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Measurement of displacement using interference fringes localized at infinity
Measurements of surface profile and refractive distribution by real-time fringe analysis
index
Institute
of Physical
8th Meeting on Lightwave Sensing Technology, Society of Lightwave Sensing Technology. Japan Applied Physics
and
Japanese Society of
A real-time fringe analysing technique using the phase-shifting electronic moire method is described. This technique can deliver phase distribution directly from a single fringe pattern which contains a spatial carrier. We multiply the input fringe by three computer-generated reference gratings with a relative phase-shift and obtain three phase-shifted moire patterns by low-pass filtering. The phase distribution is derived from these patterns with a highspeed signal processor based on the phase-shifting technique. Experiments have shown that the method is useful for analysis of various fringe patterns. which are used for real-time measurements of surface profile. refractive index distribution etc.
Measurement of displacement localized at infinity
using interference
fringes
Tomoaki Eiju. Kiyofumi Matsuda. T.H. Barnes, Yusrandihardja. D. Santika. Makoto Yamauchi 8th Meeting on Lightwave Sensing Technology, Society of Lightwave Sensing Technology, Japan Applied Physics
Japanese Society of
Fringe counting techniques are often used in modern laser interferometers for measuring displacement. These interferometers are essentially integrating devices. where the displacement is derived from an accumulated fringe count. that is. they measure travel rather than static displacement. If the interferometer optical paths are interrupted during a measurement cycle. the reference for the instrument is lost and accuracy suffers. In this paper. we describe a holographic technique whereby displacement is measured by analysing a fringe pattern localized at infinity which is equivalent to Haidinger or Brewster fringes in conventional interferometry. The phase distribution ofthe fringe pattern is measured to high accuracy using phase-stepping interferometry. and then analysed by computer. Using this technique. we were able to measure in-plane displacements with an accuracy of about 0.2 pm. whilst the accuracy for out-of-plane displacements was about :! ,um.
RCAST, Research Centre for Advanced nology. The University of Tokyo
Hidenohu Okamoto *Fuji
of optical
current
transformer
Koide*, Kouji Konno. Mamoru
Electric
for GIS
Yamada.
Tatsuo
R&D Ltd.
8th Meeting on Lightwave Sensing Technology. Society of Lightwave Sensing Technology. Japan Applied Physics
Japanese Society of
Recently. optical current and voltage measuring systems have been developed for applications in electric power systems. The authors have developed an optical current measuring system based on the magneto-optical effect (the Faraday effect). to apply to gas insulated switchgears (GIS). The test result of this system is that the ratio error was less than I! 1.00x,in the current range of lo0 A to 2000 A. and the temperature stability was less than + 1.0%in the temperature range of -20°C to 90°C. In addition. the effect of the magnetic field caused by the other conductors’ current was 0.4%~
Optics Et Laser Technology Vol24 No 3 1992
Science
bias in
and Tech-
8th Meeting on Lightwave Sensing Technology. Society of Lightwave Sensing Technology. Japan Applied Physics
Japanese Society of
Through research on the noise sources in an Optical Passive RingResonator Gyro (OPRG). the bias induced by the optical Kerr-effect has been calculated to be one of the dominant noise sources. Our group has proposed one method to reduce this bias. in which the input lightwave-intensity into the resonator is modulated with a square wave. However. in this method. requirements for the intensity modulator. such as the bandwidth and the extinction ratio. are rather severe. We propose a novel method to reduce the optical Kerr-effect induced bias. The bias is monitored by modulating the light-source intensity. and fed back into one lightwave intensity travelling in the resonator to make it zero. The basic experiment to verify the principle of this method is successfully carried out.
Spectral
image
analysis
by vector subspace
method
S. Toyooka. S. Izawa. N. Hayasaka, H Kadono. T. Jaaskelainen Saitama
University.
University
of Joensuu
8th Meeting on Lightwave Sensing Technology. Society of Lightwave Sensing Technology. Japan Applied Physics
Japanese Society of
The vector subspace method is a technique for statistical pattern recognition. In this paper. a seven-dimensional subspace which reflects a spectral feature of every visible colour in the world is used to analyse a two-dimensional colour image. Optical implementation of spectral image analysis by the subspace method is proposed. A ray of light which has a desired spectrum distribution corresponding to the basis vector of the subspace is made by a spatial filtering system including a liquid-crystal spatial filter placed at the dispersion plane. An iterative feedback method to make a spatial filter on the liquid crystal panel is proposed. A biological sample under a microscope is analysed.
Temperature measurement the vicinity of tibre end Development
induced
Koich Takiguchi. Kazuo Hotate
Junichi Kate, Ichirou Yamaguchi Optical Engineering Lab.. The Chemical Research (RIKEN)
Method to reduce the optical Kerr-effect an optical passive ring-resonator gyro
using reverse mirage effect in
Kazuya Ohta. Norihiro Umeda Faculty of Technology. Technology
Tokyo
University
of Agriculture
8th Meeting on Lightwave Sensing Technology. Society of Lightwave Sensing Technology. Japan Applied Physics
&
Japanese Society of
This paper describes a new technique to measure a temperature in a small region by the use of a reverse mirage effect. This effect is a refractive index gradient of air at the vicinity of an optical tibre end covered with an optically absorbable material. A sample in the field of the reverse mirage modifies the refractive index gradient depending on its temperature. Therefore. the sample temperature can be obtained by detecting a deflection angle of the probe beam. which measures the refractive index gradient of air. A theoretical analysis by heat conduction is discussed and the experimental results on the reverse mirage effect are presented. Also. a temperature measurement of the heating wire is demonstrated.
159
index
Institute
of Physical
8th Meeting on Lightwave Sensing Technology, Society of Lightwave Sensing Technology. Japan Applied Physics
and
Japanese Society of
A real-time fringe analysing technique using the phase-shifting electronic moire method is described. This technique can deliver phase distribution directly from a single fringe pattern which contains a spatial carrier. We multiply the input fringe by three computer-generated reference gratings with a relative phase-shift and obtain three phase-shifted moire patterns by low-pass filtering. The phase distribution is derived from these patterns with a highspeed signal processor based on the phase-shifting technique. Experiments have shown that the method is useful for analysis of various fringe patterns. which are used for real-time measurements of surface profile. refractive index distribution etc.
Measurement of displacement localized at infinity
using interference
fringes
Tomoaki Eiju. Kiyofumi Matsuda. T.H. Barnes, Yusrandihardja. D. Santika. Makoto Yamauchi 8th Meeting on Lightwave Sensing Technology, Society of Lightwave Sensing Technology, Japan Applied Physics
Japanese Society of
Fringe counting techniques are often used in modern laser interferometers for measuring displacement. These interferometers are essentially integrating devices. where the displacement is derived from an accumulated fringe count. that is. they measure travel rather than static displacement. If the interferometer optical paths are interrupted during a measurement cycle. the reference for the instrument is lost and accuracy suffers. In this paper. we describe a holographic technique whereby displacement is measured by analysing a fringe pattern localized at infinity which is equivalent to Haidinger or Brewster fringes in conventional interferometry. The phase distribution ofthe fringe pattern is measured to high accuracy using phase-stepping interferometry. and then analysed by computer. Using this technique. we were able to measure in-plane displacements with an accuracy of about 0.2 pm. whilst the accuracy for out-of-plane displacements was about :! ,um.
RCAST, Research Centre for Advanced nology. The University of Tokyo
Hidenohu Okamoto *Fuji
of optical
current
transformer
Koide*, Kouji Konno. Mamoru
Electric
for GIS
Yamada.
Tatsuo
R&D Ltd.
8th Meeting on Lightwave Sensing Technology. Society of Lightwave Sensing Technology. Japan Applied Physics
Japanese Society of
Recently. optical current and voltage measuring systems have been developed for applications in electric power systems. The authors have developed an optical current measuring system based on the magneto-optical effect (the Faraday effect). to apply to gas insulated switchgears (GIS). The test result of this system is that the ratio error was less than I! 1.00x,in the current range of lo0 A to 2000 A. and the temperature stability was less than + 1.0%in the temperature range of -20°C to 90°C. In addition. the effect of the magnetic field caused by the other conductors’ current was 0.4%~
Optics Et Laser Technology Vol24 No 3 1992
Science
bias in
and Tech-
8th Meeting on Lightwave Sensing Technology. Society of Lightwave Sensing Technology. Japan Applied Physics
Japanese Society of
Through research on the noise sources in an Optical Passive RingResonator Gyro (OPRG). the bias induced by the optical Kerr-effect has been calculated to be one of the dominant noise sources. Our group has proposed one method to reduce this bias. in which the input lightwave-intensity into the resonator is modulated with a square wave. However. in this method. requirements for the intensity modulator. such as the bandwidth and the extinction ratio. are rather severe. We propose a novel method to reduce the optical Kerr-effect induced bias. The bias is monitored by modulating the light-source intensity. and fed back into one lightwave intensity travelling in the resonator to make it zero. The basic experiment to verify the principle of this method is successfully carried out.
Spectral
image
analysis
by vector subspace
method
S. Toyooka. S. Izawa. N. Hayasaka, H Kadono. T. Jaaskelainen Saitama
University.
University
of Joensuu
8th Meeting on Lightwave Sensing Technology. Society of Lightwave Sensing Technology. Japan Applied Physics
Japanese Society of
The vector subspace method is a technique for statistical pattern recognition. In this paper. a seven-dimensional subspace which reflects a spectral feature of every visible colour in the world is used to analyse a two-dimensional colour image. Optical implementation of spectral image analysis by the subspace method is proposed. A ray of light which has a desired spectrum distribution corresponding to the basis vector of the subspace is made by a spatial filtering system including a liquid-crystal spatial filter placed at the dispersion plane. An iterative feedback method to make a spatial filter on the liquid crystal panel is proposed. A biological sample under a microscope is analysed.
Temperature measurement the vicinity of tibre end Development
induced
Koich Takiguchi. Kazuo Hotate
Junichi Kate, Ichirou Yamaguchi Optical Engineering Lab.. The Chemical Research (RIKEN)
Method to reduce the optical Kerr-effect an optical passive ring-resonator gyro
using reverse mirage effect in
Kazuya Ohta. Norihiro Umeda Faculty of Technology. Technology
Tokyo
University
of Agriculture
8th Meeting on Lightwave Sensing Technology. Society of Lightwave Sensing Technology. Japan Applied Physics
&
Japanese Society of
This paper describes a new technique to measure a temperature in a small region by the use of a reverse mirage effect. This effect is a refractive index gradient of air at the vicinity of an optical tibre end covered with an optically absorbable material. A sample in the field of the reverse mirage modifies the refractive index gradient depending on its temperature. Therefore. the sample temperature can be obtained by detecting a deflection angle of the probe beam. which measures the refractive index gradient of air. A theoretical analysis by heat conduction is discussed and the experimental results on the reverse mirage effect are presented. Also. a temperature measurement of the heating wire is demonstrated.
159