Faculty Profiles - NOMURA Takanori

Published Papers - NOMURA Takanori

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Random sparse sampling and compressive sensing based reconstruction for computational optical scanning holography

Naru Yoneda, Masamitsu Sugimoto, Yusuke Saita, Osamu Matoba, Takanori Nomura

Applied Optics ( Optica Publishing Group ) 64 ( 7 ) B102 - B102 2025.02

Optical scanning holography (OSH) is one of the single-pixel imaging (SPI) techniques. Although OSH can obtain an incoherent hologram using a single-pixel detector, OSH needs a complicated optical setup to generate Fresnel zone patterns (FZPs). Computational OSH (COSH) has been proposed to overcome the complexity of OSH by using a spatial light modulator (SLM). However, the measurement time of COSH is restricted by the refresh rate of an SLM for changing FZPs. While the number of measurements can be reduced by applying compressive sensing in conventional OSH, the scanning trajectory of FZPs is limited to the spiral manner because of the requirement of sequential scanning using galvo mirrors. The spiral scanning trajectory induces undesired artifacts in reconstructed images under sparse sampling conditions. If holograms can be randomly subsampled, these undesired artifacts can be reduced. In this paper, under COSH’s configuration, random sparse sampling of a hologram is proposed to overcome the problem of the limited trajectory of FZPs by discretely displaying FZPs on an SLM. In addition, compressive sensing is applied to reconstruct an object image from a randomly sampled hologram. The feasibility of the proposed method is confirmed numerically and experimentally. The experimental results indicate that the proposed method can identify the object even when the hologram is randomly subsampled with a sampling rate of 5%.

Single-shot Compressive Hyperspectral Imaging Utilizing Both Positive and Negative Diffracted Waves

Yusuke Saita, Ryohei Takahashi, Takanori Nomura

Advanced Devices & Instrumentation ( American Association for the Advancement of Science (AAAS) ) 2025.01

Adaptive sampling strategy for Fourier single-pixel imaging

Hongjie Liu, Yuki Matsuda, Shujun Zheng, Yusuke Saita, Xiao Lin, Takanori Nomura, Xiaodi Tan

Optics Communications ( Elsevier BV ) 573 131027 - 131027 2024.12

Computational Optical Scanning Holography

Naru Yoneda, Jung-Ping Liu, Osamu Matoba, Yusuke Saita, Takanori Nomura

Photonics ( MDPI AG ) 11 ( 4 ) 347 - 347 2024.04

Holographic techniques are indispensable tools for modern optical engineering. Over the past two decades, research about incoherent digital holography has continued to attract attention. Optical scanning holography (OSH) can obtain incoherent holograms using single-pixel detection and structured illumination with Fresnel zone patterns (FZPs). Particularly by changing the size of a detector, OSH can also obtain holograms under coherently illuminated conditions. Since 1979, OSH has continuously evolved. According to the evolution of semiconductor technology, spatial light modulators (SLMs) come to be useful for various imaging fields. By using SLM techniques for OSH, the practicality of OSH is improved. These SLM-based OSH methods are termed computational OSH (COSH). In this review, the configurations, recording and reconstruction methods, and proposed applications of COSH are reviewed.

Orthogonal matrix of polarization combinations: concept and application to multichannel holographic recording

Shujun Zheng, Jiaren Tan, Hongjie Liu, Xiao Lin, Yusuke Saita, Takanori Nomura, Xiaodi Tan

Opto-Electronic Advances ( Opto-Electronic Advances ) 7 ( 10 ) 230180 - 230180 2024

Quantitative phase imaging based on motionless optical scanning holography

Naru Yoneda, Osamu Matoba, Yusuke Saita, Takanori Nomura （Part： Last author )

Optics Letters ( Optica Publishing Group ) 48 ( 20 ) 5273 - 5273 2023.10

Optical scanning holography (OSH) can be applied to 3D fluorescent imaging. However, the optical setup for OSH is complicated due to the requirement of a phase shifter, a 2D mechanical scanner, and an interferometer. Although motionless optical scanning holography (MOSH) can overcome the problem, quantitative phase imaging (QPI) has not yet been realized because MOSH can only obtain incoherent holograms. If QPI in MOSH is realized, MOSH can be applied to various applications. In this Letter, MOSH-based QPI (MOSH-QPI) is proposed. In addition, a simple description of a coherent mode of OSH is presented. In the proof-of-principle experiment, the spatially divided phase-shifting technique is applied to reduce the number of measurements. The feasibility of MOSH-QPI is confirmed by measuring a phase distribution of a microlens array. MOSH-QPI is also applied to measure practical samples, and its results are compared with the experimental results of the conventional one using a Mach–Zehnder interferometer.

Polarization imaging by use of optical scanning holography

Naru Yoneda, Yusuke Saita, Takanori Nomura （Part： Last author )

Optical Review ( Springer Science and Business Media LLC ) 2022.11 [Refereed]

Common-path off-axis single-pixel holographic imaging

Naru Yoneda, Yusuke Saita, Takanori Nomura （Part： Last author )

Optics Express ( Optica Publishing Group ) 30 ( 11 ) 18134 - 18134 2022.05 [Refereed]

Single-shot compressive hyperspectral imaging with dispersed and undispersed light using a generally available grating

Yusuke Saita, Daiki Shimoyama, Ryohei Takahashi, Takanori Nomura （Part： Last author )

Applied Optics ( The Optical Society ) 61 ( 5 ) 1106 - 1106 2022.02 [Refereed]

[Invited Paper] Enhanced Recording Density via Multilevel Phase Retrieval and Correlation-based Multiplexed Recording in Computer-generated Holographic Data Storage

Yusuke Saita, Naru Yoneda, Aoto Matsumoto, Takanori Nomura （Part： Last author )

ITE Transactions on Media Technology and Applications ( Institute of Image Information and Television Engineers ) 10 ( 2 ) 69 - 74 2022 [Refereed]

Roadmap on digital holography [Invited]

Bahram Javidi, Artur Carnicer, Arun Anand, George Barbastathis, Wen Chen, Pietro Ferraro, J. W. Goodman, Ryoichi Horisaki, Kedar Khare, Malgorzata Kujawinska, Rainer A. Leitgeb, Pierre Marquet, Takanori Nomura, Aydogan Ozcan, YongKeun Park, Giancarlo Pedrini, Pascal Picart, Joseph Rosen, Genaro Saavedra, Natan T. Shaked, Adrian Stern, Enrique Tajahuerce, Lei Tian, Gordon Wetzstein, Masahiro Yamaguchi

Optics Express ( The Optical Society ) 29 ( 22 ) 35078 - 35078 2021.10 [Refereed] [Invited]

Three-dimensional fluorescence imaging through dynamic scattering media by motionless optical scanning holography

Naru Yoneda, Yusuke Saita, Takanori Nomura （Part： Last author )

Applied Physics Letters ( AIP Publishing ) 119 ( 16 ) 161101 - 161101 2021.10 [Refereed]

Single-shot higher-order transport-of-intensity quantitative phase imaging using deep learning

Naru Yoneda, Shunsuke Kakei, Koshi Komuro, Aoi Onishi, Yusuke Saita, Takanori Nomura （Part： Last author )

Applied Optics ( The Optical Society ) 60 ( 28 ) 8802 - 8802 2021.10 [Refereed]

Roadmap on Recent Progress in FINCH Technology

Joseph Rosen, Simon Alford, Vijayakumar Anand, Jonathan Art, Petr Bouchal, Zdeněk Bouchal, Munkh-Uchral Erdenebat, Lingling Huang, Ayumi Ishii, Saulius Juodkazis, Nam Kim, Peter Kner, Takako Koujin, Yuichi Kozawa, Dong Liang, Jun Liu, Christopher Mann, Abhijit Marar, Atsushi Matsuda, Teruyoshi Nobukawa, Takanori Nomura, Ryutaro Oi, Mariana Potcoava, Tatsuki Tahara, Bang Le Thanh, Hongqiang Zhou

Journal of Imaging ( MDPI AG ) 7 ( 10 ) 197 - 197 2021.09 [Refereed]

Fast and accurate phase-unwrapping algorithm based on the transport of intensity equation: comment

Naru Yoneda, Takahiro Sakai, Takanori Nomura （Part： Last author )

Applied Optics ( The Optical Society ) 60 ( 24 ) 7500 - 7501 2021.08 [Refereed]

Common-path angular-multiplexing holographic data storage based on computer-generated holography

Naru Yoneda, Teruyoshi Nobukawa, Toshiyuki Morimoto, Yusuke Saita, Takanori Nomura （Part： Last author )

Optics Letters ( The Optical Society ) 46 ( 12 ) 2920 - 2920 2021.06 [Refereed]

Pupil-modulation ghost phase imaging

Takafumi Ito, Koshi Komuro, Takanori Nomura （Part： Last author,　Corresponding author )

Applied Optics 60 ( 15 ) 4398 - 4403 2021.05 [Refereed]

Computational ghost imaging (CGI) allows us to reconstruct images under a low signal-to-noise-ratio condition. However, CGI cannot retrieve phase information; it is unsuitable for observation of transparent objects such as living cells. A phase imaging method with CGI architecture is proposed. The proposed method realizes phase imaging with a simple optical setup by introducing pupil modulation differential phase contrast (PMDPC) to CGI. In PMDPC, phase information can be obtained from intensity distributions, which have phase gradient information, and its optical setup is similar to that of CGI. Therefore, the two methods are highly compatible, and the introduction of PMDPC to CGI can be easily achieved. Numerical simulation and an optical experiment demonstrated the feasibility of the proposed method.

Single-shot higher-order transport-of-intensity quantitative phase imaging based on computer-generated holography

NARU YONEDA, AOI ONISHI, YUSUKE SAITA, KOSHI KOMURO, TAKANORI NOMURA （Part： Last author )

Optics Express ( OPTICAL SOC AMER ) 29 ( 4 ) 4783 - 4801 2021.02 [Refereed]

The imaging quality of quantitative phase imaging (QPI) based on the transport of intensity equation (TIE) can be improved using a higher-order approximation for defocused intensity distributions. However, this requires mechanically scanning an image sensor or object along the optical axis, which in turn requires a precisely aligned optical setup. To overcome this problem, a computer-generated hologram (CGH) technique is introduced to TIE-based QPI. A CGH generating defocused point spread function is inserted in the Fourier plane of an object. The CGH acts as a lens and grating with various focal lengths and orientations, allowing multiple defocused intensity distributions to be simultaneously detected on an image sensor plane. The results of a numerical simulation and optical experiment demonstrated the feasibility of the proposed method.

Spatially divided phase-shifting motionless optical scanning holography

Naru Yoneda, Yusuke Saita, Takanori Nomura （Part： Last author )

OSA Continuum ( OPTICAL SOC AMER ) 3 ( 12 ) 3523 - 3535 2020.12 [Refereed]

Motionless optical scanning holography (MOSH) has been proposed for threedimensional incoherent imaging in single-pixel holography with a simple optical setup. To reduce the measurement time in MOSH, a spatially divided phase-shifting technique is introduced. The proposed method realizes measurements four times faster than the original MOSH, owing to the simultaneous lateral and phase shifts of a time-varying Fresnel zone plate. A hologram reproduced by the proposed method forms a spatially multiplexed phase-shifting hologram similar to parallel phase-shifting digital holography. The effectiveness of the proposed method is numerically and experimentally verified.

Single-shot in-line Fresnel incoherent holography using a dual-focus checkerboard lens

Shota Sakamaki, Naru Yoneda, Takanori Nomura （Part： Last author,　Corresponding author )

APPLIED OPTICS ( OPTICAL SOC AMER ) 59 ( 22 ) 6612 - 6618 2020.08 [Refereed]

Fresnel incoherent correlation holography (FINCH) is a technology that can acquire three-dimensional information of incoherent objects such as fluorescence with an in-line optical system. However, it is difficult to apply FINCH to dynamic phenomena, since FINCH has to detect phase-shifted holograms sequentially to eliminate twin and zero-order images. In this paper, a method in which the phase-shifted holograms can be obtained simultaneously with an in-line setup by using an optimized simulated diffraction optical element (sDOE), realized by a phase-only spatial light modulator, is proposed. The optimized sDOE is an optical device with a dual-focus lens, 2D grating, and spatial phase shifter. Therefore, the sDOE is called a dual-focus checkerboard lens. The optical experiment confirms the feasibility of the proposed method. (C) 2020 Optical Society of America

Multiplexed recording based on the reference wave correlation for computer-generated holographic data storage

Yusuke Saita, Aoto Matsumoto, Naru Yoneda, Takanori Nomura （Part： Last author )

OPTICAL REVIEW ( OPTICAL SOC JAPAN ) 27 ( 4 ) 391 - 398 2020.08 [Refereed]

Holographic data storage (HDS) based on a computer-generated hologram (CGH) technique has been proposed as a promising approach to realize an in-line and simple HDS system. This work focuses on multiplexed recording for CGH-based HDS, and the approach based on the reference wave correlation is introduced to the HDS. For the proposed method, the processes for a CGH design are modified to generate reference waves with different phase distributions for each recording. Since holograms are recorded to the same region in a medium with independent reference waves, recorded data-pages are selectively reconstructed by the corresponding reference wave illuminations. The experimental demonstration confirms the feasibility of the proposed method, and the theoretical characteristic for the number of recordable multiplexed holograms is estimated by the numerical simulation.

Motionless optical scanning holography

Naru Yoneda, Yusuke Saita, Takanori Nomura （Part： Last author )

OPTICS LETTERS ( OPTICAL SOC AMER ) 45 ( 12 ) 2020.06 [Refereed]

Optical scanning holography (OSH) is an attractive technique since 3D information can be obtained with a single pixel detector. However, OSH requires an interferometer, scanning architecture, and a frequency shifter to scan a time-varying Fresnel zone plate (FZP), which makes the optical setup complicated. To reduce the complexity, the polarization sensitivity of a spatial light modulator (SLM) is applied. The proposed method implements a time-varying FZP with an in-line optical setup by using only an SLM. Observing results for a USAF pattern and a fluorescent bead reveals the feasibility of the new motionless holographic 3D imaging technique. (C) 2020 Optical Society of America

Computer-generated-hologram-based holographic data storage using common-path off-axis digital holography

Naru Yoneda, Yusuke Saita, Takanori Nomura （Part： Last author )

OPTICS LETTERS ( OPTICAL SOC AMER ) 45 ( 10 ) 2796 - 2799 2020.05 [Refereed]

A reconstruction method for multilevel complex encoded data-pages is proposed to increase the recording density of computer-generated-hologram-based holographic data storage by using off-axis digital holography. Although the detection process is based on off-axis digital holography, the proposed method keeps the optical setup a simple and common-path configuration owing to the computer-generated holography. Five-level complex encoded data-pages can be experimentally reconstructed. (C) 2020 Optical Society of America

Deep ghost phase imaging

Koshi Komuro, Takanori Nomura, George Barbastathis

Applied Optics ( OSA - The Optical Society ) 59 ( 11 ) 3376 - 3382 2020.04

Deep-learning-based single-pixel phase imaging is proposed. The method, termed deep ghost phase imaging (DGPI), succeeds the advantages of computational ghost imaging, i.e., has the phase imaging quality with high signal-to-noise ratio derived from the Fellgett's multiplex advantage and the point-like detection of diffracted light from objects. A deep convolutional neural network is learned to output a desired phase distribution from an input of a defocused intensity distribution reconstructed by the single-pixel imaging theory. Compared to the conventional interferometric and transport-of-intensity approaches to single-pixel phase imaging, the DGPI requires neither additional intensity measurements nor explicit approximations. The effects of defocus distance and light level are investigated by numerical simulation and an optical experiment confirms the feasibility of the DGPI.

Transport-of-intensity phase imaging with polarization directed flat lenses

Shunsuke Kakei, Koshi Komuro, Takanori Nomura

Applied Optics ( OSA - The Optical Society ) 59 ( 7 ) 2011 - 2015 2020.03

A phase imaging technique based on the transport of intensity equation with polarization directed flat lenses is demonstrated. Transport-of-intensity phase imaging enables one to obtain a phase distribution from throughfocus intensity distributions by solving the transport of intensity equation. In general, the through-focus intensity distributions are obtained by mechanical scanning of an image sensor or target object. Therefore, a precise alignment of an optical system is required. To solve this issue, the introduction of polarization directed flat lenses is presented. In the proposed method, two intensity distributions at different depth positions on the optical axis are obtained without mechanical scanning by changing polarization states of incident light. The feasibility of the proposed method is confirmed by an optical experiment.

Complex amplitude mapping based on adaptive autofocusing algorithm

Komuro, Koshi, Oe, Kazusa, Tamada, Yosuke, Nomura, Takanori （Part： Last author )

OPTICAL REVIEW ( OPTICAL SOC JAPAN ) 26 ( 3 ) 342 - 348 2019.06 [Refereed]

Since a complex amplitude distribution can be obtained in only a single two-dimensional plane using conventional imaging techniques, it is hard to obtain in-focus complex amplitude of three-dimensional structure (not a thin object) or multiple objects in different depth positions. The disadvantage often turns an obstacle to practical applications such as cell observation, particle measurement, and industrial inspection. To overcome the problem, adaptive autofocusing algorithm (AAA) is proposed. AAA consists of a complex amplitude measurement, numerical propagation, and local sharpness evaluation. In the proposed method, object positions can be determined for each pixel in the complex amplitude distribution using adaptively chosen area size of local sharpness evaluation. The proposed method gives a complex amplitude distribution which focuses on all objects or structure over an entire field of view. An optical experiment is carried out using the transport of intensity equation as a complex amplitude measurement. Performance of the proposed method is confirmed using living leaves of the moss Physcomitrella patens. Experimental results show that the object positions can be determined pixelwise and a focused complex amplitude distribution can be obtained by the proposed method.

Binary computer-generated-hologram-based holographic data storage

Naru Yoneda, Yusuke Saita, Takanori Nomura （Part： Last author )

APPLIED OPTICS ( OPTICAL SOC AMER ) 58 ( 12 ) 3083 - 3090 2019.04 [Refereed]

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

Computational ghost imaging with designed low spatial frequency masks

Yuya Yamazaki, Takanori Nomura （Part： Last author,　Corresponding author )

APPLIED OPTICS ( OPTICAL SOC AMER ) 57 ( 31 ) 9375 - 9380 2018.11 [Refereed]

Minimally invasive imaging using weak illumination is required in the biomedical field. Computational ghost imaging (CGI) achieves imaging under illumination. However, CGI requires a large number of measurements to obtain an image. The number of measurements increases as illumination weakens. In this paper, decreasing the number of measurements of CGI with designed low spatial frequency masks is proposed. The proposed method allows us to image an object with a smaller number of measurements than with the conventional method. Numerical simulations and experiments confirm the feasibility of the proposed method. (C) 2018 Optical Society of America.

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

Naru Yoneda, Yusuke Saita, Koshi Komuro, Teruyoshi Nobukawa, Takanori Nomura （Part： Corresponding author )

APPLIED OPTICS ( OPTICAL SOC AMER ) 57 ( 30 ) 8836 - 8840 2018.10 [Refereed]

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

Phase-unwrapping-free and iterative reconstruction methods for propagated refractive index tomography

Ikezaki, Aina, Nomura, Takanori （Part： Last author,　Corresponding author )

JAPANESE JOURNAL OF APPLIED PHYSICS ( IOP PUBLISHING LTD ) 57 ( 9 ) 2018.09 [Refereed]

Phase-unwrapping-free and iterative reconstruction methods for propagated refractive index ( RI) tomography, which introduces lightwave back-propagation to a filtered back-projection method, are proposed. The phase-unwrapping-free method utilizes phase retrieval using a transport-of-intensity equation that does not require phase unwrapping. This method overcomes phase unwrapping problems of high calculation cost and phase unwrapping error when measuring millimeter-thick and/or large-RI-changes specimens. In the iterative method, a simultaneous iterative reconstruction technique in X-ray computed tomography is applied to the propagated RI tomography. This method leads to the reduction of the radial artifacts and the elimination of the need for a high-pass filter regardless of the shape and size of specimens. Hence, the accuracy of a reconstructed RI map is improved. Numerical simulations and optical experiments are carried out to prove the feasibility of the proposed methods. (c) 2018 The Japan Society of Applied Physics

Refractive index tomography based on optical coherence tomography and tomographic reconstruction algorithm (vol 56, 09NB03, 2017)

Kitazawa, Takahiro, Nomura, Takanori （Part： Last author )

JAPANESE JOURNAL OF APPLIED PHYSICS ( IOP PUBLISHING LTD ) 57 ( 8 ) 2018.08 [Refereed]

Twin-image reduction method using a diffuser for phase imaging in-line digits holography

Oe, Kazusa, Nomura, Takanori （Part： Last author,　Corresponding author )

APPLIED OPTICS ( OPTICAL SOC AMER ) 57 ( 20 ) 5652 - 5656 2018.07 [Refereed]

Phase imaging by digital holography is widely used. An in-line optical setup is preferable for a practical use. A twin image, however, is a serious obstacle to achievement of high-quality phase imaging in in-line digital holography. For in-line digital holography, a time-division phase-shifting method or a wave-splitting phase-shifting method is used to eliminate the twin image. The former requires multiple exposures, and the latter requires specially designed optical elements. To solve these problems, a twin-image reduction method using a diffuser is proposed. In the proposed method, recording a digital hologram using a diffuser and signal processing enable reduction of the twin image on a reconstructed plane. A preliminary experimental result confirms the feasibility of the proposed method. (C) 2018 Optical Society of America

Transport-of-intensity computational ghost imaging

Komuro, Koshi, Yamazaki, Yuya, Nomura, Takanori （Part： Last author )

APPLIED OPTICS ( OPTICAL SOC AMER ) 57 ( 16 ) 4451 - 4456 2018.06 [Refereed]

Computational ghost imaging (CGI) allows us to obtain a sample image under a low signal-to-noise-ratio (SNR) condition. However, phase information cannot be obtained by CGI; therefore, observation of transparent objects such as living cells is difficult. Although interferometry has been applied to CGI for phase retrieval, its optical setup is cumbersome. In this paper, an alternative approach, which is based on a transport-of-intensity equation, is proposed. Compared with conventional interferometric methods, the optical setup of the proposed method is robust because it does not require additional optical elements. The proposed method achieves phase retrieval by slight modification of the standard CGI setup. Numerical and optical experiments with low SNR confirm the effectiveness of the proposed method. (C) 2018 Optical Society of America

Transport of intensity phase imaging for pure phase objects in computational ghost imaging

Koshi Komuro, Yuya Yamazaki, Takanori Nomura

Proceedings of SPIE - The International Society for Optical Engineering ( SPIE ) 10816 2018

Computational ghost imaging (CGI) is expected to be applied to noninvasive biomedical imaging because of its characteristic which allows us to obtain the object's image under a low signal to noise ratio (SNR) condition. However only an amplitude distribution can be obtained by the CGI. Therefore the imaging of the pure phase objects is difficult. Although the phase shifting digital holography has been used for reconstruction of the complex amplitude in the CGI, its experimental setup is cumbersome and sensitive to vibrations. Furthermore four holograms are required for the reconstruction of the complex amplitude because of the phase shifting algorithm, rendering the acquisition time of the phase image slow. Therefore the method is difficult to be applied to the biomedical imaging. An alternative non-interferometric method is proposed in this study. The proposed method uses the transport of intensity equation for the phase retrieval of the pure phase objects, termed transport-of-intensity CGI (TI-CGI). In the TI-CGI, the phase distribution is retrieved from a single defocused image obtained by a modulated optical setup of the CGI, achieving the fast and robust imaging compared with the conventional phase shifting method. Therefore the TI-CGI may be more suitable for the biomedical imaging than the phase shifting method. The TI-CGI is demonstrated by an optical experiment under the low SNR condition generated by the neutral density filters with 1% and 0.1% transmittance. The experimental results conform the effectiveness of the TI-CGI.

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

Yusuke Saita, Takanori Nomura

Proceedings of SPIE - The International Society for Optical Engineering ( SPIE ) 10815 2018

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.

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

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.

Correlation-Based Multiplexing of Complex Amplitude Data Pages in a Holographic Storage System Using Digital Holographic Techniques (vol 9, 375, 2017)

Teruyoshi Nobukawa, Takanori Nomura （Part： Last author )

POLYMERS ( MDPI AG ) 9 ( 10 ) 2017.10 [Refereed]

Object plane detection and phase-amplitude imaging based on transport of intensity equation

Koshi Komuro, Takanori Nomura （Part： Last author )

OPTICAL REVIEW ( OPTICAL SOC JAPAN ) 24 ( 5 ) 626 - 633 2017.10 [Refereed]

By using transport of intensity equation (TIE), phase distribution of an object is retrieved from through-focus intensity images. This technique allows simple and robust phase imaging compared with an interferometric approach. However, it is hard to measure phase distribution when a dynamic object moves in the direction of an optical axis. To clear this problem, autofocusing TIE which is based on local statistics is proposed. The proposed technique achieves the detection of the object plane and the retrieval of a focused object phase distribution simultaneously. In this approach, an object plane is determined by the focusing techniques based on local statistics such as variance, gradient, and Laplacian of amplitude distribution, after phase distribution in an image sensor plane is retrieved by the TIE. The performance of these three statistics is evaluated in numerical and optical experiments, and a suitable focus value is determined for precise phase imaging.

Refractive index tomography based on optical coherence tomography and tomographic reconstruction algorithm

Takahiro Kitazawa, Takanori Nomura （Part： Last author )

JAPANESE JOURNAL OF APPLIED PHYSICS ( IOP PUBLISHING LTD ) 56 ( 9 ) 2017.09 [Refereed]

Refractive index (RI) tomography based on not quantitative phase imaging (QPI) but optical coherence tomography (OCT) is proposed. In conventional RI tomography, the phase unwrapping process deteriorates measurement accuracy owing to the unwrapping error. To eliminate the unwrapping process, the introduction of OCT is proposed, because OCT directly provides optical thickness. The proposed method can improve measurement accuracy owing to the removal of the phase unwrapping error. The feasibility of the method is confirmed by numerical simulations and optical experiments. These results show that the proposed method can reduce measurement errors even when an object shows phase changes much larger than a wavelength. (C) 2017 The Japan Society of Applied Physics

Orthogonal polarization encoding for reduction of interpixel cross talk in holographic data storage

Teruyoshi Nobukawa, Daisuke Barada, Takanori Nomura, Takashi Fukuda

OPTICS EXPRESS ( OPTICAL SOC AMER ) 25 ( 19 ) 22425 - 22439 2017.09 [Refereed]

Interpixel cross talk decreases the quality of a reconstructed signal in holographic data storage and imposes a limitation on its storage capacity. To reduce the interpixel cross talk, an orthogonal polarization encoding method is proposed. In the proposed method, the polarization state of each pixel is set to be orthogonal with that of surrounding pixels. This prevents the interference between nearest- neighboring pixels and significantly reduces the gross of the interpixel cross talk. The quality of the data page obtained with the proposed method is numerically and experimentally evaluated. Those results suggest that the proposed method can improve the quality of a reconstructed signal. (C) 2017 Optical Society of America

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

Teruyoshi Nobukawa, Takanori Nomura （Part： Last author )

POLYMERS ( MDPI AG ) 9 ( 8 ) 2017.08 [Refereed]

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 （Part： Lead author,　Corresponding author )

APPLIED OPTICS ( OPTICAL SOC AMER ) 56 ( 24 ) 6851 - 6854 2017.08 [Refereed]

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 （Part： Last author )

OPTICAL REVIEW ( OPTICAL SOC JAPAN ) 24 ( 3 ) 351 - 360 2017.06 [Refereed]

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 2017.05 [Refereed]

© 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 （Part： Last author )

APPLIED OPTICS ( OPTICAL SOC AMER ) 56 ( 13 ) F31 - F36 2017.05 [Refereed]

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 （Part： Last author )

OPTICS EXPRESS ( OPTICAL SOC AMER ) 25 ( 2 ) 1326 - 1338 2017.01 [Refereed]

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

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

Coaxial polarization holographic data recording on a polarization-sensitive medium

Teruyoshi Nobukawa, Takashi Fukuda, Daisuke Barada, Takanori Nomura （Part： Last author )

OPTICS LETTERS ( OPTICAL SOC AMER ) 41 ( 21 ) 4919 - 4922 2016.11 [Refereed]

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 （Part： Last author )

OPTICS EXPRESS ( OPTICAL SOC AMER ) 24 ( 18 ) 21001 - 21011 2016.09 [Refereed]

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 （Part： Last author )

JOURNAL OF DISPLAY TECHNOLOGY ( IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC ) 12 ( 8 ) 815 - 821 2016.08 [Refereed]

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 ) 2016.08 [Refereed]

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 2016.07 [Refereed]

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 （Part： Last author )

APPLIED OPTICS ( OPTICAL SOC AMER ) 55 ( 19 ) 5180 - 5186 2016.07 [Refereed]

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 2016.04 [Refereed]

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 2016.04 [Refereed]

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 2015.12 [Refereed]

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 ) 2015.12 [Refereed]

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 2015.10 [Refereed]

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 2015.10 [Refereed]

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.

Digital holographic three-dimensional Mueller matrix imaging

Toshitaka Kobata, Takanori Nomura

APPLIED OPTICS ( OPTICAL SOC AMER ) 54 ( 17 ) 5591 - 5596 2015.06 [Refereed]

A digital holographic Mueller matrix imaging method is proposed. A Mueller matrix is obtained from Stokes vectors that are calculated from the complex amplitude of the two orthogonal polarized lights. The complex amplitude is obtained by digital holography. In the proposed method, three-dimensional Mueller matrix imaging is achieved by 12 recordings. Optical experimental results confirm the feasibility of the proposed method by measuring the Mueller matrices of four linear polarizers, a quarter-wave plate, and two linear polarizers placed at different positions. (C) 2015 Optical Society of America

Multiplexed recording with uncorrelated computer-generated reference patterns in coaxial holographic data storage

Teruyoshi Nobukawa, Yotaro Wani, Takanori Nomura

OPTICS LETTERS ( OPTICAL SOC AMER ) 40 ( 10 ) 2161 - 2164 2015.05 [Refereed]

A computer-generated reference pattern (CGRP) allows improvement in light efficiency and the quality of reconstructed data in coaxial holographic data storage. In this Letter, a multiplexed recording method with uncorrelated CGRPs is proposed. With this method, crosstalk from adjacent holograms is suppressed without shifting a medium. To confirm the feasibility of the proposed method experimentally, shift selectivity is investigated, and then multiplexed recording is performed. Experimental results show that the proposed method enables high-density recording compared with conventional shift multiplexing. In addition, a theoretical analysis implies that at least 100 uncorrelated CGRPs can be designed and used for multiplexed recording. (C) 2015 Optical Society of America

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

OPTICA ( OPTICAL SOC AMER ) 2 ( 5 ) 411 - 415 2015.05 [Refereed]

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. (C) 2015 Optical Society of America

Recording spatially incoherent Fourier hologram using dual channel rotational shearing interferometer

Kaho Watanabe, Takanori Nomura

APPLIED OPTICS ( OPTICAL SOC AMER ) 54 ( 1 ) A18 - A22 2015.01 [Refereed]

The method to record an incoherent Fourier hologram is proposed. The interference patterns in the dual channel rotational shearing interferometer are obtained as the figure of the cosine and the sine transformation in the vertical and the horizontal polarization, respectively. The proposed optical system is simple without spatial light modulators or mechanical phase shifting devices. The experiment, in which the letter "A" displayed on a liquid crystal display with a blue LED backlight was used as an object, confirms the proposed method to obtain an incoherent Fourier hologram. (C) 2014 Optical Society of America

Reconstruction of incoherent Fresnel-like hologram by a rotational shearing interferometer

Kaho Watanabe, Takanori Nomura

INTERNATIONAL CONFERENCE ON PHOTONICS SOLUTIONS 2015 ( SPIE-INT SOC OPTICAL ENGINEERING ) 9659 2015 [Refereed]

The systems to record incoherent holograms using a rotational shearing interferometer is demonstrated. The systems can record incoherent holograms by self-interference of the two coherent object points created by the beam splitter from one object point. In general, the rotational shearing interferometer cannot reproduce any depth information. The proposed rotational shearing interferometer has the advantage of obtaining depth information by the reconstruction owing to lenses for the shear which is parallel to the optical axis. A preliminary experiments were performed. The object images at some reconstruction distances were reconstructed numerically. The experimental results confirm the proposed system.

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 [Refereed]

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.

Image quality improvement of digital holography by use of various rectangle apertures

Takanori Nomura, Takahiko Fukuoka, Yutaka Mori

OPTICS AND PHOTONICS FOR INFORMATION PROCESSING IX ( SPIE-INT SOC OPTICAL ENGINEERING ) 9598 2015 [Refereed]

Digital holography is a useful technique for recording the fully complex field of a wavefront. However, the quality of a reconstructed image of a digital hologram is not good, because it is suffering from speckles. To improve the image quality, a speckle reduction method in digital holography using various rectangular apertures is proposed. Different-sized rectangular apertures are applied for the hologram. Furthermore, the position of the aperture is arbitrary. Owing to the various size and position, the generated speckles have the various sizes and patterns. By averaging the speckle, the speckle noise can be reduced. Some reconstructed images based on the experimental results are shown to confirm the proposed method. For quantitative evaluation, the speckle contrast is also shown.

Single-exposure generalized phase-shifting digital holography

Takanori Nomura, Masatoshi Imbe

2015 14TH WORKSHOP ON INFORMATION OPTICS (WIO) ( IEEE ) 2015 [Refereed]

As one of the wave-splitting phase-shifting digital holography, single-exposure generalized phase-shifting digital holography has been proposed. In the digital holography, the phase-shift quantity, which corresponds to the difference between the phase quantities of the reference wave on the adjacent pixels, is not restricted but generalized. Owing to the generalized phase-shifting, a random-phase wave as the reference wave can be used. The proposed phase-shifting digital holography enables us to record a fully-complex field of a dynamic phenomena without dc and conjugate terms using a commercially available optical devices. Constraints on the reference wave and the object wave suitable for the phase-shifting digital holography are introduced. Experimental results are presented to confirm the constraints.

Numerical evaluation of multilayer holographic data storage with a varifocal lens generated with a spatial light modulator

Teruyoshi Nobukawa, Takanori Nomura

OPTICAL DATA STORAGE 2015 ( SPIE-INT SOC OPTICAL ENGINEERING ) 9587 2015 [Refereed]

A multilayer recording using a varifocal lens generated with a phase-only spatial light modulator (SLM) is proposed. A phase-only SLM is used for not only improving interference efficiency between signal and reference beams but also shifting a focus plane along an optical axis. A focus plane can be shifted by adding a spherical phase to a phase modulation pattern displayed on a phase-only SLM. A focal shift with adding a spherical phase was numerically confirmed. In addition, shift selectivity and recording performance of the proposed multilayer recording method were numerically evaluated in coaxial holographic data storage.

Recording a Phase Data Page in Super-Resolution Holographic Data Storage for High Light Efficiency

Teruyoshi Nobukawa, Takanori Nomura

2015 14TH WORKSHOP ON INFORMATION OPTICS (WIO) ( IEEE ) 2015 [Refereed]

Super-resolution holographic data storage allows us to record and retrieve a data page with a smaller aperture than a Nyquist aperture. This system has a potential to realize a high-density recording compared with a conventional holographic storage system. Recording a phase data page in super-resolution holographic data storage to improve light efficiency is proposed. The phase data page is designed for the super-resolution holographic data storage to suppress the zero-order beam of a signal beam in a Fourier plane. The numerical experiments show the feasibility of the proposed method.

Incoherent holography to obtain depth information by a rotational shearing interferometer

Kaho Watanabe, Takanori Nomura

OPTICS AND PHOTONICS FOR INFORMATION PROCESSING IX ( SPIE-INT SOC OPTICAL ENGINEERING ) 9598 2015 [Refereed]

The system to record incoherent holograms using a rotational shearing interferometer is proposed. It enables us to record a hologram without coherent illumination such as a laser. The systems can record an incoherent hologram by self-interference. A rotational shearing interferometer to record incoherent cosine hologram is described. Furthermore, a rotational shearing interferometer with lenses to record incoherent hologram is described. It has the advantage of obtaining depth information by the reconstruction owing to lenses for the shear which is parallel to the optical axis. The preliminary experiments were performed. An LED and a liquid crystal display with an LED backlight were used as incoherent objects. The incoherent holograms were recorded. The object images were reconstructed numerically. The experimental results confirm the proposed incoherent holography using a rotational shearing interferometer.

Recording Spatially Incoherent Hologram Using Rotational Shearing Interferometer with a Lens for the Parallel Shear

Kaho Watanabe, Takanori Nomura

2015 14TH WORKSHOP ON INFORMATION OPTICS (WIO) ( IEEE ) 2015 [Refereed]

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 [Refereed]

Speckle reduction in holographic projection by random pixel separation with time multiplexing

Yutaka Mori, Takahiko Fukuoka, Takanori Nomura

APPLIED OPTICS ( OPTICAL SOC AMER ) 53 ( 35 ) 8182 - 8188 2014.12 [Refereed]

A speckle-reduction method with random locations of sparse object points is proposed for image quality improvement based on a time-multiplexing approach in holographic reconstruction. The object points of a reconstructed image are divided into groups of sparse object points. Pixel separation of the periodic location, in general, is used for the sparse object points. However, an unwanted periodic fringe pattern is caused, and it dominantly degrades the reconstructed image quality. The proposed random pixel separation enables the reconstructed image quality to improve more effectively. The numerical simulation and the optical experiment are presented to confirm the performance of the proposed method. (C) 2014 Optical Society of America

Single-shot three-dimensional shape measurement by low-coherent optical path difference digital holography

Yuji Tanaka, Yutaka Mori, Takanori Nomura

APPLIED OPTICS ( OPTICAL SOC AMER ) 53 ( 27 ) G19 - G24 2014.09 [Refereed]

A single-shot three-dimensional (3D) shape measurement by low-coherent optical path difference digital holography with small energy consumption is proposed. The use of a superluminescent diode makes it possible. Weighting of the single hologram and numerical reconstruction give the 3D shape of an object. Experimental results using a simple object (the surface of a button cell battery) are given. By comparison with experimental results using a vertical scanning method, the proposed method is confirmed. The effects of a shift interval of the hologram and a zero-order component on a measurement result are also discussed. (C) 2014 Optical Society of America

Holographic data storage by use of computer generated hologram

Takanori Nomura, Teruyoshi Nobukawa

Optics InfoBase Conference Papers ( OSA - The Optical Society ) 2014.07

Arbitrary pattern in an arbitrary domain can be realized by computer generated hologram (CGH). If CGH is applied to the optical data storage, the complexity of the optical system can be eased. For example, a single spatial light modulator (SLM) can be used to express a fully-complex filed of a lightwave. Holographic data storage with a single amplitude SLM by use of CGH is presented. A signal beam and a reference beam are generated by a computer generated hologram (CGH). Owing to the characteristics of the CGH, the incident angle of a reference beam can be changed. This means that angular multiplexing is available.

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

Yusuke Saita, Takanori Nomura

APPLIED OPTICS ( OPTICAL SOC AMER ) 53 ( 19 ) 4136 - 4140 2014.07 [Refereed]

A design method of an input phase mask for holographic memory is proposed. In the method, a modification of a design procedure and another restraint condition are applied to our conventional design method. The light use efficiency and the quality of a reconstructed image are improved. The performance of an input phase mask designed by the method is confirmed by numerical simulations. Finally, a suitable design condition of an input phase mask is determined from simulation results. (C) 2014 Optical Society of America

Design of high-resolution and multilevel reference pattern for improvement of both light utilization efficiency and signal-to-noise ratio in coaxial holographic data storage

Teruyoshi Nobukawa, Takanori Nomura

APPLIED OPTICS ( OPTICAL SOC AMER ) 53 ( 17 ) 3773 - 3781 2014.06 [Refereed]

A high-resolution and multilevel designed reference pattern (DRP) is presented for improvement of both light utilization efficiency and the signal-to-noise ratio (SNR) of reconstructed images in coaxial holographic data storage. With a DRP, the desired Fourier power spectrum of a reference beam is obtained. Numerical and experimental results show that the DRP increases the SNR compared with that of a random phase mask (RPM). Moreover, the light utilization efficiency of the DRP is higher than that of a high-resolution RPM. In addition, the effect of the phase level and the pixel pitch of DRPs on the SNR and the light utilization efficiency are investigated. (C) 2014 Optical Society of America

Selective calculation for the improvement of reconstructed images in single-exposure generalized phase-shifting digital holography

Masatoshi Imbe, Takanori Nomura

OPTICAL ENGINEERING ( SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS ) 53 ( 4 ) 2014.04 [Refereed]

Single-exposure generalized phase-shifting digital holography enables one to remove the zerothorder and conjugate terms from the single hologram. For the phase-shifting, a random-complex-amplitude encoded wave is used as the reference wave. This encoded wave can be made by a commercially available element. Selective calculation is proposed for the improvement of reconstructed images in single-exposure generalized phase-shifting digital holography. Three calculations are used as a function of the complex amplitude quantities of the reference wave on the each pixel of the image sensor. The selective calculation improves the quality of the reconstructed image compared with applying only one of the three calculations to the hologram. The derivation of the three calculations and the reason why the number of calculations is three are presented. A parameter is defined and used to select the appropriate calculation from the three calculations. Relationships between the proposed method and the previous method for the improvement of the reconstructed images in single-exposure generalized phase-shifting digital holography are discussed. Two kinds of experimental results are given to confirm the effectiveness of the proposed method. One shows the dependence on the speckle size of the reference wave. The other shows the feasibility to dynamic phenomena. (C) 2014 Society of Photo-Optical nstrumentation Engineers (SPIE)

Simultaneous measurement of refractive index and thickness distributions using low-coherence digital holography and vertical scanning

Kaho Watanabe, Masashi Ohshima, Takanori Nomura

JOURNAL OF OPTICS ( IOP PUBLISHING LTD ) 16 ( 4 ) 2014.04 [Refereed]

The simultaneous measurement method of a refractive index distribution and a thickness distribution using low-coherence digital holography with a vertical scanning is proposed. The proposed method consists of a combination of digital holography and low-coherence interferometry. The introduction of a datum plane enables the measurement of both a refractive index distribution and a thickness distribution. By the optical experiment, the potential of the proposed method is confirmed.

Complex amplitude-modulated data page recording in coaxial holographic data storage with phase-shifting digital holography

Teruyoshi Nobukawa, Takanori Nomura

Optics InfoBase Conference Papers ( Optical Society of American (OSA) ) 2014

Complex amplitude-modulated data page recording in coaxial holographic data storage with phase-shifting digital holography

Teruyoshi Nobukawa, Takanori Nomura

Optics InfoBase Conference Papers ( Optical Society of American (OSA) ) 2014

Complex amplitude-modulated data page recording in coaxial holographic data storage with phase-shifting digital holography

Teruyoshi Nobukawa, Takanori Nomura

Optics InfoBase Conference Papers ( Optical Society of American (OSA) ) 2014

Complex amplitude-modulated data page recording in coaxial holographic data storage with phase-shifting digital holography

Teruyoshi Nobukawa, Takanori Nomura

Optics InfoBase Conference Papers ( Optical Society of American (OSA) ) 2014

Complex amplitude-modulated data page recording in coaxial holographic data storage with phase-shifting digital holography

Teruyoshi Nobukawa, Takanori Nomura

Optics InfoBase Conference Papers ( Optical Society of American (OSA) ) 2014

Shortening method for optical reconstruction distance in digital holographic display with phase hologram

Mori, Yutaka, Nomura, Takanori

OPTICAL ENGINEERING ( SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS ) 52 ( 12 ) 2013.12 [Refereed]

We present a method to solve a distance issue. In digital holography, the reconstruction distance is different from the original one because of the difference of the pixel size between an imaging device and a display device. In general, the distance is larger because the pixel size of the display is larger than that of the imaging device. This makes it hard to recognize perception of the stereoscopic effect when holographic reconstructed images are used for the stereopsis system. Typically, a numerical propagation method and a spherical phase addition are used to shorten the distance. However, each method is not shortened enough. To clear the criterion, the limitation of each method is verified. By combining two methods, the reconstruction distance is shortened from 4440 to 547 mm. In addition, it is successfully shown that the proposed combining method is useful for the stereopsis by visual perception evaluation. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)

Coaxial Holographic Memory with Designed Reference Pattern on the Basis of Nyquist Aperture for High Density Recording

Teruyoshi Nobukawa, Takanori Nomura

JAPANESE JOURNAL OF APPLIED PHYSICS ( IOP PUBLISHING LTD ) 52 ( 9 ) 2013.09 [Refereed]

We propose the designed reference pattern on the basis of the Nyquist aperture for a coaxial holographic memory and investigate its recording performance by numerical simulations. By using the designed reference pattern, the Fourier power spectrum of a reference beam spreads uniformly within the Nyquist aperture, thereby an interference efficiency, a signal-to-noise ratio (SNR) and a symbol error rate (SER) are improved relative to conventional method with a random binary phase mask. Moreover, in the case of applying the 1.25 times aperture than the Nyquist size, the proposed method can record data pages with higher SNR and lower SER than that of conventional method with 2 times aperture than the Nyquist size. Numerical results imply that our proposed method can record data pages at a smaller area of recording media than that of conventional method. (c) 2013 The Japan Society of Applied Physics

Study of reference waves in single-exposure generalized phase-shifting digital holography

Masatoshi Imbe, Takanori Nomura

APPLIED OPTICS ( OPTICAL SOC AMER ) 52 ( 18 ) 4097 - 4102 2013.06 [Refereed]

The appropriate reference wave in single-exposure phase-shifting digital holography using a random-complex-amplitude encoded reference wave is experimentally investigated. Although the reference wave is generalized, the quality of reconstructed images depends on it. Furthermore, when the reference wave satisfies a certain condition, reconstructed images cannot be obtained in this method. After the certain condition is presented, the appropriate condition is studied using a speckle property. Experimental results are given to investigate the relations between the quality of reconstructed images and the sizes of speckles of the reference waves. The results prove that the appropriate reference wave exists in this method. (C) 2013 Optical Society of America

Synthesis method from low-coherence digital holograms for improvement of image quality in holographic display

Mori, Yutaka, Nomura, Takanori

APPLIED OPTICS ( OPTICAL SOC AMER ) 52 ( 16 ) 3838 - 3844 2013.06 [Refereed]

In holographic displays, it is undesirable to observe the speckle noises with the reconstructed images. A method for improvement of reconstructed image quality by synthesizing low-coherence digital holograms is proposed. It is possible to obtain speckleless reconstruction of holograms due to low-coherence digital holography. An image sensor records low-coherence digital holograms, and the holograms are synthesized by computational calculation. Two approaches, the threshold-processing and the picking-a-peak methods, are proposed in order to reduce random noise of low-coherence digital holograms. The reconstructed image quality by the proposed methods is compared with the case of high-coherence digital holography. Quantitative evaluation is given to confirm the proposed methods. In addition, the visual evaluation by 15 people is also shown. (C) 2013 Optical Society of America

Single-exposure phase-shifting digital holography using a random-complex-amplitude encoded reference wave

Masatoshi Imbe, Takanori Nomura

APPLIED OPTICS ( OPTICAL SOC AMER ) 52 ( 1 ) A161 - A166 2013.01 [Refereed]

The improved single-exposure phase-shifting digital holography using a random-phase reference wave is proposed. The algorithm for obtaining a complex amplitude of an object wave is improved. In the proposed algorithm, the reference wave is treated as not a random-phase but a random-complex amplitude. Therefore, the algorithm uses proper amplitude information of the reference wave. Both numerical simulations and experimental results are given to confirm the effectiveness of the proposed algorithm. (C) 2012 Optical Society of America

Digital holographic tomography using a light back propagation method and its application for refractive index measurement

Nomura, Takanori, Kitazawa, Takahiro

OPTICS AND PHOTONICS FOR INFORMATION PROCESSING VII ( SPIE-INT SOC OPTICAL ENGINEERING ) 8855 2013 [Refereed]

A lensless digital holographic tomography using not a filtered back projection method but a light back propagation method is proposed. In the proposed method, the phase distribution on the detector is used for a light propagation. On the contrary, in the conventional method, the phase information is used for a back projection. Owing to the propagation, the deflection from a true optical path is reduced in the proposed method. For the measurement of a specimen with a huge refraction angle, it is shown that our proposed method improves on measurement accuracy compared with a conventional filtered back projection method. Numerical simulations are given to confirm the feasibility of the proposed method.

Refractive Index & Physical Thickness Distributions Measurement and Consideration of Dependence of Measurement Accuracy on Scanning Interval Using Low-Coherence Digital Holography

Kaho Watanabe, Takanori Nomura

2013 IEEE/SICE INTERNATIONAL SYMPOSIUM ON SYSTEM INTEGRATION (SII) ( IEEE ) 586 - 591 2013 [Refereed]

The measurement method of a refractive index distribution and a physical thickness distribution using digital holography with a low-coherent light source is proposed. The introduction of a datum plane enables the simultaneous measurement of a refractive index and a physical thickness distributions. By the optical experiments, the potential of the proposed method is confirmed. For the reduction of measurement time, the relation between stepping intervals of a reference mirror and measurement results are also discussed.

Design of Reference Pattern and Input Phase Mask for Coaxial Holographic Memory

Yusuke Saita, Takanori Nomura, Eiji Nitanai, Takuhisa Numata

JAPANESE JOURNAL OF APPLIED PHYSICS ( JAPAN SOC APPLIED PHYSICS ) 50 ( 9 ) 2011.09 [Refereed]

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. (C) 2011 The Japan Society of Applied Physics

Single-shot phase-shifting digital holography using a conventional camera

Takanori Nomura

2011 ICO International Conference on Information Photonics, IP 2011 2011 [Refereed]

Single-exposure phase-shifting digital holography using a random-phase reference wave

Takanori Nomura, Masatoshi Imbe

OPTICS LETTERS ( OPTICAL SOC AMER ) 35 ( 13 ) 2281 - 2283 2010.07 [Refereed]

We propose a single-exposure phase-shifting digital holography based on a wave-splitting method using a random-phase reference wave. A random-phase reference wave gives random-phase distribution on the digital hologram. Using the amplitude and the phase distributions of the reference wave, the fully complex amplitude of the object wave is obtained. The proposed method requires not devised optical systems but ordinary imaging devices, such as CCD cameras. A preliminary experimental result is given to confirm the proposed method. (C) 2010 Optical Society of America

Dynamic recording of a digital hologram with single exposure by a wave-splitting phase-shifting method

Hiroyuki Suzuki, Takanori Nomura, Eiji Nitanai, Takuhisa Numata

OPTICAL REVIEW ( OPTICAL SOC JAPAN ) 17 ( 3 ) 176 - 180 2010.05 [Refereed]

The wave-splitting phase-shifting digital holography using a pixelated microretarder array is proposed. By using four intensity images recorded by the pixelated microretarder array, Stokes parameters of the incident wave can be calculated. The fully complex amplitude distribution of the object wave can be obtained by using Stokes parameters, if the polarization states of the object and reference waves are linear and orthogonal. Two sets of experimental results are provided to verify the feasibility of the proposed method. One is the result for a movie recording using a CW laser and the other is the result for instant recording using a single pulsed laser.

Profilometry and reflectmetry using low-coherent digital holography

Takanori Nomura, Kohei Yoshino, Takuhisa Numata, Eiji Nitanai

Optics InfoBase Conference Papers ( Optical Society of America (OSA) ) 2010

Improvement of Viewing-Zone Angle and Image Quality of Digital Holograms

Takanori Nomura

2009 INTERNATIONAL WORKSHOP ON INFORMATION OPTICS ( IOP PUBLISHING LTD ) 206 2010 [Refereed]

The method to improve of a viewing-zone angle and an image quality of a digital hologram is presented. A number of digital holograms of a central object are recorded from the position on the circumference. The holograms are used for a hologram synthesis to improve the image quality from whole viewing-zone angle. The synthesis is achieved by a correlation between a hologram and numerically propagated holograms. The large-sized synthesized digital hologram has a wide viewing-zone angle and less speckles. Some experimental results are shown to confirm the proposed method.

Single-Exposure Digital Holography by a Generalized Wave-Splitting Phase-Shifting Method

Takanori Nomura

2010 9TH EURO-AMERICAN WORKSHOP ON INFORMATION OPTICS ( IEEE ) 2010 [Refereed]

A single-exposure generalized phase-shifting digital holography based on a wave-splitting method. A phase-encoded reference wave is used for phase-shifting. Using the known amplitude and phase distributions of the reference wave, the fully complex amplitude of the object wave is obtained. The proposed method requires not devised optical systems but ordinary imaging devices, such as CCD cameras. A preliminary experimental results with a spherical wave and a random phase wave as reference waves are given to confirm the proposed method.

Polarization imaging of a 3D object by use of digital holography and its application

Takanori Nomura, Bahram Javidi

THREE-DIMENSIONAL IMAGING, VISUALIZATION, AND DISPLAY 2010 AND DISPLAY TECHNOLOGIES AND APPLICATIONS FOR DEFENSE, SECURITY, AND AVIONICS IV ( SPIE-INT SOC OPTICAL ENGINEERING ) 7690 2010 [Refereed]

A polarimetric imaging method of a 3D object by use of on-axis phase-shifting digital holography is presented. The polarimetric image results from a combination of two kinds of holographic imaging using orthogonal polarized reference waves. Experimental demonstration of a 3D polarimetric imaging is presented. Pattern recognition by use of polarimetric phase-shifting digital holography is also presented. Using holography, the amplitude and phase difference distributions between two orthogonal polarizations of 3D phase objects are obtained. This information contains both complex amplitude and polarimetric characteristics of the object, and it can be used for improving the discrimination capability of object recognition. Preliminary experimental results are presented to demonstrate the idea.

Optical Techniques for Information Security

Osamu Matoba, Takanori Nomura, Elisabet Perez-Cabre, Maria S. Millan, Bahram Javidi

PROCEEDINGS OF THE IEEE ( IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC ) 97 ( 6 ) 1128 - 1148 2009.06 [Refereed]

This paper presents an overview of the potential of free space optical technology in information security, encryption, and authentication. Optical waveform posses many degrees of freedom such as amplitude, phase, polarization, spectral content, and multiplexing which can be combined in different ways to make the information encoding more secure. This paper reviews optical techniques for encryption and security of two-dimensional and three-dimensional data. Interferometric methods are used to record and retrieve data by either optical or digital holography for security applications. Digital holograms are widely used in recording and processing three dimensional data, and are attractive for securing three dimensional data. Also, we review optical authentication techniques applied to ID tags with visible and near infrared imaging. A variety of images and signatures, including biometrics, random codes, and primary images can be combined in an optical ID tag for security and authentication.

Quasi-cylindrical digital hologram by superposition of digital holograms recorded on concyclic positions

Takanori Nomura, Yusuke Teranishi, Eiji Nitanai, Takuhisa Numata

Optics InfoBase Conference Papers ( Optical Society of America (OSA) ) 2009

Polarimetric imaging of 3-D object by use of wavefront-splitting phase-shifting digital holography

Takanori Nomura, Bahram Javidi

Three-Dimensional Imaging, Visualization, and Display ( Springer US ) 333 - 344 2009 [Refereed]

A polarimetric imaging method of a 3-D object by use of wavefront-splitting phase-shifting digital holography is presented. Phase-shifting digital holography with a phase difference between orthogonal polarizations is used. The use of orthogonal polarizations can make it possible to record two phase-shifted holograms simultaneously if we use pixelated polarimetric optical elements. By combining the holograms with the distributions of a reference wave and an object wave, the complex field of the object wavefront can be obtained. The polarimetric image results from a combination of two kinds of holographic imaging using orthogonal polarized reference waves. An experimental demonstration of a 3-D polarimetric imaging is presented. © 2009 Springer-Verlag New York.

Image quality improvement of digital holography by superposition of reconstructed images obtained by multiple wavelengths

Takanori Nomura, Mitsukiyo Okamura, Eiji Nitanai, Takuhisa Numata

APPLIED OPTICS ( OPTICAL SOC AMER ) 47 ( 19 ) D38 - D43 2008.07 [Refereed]

Wave-splitting phase-shifting digital holography by use of a retarder array

Takanori Nomura, Eiji Nitanai, Takuhisa Numata

2007 IEEE LEOS ANNUAL MEETING CONFERENCE PROCEEDINGS, VOLS 1 AND 2 ( IEEE ) 82 - 83 2007 [Refereed]

The phase-shifting digital holography by use of a micro-retarder array is proposed. The micro-retarder array consists of four kinds of different directions of fast axes. The combination of the micro-retarder array and a polarizer gives us the four intensity distributions corresponding to the direction of the fast axes. From four intensity images,we can calculate Stokes parameters of the incident wave. Furthermore, we can obtain fully-complex amplitude distribution of the object wave by using Stokes parameters, if the both polarization states of the object wave and the reference wave are linear and they are orthogonal. Some experimental results are given to confirm our proposed recording method.

Polarimetric imaging of a three-dimensional object by use of digital holography

Takanori Nomura, Bahram Javidi, Shinji Murata, Eiji Nitanai, Takuhisa Numata

AIP Conference Proceedings 949 107 - 113 2007 [Refereed]

Phase-shifting digital holography with a phase difference between orthogonal polarizations

Takanori Nomura, Shinji Murata, Eiji Nitanai, Takuhisa Numata

APPLIED OPTICS ( OPTICAL SOC AMER ) 45 ( 20 ) 4873 - 4877 2006.07 [Refereed]

One-shot digital holography by use of polarization

Takanori Nomura, Bahram Javidi, Shinji Murata, Eiji Nitanai, Takuhisa Numata

OPTICAL INFORMATION SYSTEMS IV ( SPIE-INT SOC OPTICAL ENGINEERING ) 6311 2006 [Refereed]

Design of an input phase mask of the optical encryption system and its application to certification

Takanori Nomura, Eiji Ninatai, Takuhisa Numata

INFORMATION OPTICS ( AMER INST PHYSICS ) 860 481 - + 2006 [Refereed]

The secure optical memory system based on a double-random phase-encoding optical encryption system is proposed. The quality of decrypted data can be improved by designing an input phase mask to utilize the bandwidth the bandwidth of the optical system effectively. We propose the certification method of the data recorded into the optical memory by using a designed input phase mask as a phase code. Computer simulations confirm the possibility of the proposed certification system.

Speckles removal in digital holography using multiple wavelengths/distances from an object

Takanori Nomura, Mitsukiyo Okamura, Eiji Nitanai, Takuhisa Numata

2006 IEEE LEOS ANNUAL MEETING CONFERENCE PROCEEDINGS, VOLS 1 AND 2 ( IEEE ) 74 - + 2006 [Refereed]

Deformation measurement by phase-shifting digital holography

Y Morimoto, T Nomura, M Fujigaki, S Yoneyama, Takahashi, I

EXPERIMENTAL MECHANICS ( SPRINGER ) 45 ( 1 ) 65 - 70 2005.02 [Refereed]

The out-of-plane displacement of a cantilever is measured by phase-shifting digital holography. From four phase-shifted holograms of a cantilever recorded by a CCD image sensor, a complex amplitude at each pixel of the CCD plane is obtained using the conventional phase-shifting method. The complex amplitude of a cantilever is reconstructed from the complex amplitude of the CCD plane using the Fresnel diffraction integral. The phase difference distribution on the cantilever before and after deformation, i.e., the out-of-plane displacement distribution, is calculated. In order to decrease the effect of speckle noise, a new method using divided holograms is proposed. The theory and experimental results are shown.

Polarization encoding for an optical security system

Takanori Nomura, Bahram Javidi

Advanced Sciences and Technologies for Security Applications ( Springer ) 1 207 - 220 2005

A polarization-encoding system for optical security verification is proposed. The polarization information is bonded to an identification card for security verification. As the polarization state cannot be imaged by an ordinary intensity-sensitive device such as a CCD camera, it can provide an additional degree of freedom in using optics to secure information. The expressions for polarization encoded input images are developed using Jones polarization calculus. A nonlinear joint transform correlator is used to provide an optical validation system. Computer simulations and optical experimental results are shown in support of the proposed method.

Optical image encryption using optimized keys

Takanori Nomura, Bahram Javidi

Advanced Sciences and Technologies for Security Applications ( Springer ) 1 193 - 205 2005

Applications of digital holography for information security

Takanori Nomura, Enrique Tajahuerce, Osamu Matoba, Bahram Javidi

Advanced Sciences and Technologies for Security Applications ( Springer ) 1 241 - 269 2005

Secure optical storage based on a configuration of a joint transform correlator (JTC) using a photorefractive material is presented. A key code designed by an optimized algorithm so that its Fourier transform has a uniform amplitude distribution and a uniformly random phase distribution is introduced. Original two-dimensional data and the key code are placed side-by-side at the input plane. Both of them are stored in a photorefractive material as a joint power spectrum. The retrieval of the original data can be achieved with the same key code. We can record multiple two-dimensional data in the same crystal by angular multiplexing and/or key-code multiplexing.

Deformation Measurement by Phase-shifting Digital Holographic Interferometry

MORIMOTO Yoshiharu, NOMURA Takanori, FUJIGAKI Motoharu, YONEYAMA Satoru, TAKAHASHI Isao

Proceedings of the 1992 Annual Meeting of JSME/MMD ( The Japan Society of Mechanical Engineers ) 2004 571 - 572 2004

Measurement of the out-of-plane displacement of a cantilever is performed by phase-shifting digital holographic interferomety. Phase-shifting method is used for the phase analysis of the hologram recorded on a CCD sensor. The complex amplitude of the reconstructed object is obtained from the complex amplitude of the CCD plane using the Fresnel diffraction algorithm. The difference of the phase distributions before and after deformation, i.e. out-of-plane displacement is calculated. In order to decrease the effect of speckle pattern, the hologram is divided into 16 parts. The phase is obtained from the phase with the maximum amplitude among the complex amplitudes obtained from all the separated holograms. As the result, by eliminating the effect of speckle, a smooth phase difference distribution is obtained.

Optical encryption using an input phase mask designed for the space bandwidth of the optical system

T Nomura, T Fujita, E Nitanai, T Numata, B Javidi

2004 IEEE LEOS ANNUAL MEETING CONFERENCE PROCEEDINGS, VOLS 1 AND 2 ( IEEE ) 344 - 345 2004 [Refereed]

Real-time analysis of isochromatics and isoclinics using the phase-shifting method

S Yoneyama, Y Morimoto, T Nomura, M Fujigaki, R Matsui

EXPERIMENTAL MECHANICS ( SPRINGER ) 43 ( 1 ) 83 - 89 2003.03 [Refereed]

This paper studies a new real-time phase-shifting method for the analysis of isochromatic and isoclinic parameters in photoelasticity. By rotating an analyzer at a constant rate and an output quarter-wave plate at a double rate of the analyzer and recording images by a CCD camera continuously, sequential images which brightness is integrated by sensors in a CCD camera during phase-shifting are obtained. Then, the distributions of the isochromatic and isoclinic parameters are obtained immediately and quantitatively using the proposed phase-shifting algorithm. The proposed method can be applied to high-speed inspection of optical elements or glass products. Also, it is expected that slowly varying time-dependent problems can be analyzed by the proposed method.

Secure optical data storage with random phase key codes by use of a configuration of a joint transform correlator

T Nomura, S Mikan, Y Morimoto, B Javidi

APPLIED OPTICS ( OPTICAL SOC AMER ) 42 ( 8 ) 1508 - 1514 2003.03 [Refereed]

A secure optical storage based on a configuration of a joint transform correlator by use of a photorefractive material is presented. A key code designed through the use of an optimized algorithm so that its Fourier transform has a uniform amplitude distribution and a uniformly random phase distribution is introduced. Original two-dimensional data and the key code are placed side-by-side at the input plane. Both of them are stored in a photorefractive material as a joint power spectrum. The retrieval of the original data can be achieved with the same key code. We can record multiple two-dimensional data in the same crystal by angular multiplexing and/or key code multiplexing. (C) 2003 Optical Society of America.

Measurement of Deflection Distribution Using Phase-shifting Digital Holography

TAKAHASHI Isao, MORIMOTO Yoshiharu, NOMURA Takanori, YONEYAMA Satoru, FUJIGAKI Motoharu

The proceedings of the JSME annual meeting ( The Japan Society of Mechanical Engineers ) 2002 175 - 176 2002

In this study, the deflection distribution of a cantilever is measured combining the holographic interferometry and phase-shifting digital holography. Holographic interferometry can measure with high accuracy, high sensitivity, and full-field by noncontacting. But the development processing of a film is troublesome by holographic interferometry. Digital holography record on CCD and it reconstructs it with a computer. Therefore, development processing is not needed and it is early reproducible by digital holography. Digital holography has the amplitudes information and phase information in digital information. By the holographic interferometer, the sum of complex amplitude before and after deformation is reconstructed. In this study, the sum of complex amplitude before and after deformation is calculated and reconstructed. Therefore, phase difference computed for digital information and the displacement of a nano-meter order will be able to measure with this method.

219 Real-time Stress and Strain Analysis Using Phase-shifting Photoelastic Coating Method

KATO Ryoji, MATSUI Ryo, MORIMOTO Yoshiharu, NOMURA Takanori, FUJIGAKI Motoharu, YONEYAMA Satoru

Proceedings of the 1992 Annual Meeting of JSME/MMD ( The Japan Society of Mechanical Engineers ) 2001 153 - 154 2001

Frequency domain methods in digital photoelasticity

Y Morimoto, T Nomura, M Fujigaki, R Matsui

SECOND INTERNATIONAL CONFERENCE ON EXPERIMENTAL MECHANICS ( SPIE-INT SOC OPTICAL ENGINEERING ) 4317 117 - 122 2001 [Refereed]

Digital holographic data reconstruction with data compression

T Nomura, A Okazaki, M Kameda, Y Morimoto, B Javidi

ALGORITHMS AND SYSTEMS FOR OPTICAL INFORMATION PROCESSING V ( SPIE-INT SOC OPTICAL ENGINEERING ) 235 - 242 2001 [Refereed]

A digital holographic data reconstruction method with data compression is proposed. We show the number of quantization level of a digital hologram can be reduced. By computer simulations it is confirmed that the method is especially useful for binary images. For gray scale images, we propose a bit plane decomposition method. By this method, we show both high reconstructed image quality and a high compression ratio can be achieved. This method is applicable to both a normal digital hologram and an encrypted digital hologram.

Three-dimensional prediction for lossless coding of digital RGB image

Nobutaka Kuroki, Takanori Nomura, Masashi Kameda, Masahiro Numa, Kotaro Hirano

Memoirs of the Faculty of Engineering, Kobe University 46 69 - 79 1999

A three-dimensional (3-D) linear prediction method for lossless coding of RGB images is proposed. In this method, an RGB signal is divided into three components and piled up as a 3-D signal. In order to remove redundancy among these components, a signal value is predicted from its neighboring points and transformed into an error signal. The prediction value is given by a linear combinaion of the neighboring points. Coefficients for those points are calculated with the least square method. Since the proposed method employs hybrid prediction including 2-D prediction and inter-component prediction, it can remove both the redundancy among adjecent pixels and that among three components at the same time. In this paper, several static or dynamic prediction methods are performed and entropies of the error signals are discussed. On an average for nine test images, the entropy of error signal generated by the proposed method is 7% smaller than that by inter-component prediction.

Hartley transformation for hybrid pattern matching

Takanori Nomura, Kazuyoshi Itoh, Yoshiki Ichioka

Applied Optics 29 ( 29 ) 4345 - 4350 1990.10 [Refereed]

A hybrid pattern matching system using the binary versions of the Hartley and related transformations is presented. These transformations can be obtained by an incoherent optical system described in this paper. *Using them, the spurious correlation signals inherent in an incoherent pattern matching system based on the optical cosine transformation are removed. Experimental demonstrations in an incoherent-optical/digital- electronic hybrid system are also presented. © 1990 Optical Society of America.

Hybrid high speed pattern matching using a binary incoherent hologram generated by a rotational shearing interferometer

T. Nomura, K. Itoh, Y. Ichioka

Applied Optics 28 ( 23 ) 4987 - 4991 1989 [Refereed]

A hybrid image processing system for high speed pattern matching is presented. The system consists of an incoherent optical system and an electronic digital image processor. The optical system makes use of the matched filtering technique based on incoherent holography. The incoherent holograms of an input object and a reference object are binarized. This binarization of holograms has two major advantages: (1) it sharpens the autocorrelation peak, and (2) it makes real time processing possible. We demonstrate the high potential of this method by presenting computer simulations and experiments. © 1989, Optical Society of America.

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