Updated on 2024/07/13

写真a

 
CHOI Samuel
 
Organization
Academic Assembly Institute of Science and Technology JOUHOU DENSHI KOUGAKU KEIRETU Associate Professor
Graduate School of Science and Technology Electrical and Information Engineering Associate Professor
Faculty of Engineering Department of Engineering Associate Professor
Title
Associate Professor
Other name(s)
「崔」は「チェ」,「サイ」または「チョエ」と読みます
External link

Degree

  • Doctor (Engineering) ( 2007.9   Tokyo University of Agriculture and Technology )

Research Areas

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Measurement engineering  / Interferometry; OCT; Frequency comb;

Research History (researchmap)

  • Niigata University   Faculty of Engineering   Associate Professor

    2020.1

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  • Niigata University   Graduate School of Science and Technology Electrical and Information Engineering   Assistant Professor

    2010.4 - 2019.12

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  • Niigata University   Faculty of Engineering Department of Electrical and Electronic Engineering Communication Systems   Assistant Professor

    2009.6

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  • Tokyo University of Agriculture and Technology   Special researcher of the Japan Society for the Promotion of Science

    2007.10 - 2009.5

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  • Niigata University Faculty of Engineering Department of Electrical and Electronic Engineering Communication Systems   Assistant Professor

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Research History

  • Niigata University   Faculty of Engineering Department of Engineering   Assistant Professor

    2017.4

  • Niigata University   Graduate School of Science and Technology Electrical and Information Engineering   Assistant Professor

    2010.4

  • Niigata University   Graduate School of Science and Technology Electrical and Information Engineering   Assistant Professor

    2010.4

  • Niigata University   Abolition organization Communication Systems   Assistant Professor

    2009.6 - 2017.3

Education

  • Tokyo University of Agriculture and Technology   Graduate School, Division of Engineering   電気電子工学

    - 2007.9

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    Country: Japan

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  • Tohoku University   Graduate School, Division of Engineering   電気・通信工学

    - 2004.3

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    Country: Japan

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  • Tohoku University   Faculty of Engineering   Department of Electrical and Communication Engineering

    - 2002.3

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    Country: Japan

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Committee Memberships

  • 日本光学会   学会誌「光学」編集委員  

    2017.4   

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    Committee type:Academic society

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  • 光波センシング技術研究会   常任幹事  

    2015.4   

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    Committee type:Academic society

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Papers

  • Phase refractive index measurement of thick glass plates with a spectrally resolved interferometer

    Kaining Zhang, Osami Sasaki, Songjie Luo, Samuel Choi, Takamasa Suzuki, Jixiong Pu

    Optics Continuum   2 ( 3 )   683 - 683   2023.3

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    Publishing type:Research paper (scientific journal)   Publisher:Optica Publishing Group  

    Measurements of phase refractive indexes of thick objects by using fitting method have been reported in many papers, but the fitting method produces errors in the fitted coefficients of a fitting function. In this paper it is made clear that the thickness of object, for which the phase refractive index can be measured exactly, is limited by the errors. Phase refractive indexes of three kinds of glass plates of 1 mm thickness are measured directly from spectral phases detected with a spectrally resolved interferometer. Instead of using the fitting method, the 2π phase ambiguity contained in a detected spectral phase is determined by using an assumption that an actual refractive index measured in experiment is almost the same as well-known data of the refractive index. The actual refractive indexes measured with an error less than 8 × 10<sup>−5</sup> are slightly different from the well-known data about the slope and the constant value in the distributions.

    DOI: 10.1364/optcon.482318

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  • Measurements of phase distributions of optical vortices based on the sinusoidal phase modulation method

    Haosen Pu, Osami Sasaki, Takamasa Suzuki, Samuel Choi

    Optics Continuum   1 ( 11 )   2287 - 2287   2022.10

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    Publishing type:Research paper (scientific journal)   Publisher:Optica Publishing Group  

    Vortex beams (VBs), a type of light beam with a spiral wavefront, have unique properties, such as the orbit angular momentum (OAM), and diverse applications in optical communications and optical trapping and tweezers. Therefore, accurate measurements and estimations of the phase distribution and topological charge are essential for their applications to ensure VB quality. In this paper, we employed a sinusoidal phase modulation (SPM) interferometry to measure the phase distributions of VBs and the topological charge of VBs were estimated by mean of a method of the process of unwrapped phase. The phase measurement of optical vortices generated by a spatial light modulator (SLM) demonstrated that the SPM interferometry-based technique had a high measurement accuracy with a simplified configuration. The estimation errors of the topological charges for various orders of VBs were within approximately 4%. The fluctuation in the surface of the SLM leading to the flatness of the wavefront was estimated to be 0.06 rad by 10 consecutive measurements

    DOI: 10.1364/optcon.473876

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  • Sparsity-Aware OCT Volumetric Data Restoration Using Optical Synthesis Model Reviewed

    Ruiki Kobayashi, Genki Fujii, Yuta Yoshida, Takeru Ota, Fumiaki Nin, Hiroshi Hibino, Samuel Choi, Shunsuke Ono, Shogo Muramatsu

    IEEE Transactions on Computational Imaging   8   505 - 520   2022.6

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    DOI: 10.1109/TCI.2022.3183396

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    Other Link: https://dblp.uni-trier.de/db/journals/tci/tci8.html#KobayashiFYONHC22

  • External-cavity laser diode using acousto-optic deflector as tunable grating

    Takamasa Suzuki, Yuzuki Kaneko, Samuel Choi, Osami Sasaki

    Optics Letters   47 ( 7 )   1871 - 1871   2022.3

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    Publishing type:Research paper (scientific journal)   Publisher:Optica Publishing Group  

    In this study, a novel, to the best of our knowledge, external-cavity laser diode (ECLD) without a diffraction grating is proposed and demonstrated. In the proposed configuration, an acousto-optic deflector (AOD) acts not only as a deflector but also as a diffraction grating. Thus, the AOD functions as a wavelength-selective device, which helps improve the overall performance of the ECLD. In fact, the proposed configuration realizes a wide range of wavelength scanning with a simple configuration, highly efficient optical feedback, and a steady optical resonator with a constant cavity length. We confirm that the wavelengths scanned with the proposed ECLD agree well with theoretical calculations. The scanning range and maximum frequency response reached approximately 60 nm and 50 kHz, respectively. Moreover, reproducible measurements of the three-dimensional thickness distribution of a thin glass plate indicates that the proposed ECLD can be used for optical coherence tomography imaging systems.

    DOI: 10.1364/ol.454021

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  • Measurement of phase refractive index directly from phase distributions detected with a spectrally resolved interferometer

    Kaining Zhang, Osami Sasaki, Samuel Choi, Songjie Luo, Takamasa Suzuki, Jixiong Pu

    Applied Optics   60 ( 31 )   10009 - 10009   2021.11

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    Publishing type:Research paper (scientific journal)   Publisher:Optica Publishing Group  

    A phase refractive index is measured directly from an unwrapped spectral phase distribution whose ambiguity is determined by fitting the spectral phase distribution with functions based on Cauchy’s equation. The phase refractive index of a quartz glass with 20 µm thickness is measured exactly from three spectral phase distributions detected in two different configurations of a spectrally resolved interferometer. Since there is a high possibility that the ambiguity cannot be correctly determined when there is a large difference between a function of the real refractive index and Cauchy’s equation, characteristics of the fitting are examined.

    DOI: 10.1364/ao.438267

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  • Optical coherence tomography using nonstationary signal processing based on continuous wavelet transform

    Takamasa Suzuki, Jiro Shimazaki, Osami Sasaki, Samuel Choi

    Twelfth International Conference on Information Optics and Photonics   2021.11

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    Publishing type:Research paper (international conference proceedings)   Publisher:SPIE  

    DOI: 10.1117/12.2606987

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  • Author Correction: Computer modeling defines the system driving a constant current crucial for homeostasis in the mammalian cochlea by integrating unique ion transports. International journal

    Fumiaki Nin, Takamasa Yoshida, Shingo Murakami, Genki Ogata, Satoru Uetsuka, Samuel Choi, Katsumi Doi, Seishiro Sawamura, Hidenori Inohara, Shizuo Komune, Yoshihisa Kurachi, Hiroshi Hibino

    NPJ systems biology and applications   7 ( 1 )   39 - 39   2021.10

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  • Large thickness measurement of glass plates with a spectrally resolved interferometer using two positions of a reference surface and a compensation glass

    Kaining Zhang, Samuel Choi, Osami Sasaki, Songjie Luo, Takamasa Suzuki, Jixiong Pu

    Optical Metrology and Inspection for Industrial Applications VIII   2021.10

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    Publishing type:Research paper (international conference proceedings)   Publisher:SPIE  

    DOI: 10.1117/12.2601233

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  • Shape measurement of large thickness glass plates with a white-light scanning interferometer using a compensation glass and a fixed reference surface

    Kaining Zhang, Samuel Choi, Osami Sasaki, Songjie Luo, Takamasa Suzuki, Yongxin Liu, Jixiong Pu

    Engineering Research Express   3 ( 2 )   025044 - 025044   2021.6

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    Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing  

    DOI: 10.1088/2631-8695/ac09d8

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    Other Link: https://iopscience.iop.org/article/10.1088/2631-8695/ac09d8/pdf

  • Large thickness measurement of glass plates with a spectrally resolved interferometer using variable signal positions

    Kaining Zhang, Samuel Choi, Osami Sasaki, Songjie Luo, Takamasa Suzuki, Yongxin Liu, Jixiong Pu

    OSA Continuum   4 ( 6 )   1792 - 1792   2021.5

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    Publishing type:Research paper (scientific journal)   Publisher:Optica Publishing Group  

    In order to measure exactly a large thickness of glass plate with a spectrally resolved interferometer using a spectral analyzer with a low resolution of 0.5 nm and a supercontinuum light source with a large bandwidth of about 300 nm, a new measurement method with a spectrally resolved interferometer is proposed where a variable signal position is generated by moving a reference surface with a piezoelectric stage. It is made clear how to decide the signal position by analyzing amplitude distribution of Fourier transform of the interference signal. Through four-step measurement by using four different optical configurations with four different signal positions the thickness of glass plate can be obtained from a slope of a spectral phase distribution which does not contain the refractive index of glass plate. A small measurement error of 50 nm is achieved in measuring 1 mm thickness of a glass plate.

    DOI: 10.1364/osac.417141

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  • Rapid optical tomographic vibrometry using a swept multi-gigahertz comb Reviewed International journal

    Samuel Choi, Takeru Ota, Fumiaki Nin, Tatsutoshi Shioda, Takamasa Suzuki, Hiroshi Hibino

    Optics Express   29 ( 11 )   16749 - 16749   2021.5

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    Authorship:Lead author, Last author, Corresponding author   Publishing type:Research paper (scientific journal)   Publisher:The Optical Society  

    DOI: 10.1364/oe.425972

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  • Optimization of spectral-domain optical coherence tomography with a supercontinuum source for in vivo motion detection of low reflective outer hair cells in guinea pig cochleae

    Fumiaki Nin, Samuel Choi, Takeru Ota, Zhang Qi, Hiroshi Hibino

    Optical Review   28 ( 2 )   239 - 254   2021.4

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    Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    <title>Abstract</title>Sound evokes sub-nanoscale vibration within the sensory epithelium. The epithelium contains not only immotile cells but also contractile outer hair cells (OHCs) that actively shrink and elongate synchronously with the sound. However, the in vivo motion of OHCs has remained undetermined. The aim of this work is to perform high-resolution and -accuracy vibrometry in live guinea pigs with an SC-introduced spectral-domain optical coherence tomography system (SD-OCT). In this study, to reveal the effective contribution of SC source in the recording of the low reflective materials with the short total acquisition time, we compare the performances of the SC-introduced SD-OCT (SCSD-OCT) to that of the conventional SD-OCT. As inanimate comparison objects, we record a mirror, a piezo actuator, and glass windows. For the measurements in biological materials, we use in/ex vivo guinea pig cochleae. Our study achieved the optimization of a SD-OCT system for high-resolution in vivo vibrometry in the cochlear sensory epithelium, termed the organ of Corti, in mammalian cochlea. By introducing a supercontinuum (SC) light source and reducing the total acquisition time, we improve the axial resolution and overcome the difficulty in recording the low reflective material in the presence of biological noise. The high power of the SC source enables the system to achieve a spatial resolution of 1.72 ± 0.00 μm on a mirror and reducing the total acquisition time contributes to the high spatial accuracy of sub-nanoscale vibrometry. Our findings reveal the vibrations at the apical/basal region of OHCs and the extracellular matrix, basilar membrane.

    DOI: 10.1007/s10043-021-00654-8

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    Other Link: https://link.springer.com/article/10.1007/s10043-021-00654-8/fulltext.html

  • Characterisation of the static offset in the travelling wave in the cochlear basal turn Reviewed

    Takeru Ota, Fumiaki Nin, Samuel Choi, Shogo Muramatsu, Seishiro Sawamura, Genki Ogata, Mitsuo P. Sato, Katsumi Doi, Kentaro Doi, Tetsuro Tsuji, Satoyuki Kawano, Tobias Reichenbach, Hiroshi Hibino

    PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY   2020.4

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    In mammals, audition is triggered by travelling waves that are evoked by acoustic stimuli in the cochlear partition, a structure containing sensory hair cells and a basilar membrane. When the cochlea is stimulated by a pure tone of low frequency, a static offset occurs in the vibration in the apical turn. In the high-frequency region at the cochlear base, multi-tone stimuli induce a quadratic distortion product in the vibrations that suggests the presence of an offset. However, vibrations below 100 Hz, including a static offset, have not been directly measured there. We therefore constructed an interferometer for detecting motion at low frequencies including 0 Hz. We applied the interferometer to record vibrations from the cochlear base of guinea pigs in response to pure tones. When the animals were exposed to sound at an intensity of 70 dB or higher, we recorded a static offset of the sinusoidally vibrating cochlear partition by more than 1 nm towards the scala vestibuli. The offset's magnitude grew monotonically as the stimuli intensified. When stimulus frequency was varied, the response peaked around the best frequency, the frequency that maximised the vibration amplitude at threshold sound pressure. These characteristics are consistent with those found in the low-frequency region and are therefore likely common across the cochlea. The offset diminished markedly when the somatic motility of mechanosensitive outer hair cells, the force-generating machinery that amplifies the sinusoidal vibrations, was pharmacologically blocked. Therefore, the partition offset appears to be linked to the electromotile contraction of outer hair cells.

    DOI: 10.1007/s00424-020-02373-6

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  • An offset component associated with the activity of outer hair cells in the cochlear travelling wave Reviewed

    Takeru Ota, Fumiaki Nin, Samuel Choi, Shogo Muramatsu, Seishiro Sawamura, Genki Ogata, Mitsuo P. Sato, Katsumi Doi, Kentaro Doi, Tetsuro Tsuji, Satoyuki Kawano, Tobias Reichenbach, Hiroshi Hibino

    Pflügers Archiv - European Journal of Physiology   2020

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  • OCT Volumetric Data Restoration with Latent Distribution of Refractive Index Reviewed

    Genki Fujii, Yuta Yoshida, Shogo Muramatsu, Shunsuke Ono, Samuel Choi, Takeru Ota, Fumiaki Nin, Hiroshi Hibino

    Proc. of 2019 IEEE International Conference on Image Processing (ICIP)   764 - 768   2019.9

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:IEEE  

    DOI: 10.1109/ICIP.2019.8803737

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    Other Link: https://dblp.uni-trier.de/db/conf/icip/icip2019.html#FujiiYMOCONH19

  • In vivo tomographic visualization of intracochlear vibration using a supercontinuum multifrequency-swept optical coherence microscope Reviewed

    Samuel Choi, Fumiaki Nin, Takeru Ota, Kouhei Sato, Shogo Muramatsu, Hiroshi Hibino

    Biomed. Opt. Express   10 ( 7 )   3317 - 3342   2019.6

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    DOI: 10.1364/BOE.10.003317

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  • Intracochlear vibration measurement using supercontinuum multifrequency-swept optical coherence microscope

    Samuel Choi, Fumiaki Nin, Takeru Ota, Hiroshi Hibino

    Optical Design and Fabrication 2019   2019.6

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  • In-vivo tomographic visualization of intracochlear vibration using supercontinuum multifrequency-swept optical coherence microscope Invited

    Samuel Choi, Fumiaki Nin, Takeru Ota, Hiroshi Hibino

    The 8th Advanced Lasers and Photon Source, OPTICS & PHOTONICS International Congress 2019   2019.4

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  • Signal correction by detection of scanning position in a white-light interferometer for exact surface profile measurement Reviewed

    Songjie Luo, Takamasa Suzuki, Osami Sasaki, Samuel Choi, Ziyang Chen, Jixiong Pu

    Appl. Opt.   58 ( 13 )   3544 - 3558   2019.4

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    DOI: 10.1364/AO.58.003548

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  • Detection of an atypical motion in cochlear sensory epithelium. Oral presentation: “Symposium 8: Biophysical mechanisms underlying nano-vibrations of the sensory epithelium in hearing organs”

    Ota T, Nin F, Choi S, Hibino H

    9th Federation of the Asian and Oceanian Physiological Societies Congress in conjunction with The 96th Annual Meeting of the Physiological Society of Japan   2019.3

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  • 聴覚の特徴に資する内耳感覚上皮帯のナノ振動の同定 解剖学会-生理学会 連携シンポジウム:「内耳蝸牛・聴覚伝導路に置ける音信号伝達・処理メカニズムの形態学的・生理学的基盤」

    太田 岳, 任 書晃, 崔 森悦, 日比野 浩

    第124回日本解剖学会総会全国学術集会   2019.3

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  • 内耳の感覚上皮帯に生じるナノ振動の抽出とその調節機構の検討

    太田 岳, 任 書晃, 崔 森悦, 日比野 浩

    第92回日本薬理学会年会   2019.3

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  • 先端的イメージング振動計測装置による内耳感覚上皮帯ナノ振動の平面分布

    崔 森悦, 任 書晃, 太田 岳, 日比野 浩

    第92回日本薬理学会年会   2019.3

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  • 改良型イメージング振動計測装置による内耳感覚上皮帯ナノ振動の深度分布

    任 書晃, 太田 岳, 崔 森悦, 日比野 浩

    第92回日本薬理学会年会   2019.3

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  • 聴覚の特徴に資する内耳感覚上皮帯のナノ振動の同定 Reviewed

    太田 岳, 任 書晃, 崔 森悦, 日比野 浩

    第124回日本解剖学会総会全国学術集会、解剖学会-生理学会 連携シンポジウム   2019.3

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  • Analysis of nanoscale vibrations in the inner ear by advanced vibrometries

    Hibino H, Ota T, Choi S, Nin F

    Symposium 79: Mechanomedicine” in 9th Federation of the Asian and Oceanian Physiological Societies Congress in conjunction with The 96th Annual Meeting of the Physiological Society of Japan   2019.3

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  • An imaging system for 3D detection of nano-vibrations in sensory epithelium of the inner ear Reviewed

    Nin F, Choi S, Ota T, Hibino H

    9th FAOPS Federation of the Asian and Oceanian Physiological Societies Congress   2019.3

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  • 内耳の感覚上皮ナノ振動の3次元計測を志向した光干渉顕微鏡の創製

    任 書晃, 崔 森悦, 太田 岳, 日比野 浩

    第65回中部日本生理学会   2019.2

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  • 感覚上皮帯の非典型な動きの同定と分析

    太田 岳, 任 書晃, 崔 森悦, 日比野 浩

    第65回中部日本生理学会   2018.11

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  • 内耳の感覚上皮ナノ振動の3次元計測を志向した新規光干渉顕微鏡の創製

    任 書晃, 崔 森悦, 太田 岳, 日比野 浩

    第28回日本耳科学会総会・学術講演会   2018.10

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  • 改良型レーザ干渉計による内耳蝸牛の感覚上皮帯ナノ振動測定

    太田 岳, 崔 森悦, 任 書晃, 日比野 浩

    第28回日本耳科学会総会・学術講演会   2018.10

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  • 改良型振動計による内耳ナノ振動の測定と解析 シンポジウム「分子から個体のメカノバイオ:多様な物理刺激とその応答」

    日比野 浩, 太田 岳, 崔 森悦, 任 書晃

    第56回日本生物物理学会年会   2018.9

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  • 階層的スパース正則化とハード制約を利用したOCTボリュームデータ復元の実データ検証

    藤井 元暉, 村松 正吾, 崔 森悦, 小野 峻佑, 太田 岳, 任 書晃, 日比野 浩

    電子情報通信学会信号処理研究会   2018.8

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  • 内耳の感覚上皮ナノ振動の3次元計測を志向した新規光干渉顕微鏡の創製

    崔 森悦, 任 書晃, 太田 岳, 日比野 浩

    第57回日本生体医工学会大会   2018.6

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  • 内耳のナノ振動計測を標的とした改良型レーザー干渉法の創出 口頭発表:第57回日本生体医工学会大会

    太田 岳, 崔 森悦, 任 書晃, 日比野 浩

    第57回日本生体医工学会大会   2018.6

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  • 階層的スパース正則化とハード制約を利用したOCTボリュームデータ復元の検討

    村松 正吾, 長 小野 峻佑, 太田 岳, 任 書晃, 日比野 浩

    電子情報通信学会信号処理研究会   2018.5

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  • OCT VOLUMETRIC DATA RESTORATION VIA PRIMAL-DUAL PLUG-AND-PLAY METHOD Reviewed

    Muramatsu S, Choi S, Ono S, Ota T, Nin F, Hibino H

    IEEE International Conference on Acoustics, Speech and Signal Processing   2018.4

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  • Exact surface profile measurement without subtracting dispersion phase through Fourier transform in a white-light scanning interferometer Reviewed

    Songjie Luo, Osami Sasaki, Ziyang Chen, Samuel Choi, Jixiong Pu

    Applied Optics   57 ( 4 )   894 - 899   2018.2

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:OSA - The Optical Society  

    A new signal processing is proposed in which the dispersion phase is not subtracted from the detected spectral phase distribution. The linear and bias components in the spectral phase distribution are used to calculate the complex-valued interference signal (CVIS). The simulations verify that the dispersion phase generates an inclination in the measured surface profile along one direction in which the magnitude of the dispersion phase changes linearly. The simulations also show that the position of zero phase nearest the position of amplitude maximum in the CVIS almost does not change due to the bias component, although the random phase noise contained in the interference signal changes the slope of the linear component. Measured surface profiles show that the new signal processing achieves highly accurate measurement by the CVIS.

    DOI: 10.1364/AO.57.000894

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  • Hearing Loss Controlled by Optogenetic Stimulation of Nonexcitable Nonglial Cells in the Cochlea of the Inner Ear Reviewed

    Mitsuo P. Sato, Taiga Higuchi, Fumiaki Nin, Genki Ogata, Seishiro Sawamura, Takamasa Yoshida, Takeru Ota, Karin Hori, Shizuo Komune, Satoru Uetsuka, Samuel Choi, Masatsugu Masuda, Takahisa Watabe, Sho Kanzaki, Kaoru Ogawa, Hidenori Inohara, Shuichi Sakamoto, Hirohide Takebayashi, Katsumi Doi, Kenji F. Tanaka, Hiroshi Hibino

    FRONTIERS IN MOLECULAR NEUROSCIENCE   10   300   2017.9

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    Light-gated ion channels and transporters have been applied to a broad array of excitable cells including neurons, cardiac myocytes, skeletal muscle cells and pancreatic b -cells in an organism to clarify their physiological and pathological roles. Nonetheless, among nonexcitable cells, only glial cells have been studied in vivo by this approach. Here, by optogenetic stimulation of a different nonexcitable cell type in the cochlea of the inner ear, we induce and control hearing loss. To our knowledge, deafness animal models using optogenetics have not yet been established. Analysis of transgenic mice expressing channelrhodopsin-2 (ChR2) induced by an oligodendrocyte-specific promoter identified this channel in nonglial cells-melanocytes-of an epithelial-like tissue in the cochlea. The membrane potential of these cells underlies a highly positive potential in a K C -rich extracellular solution, endolymph; this electrical property is essential for hearing. Illumination of the cochlea to activate ChR2 and depolarize the melanocytes significantly impaired hearing within a few minutes, accompanied by a reduction in the endolymphatic potential. After cessation of the illumination, the hearing thresholds and potential returned to baseline during several minutes. These responses were replicable multiple times. ChR2 was also expressed in cochlear glial cells surrounding the neuronal components, but slight neural activation caused by the optical stimulation was unlikely to be involved in the hearing impairment. The acuteonset, reversible and repeatable phenotype, which is inaccessible to conventional gene-targeting and pharmacological approaches, seems to at least partially resemble the symptom in a population of patients with sensorineural hearing loss. Taken together, this mouse line may not only broaden applications of optogenetics but also contribute to the progress of translational research on deafness.

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  • 3-D surface profile measurement using spectral interferometry based on continuous wavelet transform Reviewed

    Takuma Serizawa, Takamasa Suzuki, Samuel Choi, Osami Sasaki

    OPTICS COMMUNICATIONS   396   216 - 220   2017.8

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    This study proposes a signal analysis technique that uses continuous wavelet transform for signal processing in a spectral domain optical coherence tomography system. Our method enables us to calculate the optical path difference simply by taking advantage of the fact that the product of the phase and wavelength becomes constant. Experimental results obtained using a pair of gauge blocks with a thickness difference of 40 mu m confirm that the repetitive measurement accuracy was 65.1 nm. A demonstration of the three-dimensional surface profile measurement indicates that the rms measurement error is 0.17 mu m.

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  • Multifrequency-swept optical coherence microscopy for highspeed full-field tomographic vibrometry in biological tissues Reviewed

    Samuel Choi, Keita Sato, Takeru Ota, Fumiaki Nin, Shogo Muramatsu, Hiroshi Hibino

    BIOMEDICAL OPTICS EXPRESS   8 ( 2 )   608 - 621   2017.2

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    Because conventional laser Doppler vibrometry or Doppler optical coherence tomography require mechanical scanning probes that cannot simultaneously measure the wide-range dynamics of bio-tissues, a multifrequency-swept optical coherence microscopy with wide-field heterodyne detection technique was developed. A 1024 x 1024 x 2000 voxel volume was acquired with an axial resolution of similar to 1.8 mu m and an acquisition speed of 2 s. Vibration measurements at 10 kHz were performed over a wide field of view. Wide-field tomographic vibration measurements of a mouse tympanic membrane are demonstrated to illustrate the applicability of this method to live animals.(C) 2017 Optical Society of America

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  • Computer modeling defines the system driving a constant current crucial for homeostasis in the mammalian cochlea by integrating unique ion transports. Reviewed International journal

    Nin F, Yoshida T, Murakami S, Ogata G, Uetsuka S, Choi S, Doi K, Sawamura S, Inohara H, Komune S, Kurachi Y, Hibino H

    NPJ systems biology and applications   3   24 - 24   2017

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    The cochlear lateral wall-an epithelial-like tissue comprising inner and outer layers-maintains +80 mV in endolymph. This endocochlear potential supports hearing and represents the sum of all membrane potentials across apical and basolateral surfaces of both layers. The apical surfaces are governed by K+ equilibrium potentials. Underlying extracellular and intracellular [K+] is likely controlled by the "circulation current," which crosses the two layers and unidirectionally flows throughout the cochlea. This idea was conceptually reinforced by our computational model integrating ion channels and transporters; however, contribution of the outer layer's basolateral surface remains unclear. Recent experiments showed that this basolateral surface transports K+ using Na+, K+-ATPases and an unusual characteristic of greater permeability to Na+ than to other ions. To determine whether and how these machineries are involved in the circulation current, we used an in silico approach. In our updated model, the outer layer's basolateral surface was provided with only Na+, K+-ATPases, Na+ conductance, and leak conductance. Under normal conditions, the circulation current was assumed to consist of K+ and be driven predominantly by Na+, K+-ATPases. The model replicated the experimentally measured electrochemical properties in all compartments of the lateral wall, and endocochlear potential, under normal conditions and during blocking of Na+, K+-ATPases. Therefore, the circulation current across the outer layer's basolateral surface depends primarily on the three ion transport mechanisms. During the blockage, the reduced circulation current partially consisted of transiently evoked Na+ flow via the two conductances. This work defines the comprehensive system driving the circulation current.

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  • Vibration distribution measurement using phase-shifting interferometry and down-sampling technique Reviewed

    Takamasa Suzuki, Ryo Umeki, Samuel Choi, Osami Sasaki

    Optics InfoBase Conference Papers   2017   2017

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    A technique for vibration distribution measurement using a combination of phaseshifting interferometry and the down-sampling technique is proposed and demonstrated. Our system is capable of high-speed vibration measurements and does not require expensive highspeed cameras.

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  • The unique ion permeability profile of cochlear fibrocytes and its contribution to establishing their positive resting membrane potential Reviewed

    Takamasa Yoshida, Fumiaki Nin, Shingo Murakami, Genki Ogata, Satoru Uetsuka, Samuel Choi, Takashi Nakagawa, Hidenori Inohara, Shizuo Komune, Yoshihisa Kurachi, Hiroshi Hibino

    PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY   468 ( 9 )   1609 - 1619   2016.9

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    Eukaryotic cells exhibit negative resting membrane potential (RMP) owing to the high K+ permeability of the plasma membrane and the asymmetric [K+] between the extracellular and intracellular compartments. However, cochlear fibrocytes, which comprise the basolateral surface of a multi-layer epithelial-like tissue, exhibit a RMP of +5 to +12 mV in vivo. This positive RMP is critical for the formation of an endocochlear potential (EP) of +80 mV in a K+-rich extracellular fluid, endolymph. The epithelial-like tissue bathes fibrocytes in a regular extracellular fluid, perilymph, and apically faces the endolymph. The EP, which is essential for hearing, represents the potential difference across the tissue. Using in vivo electrophysiological approaches, we describe a potential mechanism underlying the unusual RMP of guinea pig fibrocytes. The RMP was + 9.0 +/- 3.7 mV when fibrocytes were exposed to an artificial control perilymph (n = 28 cochleae). Perilymphatic perfusion of a solution containing low [Na+] (1 mM) markedly hyperpolarized the RMP to -31.1 +/- 11.2 mV (n = 10; p &lt; 0.0001 versus the control, TukeyKramer test after one-way ANOVA). Accordingly, the EP decreased. Little change in RMP was observed when the cells were treated with a high [K+] of 30 mM (+ 10.4 +/- 2.3 mV; n= 7; p = 0.942 versus the control). During the infusion of a low [Cl-] solution (2.4 mM), the RMP moderately hyperpolarized to -0.9 +/- 3.4 mV (n = 5; p &lt; 0.01 versus the control), although the membranes, if governed by Cl-permeability, should be depolarized. These observations imply that the fibrocyte membranes are more permeable to Na+ than K+ and Cl-, and this unique profile and [Na+] gradient across the membranes contribute to the positive RMP.

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  • WIDE-FIELD HETERODYNE VIBROMETRY FOR MEASUREMENT OF SURFACE VIBRATIONS IN BIOLOGICAL TISSUES Reviewed

    Samuel Choi, Fumiaki Nin, Takamasa Suzuki, Hiroshi Hibino

    2016 INTERNATIONAL CONFERENCE ON OPTICAL MEMS AND NANOPHOTONICS (OMN)   2016

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    Nanovibrations in bio-tissues play pivotal roles in organ functions, but techniques for their measurement have been premature. To address this, a wide-field vibrometry is adopted in a laser microscope. 2D surface vibration distributions of paw tissues of rats could be measured without x-y mechanical beam scanning. The measurable vibration frequency and amplitude were 10 kHz and approximately 240 nm.

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  • Profile measurement of thin films by backpropagation of multiple-wavelength optical fields with two sinusoidal phase-modulating interferometers Reviewed

    Osami Sasaki, Jian Xin, Samuel Choi, Takamasa Suzuki

    OPTICS COMMUNICATIONS   356   578 - 581   2015.12

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    Optical wavelength is scanned linearly with time, and an optical field produced by a thin film on a detection plane is detected with a sinusoidal phase-modulating interferometer. Scanned wavelength is detected with another interferometer. The detected multiple-optical fields are backpropagated along the optical axis in a computer by use of the detected wavelengths. An optical field is reconstructed by summing the backpropagated fields over the multiple wavelengths. The intensity and phase distributions of the reconstructed optical field provide the positions of the thin film surfaces with an accuracy of a few nanometers. (C) 2015 Elsevier B.V. All rights reserved.

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  • Wide-field heterodyne interferometric vibrometry for two-dimensional surface vibration measurement Reviewed

    Samuel Choi, Yuta Maruyama, Takamasa Suzuki, Fumiaki Nin, Hiroshi Hibino, Osami Sasaki

    OPTICS COMMUNICATIONS   356   343 - 349   2015.12

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    Conventional laser Doppler vibrometry and heterodyne interferometry suffer during the simultaneous measurement of the spatial distribution of vibration parameters such as the amplitude, frequency and phase in a wide field of view. Although demand is increasing for methods that can measure vibrations over a wide field of view for a wide range of applications from industrial product inspections to biological measurements, full-field (FF) techniques for high-speed vibration measurements without a spatial scan are untapped. We propose a new method for high-speed FF vibration measurement that can easily be combined with profilometry and tomographic interferometry using a conventional CCD or CMOS camera. In principle, the measurable vibration frequency is unrestricted because the heterodyne signal produced by the modulated interferogram can be controlled to accommodate the CCD frame rate. The validity of the proposed method and the measurement accuracy of the spatial vibration amplitude were evaluated through simulations and experiments. In experiments, the spatial vibration parameters of a mirror vibrated at a frequency of 1 kHz and amplitude of approximately 5-65 nm were successfully measured with a spatial fluctuation of 3%-6.5%. (C) 2015 Elsevier B.V. All rights reserved.

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  • Self-pulsation laser diode interferometer based on spectral-domain optical coherence tomography Invited Reviewed

    T. Suzuki, Y. Ueno, S. Choi

    Technical digest of OIE2015   28 - 29   2015.9

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  • Phase-shifting interferometer with pulse modulation based on a downsampling technique Reviewed

    Takuma Serizawa, Takamasa Suzuki, Samuel Choi

    OPTICAL ENGINEERING   54 ( 8 )   2015.8

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    A phase-shifting interferometer that uses pulse modulation and downsampling is proposed and demonstrated. Pulse modulation is a direct modulating technique that realizes a rapid, large change in the wavelength of a laser diode with a constant optical power. For instance, an interference signal of 10 kHz is observed after the injection of pulse current. However, an expensive high-speed charge coupled device (CCD) camera is required to acquire a high-speed interference signal. If we consider a periodical signal, the same waveform repeats at every period. Therefore, the signal varying with high frequency can be captured by a low-frequency sampling pulse. This signal processing technique, the so-called downsampling, enables us to acquire rapid interference signals with a standard CCD camera. The experimental results using a flat mirror and a concave mirror showed measurement errors of 10 and 28 nm in root mean square (RMS), respectively. The repeatability of the experimental result between the first and the second is 13 nm in RMS. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)

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  • Multifrequency swept common-path en-face OCT for wide-field measurement of interior surface vibrations in thick biological tissues Reviewed

    Samuel Choi, Tomoya Watanabe, Takamasa Suzuki, Fumiaki Nin, Hiroshi Hibino, Osami Sasaki

    OPTICS EXPRESS   23 ( 16 )   21078 - 21089   2015.8

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    Microvibrations that occur in bio-tissues are considered to play pivotal roles in organ function; however techniques for their measurement have remained underdeveloped. To address this issue, in the present study we have developed a novel optical coherence tomography (OCT) method that utilizes multifrequency swept interferometry. The OCT volume data can be acquired by sweeping the multifrequency modes produced by combining a tunable Fabry-Perot filter and an 840 nm super-luminescent diode with a bandwidth of 160 nm. The system employing the wide-field heterodyne method does not require mechanical scanning probes, which are usually incorporated in conventional Doppler OCTs and heterodyne-type interferometers. These arrangements allow obtaining not only 3D tomographic images but also various vibration parameters such as spatial amplitude, phase, and frequency, with high temporal and transverse resolutions over a wide field. Indeed, our OCT achieved the axial resolution of similar to 2.5 mu m when scanning the surface of a glass plate. Moreover, when examining a mechanically resonant multilayered bio-tissue in full-field configuration, we captured 22 nm vibrations of its internal surfaces at 1 kHz by reconstructing temporal phase variations. This so-called "multifrequency swept common-path en-face OCT" can be applied for measuring microdynamics of a variety of biological samples, thus contributing to the progress in life sciences research. (C) 2015 Optical Society of America

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  • Multifrequency swept common-path en-face OCT for wide-field measurement of interior surface vibrations in thick biological tissues Reviewed

    Samuel Choi, Tomoya Watanabe, Takamasa Suzuki, Fumiaki Nin, Hiroshi Hibino, Osami Sasaki

    OPTICS EXPRESS   23 ( 16 )   21078 - 21089   2015.8

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    Microvibrations that occur in bio-tissues are considered to play pivotal roles in organ function; however techniques for their measurement have remained underdeveloped. To address this issue, in the present study we have developed a novel optical coherence tomography (OCT) method that utilizes multifrequency swept interferometry. The OCT volume data can be acquired by sweeping the multifrequency modes produced by combining a tunable Fabry-Perot filter and an 840 nm super-luminescent diode with a bandwidth of 160 nm. The system employing the wide-field heterodyne method does not require mechanical scanning probes, which are usually incorporated in conventional Doppler OCTs and heterodyne-type interferometers. These arrangements allow obtaining not only 3D tomographic images but also various vibration parameters such as spatial amplitude, phase, and frequency, with high temporal and transverse resolutions over a wide field. Indeed, our OCT achieved the axial resolution of similar to 2.5 mu m when scanning the surface of a glass plate. Moreover, when examining a mechanically resonant multilayered bio-tissue in full-field configuration, we captured 22 nm vibrations of its internal surfaces at 1 kHz by reconstructing temporal phase variations. This so-called "multifrequency swept common-path en-face OCT" can be applied for measuring microdynamics of a variety of biological samples, thus contributing to the progress in life sciences research. (C) 2015 Optical Society of America

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  • Optical multi-frequency swept sensing for wide-field vibration measurement of interior surfaces in biological tissue Reviewed

    S. Choi, F. Nin, H. Hibino, T. Suzuki

    Progress in Biomedical Optics and Imaging - Proceedings of SPIE   9792   2015

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    Multifrequency sensing technique adopting the wide field heterodyne detection technique is demonstrated for interior surface vibration measurements in thick biological tissue. These arrangements allow obtaining not only 3D tomographic images but also various vibration parameters such as spatial amplitude, phase, and frequency, with high temporal and transverse resolutions over a wide field. The axial resolution and the accuracy of vibration amplitude measurement were estimated to be 2.5 μm and 3 nm, respectively. This wide-field tomographic sensing method can be applied for measuring microdynamics of a variety of biological samples, thus contributing to the progress in life sciences research.

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  • 3-D OCT Data Denoising with Nonseparable Oversampled Lapped Transform Reviewed

    Shogo Muramatsu, Samuel Choi, Takumi Kawamura

    2015 ASIA-PACIFIC SIGNAL AND INFORMATION PROCESSING ASSOCIATION ANNUAL SUMMIT AND CONFERENCE (APSIPA)   901 - 906   2015

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    This paper proposes 3-D OCT data denoising with nonseparable oversampled lapped transform (NSOLT), and examines the effectiveness through experiments. NSOLT is a lattice-based redundant transform which simultaneously satisfies the symmetric, real-valued and compact-support property. It is possible to apply a dictionary learning technique to the design by preparing examples. NSOLT is capable of having rational redundancy by controlling the number of channels and decimation ratio. In this study, a denoising technique is proposed by combining learned NSOLT dictionary and iterative hard thresholding (IHT), and the performance of the proposed method is evaluated for 3-D OCT data. It is verified through robust median estimator of noise variance and structural similarity index measure (SSIM) that the proposed technique yields effective denoising performance with moderate redundancy.

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  • Two-dimensional thickness measurement using acousto-optically tuned external-cavity laser diode Reviewed

    Takamasa Suzuki, Shingo Abe, Samuel Choi

    OPTICAL SYSTEMS DESIGN 2015: OPTICAL FABRICATION, TESTING, AND METROLOGY V   9628   2015

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    We propose a swept source optical coherence tomography that uses an original external-cavity laser diode and demonstrate measurements of thickness distribution in two dimensions using this equipment. We first conducted high-speed, wide-range wavelength scanning with an external-cavity laser diode that was equipped with a special antireflection-coated laser diode working at 770 nm. Using an acousto-optic deflector enabled a tuning range and rate of 22 nm and 20 kHz, respectively, with no mechanical elements. Next, we applied this source to an optical coherence tomography and measured the two-dimensional distribution of thickness of a thin glass plate.

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  • Optical multi-frequency swept sensing for wide-field vibration measurement of interior surfaces in biological tissue Reviewed

    S. Choi, F. Nin, H. Hibino, T. Suzuki

    BIOPHOTONICS JAPAN 2015   9792   2015

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    Multifrequency sensing technique adopting the wide field heterodyne detection technique is demonstrated for interior surface vibration measurements in thick biological tissue. These arrangements allow obtaining not only 3D tomographic images but also various vibration parameters such as spatial amplitude, phase, and frequency, with high temporal and transverse resolutions over a wide field. The axial resolution and the accuracy of vibration amplitude measurement were estimated to be 2.5 mu m and 3 nm, respectively. This wide-field tomographic sensing method can be applied for measuring microdynamics of a variety of biological samples, thus contributing to the progress in life sciences research.

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  • Three-dimensional step-height measurement using sinusoidal wavelength scanning interferometer with four-step phase-shift method Reviewed

    Samuel Choi, Shouhei Takahashi, Osami Sasaki, Takamasa Suzuki

    OPTICAL ENGINEERING   53 ( 8 )   2014.8

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    A sinusoidal wavelength scanning interferometer with the four-step phase-shift method is demonstrated for a three-dimensional profile measurement. The interference phase-shift signal generated by the sinusoidal wavelength scanning contains information about optical path difference covering a nm-mu m scale structure. The interference phase-shift signal was obtained by the four-step phase-shifting method. The sinusoidal wavelength shifting with a frequency of approximately 180 Hz and tunable range of 5.7 nm was performed by the Littman-Metcalf external resonator-type tunable laser with a center of 772.1 nm. The full-field surface profile measurement was conducted by a charge coupled device image sensor with an accuracy on a nm scale. The surface profiles of gauge blocks with a step height up to about 10 mu m were successfully measured with a surface profile irregularity of 3.8 x 10(-2) mu m. The deviations of two measured surfaces of upper and lower steps were estimated to be 1.6 x 10(-2) mu m and 3.1 x 10(-2) mu m, respectively. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)

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  • Multi-frequency scanning interferometry using variable spatial spectral filter Reviewed

    Samuel Choi, Ryoko Sato, Heiichi Kato, Osami Sasaki, Takamasa Suzuki

    OPTICS COMMUNICATIONS   316   168 - 173   2014.4

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    Recently, a variety of the optical comb-based interferometries has been developed for profilometry and tomography. However the interference amplitude and phase characteristics involving the center frequency and mode spacing of the optical comb have not been sufficiently studied. To investigate these multi-frequency interference characteristics, we proposed a broadband frequency variable quasi-comb generator utilizing 4-f optical system and a spatial spectral filter which can perform unrestricted scanning of the center frequency and mode spacing. By using a sinusoidal phase modulating interferometer with the quasi-comb generator, fundamental proof-of-principle experiments were successfully demonstrated. The interference phase fixation during the symmetrical varying of the mode spacing produced the interference amplitude peak envelope without fringes. On the other hand, it was confirmed that the interference phase was changed linearly without the amplitude change by the center frequency shift of the multi-frequency spectrum. (C) 2013 Elsevier B.V. All rights reserved.

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  • Low-coherence interferomety based on continuous wavelet transform Reviewed

    Takamasa Suzuki, Hiroo Matsui, Samuel Choi, Osami Sasaki

    OPTICS COMMUNICATIONS   311   172 - 176   2014.1

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    The present paper proposes a low-coherence interferometry system based on continuous wavelet transform, which can simultaneously detect the peak position and frequency of a signal. Although the proposed system is analogous to conventional time-domain optical coherence tomography, it realizes accurate wide-range surface profile measurement because the wavelet transform enables accurate evaluation of the position of the reference mirror. The performance of the proposed system was evaluated through step-height measurement. (C) 2013 Elsevier B.V. All rights reserved.

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  • Full-field step profile measurement with sinusoidal wavelength scanning interferometer Reviewed

    Samuel Choi, Osami Sasaki, Takama Suzuki

    DIMENSIONAL OPTICAL METROLOGY AND INSPECTION FOR PRACTICAL APPLICATIONS III   9110   2014

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    A sinusoidal wavelength scanning interferometer is proposed for 3-D profile measurement. The interference phase-shift signal generated by the sinusoidal wavelength scanning contains information of optical path difference (OPD) covering nm-mm scale structure. The interference phase-shift signal was obtained by the four-step phase shifting method. The sinusoidal wavelength shifting bandwidth of 5.7 nm with a frequency of approximately 180 Hz was performed by the Littman-Metcalf external resonator-type tunable laser with a center of 772.1 nm. The full-field step-height surface profile measurement and 3-D surface measurement were conducted by a CCD image sensor with an accuracy of few tens nm. The surface profile of gauge blocks with a step-height of up to 10 mu m was successfully measured.

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  • Low-coherence interferometer using a pulsation laser diode Reviewed

    Takamasa Suzuki, Yusuke Ueno, Samuel Choi, Osami Sasaki

    DIMENSIONAL OPTICAL METROLOGY AND INSPECTION FOR PRACTICAL APPLICATIONS III   9110   2014

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    A self-pulsation laser diode interferometer based on spectral-domain optical coherence tomography is proposed. A visible multimode laser diode allows easy optical alignment and an economical, configurable system. A cylindrical lens and acousto-optic deflector used in our system enable rapid and stable scanning. Experimental results confirm that full-field measurement is possible without mechanical scanning devices.

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  • Two-Wavelength Multi-Gigahertz Frequency Comb-Based Interferometry for Full-Field Profilometry Reviewed

    Samuel Choi, Ken Kashiwagi, Shuto Kojima, Yosuke Kasuya, Takashi Kurokawa

    APPLIED PHYSICS EXPRESS   6 ( 10 )   2013.10

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    The multi-gigahertz frequency comb-based interferometer exhibits only the interference amplitude peak without the phase fringes, which can produce a rapid axial scan for full-field profilometry and tomography. Despite huge technical advantages, there remain problems that the interference intensity undulations occurred depending on the interference phase. To avoid such problems, we propose a compensation technique of the interference signals using two frequency combs with slightly varied center wavelengths. The compensated full-field surface profile measurements of cover glass and onion skin were demonstrated experimentally to verify the advantages of the proposed method. (C) 2013 The Japan Society of Applied Physics

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  • Wide-range wavelength tuning in a VCSEL based on pulsed modulation Invited Reviewed

    T. Suzuki, T. Ishizuka, S. Choi, O. Sasaki

    Technical digest of OIE13   23 - 24   2013.9

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  • Wavelength-scanning interferometers for shape measurement of thin films by backpropagation of multiple-wavelength optical fields Reviewed

    O. Sasaki, X. Jian, C. Samuel, T. Suzuki

    Proc. CLEO-PR 2013   TuF4-4   2013.7

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  • Profile measurement of glass sheet using multiple wavelength backpropagation interferometry Reviewed

    Samuel Choi, Kohei Otsuki, Osami Sasaki, Takamasa Suzuki

    APPLIED OPTICS   52 ( 16 )   3726 - 3731   2013.6

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    Multiple-wavelength backpropagation interferometry based on a spectral interferometer is proposed for measuring thin glass sheets with nanometer accuracy. The multiwavelength backpropagation method introduced to the spectral interferometer eliminates time-encoded wavelength sweeping and mechanical scanning, which enables high-speed profile measurements. The applicability of the proposed method is experimentally demonstrated through cross-sectional profile and vibrating surface displacement measurements of a glass sheet. (C) 2013 Optical Society of America

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  • Profile measurement of glass sheet using multiple wavelength backpropagation interferometry Reviewed

    Samuel Choi, Kohei Otsuki, Osami Sasaki, Takamasa Suzuki

    APPLIED OPTICS   52 ( 16 )   3726 - 3731   2013.6

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    Multiple-wavelength backpropagation interferometry based on a spectral interferometer is proposed for measuring thin glass sheets with nanometer accuracy. The multiwavelength backpropagation method introduced to the spectral interferometer eliminates time-encoded wavelength sweeping and mechanical scanning, which enables high-speed profile measurements. The applicability of the proposed method is experimentally demonstrated through cross-sectional profile and vibrating surface displacement measurements of a glass sheet. (C) 2013 Optical Society of America

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  • OCT based on multi-frequency sweeping Fizeau interferometer with phase modulating method Reviewed

    S. Choi, T. Watanabe, O. Sasaki, T. Suzuki

    DIMENSIONAL OPTICAL METROLOGY AND INSPECTION FOR PRACTICAL APPLICATIONS II   8839   2013

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    The Multi-frequency sweeping Fizeau-type interferometer (MFS-FI) for optical coherence tomography (OCT) is demonstrated. The multi-frequency sweeping by a variable Fabry-Perot filter permits detection of high-order low-coherence interferometric signals in the Fizeau interferometer. The sinusoidal phase modulation technique was utilized to detect accurate interference amplitude and phase distributions of back scattered light from surfaces of a sample. OCT measurements by the MFS-FI were conducted for vibrating glass plates with a frequency of 1 kHz, and cellular tissues fixed with formalin and embedded in paraffin. The tomographic 3-dimensional volume and cross-sectional surface displacements were detected with an accuracy of nano-meters.

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  • Time-Shared Multiple Optical Traps Using a Pulsed Laser Diode Reviewed

    Takamasa Suzuki, Hiroyuki Takayama, Osami Sasaki, Samuel Choi

    2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS PACIFIC RIM (CLEO-PR)   WJ3-4   2013

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    Multiple traps using a combination of a piezoelectric bimorph-type actuator and a pulsed laser diode are demonstrated. Three polystyrene beads were simultaneously trapped using a laser diode driven by a pulsed current.

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  • Coaxial phase-shifting laser diode interferometer based on pulse modulation Reviewed

    Takamasa Suzuki, Takuma Serizawa, Osami Sasaki, Samuel Choi

    DIMENSIONAL OPTICAL METROLOGY AND INSPECTION FOR PRACTICAL APPLICATIONS II   8839   2013

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    A pulse-modulated phase-shifting interferometer that employs two coaxial interferometers and an undersampling technique is proposed and demonstrated. The former improves the robustness of the optical system, while the latter makes it economical. Several measurements on flat and concave mirrors confirmed a measurement accuracy of similar to 18 nm.

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  • Surface profile measurement of a diffraction grating by a laser beam scanning interferometer using sinusoidal phase modulation Reviewed

    Osami Sasaki, Takuya Kubota, Samuel Choi, Takamasa Suzuki

    DIMENSIONAL OPTICAL METROLOGY AND INSPECTION FOR PRACTICAL APPLICATIONS II   8839   2013

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    It is difficult in interferometric metrology to maintain high spatial resolution over a large measurement region. In this paper this characteristic is achieved by scanning two focused laser beams of about 6 microns diameter over an object surface and a reference mirror surface, respectively, with a rotating mirror, a lens, and a polarization beam splitter. An electric-optic phase modulator generates the phase difference of a sinusoidal waveform of 10 MHz between the two focused beams to calculate the phase of the interference signal. Because the beam focused onto a diffraction grating of 50 microns period is not diffracted strongly, a surface profile of the grating can be exactly measured by this interferometer over the measurement region of 16 mm with the spatial resolution of 2 microns.

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  • Multi-frequency Light Source Using Spatial Light Modulator for Profilometry Reviewed

    Samuel Choi, Shunsuke Takatsuka, Osami Sasaki, Takamasa Suzuki

    2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS PACIFIC RIM (CLEO-PR)   2013

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    A multi-frequency light source with a spatial light modulator that generated a broadband spectrum with variable interval and center frequency was demonstrated. It can carry out the arbitrary multi-frequency scan for interferometric profile measurement.

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  • Step-height measurement with a low coherence interferometer using continuous wavelet transform Reviewed

    Zhang Jian, Takamasa Suzuki, Samuel Choi, Osami Sasaki

    2013 INTERNATIONAL CONFERENCE ON OPTICAL INSTRUMENTS AND TECHNOLOGY: OPTOELECTRONIC MEASUREMENT TECHNOLOGY AND SYSTEMS   9046   2013

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    With the development of electronic technology in recent years, electronic components become increasingly miniaturized. At the same time a more accurate measurement method becomes indispensable. In the current measurement of nano-level, the Michelson interferometer with the laser diode is widely used, the method can measure the object accurately without touching the object. However it can't measure the step height that is larger than a half-wavelength. In this study, we improve the conventional Michelson interferometer by using a super luminecent diode and continuous wavelet transform, which can detect the time that maximizes the amplitude of the interference signal. We can accurately measure the surface-position of the object with this time. The method used in this experiment measured the step height of 20 microns.

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  • Multi-gigahertz frequency comb-based interferometry using frequency-variable supercontinuum generated by optical pulse synthesizer Reviewed

    Samuel Choi, Ken Kasiwagi, Yosuke Kasuya, Shuto Kojima, Tatsutoshi Shioda, Takashi Kurokawa

    OPTICS EXPRESS   20 ( 25 )   27820 - 27829   2012.12

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    A multi-gigahertz frequency comb (MGFC)-based interferometer was developed for profilometry and tomography using a frequency variable supercontinuum (SC). The comparatively flattened and broadened SC light source with variable multi-gigahertz interval frequency was developed using an optical pulse synthesizer and highly nonlinear dispersion flattened fiber. The generated SC provided a stable interference output with a full width half maximum of 19 mu m during interval frequency sweeping of over 400 MHz. We experimentally confirmed that the interference signal exhibited an envelope-only waveform without fringes, which enabled the drastic reduction of the sampling points resulting in high speed measurement. A full-field 3-D image with 320 x 256 x 300 pixels was acquired with a measurement time of only 10 seconds. It was demonstrated that the MGFC-based interferometer with the novel SC light source has the potential for application in a high speed full-field 3-D metrology. (C)2012 Optical Society of America

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  • Phase-shifting laser diode interferometer using pulse modulation Reviewed

    Takamasa Suzuki, Tsubasa Adachi, Osami Sasaki, Samuel Choi

    APPLIED OPTICS   51 ( 18 )   4109 - 4112   2012.6

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    A phase-shifting laser diode interferometer that uses direct pulse modulation is proposed and demonstrated. We found that a laser beam with a wide range of wavelength variation at constant optical power could be generated when a pulsed current was injected into the laser diode. We constructed a highly accurate interferometer by using a pair of interferometers. Several experiments, such as observations of temporal interference signals and spatial interferograms, measurement of a concave mirror, and duplicate measurements, confirmed the characteristics of pulse modulation and demonstrated the effectiveness of our technique. (C) 2012 Optical Society of America

    DOI: 10.1364/AO.51.004109

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  • Phase-shifting laser diode interferometer using pulse modulation Reviewed

    Takamasa Suzuki, Tsubasa Adachi, Osami Sasaki, Samuel Choi

    APPLIED OPTICS   51 ( 18 )   4109 - 4112   2012.6

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    A phase-shifting laser diode interferometer that uses direct pulse modulation is proposed and demonstrated. We found that a laser beam with a wide range of wavelength variation at constant optical power could be generated when a pulsed current was injected into the laser diode. We constructed a highly accurate interferometer by using a pair of interferometers. Several experiments, such as observations of temporal interference signals and spatial interferograms, measurement of a concave mirror, and duplicate measurements, confirmed the characteristics of pulse modulation and demonstrated the effectiveness of our technique. (C) 2012 Optical Society of America

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  • Utilization of frequency information in a linear wavenumber-scanning interferometer for profile measurement of a thin film Reviewed

    Osami Sasaki, Satoshi Hirakubo, Samuel Choi, Takamasa Suzuki

    APPLIED OPTICS   51 ( 13 )   2429 - 2435   2012.5

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    The positions of the front and rear surfaces of a silicon dioxide film with 4 mu m thickness is measured with a novel and simple method in which both amplitude and phase of a sinusoidal wave signal corresponding to one optical path difference of a reflecting surface is utilized in a linear wavenumber-scanning interferometer. For this utilization, the scanning width and the position of the reference mirror are adjusted exactly to distinguish the two sinusoidal waves corresponding to the two surfaces of the film. The scanning width of the wavenumber and wavelength of the light source are 0.326x10(-3) nm(-1) and 140 nm, respectively. (C) 2012 Optical Society of America

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  • Utilization of frequency information in a linear wavenumber-scanning interferometer for profile measurement of a thin film Reviewed

    Osami Sasaki, Satoshi Hirakubo, Samuel Choi, Takamasa Suzuki

    APPLIED OPTICS   51 ( 13 )   2429 - 2435   2012.5

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    The positions of the front and rear surfaces of a silicon dioxide film with 4 mu m thickness is measured with a novel and simple method in which both amplitude and phase of a sinusoidal wave signal corresponding to one optical path difference of a reflecting surface is utilized in a linear wavenumber-scanning interferometer. For this utilization, the scanning width and the position of the reference mirror are adjusted exactly to distinguish the two sinusoidal waves corresponding to the two surfaces of the film. The scanning width of the wavenumber and wavelength of the light source are 0.326x10(-3) nm(-1) and 140 nm, respectively. (C) 2012 Optical Society of America

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  • Profilometry based on comb interval frequency sweeping of two supercontinua with different center wavelengths Reviewed

    Shuto Kojima, Yosuke Kasuya, Ken Kashiwagi, Samuel Choi, Takashi Kurokawa

    Technical Digest - 2012 17th Opto-Electronics and Communications Conference, OECC 2012   855 - 856   2012

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    We propose a new technique for stable interferometric measurement by calculating interferograms from obtained signals using two supercontinua whose center wavelengths are slightly different. We successfully obtained a thickness profile of a glass plate. © 2012 IEEE.

    DOI: 10.1109/OECC.2012.6276664

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  • Multi-frequency sweeping sinusoidal phase modulated Fizeau interferometer for OCT Reviewed

    S. Choi, J. Hukumoto, O. Sasaki, T. Suzuki

    Technical Digest - 2012 17th Opto-Electronics and Communications Conference, OECC 2012   568 - 569   2012

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    A novel Fizeau-type low-coherence interferometer for optical coherence tomography (OCT) is demonstrated. The multi-frequency sweeping by a Fabry-Perot filter (FPF) permits detection of high-order interference signals in the Fizeau interferometer. The sinusoidal phase modulation (SPM) technique was utilized to detect accurate interference amplitude and phase distributions. © 2012 IEEE.

    DOI: 10.1109/OECC.2012.6276575

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  • Sinusoidal wavelength-scanning interferometer for profile measurement of metal surfaces Reviewed

    Osami Sasaki, Takahiro Kurashige, Samuel Choi, Takamasa Suzuki

    INTERFEROMETRY XVI: TECHNIQUES AND ANALYSIS   8493   2012

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    Sinusoidal wavelength-scanning (SWS) interferometry is unique in that a time-varying interference signal contains phase-modulation amplitude Zb due to the SWS besides a conventional phase a. Propagation time and wavefront of the light wave diffusely reflected from a metal surface can be detected from the amplitude Zb and the phase a, respectively. A concave shape with the depth of about a few hundreds microns is measured with an error less than a few microns by using only the amplitude Zb of the detected interference signal.

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  • Multi-frequency sweeping interferometry using spatial optical frequency modulation Reviewed

    Samuel Choi, Heiichi Kato, Osami Sasaki, Takamasa Suzuki

    OPTICAL METROLOGY AND INSPECTION FOR INDUSTRIAL APPLICATIONS II   8563   2012

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    We investigated the interference amplitude and phase characteristics of a multi-frequency sweeping interferometer with sinusoidal phase modulating technique. A novel multi frequency sweeping light source that generated an interval and center frequency variable frequency comb with a bandwidth of 14 nm was demonstrated. The interference phase and amplitude distributions were investigated by observing the zeroth and first order interference signals. In addition, the zeroth and first order interference phase variations caused by center frequency sweeping were measured.

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  • Absolute measurement of optical surface profile with a Fizeau interferometer Reviewed

    Osami Sasaki, Akihiro Watanabe, Samuel Choi, Takamasa Suzuki

    OPTICAL METROLOGY AND INSPECTION FOR INDUSTRIAL APPLICATIONS II   8563   2012

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    An optical surface profile is measured with a laser diode Fizeau interferometer using a method of absolute measurement. Wavefront aberration in the interferometer causes an undesirable phase distribution in the interference signal. To eliminate this phase distribution, the object surface is shifted in two directions orthogonal to each other and the difference wavefront of the surface profile of the object is obtained. An absolute surface profile is estimated by representing the object surface with a polynomial function and by solving the difference equations with least-squares method.

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  • Real-time displacement measurement using VCSEL interferometer Reviewed

    Takamasa Suzuki, Noriaki Yamada, Osami Sasaki, Samuel Choi

    OPTICAL METROLOGY AND INSPECTION FOR INDUSTRIAL APPLICATIONS II   8563   2012

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    A displacement sensor that uses a vertical cavity surface emitting laser (VCSEL), which is superior in terms of remediation of the mode-hop issue and modulation efficiency, is proposed. The interference signal in the sensor is processed with the phase-locked technique. This device allows real-time measurement of displacement. No unstable signals due to mode-hop were observed in the experiments. Displacement measurements recorded with this device indicated that it has an rms measurement accuracy of 0.3 mu m and 50 nm for displacements of 150 mu m and 1.2 mu m, respectively.

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  • Frequency comb generator using spatial frequency optical filter and its interferometeric characteristics Reviewed

    S. Choi, H. Kato, O. Sasaki, T. Suzuki

    Proc. The ninth Japan-Finland Joint Symposium on Optics in Engineering   2011.9

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  • Rapid wavelength scanning based on acousto-optically tuned external-cavity laser diode Reviewed

    Takamasa Suzuki, Ryu-ichi Nagai, Osami Sasaki, Samuel Choi

    OPTICS COMMUNICATIONS   284 ( 19 )   4615 - 4618   2011.9

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    High-speed, wide-range wavelength scanning is demonstrated using a laser diode with an antireflection coating and an external cavity employing an acousto-optic deflector. The narrow spectral width of 0.2 nm observed in the experiment indicates the availability of a highly coherent laser beam. The scanning range of 15 nm under rapid modulation is confirmed in the prototype system. A tuning rate of more than 100 kHz is achieved without any mode hops. To the best of our knowledge, no such high-speed wavelength tuning based on an acousto-optical configuration has been demonstrated thus far. (C) 2011 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.optcom.2011.06.012

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  • Phase-shifting interferometer using a pulsed laser diode Reviewed

    T. Suzuki, T. Adachi, O. Sasaki, S. Choi

    Proc. The ninth Japan-Finland Joint Symposium on Optics in Engineering   2011.9

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  • Enhancement of optical gradient force employed in optical tweezers using a pulsed laser diode Reviewed

    T. Suzuki, T. Maeda, O. Sasaki, S. Choi

    Proc. 2011 OSA Optics & Photonics Congress   OTMD4p   2011.4

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  • Spectral interferometer using sinusoidal phase modulation and back-propagation method Reviewed

    S. Choi, K. Otsuki, O. Sasaki, T. Suzuki

    2011 Int. Quantum Electron. Conf., IQEC 2011 and Conf. Lasers and Electro-Optics, CLEO Pacific Rim 2011 Incorporating the Australasian Conf. Optics, Lasers and Spectroscopy and the Australian Conf.   325 - 326   2011

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    The multi-wavelength back-propagation (MWB) method has been developed for measuring positions of multiple reflecting surfaces longer than the optical wavelength. In this study, we demonstrate one dimensional profile measurement of a glass film by a sinusoidal phase modulating (SPM) spectral interferometer with MWB method. Displacements of front and rare surfaces of the glass film vibrating with 9.7 Hz are exactly measured. The measurement repeatability obtained from 9 repeatedly-measured results is 4.7 nm in a standard deviation. © 2011 IEEE.

    DOI: 10.1109/IQEC-CLEO.2011.6194003

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  • Profile measurement of thin films by linear wavenumber-scanning interferometry Reviewed

    Osami Sasaki, Satoshi Hirakubo, Samuel Choi, Takamasa Suzuki

    DIMENSIONAL OPTICAL METROLOGY AND INSPECTION FOR PRACTICAL APPLICATIONS   8133   2011

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    Conventional methods to measure the positions of the front and rear surfaces of thin films with multiple-wavelength interferometers are reviewed to make it clear how the method proposed here is novel and simple. Characteristics of the linear wavenumber-scanning interferometry used in the proposed method are analyzed in detail to make the measurement accuracy clearly. The positions of the front and rear surfaces of a silicon dioxide film with 4 mu m thickness is measured by utilizing the phases of the sinusoidal waves forms corresponding to each of the optical path differences contained in the interference signal. The experiments and the theoretical analysis show that the measurement error is about 15 nm.

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  • Beam scanning laser interferometer with high spatial resolution over a large field of view Reviewed

    Osami Sasaki, Tsuyoshi Saito, Samuel Choi, Takamasa Suzuki

    2011 INTERNATIONAL CONFERENCE ON OPTICAL INSTRUMENTS AND TECHNOLOGY: OPTOELECTRONIC MEASUREMENT TECHNOLOGY AND SYSTEMS   8201   2011

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    It is difficult in interferometric metrology to maintain high spatial resolution over a large field of view. In this paper this characteristic is achieved by scanning two focused laser beams over an object surface and a reference mirror surface, respectively, with a rotating mirror, a lens, and a polarization beam splitter. An electric-optic phase modulator generates the phase difference of a sinusoidal waveform of 10 MHz between the two focused beams. Sinusoidal phase-modulating interferometry is used to calculate the phase of the interference signal caused by the two focused beams. The scanning speed of the beams is 20 m/s, and the sampling interval of the interference signal is 1/80 microseconds. The spatial resolution is 2.0 microns over the measurement region of 18.8mm. The measurement results show that the measurement error is less than 5nm.

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  • Profilometry using optical comb light source and sinusoidal phase modulation technique in Fizeau-type interferometer Reviewed

    S. Choi, H. Miyatsuka, O. Sasaki, T. Suzuki

    Proc. of Photonics Asia 2010   7855   19   2010.10

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  • Profilometry using Fizeau-interferometer based on optical comb interferometry and sinusoidal phase modulation method Reviewed

    Samuel Choi, Hidetaka Miyatsuka, Osami Sasaki, Takamasa Suzuki

    OPTICAL METROLOGY AND INSPECTION FOR INDUSTRIAL APPLICATIONS   7855   2010

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    A profilometry based on Fizeau interferometer using the optical comb and the sinusoidal phase modulation technique is demonstrated. The optical comb generated with the Fabry-Perot etalon and a SLD is introduced in the Fizeau interferometer. The interval wave number of comb is swept by controlling the resonance length of the Fabry-Perot etalon. The sweeping range is about 500 mu m. The displacement measurement is performed by determination of zero-phase or pi-phase positions. The accuracy estimated from 5 repeated experiments is about 0.2 rad.

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  • Multiple-wavelength interferometers using backpropagation of optical fields for profile measurement of thin glass sheets Reviewed

    Osami Sasaki, Choi Samuel, Takamasa Suzuki

    INTERFEROMETRY XV: TECHNIQUES AND ANALYSIS   7790   2010

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    Multiple-wavelength optical fields at a detecting plane of an interferometer are generated by a computer from the detected interference signals of a thin glass sheet. The generated optical fields are backpropagated towards the glass sheet along the optical axis. An optical field along the optical axis is reconstructed by summing the backpropagated fields over the multiple wavelengths. The amplitude and phase distributions of the reconstructed optical field provide the positions of the two surfaces of the glass sheet where peak values of the amplitude and zero or p values of the phase appear. The accuracy of the position measurement is several nanometers.

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  • Sinusoidal wavelength-scanning common-path interferometer with a beam-scanning system for measurement of film thickness variations Reviewed

    Osami Sasaki, Takafumi Morimatsu, Samuel Choi, Takamasa Suzuki

    OPTICAL METROLOGY AND INSPECTION FOR INDUSTRIAL APPLICATIONS   7855   2010

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    Two light beams reflected from a front and rear surfaces of a glass film of 20 micron thickness interfere with each other in a common path interferometer. Sinusoidal wavelength-scanning light with the scanning amplitude of 5 nm and frequency of 15 KHz is used to generate a sinusoidal phase-modulated interference signal with the modulation amplitude of 2.6 rad. The phase of the interference signal provides the thickness variation of the film, whose measurement accuracy is a few nanometers. Moreover, in order to achieve a high spatial resolution and a wide measurement region a focused beam is scanned on the surface of the film with a rotating mirror.

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  • Profile measurement based on spectral interferometer with multi-wavelength back-propagation methods Reviewed

    Kohei Otsuki, Samuel Choi, Osami Sasaki, Takamasa Suzuki

    OPTICAL METROLOGY AND INSPECTION FOR INDUSTRIAL APPLICATIONS   7855   2010

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    The multi-wavelength back-propagation (MWB) method enables to determine precisely the optical path different (OPD) longer than the optical wavelength from detecting the amplitude and phase of the interference signal for the multiple wavelengths. In this study, we demonstrate a 1-dimensional thickness profile measurement by the MWB and sinusoidal phase modulation (SPM) technique with a spectral interferometer. The OPD for the front and rear reflecting surfaces of a glass film with the thickness of 100 mu m are measured. The thickness profile is successfully measured with repeatability of 2 nm estimated from a standard error between 9 repeatedly-measured profiles.

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  • Highly Precise Optical Pulse Synthesis for Flat Spectrum Supercontinuum Generation with Wide Mode Spacing Reviewed

    Ken Kashiwagi, Hiroyuki Ishizu, Yuichiro Kodama, Samuel Choi, Takashi Kurokawa

    2010 36TH EUROPEAN CONFERENCE AND EXHIBITION ON OPTICAL COMMUNICATION (ECOC), VOLS 1 AND 2   2010

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    We demonstrate highly precise pulse synthesis technique using an optical pulse synthesizer for spectrally flat supercontinuum generation. The technique achieved further 4-dB suppression of background noise of synthesized pulse and 3-dB suppression of supercontinuum spectrum peak at pump pulse wavelength.

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  • Supercontinuum Comb Generation Using Optical Pulse Synthesizer and Highly Nonlinear Dispersion-Shifted Fiber Reviewed

    Samuel Choi, Naoyuki Tamura, Ken Kashiwagi, Tatsutoshi Shioda, Yosuke Tanaka, Takashi Kurokawa

    JAPANESE JOURNAL OF APPLIED PHYSICS   48 ( 9 )   2009.9

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    We propose a novel supercontinuum (SC) generation technology using an optical pulse synthesizer and highly nonlinear dispersion-shifted fiber. The optical pulse synthesizer enables us to reshape seed pulses optimized for broadband SC generation. 25.0 and 12.5GHz SC combs were successfully generated by propagating synthesized seed pulses in the highly nonlinear fiber. We investigated how seed pulse conditions including shape, peak power, repetition rate, and center wavelength affect SC spectral bandwidth. We also evaluated interferometric signal waveforms from a Michelson interferometer using the generated SC comb as the light source. Interferometric peak width improved to 35.5 mu m when peak power reached 7.9 W for the Gaussian pulse-based SC comb. Numerical simulation results almost agreed with experimental results. The difference between SC combs generated from Gaussian and sech(2) pulses was confirmed by the simulations. (C) 2009 The Japan Society of Applied Physics

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  • Profilometry based on optical frequency comb Reviewed

    Samuel Choi, Takashi Kurokawa

    2009 LASERS & ELECTRO-OPTICS & THE PACIFIC RIM CONFERENCE ON LASERS AND ELECTRO-OPTICS, VOLS 1 AND 2   1229 - 1230   2009

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    We present a frequency-comb-based interferometric microscope Broadband optical frequency comb (OFC) was generated using optical pulse synthesizer and non-linear fiber as the light source of interferometer Three-dimensional surface profile was successfully observed with a resolution of 44 mu m and measurement speed of 30 frame/s

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  • Three-dimensional microscopic interferometer by frequency sweep of supercontinuum frequency comb Reviewed

    Samuel Choi, Naoyuld Tamura, Ryo Kobe, Thtsutoshi Shioda, Yosuke Tanaka, Takashi Kurokawa

    2008 CONFERENCE ON LASERS AND ELECTRO-OPTICS & QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE, VOLS 1-9   450 - 451   2008

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    A three-dimensional microscopic interferometer by the interval frequency sweep of the supercontinuum frequency comb generated by an optical pulse synthesizer was demonstrated. The spectral bandwidth was 80 nm. The interferometric peak width was 35 mu m. (c) 2006 Optical Society of America

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  • Frequency-comb-based interference microscope with a line-type image sensor Reviewed

    Samuel Choi, Tatsutoshi Shioda, Yosuke Tanaka, Takashi Kurokawa

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS   46 ( 10A )   6842 - 6847   2007.10

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    We present a frequency-comb-based interferometric microscope using a broadband comb light source and a line-type image sensor for proflometry and optical tomography. A waveguide-type frequency comb generator and wavelength equalizer were introduced to broaden the comb spectrum. In this paper, we demonstrate the surface profilometry of a coin and the observation of a cross-sectional tomography image of transparent glass. The three-dimensional images were captured using a line-type image sensor without any mechanical moving parts with a frequency interval variation of 25 GHz. The dynamic range in the depth direction was about 1.4 mm, and the measurement resolution was 35 pm. The standard deviation of seven thickness measurements was 5 mu m.

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  • Application of faraday rotator reflector and faraday rotator transmitter to profilometry and tomography Reviewed

    Tatsutoshi Shioda, Daisuke Moteki, Samuel Choi, Yosuke Tanaka, Takashi Kurokawa

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS   46 ( 10A )   6848 - 6852   2007.10

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    The polarization compensation of a Faraday rotator reflector was quantitatively measured while applying mechanical stress to an optical fiber. A novel device called a Faraday rotator transmitter was developed to illuminate a sample. It was confirmed that the installation of both a Faraday rotator reflector and a Faraday rotator transmitter in a fiber-optic interferometer greatly improves the accuracy of film thickness measurements compared with measurements obtained using an interferometer that employed polarization-maintaining optical fibers.

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  • Frequency comb based interference microscope with a line-type image sensor Reviewed

    Samuel Choi, Tatsutoshi Shioda, Yosuke Tanaka, Takashi Kurokawa

    2007 PACIFIC RIM CONFERENCE ON LASERS AND ELECTRO-OPTICS, VOLS 1-4   399 - 400   2007

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    We present a frequency comb based interferometry with a broadband comb light source and a line-type image sensor for profilometry and optical tomography. The cross-sectional images were captured by varying the frequency interval of 25 GHz without mechanical shift. The resolution in depth direction was 35 mu m.

    DOI: 10.1109/CLEOPR.2007.4391287

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  • Frequency-comb-based interferometer for profilometry and tomography Reviewed

    S Choi, M Yamamoto, D Moteki, T Shioda, Y Tanaka, T Kurokawa

    OPTICS LETTERS   31 ( 13 )   1976 - 1978   2006.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:OPTICAL SOC AMER  

    A novel interferometry technique using a frequency-comb light source is proposed for surface profilometry and tomography of discontinuous objects. Surface profile measurement is performed by sweeping the comb interval frequency without mechanical scanning. Step heights of 0.5 and 1.0 mm are successfully measured by use of the scheme with 9 mu m accuracy. (c) 2006 Optical Society of America.

    DOI: 10.1364/OL.31.001976

    Web of Science

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  • Interferometer for profilometry and tomography using waveguide-type frequency comb generator Reviewed

    Samuel Choi, Daisuke Moteki, Tatsuya Sugimoto, Yosuke Tanaka, Takashi Kurokawa

    Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, CLEO/QELS 2006   2006

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    Language:English   Publishing type:Research paper (international conference proceedings)  

    A novel profilometry using a waveguide-type frequency comb generator was presented. Thickness measurement of a glass plate was successfully demonstrated by sweeping comb interval frequency without mechanical scanning. © 2006 Optical Society of America.

    DOI: 10.1109/CLEO.2006.4627912

    Scopus

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  • A novel profilometry using frequency comb light source Reviewed

    S Choi, M Yamamoto, D Moteki, T Shioda, Y Tanaka, M Takeda, T Kurokawa

    2005 PACIFIC RIM CONFERENCE ON LASERS AND ELECTRO-OPTICS   1007 - 1009   2005

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:IEEE  

    A novel profilometry using a frequency comb light source is proposed. This method realizes step height measurement without mechanical scanning. We have confirmed the system with high accuracy with this method.

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MISC

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Awards

  • 第3回学長賞

    2016.11   新潟大学   若手教員研究奨励

    崔 森悦

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  • コニカミノルタ画像科学奨励賞(優秀賞)

    2015.3   コニカミノルタ画像科学技術振興財団   生体内3次元振動分布の可視化技術の開発

    崔 森悦

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Research Projects

  • Development of en-face OCT vibromery technology for medical applications

    Grant number:19KK0364

    2022 - 2024

    System name:Grants-in-Aid for Scientific Research

    Research category:Fund for the Promotion of Joint International Research (Fostering Joint International Research (A))

    Awarding organization:Japan Society for the Promotion of Science

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    Grant amount:\15210000 ( Direct Cost: \11700000 、 Indirect Cost:\3510000 )

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  • 周期可変回折格子を用いた高速広帯域波長走査光源の構築とOCTへの展開

    Grant number:21K04922

    2021.4 - 2024.3

    System name:科学研究費助成事業

    Research category:基盤研究(C)

    Awarding organization:日本学術振興会

    鈴木 孝昌, 崔 森悦

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    Grant amount:\4160000 ( Direct Cost: \3200000 、 Indirect Cost:\960000 )

    本研究の目的は、音響光学偏向器(AOD)を単なる光偏向器としてではなく、周期可変な回折格子として捉え、新たな原理の波長走査光源(SS)を構築するとともに、光コヒーレンストモグラフィ(OCT)への展開を図ることにある。
    令和3年度は、研究実施計画に従い、以下の通り研究を進めた。
    外乱の影響を排除しつつ機械的安定度を高めるため、専用の筐体を設計し、これまで使用実績のある840nm帯の無反射コート半導体レーザ(AR-LD)を用いて新提案の波長走査光源(SS)を構築した。ここで音響光学偏向器(AOD)の印過電圧を制御し、波長走査幅を測定したところ、約60nmの波長走査幅が得られた。また、測定された波長は、理論曲線に沿って変化することを確認した。ただし、ゲイン特性から期待される波長走査幅目標値(約80nm)の達成は困難であった。LDの損傷や劣化を考慮し、注入電流を低めに抑えたことが一因と考えられるが、他の要因に関して検証を行っていく必要がある。一方、波長走査周波数(速度)の上限値は、約50kHzであった。圧電素子(PZT)等を用いた機械的な波長走査に比較すると走査周波数は飛躍的に向上することが示された。ここまでの内容が、令和3年度実施計画に示された内容であり、研究は当初の計画通り遂行することができた。特に、AODを周期可変な回折格子とし用い、新たな原理に基づいてSSを構築できた意義は大きく、今後の光計測技術進展への寄与は大きいものと考えられる。
    加えて、令和3年度は、以下に詳述の通りOCTシステムでの動作検証、特許出願、論文発表を行った。

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  • Structured Convolutional Networks for High-dimensional Signal Restoration

    Grant number:19H04135

    2019.4 - 2022.3

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (B)

    Awarding organization:Japan Society for the Promotion of Science

    Muramatsu Shogo

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    Grant amount:\17680000 ( Direct Cost: \13600000 、 Indirect Cost:\4080000 )

    The purpose of this study was to clarify effective structural constraints on generative models of high-dimensional signals in order to improve the efficiency and performance of high-dimensional signal restoration. New structured dictionaries and structured convolutional networks were constructed, and efforts were made to improve the efficiency of complex extension, parallelization, hierarchization, multilayering, learning design, and restoration algorithms. We evaluated the effectiveness of the proposed restoration process on a variety of real data, including volumetric data, complex image data, and high-dimensional time series data.
    As research results, we made 21 presentations at domestic conferences, 16 presentations at international conferences, and published 3 papers in academic journals.

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  • Development of optical tomographic imaging system for in-vivo nano-vibration measurement of whole 3D structure in biological tissue

    Grant number:19H02151

    2019.4 - 2022.3

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (B)

    Awarding organization:Japan Society for the Promotion of Science

    Choi Samuel

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    Grant amount:\17940000 ( Direct Cost: \13800000 、 Indirect Cost:\4140000 )

    In this study, we aimed to develop an optical tomography imaging system oriented to nano-vibration measurement of the entire 3D structure at the biological tissue. First, we proposed the principle of a heterodyne coherence microscope that can measure the vibration distribution along with a three-dimensional tomographic scan, and demonstrated its usefulness through validation experiments. Next, we constructed a system using a DD-MZM comb generator and proposed a method to realize ultra high-speed measurement at a scan rate of 20 MHz, which enables transient measurement of the vibration state as well as depth profile. Furthermore, by applying the same light source to a spatial interference microscope, it was shown that 3D measurements with nano-order precision over a wide depth range of several hundred micrometers to millimeters are possible. The possibility of the proposed methodwas demonstrated.

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  • 先端遺伝子工学を駆使した変動性難聴モデル動物の確立とその応用

    2018.4 - 2022.3

    System name:科学研究費助成事業 基盤研究(A)

    Awarding organization:日本学術振興会

    日比野 浩

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    Grant type:Competitive

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  • 難聴モデル動物の病態解明を志向した内耳ナノ振動の新規計測プラットフォームの構築

    2018.4 - 2021.3

    System name:科学研究費助成事業 基盤研究(B)

    Awarding organization:日本学術振興会

    任 書晃

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    Grant type:Competitive

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  • 超音波駆動波長走査光源とウェーブレット変換処理を用いた実時間フルフィールドOCT

    2016.4 - 2019.3

    System name:科学研究費助成事業 基盤研究(C)

    Awarding organization:日本学術振興会

    鈴木 孝昌

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    Grant type:Competitive

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  • 周波数可変広帯域光コムを用いた生体3次元断層振動撮像装置の開発

    2016.4 - 2019.3

    System name:科研費 基盤研究(B)

    Awarding organization:日本学術振興会

    崔 森悦

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\17940000 ( Direct Cost: \13800000 、 Indirect Cost:\4140000 )

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  • 光コムを用いた超高精細な生体断層振動イメージング装置の開発

    2016.4 - 2017.3

    System name:自然科学研究助成

    Awarding organization:双葉電子記念財団

    崔 森悦

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    Authorship:Principal investigator  Grant type:Competitive

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  • 内耳による音のナノ振動の受容・応答機構の解明と難聴治療への展開

    2015.12 - 2021.3

    System name:革新的先端研究開発支援事業 AMED-CREST 「メカノバイオロジー機構の解明による革新的医療機器及び医療技術の創出」

    Awarding organization:国立研究開発法人日本医療研究開発機構

    日比野 浩

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    Grant type:Competitive

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  • プリンタブルエレクトロニクス用機能性フィルムの高精度断層検査装置の開発

    2015.12 - 2016.12

    System name:マッチングプランナー・プログラム

    Awarding organization:国立研究開発法人 科学技術振興機構

    崔 森悦

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    Authorship:Principal investigator  Grant type:Competitive

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  • 生体内3次元振動分布の可視化技術の開発

    2015 - 2016

    System name:コニカミノルタ画像科学奨励

    Awarding organization:コニカミノルタ科学技術振興財団

    崔 森悦

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    Authorship:Principal investigator  Grant type:Competitive

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  • 生体内3次元振動分布の可視化へ向けた多波長光ホログラフィック・トモグラフィー装置の開発

    2014.12 - 2015.12

    System name:研究成果展開事業(研究成果最適展開支援プログラム(A-STEP))

    Awarding organization:国立研究開発法人 科学技術振興機構

    崔 森悦

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    Authorship:Principal investigator  Grant type:Competitive

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  • 多波長ホログラフィック高精細生体断層撮像装置の開発

    2014.4 - 2016.3

    System name:科研費 若手研究(B)

    Awarding organization:日本学術振興会

    崔 森悦

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\4030000 ( Direct Cost: \3480000 、 Indirect Cost:\550000 )

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  • 光周波数コムを用いた構造物の広視野3次元振動歪み形状検査装置の開発

    2014 - 2016

    System name:研究助成

    Awarding organization:内田エネルギー科学振興財団

    崔 森悦

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    Authorship:Principal investigator  Grant type:Competitive

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  • 表面プラズモン光を用いる干渉断層像センシング

    2012.4 - 2014.3

    System name:科研費 挑戦的萌芽研究

    Awarding organization:日本学術振興会

    佐々木 修己

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    Grant type:Competitive

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  • 空間周波数コム光源を用いた計測システムの開発

    2011.4 - 2014.3

    System name:科研費 若手研究(B)

    Awarding organization:日本学術振興会

    崔 森悦

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\4290000 ( Direct Cost: \3480000 、 Indirect Cost:\810000 )

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  • 光コムと正弦波位相変調法による光コヒーレンス・トモグラフィーの開発

    2010 - 2011

    System name:奨励研究助成

    Awarding organization:中谷電子計測技術振興財団

    崔 森悦

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    Authorship:Principal investigator  Grant type:Competitive

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Teaching Experience

  • 電子情報通信実験II

    2023
    Institution name:新潟大学

  • 光計測特論

    2021
    Institution name:新潟大学

  • 論文輪講I

    2020
    Institution name:新潟大学

  • 卒業研究

    2020
    Institution name:新潟大学

  • 電子情報通信設計製図

    2020
    Institution name:新潟大学

  • 論文輪講II

    2020
    Institution name:新潟大学

  • 卒業研修

    2020
    Institution name:新潟大学

  • 電子情報通信実験IIB

    2020
    -
    2022
    Institution name:新潟大学

  • 電子情報通信実験IIA

    2020
    -
    2022
    Institution name:新潟大学

  • 先端科学技術総論

    2020
    Institution name:新潟大学

  • 電子情報通信実験IIIA

    2020
    Institution name:新潟大学

  • リメディアル演習

    2020
    Institution name:新潟大学

  • 電子情報通信実験IIIB

    2020
    Institution name:新潟大学

  • 工学リテラシー入門(情報電子分野)

    2019
    Institution name:新潟大学

  • 総合技術科学演習

    2019
    Institution name:新潟大学

  • プログラミングBII

    2018
    -
    2022
    Institution name:新潟大学

  • プログラミングBI

    2018
    -
    2022
    Institution name:新潟大学

  • 電子情報通信概論

    2017
    Institution name:新潟大学

  • 電気数理II

    2016
    -
    2022
    Institution name:新潟大学

  • プログラミング演習

    2016
    -
    2017
    Institution name:新潟大学

  • 光コヒ-レンス工学

    2015
    Institution name:新潟大学

  • 光応用工学

    2014
    Institution name:新潟大学

  • 電気電子工学研究発表(外部発表)

    2014
    -
    2015
    Institution name:新潟大学

  • 電気電子工学文献詳読Ⅱ

    2014
    -
    2015
    Institution name:新潟大学

  • 光コヒ-レンス工学

    2013
    Institution name:新潟大学

  • 電気電子工学特定研究Ⅱ

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学セミナーⅡ

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学特定研究Ⅰ

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学研究発表演習(中間発表)

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学セミナーⅠ

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学文献詳読Ⅰ

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学研究発表演習(外部発表)

    2013
    Institution name:新潟大学

  • 電気回路演習I

    2013
    Institution name:新潟大学

  • 電磁気学演習I

    2011
    -
    2015
    Institution name:新潟大学

  • 電磁気学演習II

    2011
    -
    2012
    Institution name:新潟大学

  • エレクトロニクスへの招待

    2010
    -
    2016
    Institution name:新潟大学

  • 工学リテラシー入門(電気電子工学科)

    2010
    -
    2015
    Institution name:新潟大学

  • 連続時間アナログ信号処理

    2010
    -
    2012
    Institution name:新潟大学

  • プログラミング基礎演習

    2010
    Institution name:新潟大学

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