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Mitsunori SAITO, Katsuhiro KIKUCHI
1997 Volume 4 Issue 5 Pages
527-538
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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Notably improved performance as well as extended application areas is expected in the technology of optical fiber sensors using infrared fibers that transmit radiation in a wavelength range beyond 2 μm. Measurement of infrared radiation is particularly important in thermometry and spectrometry. In these areas, the use of infrared fibers has been studied extensively not only as a transmission waveguide but also as a sensor chip. Of various infrared fibers, fluoride glass fibers exhibit the lowest transmission loss and hence are useful for remote sensing that requires light transmission over a long distance. The wide transmission range of chalcogenide glass fibers and halide crystalline fibers is valuable for thermometry in a low temperature range and for spectrometry of various molecules. Hollow waveguides are useful as a capillary flow cell that realizes fast-response spectrometry. The advantages and disadvantages of infrared fibers must be considered carefully in the development of fiber sensors. In this paper, the progress of infrared optical fiber sensors is reviewed with particular interest in thermometry and spectroscopy.
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Jianping DING, Masahide ITOH, Toyohiko YATAGAI
1997 Volume 4 Issue 5 Pages
539-542
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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An optimal incoherent filter is proposed for distortion-invariant correlation. The optical transfer function (OTF) of the correlator is specified as a realizable phase-only term which is optimized by the simulated annealing algorithm. The phase-only OTF is used in image recognition to produce a sharp peak response and can be generated by dual-filter synthesis. Image recognition is achieved by subtracting two spatially incoherent correlation outputs produced from a positive and negative filters with an input image. Computer simulations show that the proposed correlator can yield a sharp correlation peak with excellent distortion tolerance.
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Hideaki OKAYAMA, Takeshi KAMIJOH
1997 Volume 4 Issue 5 Pages
543-545
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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We propose a wavelength router design to improve insertion loss uniformity. Branched waveguides are placed at junctions between the waveguide array and a planar waveguide. The diffracted light injected into planar waveguides is forwarded in different directions. At the image plane of the planar waveguide, a flat top envelope is attained to ensure loss uniformity among output ports.
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Chang–qing XU, Hideaki OKAYAMA, Takeshi KAMIJOH
1997 Volume 4 Issue 5 Pages
546-549
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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A novel configuration is proposed for polarization insensitive wavelength conversions using a LiNbO
3 waveguide with a periodically domain inverted structure. The proposed configuration consists of multiple rings, which are connected by a polarization sensitive wavelength converter such as the LiNbO
3 waveguide described. One ring containing a pump light source is used to pump the wavelength converter bidirectionally, while the other rings containing a polarization beam splitter and a 90polarization rotator are used to couple in the input signal and extract the converted light. The proposed method is proven experimentally by the wavelength conversion based on sum frequency generation.
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Marc BRUNEL, Olivier EMILE, Fabien BRETENAKER, Albert LEFLOCH, Bernard ...
1997 Volume 4 Issue 5 Pages
550-552
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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We built a compact two-tunable-frequency longitudinally pumped solid-state laser specially designed to measure atomic lifetimes. Weak coupling between the laser eigenstates permits the obtaining of a continuously tunable frequency difference between 0 and 10 GHz. Such a source provides either a linear polarization rotating at such frequencies, or a sinusoidally modulated intensity with a 100% modulation amplitude. As an example, the fluorescence lifetime of the first excited state of Cr
4+ in YAG is measured in the zero-fluence limit using a two-frequency Nd:YAG laser at 1064 nm.
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Bruno ULLRICH, Mitsuhito SASAKI, Takayoshi KOBAYASHI
1997 Volume 4 Issue 5 Pages
553-555
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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All-optical photo-thermally induced bistabilities in luminescence of a thin (10 μm) CdS:Cu film were studied at 170 K. The bistable effect was induced by the 514.5 nm line of an argon laser and measured by putting low-pass filters for yellow and red light in the reflected and transmitted beams. In the visible part of the spectrum, the loop contrasts measured in reflection geometry are considerably smaller than those achieved in transmission geometry. In the near infrared, however, the loop contrasts do not depend on the geometry used. This is due to the observation that visible emissions from the surface region depend less sensitively on temperature than do those from the bulk.
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Chi Ching CHANG
1997 Volume 4 Issue 5 Pages
556-560
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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We demonstrate the simultaneous phase conjugation of multiple beams incident on the a face of a photorefractive barium titanate crystal. The input beam power, angle and position were set so that no phase conjugation occurs unless a switchable incoherent inducing beam is present on the -c face of the crystal. The use of the inducing technique with two mutually pumped phase conjugations for four input beams, or one self-pumped and one mutually pumped phase conjugation for three input beams can be performed in a crystal. Unlike the setup of conventional phase conjugation, which requires more precise arrangements, the novel setup of the multi-beam induced phase conjugation is relatively relaxed. The mechanism responsible for our discovery is qualitatively explained, and possible applications are mentioned.
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Wanji YU, Takumi MINEMOTO, Takao IKUNO
1997 Volume 4 Issue 5 Pages
561-566
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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A new method for rotation and brightness invariant pattern recognition was proposed by applying multiple circular harmonic expansions to the joint transform correlator. The amplitudes of the multiple orders of circular harmonic expansions made from a detecting image were synthetically modified to respond to the same auto-correlation peaks. These modified circular harmonic expansions were arranged in the input plane as reference patterns together with an arbitrary target pattern, and the correlation signals between them were calculated in the subtracted joint transform correlator. The fraction of the correlation-peak intensities between the target and the references were extracted as a new discrimination parameter. This new parameter performs pattern recognition under rotation and brightness invariance with good discriminability. Its high discriminability has been proved in computer simulations using the face image patterns of many individuals.
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Ting–Chung POON, Kyu B. DOH, Bradley SCHILLING, Kazunori SHINOD ...
1997 Volume 4 Issue 5 Pages
567-571
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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Three-dimensional (3-D) or holographic information extracted by two-dimensional active optical heterodyne scanning has been demonstrated recently. The technique is called optical scanning holography. To reconstruct the obtainable 3-D holographic information, digital techniques have been used and demonstrated. For real-time applications, we need to investigate spatial-light-modulator-based systems. In this paper, we first briefly review optical scanning holography, and then present experimental results of 3-D image reconstruction using an electron-beam-addressed spatial light modulator.
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Rafal KASZTELANIC, Juan CAMPOS, Katarzyna CHALASINSKA–MACUKOW
1997 Volume 4 Issue 5 Pages
572-577
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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The present paper proposes a modification of a simple optoelectronic architecture (A. Bergeron et al.: Appl. Opt. 33 (1994) 1463) for carrying out optical thresholding operations. The threshold operation is achieved by means of a feedback loop. The setup is modified by inserting an attenuator adapted in each iteration to the total incident energy measured by an intensity detector. The proposed architecture does not need an additional light source, assures translation invariance and does not break the beam propagation path. The adaptive attenuator permits working under different lighting conditions (illumination, partially occluded objects, etc.). This kind of architecture is suitable for an optical pattern recognition task, optical neural network or optical associative memory. Application of the modified thresholder to the recognition task based on an optical correlator is reported.
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De–Kui QING, Ichirou YAMAGUCHI, Kiminori ITOH, Masayuki MURABAYA ...
1997 Volume 4 Issue 5 Pages
578-583
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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An optical waveguide sensor structure, i.e. a coupling-wave structure, is presented and analyzed on the basis of a codirectional coupler. Potential uses for absorption-and fluorescence based sensors are theoretically explained by the group index method (D.-K. Qing, X-.M-. Chen, K. Itoh, M. Murabayashi: J. Lightwave Technol. 14 (1996) 1907). Refractive-index-based sensors were also analyzed. An actual coupling-wave structure was realized by combining the ion-exchange and the sol-gel methods. The coupling-wave structure that provides effective sensing interaction is easy to fabricate and can be used to realize optical waveguide chemical or biological sensors.
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Minoru SASAKI, Yuji ARAI, Kazuhiro HANE
1997 Volume 4 Issue 5 Pages
584-587
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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Properties of the shape memory alloy of 29 μm thick Ni-Ti foil are investigated as an actuator to align optical elements. Since the intrinsic properties of the Ni-Ti foil are not satisfactory in reproducibility and hysteresis, a simple feedback control is used. A pinhole integrated with a surrounding position sensor is proposed to realize a confocal optical system having an automatic alignment function. Large displacement (~mm) and precision at the level of the optical wavelength are found to be possible.
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Yoshihiro OSHIDA, Yoshihisa IWAHASHI, Koichi IWATA
1997 Volume 4 Issue 5 Pages
588-592
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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A method for accurately measuring information about the deformation of a rough surface object using a phase-shifting speckle interferometer with a television camera and a computer is considered. In this case, the intensity change of the speckle by phase-shifting varies randomly in space because of the statistical property of the speckle. Then, at points with small intensity change, the accuracy of the phase measurement is affected significantly by the quantization error of an analog to digital converter for data recording. To improve the accuracy, the statistical property of the interference speckle must be clarified. This is done theoretically and experimentally, and the experimental results show that higher measurement accuracy can be attained by selecting large amplitude points.
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Naoshi BABA, Kaichirou SHIBAYAMA
1997 Volume 4 Issue 5 Pages
593-595
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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Geometric and dynamic phases are separately observed using dispersed fringes, and the difference between them is clearly demonstrated. Independence of geometric phase of wavelength is straightforwardly shown in the dispersed fringe.
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Takeshi YAGI, Naofumi KUBOKI, Yoshihisa SUZUKI, Naotaka UCHINO, Kazuno ...
1997 Volume 4 Issue 5 Pages
596-600
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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A new fiber-optic ammonia sensor utilizing rectangular-cladding eccentric-core fiber and a sensitive film containing an indicator dye is demonstrated. The sensitive film is a SiO
2-GeO
2 gel film including an indicator dye of bromocresol purple or bromocresol green, which is dip-coated by a sol-gel technique. The attenuation of this sensor changes depending on the concentration of ammonia at the wavelength range of 500-700 nm. This sensor can detect several ppm of gaseous ammonia. Various factors determining the sensitivity to detect the ammonia gas and time response of the sensor are also studied.
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Tetsuya KAWANISHI, Kouichiro TAMADA, Masao KITANO
1997 Volume 4 Issue 5 Pages
601-604
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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We studied the image deformation due to the surface inclination of objects in photon scanning tunneling microscopes (PSTM). A novel collection mode PSTM with two light sources is proposed to reduce the deformation and experimental results show that the PSTM system is effective.
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Young Je PARK, Hong Jin KONG
1997 Volume 4 Issue 5 Pages
605-609
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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An iterative deconvolution algorithm for improving range resolution of long-pulse lidars is proposed, and can be applied to the lidar data obtained with the typical pulse of a CO
2-laser which consists of a gain-switching peak and a long tail. The lidar signal itself with certain temporal shift is set to be the start profile for the unknown maximally resolved profile in the proposed technique, and then is corrected in proportion to the difference between the lidar return calculated with the assumption and the real one. The same process is repeated until the correction is smaller than tolerance. Simulations are made to test the performance of the proposed algorithm. We investigate the errors in the vicinity of data boundary in the retrieved profile when a part of lidar data is absent. The sensitivity of the iteration algorithm to noise in the lidar signals and the laser pulse profile is also numerically determined.
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Kyu YOSHIMORI, Kohzaburo OHNAKA, Kazuyoshi ITOH, Hiroshi KAWAMURA, Yos ...
1997 Volume 4 Issue 5 Pages
610-619
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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A method for numerical realization of a full gravity-capillary wave surface that is specified by a wave-spectral model and a dispersive relationship of the surface wave is developed on the basis of the angular spectral representation of a random water surface. A significant aspect of the method is that it requires a smaller number of spectral samples than that required by the Whitteker-Shannon sampling theorem for the complete generation of a full gravity-capillary wave surface, without resulting in any appreciable errors in auto-correlation functions for the surface displacement or surface slopes. The method enables the unified treatment of gravity and capillary waves in numerical studies of higher order characteristics of the thermal radiation emitted from, and the light scattered by, the wave surface.
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Makoto YAMAUCHI, Yukio YAMADA, Yasuo HASEGAWA
1997 Volume 4 Issue 5 Pages
620-621
Published: October 01, 1997
Released on J-STAGE: March 28, 2000
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Photon propagation in a highly scattering medium such as living tissue is well described by the photon diffusion equation. In a homogeneous and isotropic case, the equation has analytically been solved for a medium with a simple geometrical shape. We report frequency-domain measurements using slab-shaped solid phantoms. Comparison of the results with computer simulations proves the validity of extrapolated boundary conditions.
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