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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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

DOI： 10.1117/12.2606987

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

DOI： 10.1117/12.2601233

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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

Publishing type：Research paper (scientific journal)   Publisher：The Optical Society  

DOI： 10.1364/oe.425972

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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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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1117/1.OE.59.3.034112

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DOI： 10.1088/1361-6501/ab4642

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Near-infrared photoimmunotherapy (NIR-PIT) is a new and promising cancer therapy based on a monoclonal antibody conjugated to a photosensitizer which is activated by near-infrared light irradiation, causing cell death. We investigated NIR-PIT using a small protein mimetic (6-7 kDa), Affibody molecules, instead of a monoclonal antibody for HER2-overexpressing cancer. Because of its small size, the Affibody has rapid clearance, high imaging contrast, and good tumor penetration. Due to the small size of the Affibodies, which can cross the blood-brain barrier, NIR-PIT using Affibodies has the potential to extend the target cancer of NIR-PIT, including brain metastases. In vitro, NIR-PIT using HER2 Affibody-IR700Dye conjugates induced the selective destruction of HER2-overexpressing breast cancer cells without damage to control cells having low level expression of HER2. HER2-overexpressing cancer cells showed necrotic cell death and their viability maintained at low levels, even 5 days after NIR-PIT. In contrast, treatment with high concentration of HER2 Affibody-IR700Dye conjugate alone or irradiation with high dose of NIR light alone was without effect on cell viability. Affibody and IR700Dye are currently used clinically, and therefore, we would expect the current formulation to be safely and quickly transitioned into clinical trials.

DOI： 10.3390/ijms20235835

PubMed

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DOI： 10.1117/1.OE.58.10.104108

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

KAGRA is a second-generation interferometric gravitational-wave detector with 3 km arms constructed at Kamioka, Gifu, Japan. It is now in its final installation phase, which we call bKAGRA (baseline KAGRA), with scientific observations expected to begin in late 2019. One of the advantages of KAGRA is its underground location of at least 200 m below the ground surface, which reduces seismic motion at low frequencies and increases the stability of the detector. Another advantage is that it cools down the sapphire test mass mirrors to cryogenic temperatures to reduce thermal noise. In April-May 2018, we operated a 3 km Michelson interferometer with a cryogenic test mass for 10 d, which was the first time that km-scale interferometer was operated at cryogenic temperatures. In this article, we report the results of this 'bKAGRA Phase 1' operation. We have demonstrated the feasibility of 3 km interferometer alignment and control with cryogenic mirrors.

DOI： 10.1088/1361-6382/ab28a9

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1364/AO.58.003548

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DOI： 10.3390/ijms20020427

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Language：English   Publisher：Japanese Society for Engineering Education  

The practical R&D projects conducted among private companies and university laboratories contains the educational factors for students who learning engineering skills and knowledge. The authors established a novel educational program called "Smart Dormitory" as one of the educational reform activities, where the students can freely discuss, plan, measure and estimate their own engineering activities by themselves. For an example, the authors focus on the students who built a team together in a certain laboratory studying forefront scientific researches on superconductivity. The program has been characterized as a kind of research internship programs nurturing the leadership for elite students. The students were assigned the scientific presentations on their research results in certain international meetings, which enhanced their motivation to scientific studies.

DOI： 10.20549/jseeen.2019.0_58

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Language：Japanese  

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Language：Japanese   Publisher：Japanese Society for Engineering Education  

DOI： 10.20549/jseeja.2018.0_334

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

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.

DOI： 10.1016/j.optcom.2017.03.053

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

The university students from freshman to junior grades before starting their graduation studies have participated in the forefront researches conducted in the academic/scientific research laboratories in Niigata University. Since the practical research activities conducted in the laboratories must intrinsically contain the educational elements for the university students, it should be effective for the students to obtain the proper skills, abilities, attitudes, and knowledge of engineering even before the acquisition of their basic skills and knowledge of science. This education program called "Smart Dormitory" project has been carried out as one of the novel educational reform activities. There, the students from the freshman to junior make their teams together, and studies the forefront scientific researches about the topics they freely chose. In the process, the students have been assigned the scientific presentations about the results of their on-going investigations in the international meetings, which have been held in the domestic areas or overseas. The students are well motivated to their scientific researches through the presentations when they were given the opportunities in their early stage of university life. This engineering education program is characterized as one of the leadership programs for the scientific engineering leaders in the internationalized practical industries. Actually, the averaged academic score of dormitory students has firmly raised through the planned period, which means the program stimulated the student' motivation to their academic studies.

DOI： 10.1109/WEEF.2017.8467132

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：OSA - The Optical Society  

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.

DOI： 10.1364/OFT.2017.OW4B.4

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Language：English   Publisher：Japanese Society for Engineering Education  

The recent shifts in the circumstances of engineering education are generally attributed to the internationalization of the whole society. The authors have been conducting various international cooperative activities on the engineering education to develop the programs for university students. The major purpose of the activities is to announce the results of engineering educational reforms we have conducted so far in the international conferences in order to gather the information and to discuss about its exchanges. We have performed 58 presentations in the international conferences for the last ten years, and investigated the international educational issues which were investigated in each university. Since the current major issues on the engineering education are common to every country and society, it is well effective to discuss the topics on the educational programs and to exchange information about them. The information exchanges with foreign faculties and researchers in the worldwide conferences enable us to gaze at the targets to internationalize our educational programs and activities on the engineering education.

DOI： 10.20549/jseeen.2017.0_25

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

We report simultaneous measurement of thickness and refractive index (RI) using Coherent Gradient Sensing (CGS) based interferometric setup. The collimated light beam transmitted through the specimen is analyzed using two gratings in tandem and a spatial filtering arrangement. At the imaging plane, the desired orders superpose yielding interference fringes. Phase shifting interferometric (PSI) technique has been used to obtain the phase information directly. For decoding the information of thickness and RI, the specimen is rotated and the variation in interferometric phase before and after the specimen rotation determined. Simultaneous measurement on a glass plate of thickness 6.019 mm and refractive index of 1.4570 has been demonstrated. Detailed uncertainty analysis is also reported. The expanded uncertainty for thickness and RI in the measurement process was determined to be +/- 0.005 mm and +/- 0.00008 respectively. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.optlastec.2016.06.015

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

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.

DOI： 10.1109/OMN.2016.7565864

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

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.

DOI： 10.1016/j.optcom.2015.08.016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

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.

DOI： 10.1016/j.optcom.2015.08.066

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

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)

DOI： 10.1117/1.OE.54.8.085107

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

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

DOI： 10.1364/OE.23.021078

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

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.

DOI： 10.1117/12.2204984

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.2204984

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.2193027

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

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)

DOI： 10.1117/1.OE.53.8.084110

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

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.

DOI： 10.1016/j.optcom.2013.12.015

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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.

DOI： 10.1016/j.optcom.2013.08.018

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

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 μm was successfully measured. © 2014 SPIE.

DOI： 10.1117/12.2053539

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.2050190

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

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. © 2013 Optical Society of America.

DOI： 10.1364/AO.52.003726

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

A laser beam is scanned on an object surface with a fast scanning system which consists of a rotating mirror, a flat mirror, and a concave spherical mirror. Propagation direction of the laser beam reflected by a sample surface is detected with a lens and a position sensitive detector. A one-dimensional surface profile of the sample surface is measured by integrating a slop distribution obtained from the propagation direction of the reflected beam. The measurement is insensitivity to mechanical vibrations because of a high-speed scanning of a few milliseconds. The required positioning accuracy of the sample surface is lower than a few millimeters. The measurement repeatability is less than 10 nm.

DOI： 10.1117/12.2020983

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.2023531

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.2025328

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

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.

DOI： 10.1109/CLEOPR.2013.6600579

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.2023816

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.2042640

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

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

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

The positions of the front and rear surfaces of a silicon dioxide film with 4 μm 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 0.326×10-3 nm-1 and 140 nm, respectively. © 2012 Optical Society of America.

DOI： 10.1364/AO.51.002429

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Language：Japanese   Publisher：一般社団法人 映像情報メディア学会  

本研究では,デジタルカメラを用いた高精度且つ低コストな板金検査システムを提案する.提案検査システムは単一のデジタルカメラにより板金の画像を取得し,設計データと比較することで板金の加工誤差を検出する.デジタルカメラにより取得した画像はレンズ歪を有するため,高精度検査システムの実現にはレンズ歪の推定及び補正が必要となる.また,台座の高さや板金の厚みによるズレも考慮する必要がある.本研究では半径歪モデルと位相限定相関法を組み合わせた歪推定,局所的射影変換を用いた歪補正及び高さ・厚み補正の方法を提案する.実験により提案検査システムの検査精度を評価し,精度0.5mmの達成を確認する.

DOI： 10.11485/itetr.36.34.0_23

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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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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

A non-traditional processing cycle for sheet-metal working based on the computerized image processing techniques is proposed. This novel system enables the effective fabrication cycle that realizes automatic inspection, quick delivery, and cost reduction.

DOI： 10.4028/www.scientific.net/AMM.152-154.331

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.999720

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We propose an effective technique for optically detecting images of the inner hole-surface of a hole (hereafter, referred to as the hole-surface) using the polarization property of a 3D television (TV) monitor. The polarized light emitted by the TV monitor illuminates the hole-surfaces present in the test target placed on the screen of the monitor. When the polarizer placed in front of a camera lens is adjusted such that the camera captures a dark image for the transmitted light, only the highlighted hole-surfaces are visible in the captured image.

DOI： 10.1117/12.999726

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.2000145

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.999555

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Sinusoidal wavelength-scanning (SWS) interferometry is unique in that a time-varying interference signal contains phase-modulation amplitude Z b due to the SWS besides a conventional phase α. Propagation time and wavefront of the light wave diffusely reflected from a metal surface can be detected from the amplitude Zb and the phase α, 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. © 2012 SPIE.

DOI： 10.1117/12.929137

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

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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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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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.910102

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.894454

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We propose and demonstrate a novel processing cycle for sheet-metal working based on the computerized image processing techniques. The interconnected test system based on the cross network communication enables the effective fabrication cycle that realizes automatic inspection, quick delivery, and cost reduction.

DOI： 10.1117/12.906564

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

DOI： 10.1117/12.870985

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-SOC PHOTOPTICAL INSTRUMENTATION ENGINEERS  

An external-cavity laser diode that performs static wavelength scanning eliminates problems such as repeatability and tuning rate that arise due to mechanical movements induced in the external cavity of conventional systems, because it requires no mechanical elements. Experiments reveal that the scanning range and tuning rate are 1.1 nm and 1 kHz, respectively. (C) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3306642]

DOI： 10.1117/1.3306642

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We exploited the wavelength tunability of the laser diode of a phase-shifting Sagnac interferometer to realize disturbance-free measurements. The Sagnac interferometer is robust against mechanical disturbances because it has a common path configuration and requires no special references. An unbalanced optical path was introduced between p- and s-polarized beams to enable easy phase shifting by direct current modulation. The experimental results indicate that the proposed system is effective for performing precise disturbance-free measurements. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2009.09.052

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.861534

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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 μm. The displacement measurement is performed by determination of zerophase or π-phase positions. The accuracy estimated from 5 repeated experiments is about 0.2 rad. © 2010 Copyright SPIE - The International Society for Optical Engineering.

DOI： 10.1117/12.870985

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.870987

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

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.

DOI： 10.1117/12.871030

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We introduced the vertical cavity surface emitting laser (VCSEL) as the laser diode in tour external cavity system. Because VCSELs are now commercially available, and the External cavity diode laser (ECDL) systems using them are expected to improve their frequency stability, we have replaced a Fabry-Perot type laser diode with a VCSEL, and examined its oscillation-frequency stability. Therefore we were able to expect that the VCSELs with our double optical feedback system have good oscillation frequency stability. The obtained VCSEL's oscillation-frequency stability, i.e., the square root of Allan variance σ was 4×10-10, at an averaging time of τ=1 sec. © 2010 Copyright SPIE - The International Society for Optical Engineering.

DOI： 10.1117/12.840609

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

A feedback-control-equipped phase-shifting laser diode interferometer that eliminates external disturbance is proposed. The feedback loop is stabilized by adaptive control of the polarity of the interference signal. Conventional phase-shifting interferometry can be used with the feedback control, resulting in simplified signal processing and accurate measurement. Several experiments confirm the stability of the feedback control with a measurement repeatability of 1.8nm. (C) 2009 Optical Society of America

DOI： 10.1364/AO.48.005561

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/15421400902946103

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A new Mach-Zehnder type optical-interferometer utilizing evanescent wave illuminations of a reflected beam at a prism surface was constructed to evaluate photoreactive molecular thin films on a prism surface. Refractive index changes of the films due to photoisomerization of azo molecules on the prism caused by an irradiation beam were observed from phase changes between an incident beam and the reflected one at the prism surface. Real-time measurements were also demonstrated using the interferometer microscopy, exhibiting two dimensional distributions of the refractive indices in the molecular films partially excited by the focused irradiation laser beam. Copyright © Taylor &amp
Francis Group, LLC.

DOI： 10.1080/15421400902946103

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A halogen lamp and an acousto-optic tunable filter are used to construct a sinusoidal wavelength-scanning interferometer with the scanning width of 210 nm. A linear wavelength-scanning with the scanning width of 220 nm is utilized to determine amplitudes of three different interference signals produced from multiple-reflection lights by front and rear surfaces of a thin film. Amplitudes of time-varying phases produced by a sinusoidal wavelength-scanning and constant phases in the interference signals are estimated by minimizing a difference between detected signals and theoretical ones. From the estimated values, the positions of the front and rear surface of the thin film with a thickness of about 460 nm are measured with an error less than 4 nm. © 2009 SPIE.

DOI： 10.1117/12.840190

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Optical path difference (OPD) and amplitude of a sinusoidal wavelength-scanning (SWS) are controlled with double feedback control system in an SWS interferometer, so that a ruler marking every wavelength and a ruler with scales smaller than a wavelength are generated. These two rulers enable us to measure an OPD longer than a wavelength. An acousto-optic tunable filter (AOTF) is adopted as a wavelength-scanning device. The frequency of the SWS is 10 KHZ, and the measurement time required to reach a stable point of the control system is about 7ms. The measurement range is from 65 mu m to 190 mu m with the measurement error less than 4nm.

DOI： 10.1117/12.817855

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Fringe analysis methods that employ wavelet transform are described. The performances of the methods are examined from the viewpoints of required calculation time and accuracy. Further, accuracies of calculations performed using linear and logarithmic scales in wavelet transform are compared. Experimental results show that wavelet signal processing is effective in measuring profiles having large and gradual asperities.

DOI： 10.1117/12.817853

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

A collimated line beam is incident at an oblique incident angle of 0.61 rad into an inner surface of a hydrodynamic bearing whose inner diameter and length are 3 mm and 3.5 mm, respectively. Lights reflected in specified directions from the inner surface are selected to obtain an optical field whose phase distribution is proportional to the inner surface profile. This optical field interferes with a reference optical field in a two-wavelength interferometer using a tunable external cavity laser diode. Shapes of grooves with depth of about 5 mu m and width of about 0.15 mm formed on the inner surface can be measured with an error less than 0.3 mu m.

DOI： 10.1117/12.827352

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

A real-time displacement sensor based on a laser diode interferometer that has a coaxial structure is proposed and demonstrated. Several measurements indicate measurement accuracy of 0.1 mu m.

DOI： 10.1109/CLEOPR.2009.5292076

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

An external-cavity laser diode that performs static wavelength scanning is proposed. It eliminates problems such as repeatability and tuning rate that arise due to mechanical movements induced in the external cavity of conventional systems because it requires no mechanical elements. Experiments have revealed that the scanning range and tuning rate are 1.3 nm and 1 kHz, respectively. © 2009 SPIE.

DOI： 10.1117/12.839828

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

An external-cavity laser diode that performs static wavelength scanning is proposed. It eliminates problems such as repeatability and tuning rate that arise due to mechanical movements induced in the external cavity of conventional systems because it requires no mechanical elements. Experiments have revealed that the scanning range and tuning rate are 1.3 nm and 1 kHz, respectively. © 2009 SPIE.

DOI： 10.1117/12.839828

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

A multi-period fringe-projection interferometry with back-propagation method is described to measure surface profiles of a glass plate. Phase distribution of the multi-period fringe formed by interfering the two calumniated laser beams is utilized to determine the position of the two surfaces of the glass plate. The multiple optical fields of the different fringe periods on the two surfaces, which are obtained from the sinusoidal phase-modulated interference signals, are back-propagated to a position where all of the phases of the multiple optical fields become zero. At the same time, the amplitude of the sum of the multiple back-propagated fields becomes maximum. The distances of the back-propagation provide the positions of the two surfaces of the glass plate. In the experiment a glass plates of 2mm-thickness is measured with a precision of 2.3 mu m.

DOI： 10.1117/12.768064

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

DOI： 10.1117/12.756447

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

Interference fringes with different periods are projected on an object surface. There is a constant phase point where the phase of the fringe is kept at a constant value while the period is scanning. Multiple optical fields with different periods on the object surface are made from detected phases of the fringes. The multiple optical fields are backpropagated to the constant phase point of the phase where all of the phases of the multiple backpropagated fields become the same value and the amplitude of the sum of the multiple backpropagated fields becomes maximum, The distance of the backpropagation provides the position of the object surface. Some experiments show that this method can measure an object surface with discontinuities of several millimeters with high accuracy of several micrometers. © 2007 Optical Society of America.

DOI： 10.1364/AO.46.007268

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Multiple-wavelength optical fields on a detecting plane of an interferometer are generated from the interference signals detected for an object surface. The generated optical fields are backpropagated along the optical axis. An optical field along the optical axis is reconstructed by summing the backpropagated fields over the multiple wavelengths. The intensity and phase distributions of the reconstructed optical field provide the position of the object surface with an accuracy of a few nanometers. © 2007 Optical Society of America.

DOI： 10.1364/OL.32.002683

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

The optical path difference (OPD) and amplitude of a sinusoidal wavelength scanning (SWS) are controlled with a double feedback control system in an interferometer, so that a ruler marking every wavelength and a ruler with scales smaller than a wavelength are generated. These two rulers enable us to measure an OPD longer than a wavelength. A liquid-crystal Fabry-Perot interferometer (LC-FPI) is adopted as a wavelength-scanning device, and double sinusoidal phase modulation is incorporated in the SWS interferometer. Because of a high resolution of the LC-FPI, the upper limit of the measurement range can be extended to 280 μm by the use of the phase lock where the amplitude of the SWS is doubled in the feedback control. The ruler marking every wavelength is generated between 80 μm and 280 μm, and distances are measured with a high accuracy of the order of a nanometer in real time. © 2007 Optical Society of America.

DOI： 10.1364/AO.46.005800

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

In this work we describe a simple external-cavity laser diode equipped with a feedback control system, in which a high-resolution position-sensitive detector detects the slight misalignment of the light within the cavity. Our system not only provides a stable wavelength that can be tuned within a maximum scanning range of 1.87 nm, but also allows for faster scanning, through precise control of the reflection angle within the cavity. The simultaneous controls on the rotation-angle of the external mirror and the injection current enabled us to realize continuous wavelength-tuning. (c) 2007 The Optical Society of Japan.

DOI： 10.1007/s10043-007-0023-3

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

Two-wavelength interferometer that is applicable to step-height measurement under the large disturbance is proposed and demonstrated. A step-height of 2 mu m was measured for the high-speed rotating object without any special devices. The applicable rotating speed reached over 1000 rpm in our demonstration.

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Two-wavelength interferometer that is applicable to step-height measurement under the large disturbance is proposed and demonstrated. A step-height of 2 μm was measured for the high-speed rotating object without any special devices. The applicable rotating speed reached over 1000 rpm in our demonstration.

DOI： 10.1109/CLEOPR.2007.4391799

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Movements of a surface profile are measured with a two-grating interferometer using sinusoidal phase-modulation. Since sinusoidal phase-modulating (SPM) interferometry can record a phase change due to the movement of an object in the interference signal, the SPM interferometer is suitable for measuring the movement of the object. Some experiments show that the two-grating interferometer can measure a sinusoidal vibration with amplitude of several tens of microns and a step movement with a magnitude of several microns. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2006.06.038

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-INT SOCIETY OPTICAL ENGINEERING  

A two-dimensional small-rotation-angle measurement system based on fringe projection is proposed and demonstrated. Simple and effective signal processing is described and applied to the angular calculation. Several measurements indicate a measurement accuracy of approximate to 0.4 arcsec, which is comparable to that of a high-priced autocollimator. The two-dimensional two-pitch grating used in our prototype system provides a wide measurement range, which is expected to reach 1300 arcsec for both x- and y-direction rotations. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.2188945

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A method for measuring external diameters of metal cylinders is proposed in which a sinusoidally vibrating interference pattern (SVIP) of 100-mu m period is used as an exact scale. Lights from the end-points of a metal cylinder are extracted with a spatial filtering in an imaging system to form a cross-sectional image of the metal cylinder. On the image a sinusoidally phase-modulated signal owing to the SVIP is detected with a CCD image sensor to measure the phases of the SVIP at the two end-points of the cylinder. The coordinates of the two end-points are obtained from the phases at the two end-points.. the phase distribution of the SVIP, and the coordinates of the pixels of the CCD image sensor. Metal cylinder diameters of 7.99, 8.00, and 9.00 mm are measured along their length directions with an error less than 1 mu m. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2005.11.009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-INT SOCIETY OPTICAL ENGINEERING  

A method is proposed for accurately measuring a sectional profile of a metal cylinder. In this method a sinusoidally vibrating sinusoidal interference pattern is used to generate an exact spatial scale along one direction. Light from top points of a metal cylinder surface is extracted by spatial filtering in an afocal imaging system to form an image of the top points. A time-varying signal is detected in the image, and a sectional profile of the metal cylinder is measured from the phase of the detected signal on a position where the amplitude of the signal has a maximum value. Detection of the amplitude and the phase is carried out easily and exactly with sinusoidal phase-modulating interferometry. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.2166848

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An inspection system for the surface-profile properties of an organic photoconductor (OPC) drum substrate is studied. Defective substrates have approximately 1-mm-period waves in their surface profiles along the axial direction. The slope distribution of the surface profile is measured with an optical inspection system, which detects the angular deflection of a laser beam scanned over the surface at a high speed of 15 mm/ms. To discriminate between good and defective substrates, a threshold decision is made on components of the experimentally measured power spectrum of the slope distribution around 1-mm spatial period. The inspection system provides the same results as visual inspection with an accuracy better than 6 sigma. The setup dose not require any vibration isolators, because of its short inspection time of 2 ms. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.2150821

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

A disturbance-free sinusoidal phase modulating laser diode interferometer using an accelerated integrating-buckets processing system is described. Several techniques make it suitable for use in on-machine measurements: the charge-coupled device (CCD)-based additive operation on integrating buckets shares the burden of data processing imposed on the computer to shorten the measurement time; the use of high-speed shutter function of the CCD camera enables each bucket to be collected without disturbance, while the interference signal's stability is enhanced with the feedback control during the entire data-collecting time; by using a dedicated waveform generator, the phase modulating system is more compact and the modulating signal matches the CCD camera's exposure time easily and exactly. A surface profile measurement on a diamond-turned aluminum disk is demonstrated to evaluate the performance of this system. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.2148447

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DOI： 10.2493/jspe.71.1525

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

A sinusoidal wavelength-scanning interferometer for measuring thickness and surfaces profiles of a thin film has been proposed in which a superluminescent laser diode and an acousto-optic tunable filter are used. The interference signal contains an amplitude Zb of a time-varying phase and a constant phase a. Two values of an optical path difference (OPD) obtained from Zb and a, respectively, are combined to measure an OPD longer than a wavelength. The values of Zb and a are estimated by minimizing the difference between the detected signals and theoretical ones. From the estimated values, thickness and surface of a silicon dioxide film coated on an IC wafer with different thicknesses of 1 mu m and 4 mu m are measured with an error less than 5 nm. (c) 2005 Optical Society of America.

DOI： 10.1364/OPEX.13.010066

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We propose a sinusoidal wavelength-scanning interferometer for measuring thickness and surface profile of a thin film. The interference signal contains phase modulation amplitude Z and phase α which are related to the positions and profiles of the reflecting surfaces, respectively. By reducing the difference between the detected signal and the estimated signal using the multidimensional nonlinear least-squares algorithm, we estimate values of Z and α. Experimental results show that the front and rear surfaces of a silica glass plate of 20 μm-thickness could be measured with an error less than 10 nm. © 2005 The Optical Society of Japan.

DOI： 10.1007/s10043-005-0319-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

A two-grating interferometer for measurement of profiles of polished surfaces is proposed. The +/- first-order beams diffracted by the first grating produce parallel fringes of about 50-mu m spacing on an object surface. By using the second grating, we eliminate the parallel fringes and extract a phase distribution produced by the surface profile of the object. Moreover, the vibration of the second grating of a small size enables us to use the sinusoidal phase-modulating interferometry. Measurement resolution is higher than 0.3 mu m at the equivalent wavelength of 35 mu m. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.1883083

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

The rough surface of a aluminum cylindrical drum cut by turning tool is measured with a fast scanning method by detecting angular deflection of a laser beam. Reflection pattern from the surface extended into a large region; and contained two kinds of components of narrow and wide patterns. To detect rough surface's slope, the barycentric position of the wide pattern was measured with a PSD, and a beam diameter of 5mm on the surface was adopted. After a proportionality coefficient to convert from PSD output to the surface's slope was determined, an one-dimensional surface profile measurement of the rough surface was performed without a vibration isolator. Measurement error was estimated to be 0.27 mu m.

DOI： 10.1117/12.577647

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We propose a sinusoidal wavelength scanning interferometer for measuring thickness and surfaces profiles with a thin film. An acousto-optic tunable filter (AOTF) is used to produce sinusoidally wavelength-scanned light from a superluminescent laser diode (SLD) with a wide spectral bandwidth of 46nm. The interference signal contains an amplitude Zb of a time-varying phase and a constant phase α. Two measured values of OPD, which are denoted by Lz and Lα, are obtained from Zb and α. By combining Lz and Lα, an OPD longer than a wavelength is measured with an error less than a few nanometers. When the object has two reflective surfaces, the detected interference signal contains two interference signals which are caused by the front and rear surfaces. In this case we must determine the values of Zb1, Zb2, α1, and α2 where suffixes of 1 and 2 are corresponding to the front and rear surfaces, respectively. We define an error function that is the difference between the detected signal and the theoretical signal, and reduce the value of the error function with the multidimensional nonlinear least-squares algorithm to search the values of Zb1, Z b2, α1, and α2. Experimental results show that the thickness and surfaces profiles of a silica glass plate of 20μm-thickness are measured with error less than 1.5nm.

DOI： 10.1117/12.666811

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A method for measuring diameters of metal cylinders is proposed. In this method a sinusoidally vibrating interference pattern (SVIP) of 100μm-period is used to generate an exact spatial scale along x-axis. Detection of the amplitude and the phase of the SVIP are carried out easily and exactly with sinusoidal phase-modulating interferometry. First, phase values of the SVIP on the pixels of the CCD image sensor are measured as the exact scale along the x-axis. Next, an image of the end-points of the cylinder surface is formed by extracting lights from the end-points of the cylinder. The phase of the SVIP on the end-point of the cylinder appears at a position where the amplitude of the image has maximum value along the x-axis. The x-coordinate of the end-point of the metal cylinder is calculated from the phase value of the end-point and the exact scale. The diameter is obtained from the x-coordinates of the two end-points. Metal cylinders of 9mm and 8mm-diameters are measured with an error of about ±2μm.

DOI： 10.1117/12.666832

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

A method is proposed for accurately measuring a sectional profile of a thread gauge. In this method a sinusoidally vibrating sinusoidal intensity (SVSI) is used to generate an exact spatial scale along one direction. Lights from top points of a thread gauge surface are extracted by spatial filtering in an afocal imaging system to form an image of the top points. A time-varying signal is detected in the image, and a sectional profile of the thread gauge is measured from the phase of the detected signal on a position where the amplitude of the signal has a maximum value. Detection of the amplitude and the phase is carried out easily and exactly with sinusoidal phase-modulating interferometry.

DOI： 10.1117/12.576666

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It is easy to extract a signal proportional to a phase fluctuation from a sinusoidally phase-modulated interference signal, This fluctuation is caused by mechanical vibration or air turbulence. In a sinusoidal phase-modulating interferometer using a laser diode (LD) the phase fluctuation is reduced by changing the injection current of the LD with a feedback control system. This control is very useful to a Fizeau type interferometer for surface profile measurement of a large size object. IC wafers of 100 mm diameter are measured with an interferometer insensitive to mechanical vibration and air turbulence. The phase fluctuation with nearly constant amplitude which corresponds to 30nm in surface height is reduced by about 10%. However the reduction in the phase fluctuation is not performed well for an instantaneous and large phase fluctuation. In order to be insensitive to all kinds of phase fluctuations the feedback signal is always observed, so that the interference signal is captured when the amplitude of the feedback signal is less than a specified level during the capturing time of 0.53 s. Thus surface profiles of the IC wafers can be measured with a high repeatability of a few nm even when any kind of vibration exists.

DOI： 10.1117/12.666829

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

A sensor using sinusoidal phase-modulation of 1.5MHz generated by modulating the injection current of a laser diode measures a phase of the interference signal with a measuring time of 0.25 mu s and an error less than 20nm in displacement.

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A system for two-dimensional small rotation-angle measurement is proposed and demonstrated. Because the measurement is not conducted by the interference but the fringe projection, it is basically robust for the external disturbance. While the setup is very simple, there is no requirement on the size of the object. We also proposed two-dimensional two-grating method and a unit that miniaturizes the system. Several measurements confirm us that the measurement accuracy of our proposed system is similar to 0.4 arcsec.

DOI： 10.1117/12.580662

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A disturbance-free sinusoidal phase modulating laser diode interferometer using integrating bucket method is described. Several techniques make it suitable for use in the in-process measurement: the charge-coupled device (CCD) based additive operation on integrating-buckets shares the burden of data processing imposed on the computer; the modulating signal is matched with the CCD camera's exposure time easily and exactly by using a dedicated waveform generator; the use of high speed shutter function of the CCD camera enables each bucket collection to be insensitive to the noise, while the interference signal's stability is enhanced with the feedback control during entire measurement time. A surface profile measurement on a diamond-turned aluminum disk was demonstrated to evaluate the performance of this system.

DOI： 10.1117/12.603826

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A sensor using sinusoidal phase-modulation of 1.5MHz generated by modulating the injection current of a laser diode measures a phase of the interference signal with a measuring time of 0.25μs and an error less than 20nm in displacement.

DOI： 10.1109/CLEOPR.2005.1569858

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Interferometric displacement sensor based on a two-wavelength interferometry is proposed and demonstrated. A combination of time-shared two-wavelength laser diode and sinusoidal phase-modulating interferometry enables us to realize accurate and wide-range displacement measurement with a simple optical setup.

DOI： 10.1117/12.666819

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The optical telemeter system has been developed, which converts the temperature of rotating spindle to the digital data and carries the digital data from LED on the rotating side toward PD on the stationary side by the optical data transmission. Based upon the temperature distribution of hollow ball-screw obtained by the telemeter system, the thermal elongation of the ball-screw is estimated as the one-dimensional thermal elongation Estimation accuracy, which is the difference between the estimated thermal elongation and the measured thermal elongation, is 3.1∼+3.2 μm for the thermal elongation of 50-60 μm over the length of 935.5 mm of the ball-screw.

DOI： 10.1299/jsmec.47.1175

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Precision Engineering  

This paper deals with the data-transmission system adopting the opto-electronic parts for the remote-controller of electric appliances. The signal with appropriate bit-pattern and specified wave-form is used, and the system has much longer distance nearly 1,000mm between the light-emitting-diode and the light-receiving-module than the maximum length of 3-20mm in the reported system of faster-transmission rate. Then the data-transmission from not only rotating spindle but also revolving body is realized. Three techniques, which are adoption of one-way data-transmission, one-chip micro-controller and digital-filtering process, are adopted as same as in the faster-transmission system. The data-transmissions from the end-surface of rotating spindle and from the cylindrical-surface are confirmed.

DOI： 10.2493/jspe.70.1559

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An interferometric range finder that uses both phase-locked and modulation-amplitude-locked techniques in a sinusoidal phase-modulating interference signal is described. It allows us to perform unambiguous and real-time distance measurement. Also, external disturbance superimposed on the interference signal is eliminated by the feedback control. Our preliminary experiments indicate a measurement error of 17.7 mum rms. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.1799071

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

A new range-finding technique that uses both double sinusoidal phase modulation and quasi-two-wavelength interferometry is described. Two independent interference signals are generated with respect to two different wavelengths on a time-sharing basis. We clarify that external disturbances of these interference signals are eliminated by both feedback control and differential detection and that the feedback control does not affect the distance measurement. A single distributed Bragg reflector laser diode allows us to simplify the optical setup and to improve the measurement accuracy. After discussing a measurement range, we estimate a measurement error by making several measurements. (C) 2004 Optical Society of America.

DOI： 10.1364/AO.43.004482

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Precision Engineering  

This paper deals with the optical telemeter system of strain-gauge output in rotating object. Bridge circuit composed of strain-gauges is connected to an amplifier and the output of amplifier is A/D converted according to the control series generated by a one-chip micro-controller, and the A/D result of serial data series is fed to LED on rotating object and sent as the optical data series. The optical data series is received by PD on stationary head, and the serial PD output is converted to parallel datum and inputted to personal computer. Tensile force acting on the sensing plate based upon the centrifugal force due to the spindle rotation is measured by the strain-gauge and the optical telemeter system. Theoretical tensile force is calculated. It is confirmed that the measured force coincides well with the theoretical force. This system has the function of quick-input of known-strain.

DOI： 10.2493/jspe.70.1101

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A fast scanning method for one-dimensional surface profile measurement is proposed. The profile is measured by integration of a slope distribution of the surface obtained from angular deflection of a scanning laser beam. A scanning optical system that consists principally of a spherical concave mirror and a rotating scanner mirror has reasonably low cost and is insensitive to mechanical vibration because of its high-speed scanning, of the order of milliseconds. A surface profile of a polygonal mirror along a 5-mm width was measured with the scanning method and with an interferometer. The root-mean-square difference between the two measured results is 0.98 nm. (C) 2004 Optical Society of America.

DOI： 10.1364/AO.43.004157

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A linear CCD image sensor is used to electrically scan a measuring point and measure 1-D step-profiles in real time with a sinusoidal wavelength-scanning (SWS) interferometer using double feedback control. In this interferometer, the optical path difference (OPD) and the amplitude of the SWS are controlled so that a ruler marking every wavelength and a ruler with scales smaller than a wavelength are generated. These two rulers enable us to measure an OPD longer than a wavelength in real time. Two different step profiles with step heights of 1 and 20 mum, respectively, are measured with a measurement error of less than 8 nm. Measuring time for one measuring point is 0.04 S. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.1737375

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

We propose a sinusoidal phase-modulating laser diode interferometer that uses a charge-coupled device (CCD)-based additive operation on four integrating buckets. By shifting the injection-current bias of a laser diode to introduce additional phase shifts, a portion of the subtractive operations on the integrating buckets become additive operations, which are achieved in the CCD. This approach serves to reduce both data processing and measurement time. (C) 2004 Society of PhotoOptical Instrumentation Engineers.

DOI： 10.1117/1.1645252

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

We describe a double-grating interferometer for the measurement of cylinder diameters. The unique characteristic of this interferometer is that one can freely change the period of the interference fringes by turning the grating, which permits the measurement range of the interferometer also to be changed freely according to the cylinder diameter to be measured. A clear image of the cylinder can be obtained because the aperture diaphragm blocks the beams diffracted from the edge of the cylinder. The outside and inside diameters of the M4 X 0.7 nun hand tap are measured with this double-grating interferometer. (C) 2004 Optical Society of America.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

This paper describes a range-finder that uses two feedback loops. Each feedback loop is respectively used to control the phase and the modulation-amplitude in a sinusoidal phase-modulating interference signal. It enables us to perform unambiguous measurement and real-time processing on the interference signal. Also external disturbance superimposed on the interference signal is eliminated by the feedback control. A distributed-Bragg-reflector laser diode that has wide range in wavelength-tuning allows us to improve the measurement accuracy.

DOI： 10.1117/12.518640

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We propose a two-wavelength interferometer that is used to a stroboscopic step height measurement. Different from most two-wavelength interferometers, in present experiment, two slightly different wavelengths are simultaneously oscillated by currently and thermally controlling a laser diode to work at mode hop region. By use of this two-wavelength laser source, a Twyman-Green interferometer, whose reference arm and object arm have known step height r and unknown step height h, respectively, is constructed. Three independent interference patterns corresponding to different OPDs are formed and they can be simultaneously taken by a CCD camera. Furthermore, tilting the reference, spatial frequencies are introduced into the interference patterns. Taking the Fourier transform of these patterns, three fringe amplitudes are obtained and their expressions can be solved for the unknown step height. As we can capture clear image of the interference patterns in a very short time by use of the high speed shutter function of the CCD camera, the error induced by the external disturbance is farthest reduced.

DOI： 10.1117/12.518642

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

We describe a novel method that operates a laser diode with dual colors. Our system requires no external optical parts but does require current and temperature control. We can use either a single color on a time-sharing basis or dual colors simultaneously. The difference between the wavelengths is similar to0.6 nm, which is as much as 10 times that generated by current control alone. Temporal stability of the generated two wavelengths and the response time of the wavelength change were confirmed through a number of experiments. (C) 2003 Optical Society of America.

DOI： 10.1364/AO.42.006640

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Precision Engineering  

This paper deals with the optical telemeter system in which data-transmission and power-supply through cylindrical surface of rotating spindle are realized. Data-transmission is carried out by means of one LED on the cylindrical surface of rotating head and enough numbers of PD facing to LED rotational locus. Non-contact power-supply is carried out by means of two pairs of coil and ferrite-core arranged on the rotating side and the stationary side respectively. These schemes through cylindrical surface are realized in a demonstration unit to clarify the effectiveness of the newly developed system. The measurement accuracy of the developed system is superior than 0.05°C for 0〜50°C range from the view point of temperature change.

DOI： 10.2493/jjspe.69.1600

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Language：English   Publishing type：Research paper (other academic)   Publisher：The Japan Society of Mechanical Engineers  

The optical telemeter system, which converts the temperature of rotating spindle to the digital data and carries out the optical transmission of the digital data from rotating side toward stationary side with LED and PD, has been developed. Based upon the temperature distribution obtained by adopting the telemeter system on hollow ball-screw, the thermal elongation of the ball-screw is estimated as the one-dimensional thermal elongation. Estimation accuracy, which is the difference between the estimated thermal elongation and the measured thermal elongation, is -3.1∿+3.2μm for the thermal elongation of 50∿60μm over the length of 935.5mm of the ball-screw.

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Language：English   Publishing type：Research paper (other academic)   Publisher：The Japan Society of Mechanical Engineers  

This paper deals with the development of the optical telemeter system, in which thetemperature of rotating spindle is measured with thermo-couple and the output is A/D converted and the digital data is transmitted from LED on the rotating head as optical data series. The size decreasing of the rotating head is achieved by three methods; the adoption of one-way data-transmission from the rotating head toward the stationary head, the adoption of one-chip micro-controller and the adoption of digital-filtering process in personal computer of stationary side. The measurement accuracy of the developed system is superior than 0.1--0.05℃ for 0--50℃ range. The data transmission rate is 6,200data/s of 12 bits data. And power for electric circuit in the rotating head is supplied by non-contact electro-magnetic phenomenon.

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

We propose a grating interferometer for step-profile altitude difference measurement. There are two main characteristics in this interferometer. The first is that the intensity distribution of the interference pattern is independent of the wavelength of the laser-diode used. No change of the intensity distribution occurs when the wavelength fluctuates. The second is that the measuring range is much larger than the wavelength of the light source because the spatial period of the grating is much larger than the wavelength. Sinusoidal phase modulating interferometry is easily applied to detect the phase variation of the interference pattern by vibrating the grating sinusoidally. The thickness of a 3.5-inch disk is measured with an accuracy of less than 0.5 mum.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Precision Engineering  

This paper deals with the measurement accuracy superior than 0.05〜0.1℃ for 0〜50℃ range of the developed data-transmission system. To realize the measurement accuracy best, it is necessary to satisfy several conditions; namely the calibration of the system should be carried out under several different temperatures or more and under sufficiently insulated condition, the output of all channels should be compensated based upon the temperature of electric circuit board and the warm-up operation for electric parts is needed.

DOI： 10.2493/jjspe.69.1480

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

We describe a double-grating interferometer that has a one-to-one correspondence with a Michelson interferometer. The half spatial periods of the gratings are equivalent to the wavelengths of the interferometer. The widths of the interference fringes can be changed easily. The intensity distribution of the interference pattern is independent of the wavelength of the light source used. The surface profile of an object can be measured because two interference beams can coincide precisely on the image plane of the object. The measuring range is much larger than that of a Michelson interferometer. (C) 2003 Optical Society of America.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-INT SOCIETY OPTICAL ENGINEERING  

We propose an optical method for detecting the displacement of an object in stereo images. Two images are displayed on two liquid crystal displays (LCDs), respectively, which are placed at a constant distance. Several plane waves of different propagating directions are illuminated to the LCDs. We can measure the displacement of the object by detecting which plane wave presents the strongest intensity after the plane waves pass through the LCDs. The method is applied to measuring the distance between cars from stereo images of a car. (C) 2003 society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.1577576

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-INT SOCIETY OPTICAL ENGINEERING  

We propose a simple setup for measurement of a small 2-D rotation angle using a Twyman-Green laser diode interferometer. Sinusoidal phase-modulating interferometry is adopted to detect the phase of the interference signal with a high accuracy and to perform the phase lock to eliminate the phase fluctuation at the standard detection point. By detecting the phases at three points along an axis, the 1-D rotation angle is measured with an accuracy of 0.5 arcsec in the range of 282 arcsec and with a spatial resolution of 3 mm. The 2-D rotation angle measurement is easily made by adding two more detection points. 0 2003 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.1554407

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

A previously proposed double sinusoidal phase-modulating (DSPM) laser-diode interferometer measures distances larger than a half-wavelength by detecting modulation depth. Although it requires a vibrating mirror to provide the second modulation to the interference signal, such vibrations naturally affect measurement accuracy. We propose a static-type DSPM laser-diode interferometer that uses no mechanical modulation. Our experimental results indicate a measurement error of +/-1.6 mum. (C) 2003 Optical Society of America.

DOI： 10.1364/AO.42.000060

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

We propose a stroboscopic two-wavelength interferometer that is applicable to displacement measurement of rotating object. The system we propose uses two different wavelengths and two CCD cameras which are equipped with a high-speed electrical shutter. It allows us to measure displacement through the disturbance-free phase measurement.

DOI： 10.1109/CLEOPR.2003.1277184

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Phase modulation amplitude Z(b) caused by a sinusoidal wavelength-scanning and conventional phase alpha of an interference signal are kept at pi and 3pi/2, respectively, with feedback control systems for a displacement of an object larger than a half-wavelength. A voltage applied to a device that provides the wavelength-scanning becomes a ruler marked out every a wavelength. Real-time distance measurement is. carried outwith this interferometer.

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addition to a conventional phase a the interference signal of a sinusoidal-wavelength-scanning interferometer has a phase-modulation amplitude Z(b) that is proportional to the optical path difference L and amplitude b of the wavelength scan. L and b are controlled by a double feedback system so that the phase a and the amplitude Zb are kept at 3pi/2 and pi, respectively. The voltage applied to a device that displaces a reference mirror to change the optical path difference becomes a ruler with scales smaller than a wavelength. Voltage applied to a device that determines the amplitude of the wavelength scan becomes a ruler marking every wavelength. These two rulers enable one to measure an absolute distance longer than a wavelength in real time. (C) 2002 Optical Society of America.

DOI： 10.1364/AO.41.003906

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

A method for accurately measuring a sectional profile of a cylinder is proposed in which a sinusoidally vibrating sinusoidal grating is used to generate a sinusoidally vibrating sinusoidal intensity distribution. A light coming from the top point of the cylinder surface is extracted with an optical system to make an image of this point. A sectional profile of the cylinder is measured by detecting a phase of a time-varying signal contained in the image intensity at a position where the amplitude of the signal is maximum. Detection of the amplitude and the phase is carried out easily and exactly.

DOI： 10.1007/s10043-002-0159-0

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

We describe an interferometer system that uses two separate wavelengths to measure step height. The overlapping interference images detected by a CCD camera are easily separated by an ordinary integrating-bucket method and time-sharing sinusoidal phase modulation, in which two laser diodes are alternately modulated with a sinusoidal signal. A phase map is obtained only for the laser diode into which the modulation signal is injected. In this instance, a 1-mum step height was accurately detected. (C) 2002 Optical Society of America.

DOI： 10.1364/AO.41.001972

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

A surface profiler that incorporates a feedback controller to eliminate external disturbances is proposed and demonstrated. Its overall performance is dependent on the frequency response of the feedback loop. The frequency of the modulating signal strongly influences the response of the feedback controller. When we used the integrating-bucket method, the CCD camera had to be operated at a low-frequency video rate. Our technique uses a CCD camera equipped with an electronic shutter. The shutter function enables us to apply high-speed sinusoidal phase modulation to the conventional integrating-bucket method under the standard video rate. (C) 2002 Optical Society of America.

DOI： 10.1364/AO.41.001949

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We propose a photothermal phase-modulating laser diode interferometer equipped with a high-speed feedback control system. The CCD camera's shutter-function raises the modulating frequency, which in turn elicits a higher feedback response, thus enabling us to eliminate nearly all external disturbance. With the recent application of a system purpose-built for discriminating between numerous fringe sequences, we have also reduced processing time.

DOI： 10.1007/s10043-002-0013-4

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This paper describes that the proposed method is able to evaluate accurately the resistant torque acting on rotating spindle system which includes rolling bearing, under high-dm · N condition lower than two million mm · rpm. The resistant torque is calculated as the product of the angular acceleration during free-running and the equivalent moment of inertia of spindle. The acceleration is calculated from the accurate measurement of change in series of each rotation-cycle under free-running. The equivalent moment of inertia is the sum of the moment of inertia of spindle rotor, the effect of rolling elements and the effect of retainer for the elements.

DOI： 10.2493/jjspe.68.93

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We propose a new range finding technique that uses two-wavelength interferometry. The system we propose uses a single laser diode to realize a two-wavelength interferometer, which expands measurement range. The single light-source allows us to simplify, the optical setup. Our devise generates two independent interference signals with respect to the wavelengths generated by offset current. The external disturbances on these interference signals are eliminated by the feedback control. Although die feedback control eliminates disturbance as well as the information about the distance,. we are able to detect the distance from the phase difference between those compensated interference signals.

DOI： 10.1117/12.465657

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Because the wavelength of a laser diode (LD) has the temperature-sensitivity, in conventional LD interferometers, a temperature control is required to stabilize the wavelength in long-term measurements. We propose a self-mixing laser diode interferometer that has two coaxial measurement arms. Two interference signals are used for the measurement of displacement and wavelength stabilization in our system. As the wavelength is not stabilized thermostatically, but by adjusting current feedback, compensation is simple and response-time minimal. The feedback controls for displacement measurement and wavelength stabilization were implemented on a time-sharing basis. The devise we propose enables us to conduct long-term measurements of microscopic levels of displacement.

DOI： 10.1117/12.472249

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Two-dimensional step-profile measurement is carried out with a sinusoidal wavelength-scanning interferometer where a large scanning width of 41 nm is easily achieved using a superluminescent laser diode of a wide spectral bandwidth of 46 nm. To detect a time-varying interference signal with a short integration time of 118 mus, a shutter function of a two-dimensional CCD image sensor is utilized. A step profile with a step height of 1 mum is measured with an error less than a few nanometers. A Step profile with a step height of 20 mum is also measured with a scanning width of 23 nm.

DOI： 10.1117/12.465815

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

An optical path difference (OPD) and the amplitude of sinusoidal wavelength-scanning are controlled with double feedback control system in an interferometer, so that a ruler marking every wavelength and a ruler with scales smaller than a wavelength are generated. These two rulers enable us to measure an OPD longer than a wavelength in real time. A linear CCD image sensor is used to measure one-dimensional step-profiles in real-time. Two different step profiles with a step height of 1 mum and 20 mum, respectively, are measured with the measurement error less than 8 nm. Measuring time for one measuring point is 0.04 s.

DOI： 10.1117/12.465819

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The tunability of the laser diode's operative wavelength is very attractive to realize active interferometer. We review here, a system that possesses this important capability, by virtue of its built-in electrical feedback loop. After describing the basic principles of its phase-control and feedback-signal generation. some selected examples of its implementation'. such as displacement-, profile- and distance-measurements, as well as disturbance elimination are presented.

DOI： 10.1117/12.465656

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We propose a sinusoidal phase modulating laser diode interferometer using an additive operating type of integrating bucket method. In previous integrating bucket method, four images, which are integrated values of the interference pattern detected by a CCD image sensor, are required. According to additive and subtractive operations in a calculator, the quadrature signals can be calculated from these images. While these operations are associated with the technical computing software, such as MATLAB, in a personal computer, it is quite fast, even if the images possess large size. In a standard-alone system with a CPU, however, this kind of operation expends unbearable time. To lighten the burden of the calculator, we tried to simplify the operation. That is, on the basis of integrating bucket method, the subtraction in the signal processing is transformed to the addition by use of the phase shifting technique. All additive operations are achieved with the CCD image sensor. In this interferometer, not only the calculating quantity is reduced, but also the number of required images is reduced. The surface profile of a diamond-turned aluminum disk was measured. The repeatability in the measurements was 5.93 nm rms.

DOI： 10.1117/12.465814

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Precision Engineering  

This paper deals with the size decreasing and the power decreasing of rotating-head. The head is the most important part of the developed data-transmission system and is installed on the rotating spindle. The size decreasing is achieved by three methods; the adoption of one-way data-transmission from the rotating head toward the stationary head, the realization of function of nine electric-IC-parts by a one-chip micro-controller and the adoption of digital-filtering process after data transmission accompanying no RC-hardware filter in the rotating head. As a result of the three methods, also the power consumption at the electric circuit in the rotating head is decreased to 40mW, and the coin-type battery system and the non-contact power supply system are developed. Characteristics and composition know-how of the electric-circuit including thermo-couple in the rotating head are experimentally analyzed in detail.

DOI： 10.2493/jjspe.67.2037

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

We propose a phase-shifting interferometer that uses both phase-locked and photothermal modulating techniques. In this interferometer the measurement accuracy is not affected by the intensity modulation that usually appears in current modulation. The surface profile of a diamond-turned aluminum disk was measured; the rms repeatability obtained was lambda /460. (C) 2001 Optical Society of America.

DOI： 10.1364/AO.40.002126

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-INT SOCIETY OPTICAL ENGINEERING  

A system of small-rotation-angle measurement based on fringe projection is proposed and demonstrated. This system has potential for a broad range of uses and robustness to external disturbances, because it requires no coherent light. The setup is very simple and applicable to automatic on-line measurement. Several measurements indicate a sensitivity of 3 arcsec. (C) 2001 Society of Photo-Optical Instrumentation Engineers.

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A surface profiler incorporating a feedback controller that eliminates external disturbances is proposed and demonstrated. Its overall performance is dependent upon the frequency response of the feedback loop. The frequency of modulating signal strongly influences response of the feedback controller. When using an integrating-bucket method, however, the CCD camera must be operated at the NTSC-approved modulating frequency. Our technique uses electronic-shutter equipped CCD camera. The shutter function enables us to apply high-speed sinusoidal phase modulation to the conventional integrating-bucket method under the NTSC standards.

DOI： 10.1117/12.427093

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The system we propose uses two separate wavelengths to measure step-height. Two laser diodes alternately modulated with a sinusoidal signal separate a like number of overlapping interference images detected by CCD camera, the phase map being obtained by a modulated LD. In this instance, the 1 mum step-height was accurately detected.

DOI： 10.1117/12.427082

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We propose a new method for measuring a position of an endpoint of a metal cylinder in which a sinusoidal intensity distribution vibrating sinusoidally is used. The position of the endpoint is measured as a phase of a sinusoidally phase-modulated signal which is generated from a light diffracted from the endpoint. En order to extend the measurement range and measure a diameter of a metal cylinder two sinusoidal intensity distributions with two different periods of P-1 = 100 mum and P-2 = 98 mum are used. Cylinder diameters are exactly determined from the measurements for two endpoints of a cylinder using the two periods. Experimental results make it clear that the measurement error is less than 0.3 mum for a cylinder metal of 3885.2 mum diameter.

DOI： 10.1117/12.427062

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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The application of a Michelson interferometer with a self-pumped phase-conjugate mirror to measure small vibration amplitudes of a rough surface is described. The distorted wave front of the light that is diffusely reflected from the rough surface is restored by phase conjugation to provide an interference signal with a high signal-to-noise ratio. The vibration amplitudes of a stainless-steel sample are measured with a precision of similar to 5 nm. (C) 2000 Optical Society of America OCIS codes: 120.3180, 190.5040, 120.7280.

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in sinusoidal phase-modulating interferometry an optical path length (OPD) larger than a wavelength is measured by detection of sinusoidal phase-modulation amplitude Z(b) of the interference signal that is produced by sinusoidal scanning of the wavelength of a light source. A light source with a large scanning width of wavelength is created by use of a superluminescent laser diode for the error in the measured value obtained by Z(b) to be smaller than half of the central wavelength. In this situation the measured value can be combined with a fractional value of the OPD obtained from the conventional phase of the interference signal. A sinusoidal wavelength-scanning interferometer with the light source measures an OPD over a few tens of micrometers with a high accuracy of a few nanometers. (C) 2000 Optical Society of America OCIS codes: 120.3180, 120.5050, 120.6650.

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A method of tomographic imaging is proposed in which two-wave mixing in a photorefractive crystal is used with wavelength scanning of a laser diode and phase modulation of the pump beam. This method provides full optical processing and is effective for weak light from objects because of the use of two-wave mixing. The depth resolution of the method was similar to 1 cm when the wavelength-scanning width was similar to 0.02 nm. (C) 2000 Optical Society of America OCIS codes: 170.4500, 170.1650, 190.7070.

DOI： 10.1364/OL.25.001174

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We propose interferometric reflectometry in which a sinusoidal wavelength-scanning tunable laser diode is used to detect positions and profiles of multiple reflecting surfaces. An objective signal extracted from an interference signal contains modulation amplitude Z and phase a, which are related to the positions and profiles, respectively, of multiple reflecting surfaces. By using values of the objective signal at special times, we can produce an image intensity that shows where the reflecting surfaces exist. To obtain exact values of Z or values of a, we estimated the objective signal by using a conjugate gradient method. Experimental results show that a resolution of two-optical-path difference (OPD) in the image intensity is similar to 60 mu m, and the final OPD precisions are 2 and 8 mu m for two and three reflecting surfaces, respectively, for a wavelength-scanning width of 7 nm. Profiles of the front and rear surfaces of a silica glass plate with a thickness of 20 mu m have been measured with a precision of similar to 10 nm. (C) 2000 Optical Society of America OCIS codes: 120.3180, 110.4500, 120.6650.

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A two-wavelength interferometer that uses two separate modulating currents with different phases but the same frequencies to detect a greater degree of object displacement in real time is proposed and demonstrated. The measurement error was 57 nm, roughly 1/80 of the synthetic wavelength. We have confirmed that this modulating technique enables us to equip our prototype interferometer with a simple feedback-control system that eliminates external disturbance. (C) 2000 Optical Society of America OCIS codes: 120.3180, 120.5050, 120.5060, 140.2020.

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A laser-diode (LD) interferometer that uses an accurate photothermal-modulating technique is proposed. Since this technique with the photothermal method modulates only a wavelength of the LD, measurement accuracy is not affected by an intensity modulation that usually appears in the current modulation. The fundamental characteristics of this technique are investigated in detail. The new setup is tested, and its accuracy is compared with that of a previous system. (C) 1999 Optical Society of America OCIS codes: 120.3180, 120.3930, 120.5050, 120.5060, 140.2020, 140.6810.

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A superluminescent diode interferometer that uses sinusoidal phase-modulating interferometry and the shifting method is applied to measure the front and rear surface profiles of a glass plate with an accuracy of a few nanometers. Since the roughness of the reference surface is large, a glass plate is put behind the object as another reference surface, which is estimated by the shifting method with an accuracy of a few nanometers. (C) 1999 Society of Photo-Optical Instrumentation Engineers. [0091-3286(99)01310-0].

DOI： 10.1117/1.602038

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We describe a new method for measuring spatially nonuniform phase changes of a light beam from the spatial nonuniformity of the phase changes, which is obtained by detecting the relative reflectivity change of a self-pumped phase-conjugate mirror. The method is designed to decrease the accumulation of calculating errors. The usefulness of these methods is verified through computer simulations and measurements of the phase changes caused by spatially nonuniform deformation of a semitransparent sheet of silicone gum. (C) 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(99)00609-1].

DOI： 10.1117/1.602206

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE-INT SOCIETY OPTICAL ENGINEERING  

A new type of phase-locked laser diode interferometer that uses self-mixing interference in the optical system is described. The self-mixing interference (SMI) signal is obtained easily by optical feedback, i.e., feeding back the laser beam from the object to the laser diode (LD). The SMI signal can be detected by a photodiode in the package of the LD. Therefore, a beamsplitter, reference mirror, and external photodetector are not required, and an interference signal is obtained using a simple optical system. Although the mechanism of SMI is completely different from that of conventional interference, it is shown that the response of the SMI signal to phase changes is the same as that of conventional interference, We used the phase-locked technique to fix the phase change and demonstrated measurement of absolute distance and displacement, (C) 1999 Society of Photo-Optical instrumentation Engineers. [S0091-3286(99)01503-2].

DOI： 10.1117/1.602132

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DOI： 10.2493/jjspe.65.150

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

In this paper we use a superluminescent diode (SLD) as the light source of an interferometer and extract a narrow spectrum from a wide spectrum of the SLD with a Fabry-Perot Etalone (FPE). By varying sinusoidally the distance between the two mirrors of FPE, the central wavelength of the narrow spectrum is scanned sinusoidally. The distance between the mirrors is exactly set by a feedback control system, and sinusoidal phase-modulated SLD light that has a large scanning width of about 10 nm can be obtained with high stability and spatial uniformity. The phase of the interference signal has two different components. One is amplitude Z(b) Of sinusoidal phase modulation, which is proportional to the optical path difference (OPD) and the scanning width. The other is conventional phase alpha, which provides a fractional value of the OPD in the range of the wavelength. By combining the two values of the OPD obtained from Z(b) and alpha, an exact OPD larger than the wavelength can be measured with high accuracy in alpha. Characteristics of the interferometer are made clear through step-profile measurements.

DOI： 10.1007/s10043-999-0062-z

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

A system of small rotation angle measurement based on the fringe projection is proposed and demonstrated. This system has potential for a broad range of uses and a robustness for the external disturbances, because it requires no coherent light. The setup is very simple and applicable to the automatic on-line measurement. Several measurements indicate a sensitivity of 3 arcsec.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

A system of rotation angle measurement based on the fringe projection is proposed and demonstrated. This system has potential for a broad range of uses and a robustness for the external disturbances, because it requires no coherent light. The setup is very simple and applicable to the automatic on-line measurement. Several measurements indicate a sensitivity of 5 arcsec.

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Two different sinusoidal wavelength-scanning (SWS) interferometers with a SWS light source using a superluminescent laser diode are proposed for step-profile measurement and real-time distance measurement, respectively. An optical path difference (OPD) longer than a wavelength is measured from detection of sinusoidal phase-modulation amplitude Z(b) of the interference signal that is proportional to the OPD and the scanning width 2b. In step-profile measurement, if measurement error in the OPD obtained from Z(b) is Smaller than a half wavelength, this measured value of the OPD is combined with a fractional value of the OPD obtained from the conventional phase of the interference signal. This combination enables us to measure the OPD longer than a wavelength with a high accuracy of a few nm. In real-time distance measurement, the amplitude Z(b) is kept at a specified constant value for changes of OPD by controlling the scanning width 2b of the wavelength with a feedback system. The amplitude Z(b) is detected by processing the interference signal with electric circuits in real-time. The value of b is easily controlled in the SWS light source, and an OPD longer than a wavelength is measured from the value of b with an accuracy of about a wavelength.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We propose an interferometric reflectometry using a sinusoidal wavelength-scanning tunable laser diode to detect positions and profiles of multiple reflecting surfaces. An objective signal extracted from an interference signal contains the modulation amplitude Z and the phase alpha which are related to positions and profiles of multiple reflecting surfaces, respectively. By using values of the objective signal at special times, we can produce an image intensity which shows where the reflecting surfaces exist. To obtain exact values of Z or values of alpha the objective signal is estimated with a conjugate gradient method. Experiments results show that a resolution of two-optical path difference (OPD) in the image intensity is 87 mu m, and a final OPD accuracy is 2 mu m and 8 mu m for the two and three reflecting surfaces, respectively, in the case of the wavelength-seaming width of 7 nm. Profiles of bent and rear surfaces of a silica glass plate with thickness of 20 mu m are measured, with an accuracy of about 10 nm.

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A laser diode interferometer that uses accurate photo-thermal modulating technique is proposed. Since this technique of photo-thermal method modulates just a wavelength of the laser diode, measurement accuracy is not affected by an intensity modulation that is used to be appeared in the current modulation. The fundamental characteristics of this technique is investigated in detail. The new setup is tested, and its accuracy compared with that of an earlier system.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SHAKER VERLAG GMBH  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SHAKER VERLAG GMBH  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPIE - INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING  

A memory matrix provides output vectors that are specified by the corresponding input vectors. If the input vectors represent input characters, the memory matrix performs character recognition. When the input characters contain noise, it is difficult to recognize the characters. To overcome this difficulty, we generate a new memory matrix by using singular value decomposition and manipulating the singular values. The effectiveness of the memory matrix is made clear by recognizing 26 alphabets characters containing noise with an optical recognition system, (C) 1998 Society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.601781

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DOI： 10.2493/jjspe.64.1355

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We propose an interferometer in which the relationship between the degree of coherence (DCH) and the optical path difference (OPD) is utilized for determining an OPD longer than a wavelength. A superluminescent diode is employed as the source of the interferometer, and sinusoidal phasemodulating interferometry is used to detect the DCH and the phase of the interference signal. The combination of the OPD determined from the DCH and the phase of an interference signal enables us to measure an OPD longer than a wavelength with a high accuracy of a few nanometers. Experimental results show clearly the usefulness of the interferometer for a step-profile measurement. © 1998 Optical Society of America.

DOI： 10.1364/AO.37.005126

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

We propose an interferometer in which the relationship between the degree of coherence (DCH) and the optical path difference (OPD) is utilized for determining an OPD longer than a wavelength. A superluminescent diode is employed as the source of the interferometer, and sinusoidal phase-modulating interferometry is used to detect the DCH and the phase of the interference signal. The combination of the OPD determined from the DCH and the phase of an interference signal enables us to measure an OPD longer than a wavelength with a high accuracy of a few nanometers. Experimental results show clearly the usefulness of the interferometer for a step-profile measurement. (C) 1998 Optical Society of America.

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A method is proposed in which handwritten characters are recognized using feature extraction and an associative memory matrix. In feature extraction, simple processes such as shifting and superimposing patterns are executed. A memory matrix is generated with singular value decomposition and by modifying small singular values. The method is optically implemented with two liquid crystal displays. Experimental results for the recognition of 26 handwritten alphabet characters clearly show the effectiveness of the method. (C) 1998 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(98)00206-2].

DOI： 10.1117/1.601832

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

In sinusoidal phase-modulating interferomety an optical path length (OPD) larger than a wavelength is measured by detecting sinusoidal phase-modulation amplitude of the interference signal. This interference signal is produced by scanning sinusoidally wavelength of a light source. If the measurement accuracy in OPD is higher than half of the central wavelength, this measured value is combined with a fractional value of the OPD which is obtained from the conventional phase of the interference signal. The measurement accuracy in OPD is higher as the scanning width of wavelength is larger. We propose two different methods to create a light source with a large scanning width of wavelength by using superluminescent laser diode and external-cavity tunable laser diode. Experimental results clearly show that sinusoidal wavelength-scanning interferometers using these light sources measure an OPD over a few tens of microns with a high accuracy of a few nm.

DOI： 10.1117/12.312959

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

A laser diode interferometer that uses an optical fiber is proposed. The laser diode simultaneously functions as a light source, a phase modulator, and a phase compensator. Detection of the vibration and reduction of external disturbance are carried out using a feedback control for the injection current of the laser diode. Thus it can measure vibration accurately in real time with a simple signal processing circuit. The optical fiber not only functions as a flexible probe, enabling us to measure the vibration of an object that cannot be moved onto the optical bench, it also acts as a reference mirror, thereby simplifying the unit construction. The principle of the feedback control in laser diode interferometer is also described in detail. (C) 1997 society of Photo-Optical Instrumentation Engineers.

DOI： 10.1117/1.601475

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

We propose a new signal-processing method for eliminating measurement errors that occur in the wavelength-multiplexed phase-locked laser diode interferometer. The basic idea proposed here is a very simple but effective way to improve measurement accuracy. With our scheme, the phase in the interference signal is strictly shifted by 2 pi, which enables us to eliminate measurement errors, The equivalent wavelength Lambda is 80 mm, and the measurement accuracy reaches similar to Lambda/600. A step-height measurement was also carried out in the experiment. (C) 1997 Optical Society of America.

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

Eased on the idea of measuring small rotation angles with a parallel interference pattern (PIP), a method is developed to measure large rotation angles accurately. Two parallel PIP's that have different periods are used to measure a rotation angle of an object. The measurement made with a small-period PIP provides a high accuracy, and the measurement made with a large-period PIP provides a wide range. An accurate measurement for wide-range angles is made by combining the two measured values. The accuracy of the phase detection is determined by the periods of two PIP's. Rotation angles from approximately -30 to 30 are min can be measured with an accuracy of 0,2 are sec. Analytical results are supported by experimental results. (C) 1997 Optical Society of America.

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A new type of phase-locked laser diode interferometer which uses self-mixing interference in the optical system is described. The self-mixing interference signal is obtained easily by the optical feedback or feeding back laser beam from the object to the laser diode (LD). The interference signal can be detected by a photodiode which is in the package of the LD. Therefore, a beam splitter, reference mirror and external photodetector are not required, and a kind of interference signal is obtained by a simple optical system. But the signal is not as same as that, which is obtained in a conventional interferometer. We used the phase-locked technique to measure the phase change in the self-mixing interference signal. This technique enables us to detect the displacement of an object. We describe our principle, experimental setup, and experimental results.

DOI： 10.1117/12.279138

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE - INT SOC OPTICAL ENGINEERING  

A new type of two-wavelength interferometer for the measurement of absolute distance is described. Since the wavelength of the laser diode is temporally multiplexed, only one laser diode light-source is required, thus eliminating the necessity of aligning two independent optical axes. Absolute distance is calculated from the difference of the phases in the interference signals generated by each wavelength. The self-correlation function is applicable in our system for detecting this phase-difference between two kinds of interference signals, thereby, the signal processing is very simple and there is a possibility that the real-time distance measurement becomes possible in our new method.

DOI： 10.1117/12.270028

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

Based on measuring one-dimensional small rotation angles by using a parallel interference pattern (PIP), a method for measuring two-dimensional (2D) small rotation angles by using two different PIP's that are orthogonal to each other is proposed. We simultaneously measure the 2D small rotation angles Delta theta and Delta phi by detecting the phases of the orthogonal PIP's reflected by an object at two detection points. A sensitivity of 4.9 mrad/arcsec and a spatial resolution of 1.5 x 1.5 mm(2) are achieved in the measurement. Theoretical analysis and experimental results show that error epsilon(1) in the measurement of Delta phi is almost equal to -0.01 Delta theta and error epsilon(2) in the measurement of Delta theta is almost equal to -0.01 Delta phi. For small rotation angles of less than a few tens of arcseconds, the random errors whose standard deviations are 0.6 arcsec are dominant. (C) 1996 Optical Society of America

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DOI： 10.2493/jjspe.62.1009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC PHOTO-OPT INSTRUM ENG  

A new type of two-wavelength interferometer which applies a phase-lock technique is described. The wavelength tunability of a laser diode (LD) is used for phase modulation and phase control in this interferometer. Since the two wavelengths are derived from a single LD in our system, the optical system is simple and there is no need to consider the fluctuation of relative wavelength between the two LD's in the conventional two-wavelength interferometers. The equivalent wavelength Lambda is 15 mm and the measurement accuracy reaches <similar similar to Lambda/400. The error sources in the system and the error analysis are also described. (C) 1996 Society of Photo-Optical instrumentation Engineers.

DOI： 10.1117/1.600921

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DOI： 10.2493/jjspe.62.210

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society for Precision Engineering  

The present research aims at establishing an accurate and reliable methodology to estimate the heat quantity generated during the rotation of spindle and to evaluate the characteristics of the spindles employed for various types of machining. The technique proposed here basically depends on the accurate measurement of the change in the rota-tional speed of spindle during its free run. A new method is presented in the present report to measure the rotational speed of spindle accurately in a rotational speed range up to 100000 rpm by applying a reflective sensor system. The method developed here was applied to estimate the heat quantity of various types of spindle. It was clarified through experiments that the surface roughness of the spindle rotor affects the heat quantity generated, and also that the coefficients of the thermal expansion of the rotor and spindle housing affect the clearance between the two and consequently the heat genera-tion. The effect of air stirring by the bolt holes is also discussed.

DOI： 10.2493/jjspe.61.1584

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We propose a method of exact measurement of flat surface profiles in a phase-conjugate Fizeau interferometer. Aberration of lenses causes an undesirable phase distribution in the interference signal of the phase-conjugate Fizeau interferometer. To eliminate this phase distribution, we shift the object in two directions orthogonal to each other and we get difference values of the surface profile of the object. Additional displacements of the object surface involved in the shifts lead to some small errors in the difference values. We estimate an exact surface profile by solving the difference equations. Characteristics of the method are made clear through computer simulations and measurements of a 40-mm-diam flat mirror.

DOI： 10.1117/12.210750

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We propose a method for measuring rotation angles by using a parallel interference pattern. At two points on a parallel interference pattern reflected by an object, we detect phase changes in the reflected parallel interference pattern caused by rotations of the object. A high sensitivity, or a high ratio of the phase change to the rotation angle, 17 mrad/arcsec, can be achieved by determining the positions of two detection points. A high spatial resolution of similar to 0.5 mm is also obtained. We analyze the measurement error caused by the alignment of the parallel interference pattern and a random measurement error caused by the phase detection. The theoretical analyses and the experimental results make the characteristics of the method clear and show that the method has an accuracy of 0.2 arcsec for small rotation angles.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC PHOTO-OPT INSTRUM ENG  

The response of a self-pumped phase-conjugate mirror to spatially nonuniform phase change of incident wave is examined with a phase-conjugate Fizeau interferometer. The experimental results make it clear that the spatially nonuniform phase change of the incident wave is not reversed by the self-pumped phase-conjugate wave (SPPCW) immediately after the phase change, and the decrease of phase-conjugate reflectivity caused by the nonuniform phase change is proportional to the nonuniformity of the phase change. The phase characteristic of the SPPCW makes the phase-conjugate Fizeau interferometer for surface profile measurements insensitive to object vibrations. The reflectivity characteristics enable us to measure the nonuniform phase change by detecting the intensity of the SPPCW.

DOI： 10.1117/12.196557

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2493/jjspe.61.511

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Language：English   Publishing type：Research paper (scientific journal)  

We propose a method for measuring rotation angles by using a parallel interference pattern. At two points on a parallel interference pattern reflected by an object, we detect phase changes in the reflected parallel interference pattern caused by rotations of the object. A high sensitivity, or a high ratio of the phase change to the rotation angle, 17 mrad/arcsec, can be achieved by determining the positions of two detection points. A high spatial resolution of 0.5 mm is also obtained. We analyze the measurement error caused by the alignment of the parallel interference pattern and a random measurement error caused by the phase detection. The theoretical analyses and the experimental results make the characteristics of the method clear and show that the method has an accuracy of 0.2 arcsec for small rotation angles. © 1995 Optical Society of America.

DOI： 10.1364/AO.34.006380

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE - INT SOC OPTICAL ENGINEERING  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE - INT SOC OPTICAL ENGINEERING  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE - INT SOC OPTICAL ENGINEERING  

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Language：English   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC PHOTO-OPT INSTRUM ENG  

A real-time 2-D surface profile measurement system is described. In this system, a laser diode and a 2-D charge-coupled device image sensor are used as a light source and a photodetector, respectively. The phase is detected from the sinusoidal phase-modulating interference signal using the high-speed electrical circuit. The time required for phase detection is 20 ms for 50 x 40 measuring points. Because the phases can be obtained for even and odd fields of the image sensor, the' original spatial resolution of the image sensor is not reduced in this system. Repeatability of the measurement is approximately 14 nm, rms.

DOI： 10.1117/12.173561

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC PHOTO-OPT INSTRUM ENG  

A sinusoidal phase-modulating Fizeau interferometer using a BaTiO3 self-pumped phase conjugator is constructed to measure surface profiles of objects with a high accuracy. An object field is formed on a surface of a glass plate where the object wave interferes with its phase conjugate wave. Because the size of the glass plate can be much smaller than that of the object, the sinusoidal phase modulation by vibrating the glass plate is easy and accurate for measurements of the surface profiles of large-diameter objects. The interferometer is self-referencing and free of the phase fluctuations of the object wave caused by spatially uniform movements of objects. The usefulness of the interferometer is made clear through the surface profile measurements of a diamond-turned aluminum disk and mirror.

DOI： 10.1117/12.173590

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Language：Japanese   Publishing type：Doctoral thesis  

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

Improvement of the response time of the BaTiO3 self-pumped phase-conjugate mirror is demonstrated with a simple configuration. It is based on beam amplification in the crystal driven by an additional bias beam.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC PHOTO-OPT INSTRUM ENG  

A real-time displacement measurement system using a sinusoidal phase modulating interferometer is proposed and demonstrated. The system utilizes the frequency components of the interference signal to detect the desired phase or the displacement in real time. The real-time phase detector is constructed with simple electronic circuits. The system also has a feedback loop to eliminate external disturbance. It is easy to measure the relatively large displacement that exceeds a half wavelength of the light because the compensation circuit is incorporated into the system to obtain continuous phase outside the region from 0 to 2pi.

DOI： 10.1117/12.130252

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE - INT SOC OPTICAL ENGINEERING  

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

A phase-locked laser diode interferometer with differential detection to eliminate external disturbance is proposed. In this interferometer, the measurements are implemented at two different points at the same time. The surface profile that contains the disturbance is obtained at the scanned measuring point, and the disturbance is obtained at the fixed measuring point. The exact profile is obtained by subtracting the latter from the former. The limitations and characteristics are examined theoretically. The analytical results agree well with the experimental results. The repeated measurement accuracy is estimated to be approximately 5 nm in this interferometer.

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

A novelty imaging system using photorefractive crystal BaTiO3 and a controlled shutter sequence, which can be applied to the slow-motion detection of the object, is proposed. In this system the observation time scale is set to the desired long value uninfluenced by the time constant of the crystal that is used. This system utilizes a photorefractive beam-fanning effect in the BaTiO3 crystal, so it is constructed simply by using only the object beam without suffering from the external disturbance that is intrinsic when the reference beam is used. Moreover, the visibility for an opaque object is also maintained by the use of an additional random-phase plate. We examine the basic characteristics and determine the appropriate conditions of the system.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE - INT SOC OPTICAL ENGINEERING  

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

We describe a two-wavelength laser-diode interferometer that is insensitive to external disturbances such as fluctuations in the wavelength of the laser diode and mechanical vibrations of the optical components. In sinusoidal phase-modulating interferometry this insensitivity is easily obtained by controlling the injection current of the laser diode with a feedback control system. Using an equivalent wavelength of 152-mu-m provided by two single-frequency laser diodes, we can measure the distance, rotation angle, and surface profile measurements with great accuracy.

DOI： 10.1364/AO.30.004040

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

We have previously proposed a phase-locked laser diode interferometer. In that previous interferometer, however, there was substantial room for improvement in the reduction of measurement time. This reduction is achieved by using a different process for generation of the feedback signal in which the output of a charge-coupled device image sensor is used effectively. We analyze the feedback control system of the interferometer as a discrete-time system and discuss the characteristics of the interferometer. It is shown that the measurement time is much shorter than that of the interferometer proposed previously.

DOI： 10.1364/AO.30.003622

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

Sinusoidal phase-modulating interferometry is used to detect exactly the sinusoidal phase variation of an interference signal even when the amplitude of the interference signal is varied by modulation of the injection current. We can easily provide a sinusoidal phase-modulating interferometer with a feedback control system that eliminates the phase fluctuations caused by mechanical vibrations. The methods using sinusoidal phase-modulating interferometry improve the resolution of distance measurements. Experimental results show that the thickness of gauge blocks is measured with a resolution of approximately 0.5-mu-m.

DOI： 10.1364/AO.30.003617

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Language：English   Publishing type：Research paper (scientific journal)  

We describe a two-wavelength laser-diode interferometer that is insensitive to external disturbances such as fluctuations in the wavelength of the laser diode and mechanical vibrations of the optical components. In sinusoidal phase-modulating interferometry this insensitivity is easily obtained by controlling the injection current of the laser diode with a feedback control system. Using an equivalent wavelength of 152 limprovided by two single-frequency laser diodes, we can measure the distance, rotation angle, and surface profile measurements with great accuracy. © 1991 Optical Society of America.

DOI： 10.1364/AO.30.004040

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Language：English   Publishing type：Research paper (scientific journal)  

Sinusoidal phase-modulating interferometry is used to detect exactly the sinusoidal phase variation of an interference signal even when the amplitude of the interference signal is varied by modulation of the injection current. We can easily provide a sinusoidal phase-modulating interferometer with a feedback control system that eliminates the phase fluctuations caused by mechanical vibrations. The methods using sinusoidal phase-modulating interferometry improve the resolution of distance measurements. Experimental results show that the thickness of gauge blocks is measured with a resolution of ∽-0.5 μm. © 1991 Optical Society of America.

DOI： 10.1364/AO.30.003617

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC PHOTO-OPT INSTRUM ENG  

DOI： 10.1117/12.55754

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

DOI： 10.1364/AO.28.005270

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Language：English   Publishing type：Research paper (scientific journal)  

We propose a new type phase locked interferometer which uses tunability of the wavelength of a laser diode. The phase lock is achieved by controlling the injection current of the laser diode. A CCD image sensor is used as a photodetector to scan electrically a measuring point along the surface of the object. Since this interferometer uses no mechanical elements such as a piezoelectric transducer and galvanomirror, the measurement accuracy is not limited by the mechanical properties. The characteristics of the feedback control system for the phase lock are examined through measurements of surface profiles of the diamond-turned aluminum disks. © 1989, Optical Society of America.

DOI： 10.1364/AO.28.004407

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

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE - INT SOC OPTICAL ENGINEERING  

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Language：English   Publishing type：Research paper (scientific journal)  

CiNii Article

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Language：Japanese  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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J-GLOBAL

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Language：Japanese   Publisher：Japanese Society for Engineering Education  

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