研究者詳細 - 野村　孝徳

論文 - 野村　孝徳

分割表示125 件中 61 - 80 件目／全件表示 >>

Digital holographic three-dimensional Mueller matrix imaging

Toshitaka Kobata, Takanori Nomura

APPLIED OPTICS ( OPTICAL SOC AMER ) 54 ( 17 ) 5591 - 5596 2015年06月 [査読有り]

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年05月 [査読有り]

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年05月 [査読有り]

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年01月 [査読有り]

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年 [査読有り]

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年 [査読有り]

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年 [査読有り]

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年 [査読有り]

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年 [査読有り]

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年 [査読有り]

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年 [査読有り]

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年 [査読有り]

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

Yusuke Saita, Hironobu Shinto, Takanori Nomura

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

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年12月 [査読有り]

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年09月 [査読有り]

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年07月

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年07月 [査読有り]

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年06月 [査読有り]

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年04月 [査読有り]

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年04月 [査読有り]

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.

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