A model for estimating the bending loss of 1.3 µm zero-dispersion single-mode fibers at 1.58 µm from the value at 1.55 µm is investigated experimentally and theoretically. An approximated equation for estimating the bending loss ratio of 1.58 µm to 1.55 µm is proposed, which provides good agreement with the experimental results.

We propose low Rayleigh scattering Na2O-MgO-SiO2 (NMS) glass as a candidate material for low-loss optical fibers. This glass exhibits Rayleigh scattering which is only 0.4 times that of silica glass, and a theoretical evaluation suggests that it is dominated by density fluctuation. An investigation of the optical properties of NMS glass reveals that a minimum loss of 0.06 dB/km is expected at a wavelength of 1.6 µm and that the zero-material dispersion wavelength is found in the 1.5 µm band. To establish the waveguide structure, we evaluated the feasibility of using F-doped NMS (NMS-F) glass as a cladding layer for an NMS core and found that it is suitable because it exhibits low relative scattering (e.g. 0.7) and is versatile in terms of viscosity matching. We also describe an attempt to draw optical fibers using the double crucible technique.

A light emitting diode (LED) array unit for use as a light source in isolated power transmission and a display panel was fabricated using LED chips mounted on a silicon microreflector. The reflector was formed on a (100) silicon wafer by anisotropic chemical etching. An isolated power supply consisting of an infrared LED array unit and single silicon crystal solar cells had a maximum transmission efficiency of 2.3%. The silicon microreflector absorbs the heat generated by the LED chips and improves their light directive characteristics. A small, high-resolution, full color LED display panel can also be constructed using LED array units fabricated on silicon microreflectors. The LEDs in a unit are arrayed with a matrix structure and the electric contacts between the LED chips, the reflector and the upper cover glass are formed using conducting silver resin.

A method is proposed for forming hillock-free aluminum-based alloy bus lines for active-matrix liquid-crystal displays (LCDs). Aluminum (Al)-based alloy films are deposited using an Al target containing boron (B) or nickel (Ni) in a sputtering ambient containing nitrogen. The Al-Ni films deposited using an Al target containing Ni showed excellent hillock resistance: virtually no hillock formation after thermal treatment at around 400 and no significant increase in resistivity. These films also showed good patternability with a simple wet etching: a smooth line edge and a gently tapered profile. These films are thus suitable for the bus lines of active matrices.

Resonance characteristics of a coupled dielectric resonator which consists of a Whispering Gallery mode dielectric disk resonator and a ring resonator located eccentrically are analyzed. New analytical results of resonance characteristic based on the distributed coupling phenomena between the disk and the ring are obtained. The resonance performances have also been verified experimentally on X band model. We have found that Free Spectral Range of the coupled resonator is several times larger than that of the single disk resonator and the single ring resonator, respectively. As a result, the eccentric coupled resonator discussed in this paper can be used as a frequency selective element in millimeter wave integrated circuits.

The status of the plastic optical fiber (POF) for high-speed data communication is described. Very recently, the low-loss and high-bandwidth perfluorinated GI POF which has no serious absorption loss from visible to 1.3-µm wavelength was successfully prepared at Keio University. Since the core diameter (300-1000 µm) of the GI POF is much larger than that of the multimode silica fiber (62.5 µm), the serious modal noise in the conventional multimode silica fiber was virtually eliminated, resulting in stable giga bit order data transmission with inexpensive couplers and connectors.

We studied the application of precursor solutions that can be fired into oxides to form a protective layer for AC-type Plasma Display Panel (AC-PDP). Our study of alkoxide and metallic soap as MgO precursors revealed that the crystallinity of MgO films depends on the starting substance. Since the electric discharge characteristics of a panel and the lamination effect of the protective layer depend on precursors, it was confirmed that binders having higher crystallinity provide better characteristics. Our study revealed that a compound-oxide film has high crystallinity. The application of a Ba0.6Sr0.4Gd2O4 formation solution to a binder and the application of a Sr0.6Mg0.4Gd2O4 formation solution to a protective layer both are seemed promising We also found that a double-layer film, made by forming a protective layer of fine MgO powder and a Ba0.6Sr0.4Gd2O4 binder, on top of a protective layer made of fine MgO powder and a MgO binder, provides a luminous efficiency 5.3 times higher than that of sputtered MgO film which is one of candidates for the large panel, and the conventional electron beam evaporation is not suitable for the large panel. We further found that a triple-layer protective film made by forming a thin film of Sr0.6Mg0.4Gd2O4 provides low voltages of 1 V in firing voltage (Vf) and 35 V in sustaining voltage (Vs) compared to the double-layer film and provides a luminous efficiency 5.5 times higher than that of sputtered MgO film. A life test revealed the triple-layer film in particular providing a useful life of more than 10,000 hours. From these findings, we concluded that the compound-oxides which is composed of alkaline-earth-metal and rare-earth-element could be applied effectively to a protective layer for AC-PDP.

Amorphous silicon thin film transistors(a-Si TFTs) with a channel-etched structure were fabricated. The key technologies to realize these simple-process TFTs were 1) fabricating data lines and pixel electrodes of indium tin oxide(ITO); 2) carrying out tapered dry etching of plural layers of the a-Si and gate insulator silicon nitide; and 3) forming silicide layer to reduce the contact resistance between the phosphorousdoped a-Si and ITO. Excellent image quality, with a high contrast ratio of more than 100: 1, was obtained for video graphic array(VGA) mode TFT-LCDs using a dot inversion driving method. Furthermore, the transmission distribution was uniform with less than a 4.5% deviation on the whole display area although the ITO data line resistances were as large as 120 kΩ per line.

We report recent progress in the development of Liquid Crystal(LC) materials for the TN-TFT and ECB-TFT technologies, which require LC materials with positive and negative dielectric anisotropy, respectively. Many kinds of new LC materials have been synthesized and have been evaluated based on their fundamental physical properties. We have succeeded in identifying new LC materials, and developing new LC mixtures based on those, so that the current typical requirements of TFT-LCDs e.g. fast switching times, low power consumption, good viewing angles and wide operation temperature ranges together with high reliability can be fulfilled.

The characteristics of a-Si bottom-gate TFT test devices with several kinds of inorganic "quasi-black matrix," such as metal, semiconductor, and insulator, on the top were investigated for various black matrix(BM) resistivities. In the Ia-Vg characteristics, for a BM sheet resistance of about1 1012 Ω/, a high off current and large Vth shift were observed due to the back-gating effects when the BM is charged up. Accrding to the ac dynamic characteristics, there was almost no leakage due to the capacitive coupling between source and drain after 16.6 msec(one frame) when the BM sheet resistance was above 7 1013 Ω/ . It was found that hydrogenated amorphous silicon germanium(a-SiGe:H) film, which has enough optical density, with the sheet resistance above the order of 1014 Ω/ is a promising candidate for an inorganic BM on TFT array.

Super twisted nematic (STN) liquid crystal displays(LCDs) using spiral polymer aligned nematic (SPAN) liquid crystals have been achieved by photo-polymerization of some kinds of chiral monoacrylates in liquid crystalline hosts.The spiral polymer made of a chiral monoacrylate in STN LCD has effect to reduce the driving voltage without any disadvantages for the STN LCD. The relation of chemical structure of a chiral monoacrylate and nature of spiral polymer is discussed.

To overcome the problem of narrow viewing angle in active matrix liquid crystal displasy(LCDs) in the twisted nematic mode(TN mode), we have proposed a new LCD mode using a bend-alignment cell with an optical compensator. In this new mode, we have successfully obtained a black state with almost no leakage over a wide viewing angle range with very fast response. We describe the fundamental principle and design rule of the optical compensator and discuss the properties obtained in theoretical and experimental term.

A directed graph G = (V,E) is called the n-rotator graph if V = {a1a2an|a1a2an is a permutation of 1,2,,n} and E = {(a1a2an,b1b2bn)| for some 2 i n, b1b2bn = a2aia1ai+1an}. We show that for any pair of distinct nodes in the n-rotator graph, we can construct n - 1 disjoint paths, each length < 2n, connecting the two nodes. We propose a nonadaptive fault-tolerant file transmission algorithm which uses these disjoint paths. Then the probabilistic analysis of its reliability is given.

Based on the test method proposed by Sub-Committee G of the International Special Committee on Radio Interference, most telephone receivers in Japan have insufficient immunity to acoustic noise caused by radio-frequency fields. This is because the modulation depth of the RF signal used is too high to accurately simulate the audio-frequency components of TV video signals. Reducing the modulation depth from 80% to 5% produces a more realistic simulation.

The local moment functions for discrete Wigner trispectrum are examined in ambiguity and in time-frequency domain. A concept of multiple and multidimensional circular convolution in frequency domain is introduced into the discrete Wigner higher order time-frequency signal representation of any order. It is shown that this concept based on the 1st order spectra of the signal offers an insight into the properties of inconsistent local moment functions and their representation both in ambiguity and time-frequency domain. It allows to prove that midfrequency crossterms of a multicomponent signal can not be removed by any generalized 4th order ambiguity function which employ kernel function in the ambiguity domain. It is shown, that the concept of multiple convolution in frequency domain can lead to the crossterm-reduced discete time-frequency representations of any order

Protective layers in AC plasma display panels (PDP) are usually formed by vacuum vapor deposition or sputtering. It is important to study the protective MgO layer by means of screen-printing for fabricating a large size PDP and reducing its cost. With the objectives of enlarging the panel size and reducing cost, we studied the fabrication of the protective MgO layer by means of screen-printing. In this study, we succeeded in lowering the drive voltage by using a MgO powder prepared by vapor phase oxidation instead of conventional decomposition of the magnesium salt. Further, by adding a MgO liquid binder, we attained a good luminous efficiency twice as high as that attained with a sputtered protective layer and lowered the drive voltage. When this protective layer was combined with He-Xe gas enclosure, the half-life of luminance was 5,000 hours. With Ne-Xe gas, the luminance deteriorated no more than 40% after 5,000 hours. A screen-printed protective MgO layer containing no MgO liquid binder showed a short half-life of 800 hours even with the use of Ne-Xe gas. In this case, the discharge voltage changed greatly and some cells did not discharge. It is concluded that the combination of an ultrafine MgO powder prepared by vapor phase oxidation and a MgO liquid binder can clear the way for making AC PDPs with a long lifetime, high efficiency, and low voltage a practical reality.

This paper presents a technique for disparity selection in the context of binocular pursuit. For vergence control in binocular pursuit, it is a crucial problem to find the disparity which corresponds to the target among multiple disparities generally observed in a scene. To solve the problem of the selection, we propose an approach based on histogramming the disparities obtained in the scene. Here we use an extended phase-based disparity estimation algorithm. The idea is to slice the scene using the disparity histogram so that only the target remains. The slice is chosen around a peak in the histogram using prediction of the target disparity and target location obtained by back projection. The tracking of the peak enables robustness against other, possibly dominant, objects in the scene. The approach is investigated through experiments and shown to work appropriately.

A new method is proposed for realizing a flexible change detection which is free from the limitation that multitemporal images must have the same spectral bands whose center wavelength and bandwidth are identical. As spaceborne multispectral scanners are continuously improved for performance and new scanners do not necessarily have the same spaectral bands for observation, this limitation is a serious obstacle for detecting long term temporal change. The proposed method removes this limitation by using an image normalization technique based on multiple regression analysis. The method is successfully applied to actual remotely sensed multitemporal images.

In order to estimate elasticity distribution of living soft tissue by ultrasonic pulse-echo method, we developed an algorithm by which we estimate 2-D displacement vector field from two successive rf echo data frames. The algorithm estimates a displacement vector iteratively by matching the phase characteristics of the local regions of two data frames. The estimation process is composed of coarse one and the fine one. In the coarse estimation process, the displacement is estimated by detecting the peak of the 2-D cross-correlation function. In the fine process, the displacement is estimated iteratively by shifting the 2nd frame data so that the phase characteristics matches with that of the 1st frame data. In each iterative step of both processes, the estimated displacement vector field is spatially smoothed. This proposed algorithm exhibits excellent performance in obtaining accurate and smooth distribution of displacement vector which is required to obtain strain distribution and finally shear modulus distribution. We conducted an experiment on an agar phantom which has inhomogeneous shear modulus distribution. Using the proposed method, we obtained 2-D displacement field with reasonable accuracy. We reconstructed a relative shear modulus map using axial strain assuming 1-D stress condition. The reconstructed map using the calculated axial strain through 2-D displacement estimation algorithm was satisfactory, and was clearly superior to the one through 1-D displacement estimation algorithm. The proposed 2-D displacement field estimation algorithm seems to be a versatile and powerful tool to measure strain distribution for the purpose of tissue elasticity estimation under various deformation conditions.

To evaluate the radial eigenmode field distributions and the resonance wavelengths of axially symmetric pillbox resonator, a numerical method is described which is based on the FE-BPM expression in cylindrical coordinates. Under the weakly guiding approximation, we solve Fresnel equation and can get a fairly accurate result. By using effective index method, 3-D pillbox guiding structure is reduced to 2-D one which is then used for the analysis. One advantage of this method is that it is applicable for the axially symmetric optical waveguides with arbitrary index distribution. The validity of this method is checked by comparing the results of this method with those of the analytical ones. This method is applied for the evaluation of the coupling properties of a coupled structure consisting of a pillbox resonator and a curved waveguide placed outside the pillbox. This coupled structure has a good prospect to be used as optical wavelength filter. By varying the separation distance between the pillbox and the outer curved waveguide, the power transfer due to coupling is determined near the resonance wavelength 0.9 µm.