proposed method is confirmed by a computer simulation using two-dimensional images.

Roadmap on optical security

Bahram Javidi, Artur Carnicer, Masahiro Yamaguchi, Takanori Nomura, Elisabet Perez-Cabre, Maria S. Millan, Naveen K. Nishchal, Roberto Torroba, John Fredy Barrera, Wenqi He, Xiang Peng, Adrian Stern, Yair Rivenson, A. Alfalou, C. Brosseau, Changliang Guo, John T. Sheridan, Guohai Situ, Makoto Naruse, Tsutomu Matsumoto, Ignasi Juvells, Enrique Tajahuerce, Jesus Lancis, Wen Chen, Xudong Chen, Pepijn W. H. Pinkse, Allard P. Mosk, Adam Markman

JOURNAL OF OPTICS ( IOP PUBLISHING LTD ) 18 ( 8 ) 2016年08月 [査読有り]

Information security and authentication are important challenges facing society. Recent attacks by hackers on the databases of large commercial and financial companies have demonstrated that more research and development of advanced approaches are necessary to deny unauthorized access to critical data. Free space optical technology has been investigated by many researchers in information security, encryption, and authentication. The main motivation for using optics and photonics for information security is that optical waveforms possess many complex degrees of freedom such as amplitude, phase, polarization, large bandwidth, nonlinear transformations, quantum properties of photons, and multiplexing that can be combined in many ways to make information encryption more secure and more difficult to attack. This roadmap article presents an overview of the potential, recent advances, and challenges of optical security and encryption using free space optics. The roadmap on optical security is comprised of six categories that together include 16 short sections written by authors who have made relevant contributions in this field. The first category of this roadmap describes novel encryption approaches, including secure optical sensing which summarizes double random phase encryption applications and flaws [Yamaguchi], the digital holographic encryption in free space optical technique which describes encryption using multidimensional digital holography [Nomura], simultaneous encryption of multiple signals [Perez-Cabre], asymmetric methods based on information truncation [Nishchal], and dynamic encryption of video sequences [Torroba]. Asymmetric and one-way cryptosystems are analyzed by Peng. The second category is on compression for encryption. In their respective contributions, Alfalou and Stern propose similar goals involving compressed data and compressive sensing encryption. The very important area of cryptanalysis is the topic of the third category with two sections: Sheridan reviews phase retrieval algorithms to perform different attacks, whereas Situ discusses nonlinear optical encryption techniques and the development of a rigorous optical information security theory. The fourth category with two contributions reports how encryption could be implemented at the nano- or micro-scale. Naruse discusses the use of nanostructures in security applications and Carnicer proposes encoding information in a tightly focused beam. In the fifth category, encryption based on ghost imaging using single-pixel detectors is also considered. In particular, the authors [Chen, Tajahuerce] emphasize the need for more specialized hardware and image processing algorithms. Finally, in the sixth category, Mosk and Javidi analyze in their corresponding papers how quantum imaging can benefit optical encryption systems. Sources that use few photons make encryption systems much more difficult to attack, providing a secure method for authentication.

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]

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

Quantitative phase imaging using transport of intensity equation with multiple bandpass filters

Koshi Komuro, Takanori Nomura (担当区分：最終著者 )

APPLIED OPTICS ( OPTICAL SOC AMER ) 55 ( 19 ) 5180 - 5186 2016年07月 [査読有り]

A phase imaging based on the transport of intensity equation using multiple bandpass filters is proposed. The proposed method enables us to measure a phase distribution quantitatively from through-focus intensity images obtained by using a white light source and multiple bandpass filters. The technique improves the accuracy of a phase measurement by increasing the number of intensity images obtained at different defocused positions. The feasibility of the phase measurement and the improvement in the accuracy with increasing the through-focus images are confirmed by numerical simulations and optical experiments. (C) 2016 Optical Society of America

Linear phase encoding for holographic data storage with a single phase-only spatial light modulator

Teruyoshi Nobukawa, Takanori Nomura

APPLIED OPTICS ( OPTICAL SOC AMER ) 55 ( 10 ) 2565 - 2573 2016年04月 [査読有り]

A linear phase encoding is presented for realizing a compact and simple holographic data storage system with a single spatial light modulator (SLM). This encoding method makes it possible to modulate a complex amplitude distribution with a single phase-only SLM in a holographic storage system. In addition, an undesired light due to the imperfection of an SLM can be removed by spatial frequency filtering with a Nyquist aperture. The linear phase encoding is introduced to coaxial holographic data storage. The generation of a signal beam using linear phase encoding is experimentally verified in an interferometer. In a coaxial holographic data storage system, single data recording, shift selectivity, and shift multiplexed recording are experimentally demonstrated. (C) 2016 Optical Society of America

Speckle Reduction by Spatial-Domain Mask in Digital Holography

Takahiko Fukuoka, Yutaka Mori, Takanori Nomura

JOURNAL OF DISPLAY TECHNOLOGY ( IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC ) 12 ( 4 ) 315 - 322 2016年04月 [査読有り]

The image quality improvement method using a spatial-domain mask is proposed. In the proposed method, a single hologram is required for speckle reduction. The speckle noise of the reconstructed image is suppressed by averaging different speckle patterns. The different speckle patterns are generated by shifting the rectangular aperture in the hologram plane. The experiment results including a modulation transfer function are presented to confirm the performance of the proposed method.

Multilayer recording holographic data storage using a varifocal lens generated with a kinoform

Teruyoshi Nobukawa, Takanori Nomura

OPTICS LETTERS ( OPTICAL SOC AMER ) 40 ( 23 ) 5419 - 5422 2015年12月 [査読有り]

A multilayer recording method using a varifocal lens generated with a kinoform is presented. In this recording method, a focus position is axially displaced by adding a defocus phase to a phase modulation pattern, which consists of a random phase mask and a computer-generated reference pattern. Shift selectivity and multiplexed recording are experimentally investigated in coaxial holographic data storage. Experimental results show that the proposed method allows the recording of holograms along an optical axis without any mechanical movement. (C) 2015 Optical Society of America

Extended focused imaging in digital holography by spatial-domain mask method

Yutaka Mori, Takahiko Fukuoka, Takanori Nomura

JOURNAL OF OPTICS ( IOP PUBLISHING LTD ) 17 ( 12 ) 2015年12月 [査読有り]

In a digital holographic reconstruction, only images located at the reconstruction distance are in focus. A speckle reduction technique is proposed to improve digital holographic in-focus imaging. The extended focused image is obtained from a depth map created by evaluating the edge sharpness of object images. In order to show the performance and effectiveness of the proposed technique for extended focused imaging, we conducted the demonstration experiments using two objects, which are a resolution chart and two screws.

Preface

Takanori Nomura

OPTICAL REVIEW ( OPTICAL SOC JAPAN ) 22 ( 5 ) 828 - 828 2015年10月 [査読有り]

Speckle Reduction in Hologram Generation Based on Spherical Waves Synthesis Using Low-Coherence Digital Holography

Yutaka Mori, Takanori Nomura

JOURNAL OF DISPLAY TECHNOLOGY ( IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC ) 11 ( 10 ) 867 - 872 2015年10月 [査読有り]

A speckle reduction method based on a spherical waves synthesis with low-coherence digital holography for hologram generation is proposed. An object information is experimentally obtained from a number of recorded low-coherence digital holograms. A hologram is generated by synthesizing the fields of spherical waves with the obtained information. The performance of the proposed method as hologram generation from a distribution contained spike noises like speckles is confirmed. The image quality is evaluated by the speckle contrast of the reconstructed image.

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