Kiyoshi Tsutsumi

Synthesis of Hadamard transformers by use of multimode interference optical waveguides

We propose a synthesis method of optical Hadamard transformer using multimode interference (MMI) couplers. By using the signal transfer matrix of 2 x 2, 4 x 4, and 8 x 8 MMI couplers, we show that sum and difference units of input signals can be synthesized. An interchange unit of two signals can also be synthesized. One synthesis method of Hadamard transformers is a combination of only 2 x 2 units, and the other is a combination of N x N(N > or = 4) units as well as 2 x 2 units. The design examples of operation units are shown, and the size and the output power of Hadamard transformers are estimated.

Relation between the ordinary and extraordinary index profiles of ion-exchanged glass waveguides

The relation between the ordinary and extraordinary index profiles of ion-exchanged glass waveguides is investigated on the basis of the stress-optic law and the Clausius-Mossotti relation. For K(+) exchange and Ag(+) exchange, the experimental results are consistent with our analysis. The values of the coefficient that relates the ordinary and extraordinary index profiles are presented.

Fields of nonlinear cladding optical waveguides excited by butt-coupled linear waveguides at medium power levels.

The evolution of medium power fields of nonlinear optical waveguides is investigated numerically. The analysis method is based on mode matching of local normal modes of bounded waveguides. Nonlinear cladding waveguides are butt-coupled to linear waveguides. The path of a medium power level beam winds between the film and the nonlinear cladding. The input beam travels toward the nonlinear modal field, at which point the beam is not stationary. After the beam passes the location, it is forced to turn back. The lateral shift of an incident waveguide affects the path of a beam. Saturation and linear absorption lessens the oscillation of a winding path.

Radiative Guides for Decreasing Reflection at Output Ends of Photonic-Crystal Optical Waveguides

We propose new structures for decreasing reflection at output ends of photonic-crystal optical waveguides. These are waveguides gradually radiating guided waves. We analyzed 2-D models numerically by the finite difference time domain method. A large decrease in reflection is shown.

Effects of the Film Thickness on the Fields of Nonlinear-Cladding Optical Waveguides With Butt-Coupled Linear Waveguides

Effects of the film thickness of nonlinear-cladding optical waveguides on the evolution of fields at medium power levels are investigated numerically. The analysis method is based on mode matching of local normal modes of bounded waveguides. For the analyzed waveguide structures and power levels, the path of a beam winds between the film and the nonlinear cladding or in the film. Fields travel in the nonlinear cladding in the case of a thin film, whereas fields are confined to the film in the case of a thick film. The lateral shift of a butt-coupled linear waveguide toward the substrate makes a beam emit toward the nonlinear cladding. The excitation from a linear waveguide whose film is thicker than that of a nonlinear waveguide is effective in causing spatial soliton emission. Saturation and linear absorption weaken the winding of a path or decrease the angle of emission.

One Method for Elimination of Shadow of Walkers by Stereo Vision.

屋外の歩行者を抽出するとき, 2つのカメラを用いて, 人物の影を消去するための画像変換を提案する.この方法は, 同時に地面の模様なども消去することができるものである.実験により, 本方式の有効性を示した.

Rotated checker-pattern projection and its cross-point extraction and tracking for 3-D object profilometry

In the measurement of 3-D shape by projecting a regular pattern on the object surface, it is required to extract feature points with a high accuracy and to determine their mutual relations. In this paper, 45-deg rotated checker-pattern projection is proposed, and a method for extracting and tracking the crossing point is presented in which the geometrical properties of the rotated checker pattern are utilized. If the pattern projector and the camera are on the same horizontal plane, a large brightness difference is produced between the horizontal and nonhorizontal (vertical and slant directions) neighbors of the crossing-point pixel. By utilizing this property, crossing points are extracted. The projection profile of the brightness pattern along the vertical direction has a triangular form, and the location of the extremum of the profile gives the vertical coordinate of the crossing point. By utilizing this profile, the crossing points are classified (segmentation). On the basis of the result of segmentation, the crossing points are successively tracked and their mutual relations are determined. To demonstrate the usefulness of the method, the experiment of 3-D shape measurement was made. The error of the measurement was less than 2 mm, which is due to the error in extracting the crossing point (i.e., 1 pixel at the maximum). In the measurement of a cylinder, the measurement was made along the circumference. It is shown that the measurement of the position of the crossing point on the reference plane is not required if the rotation of the object is utilized.

Honeycomb optical-waveguide networks for parallel signal processing.

A honeycomb waveguide network for parallel signal processing, consisting of single-mode symmetrical Y junctions, is proposed. In this waveguide network, input guided-wave amplitudes are divided and then combined with the amplitudes of the adjacent waveguides. It is shown that the operations of spatial filtering, such as smoothing, edge extraction, and edge enhancement, can be performed. An example of the honeycomb waveguide network is discussed.