Detection of moving object by mobile stereo omnidirectional system (SOS)

Moving object detection with a mobile image sensor is an important task in robotics and computer vision, when considering the practical use of robotics in human environments. In this paper, we propose a robust method that detects moving objects in the environment using the omnidirectional depth information obtained by a mobile Stereo Omnidirectional System (SOS). In order to detect only the moving objects within the depth image that are obtained by a sensor in motion, we first estimate the ego‐motion of the sensor, and generate a predicted depth image for the current time from the depth obtained at the previous time by only considering the ego‐motion of the sensor. Then the predicted depth image is compared with the actual one obtained at the current time, and the inconsistent regions are detected as moving objects. When the sensor moves, occlusions will occur in the scene and they will cause false detections. However, these false detections can be suppressed by estimating the occlusion regions using the ego‐motion parameters of the sensor and the jump edges in the depth image. The effectiveness of the method is shown with experimental results for a real environment. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(3): 29–38, 2005; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20155     

Tunable wavelength-selective demultiplexer using a liquid-crystalfilter

The authors describe a new tunable wavelength-selective demultiplexer with a liquid crystal Fabry-Perot interferometer. The demultiplexer has six output ports, and, at each output port, any wavelength can be tunably selected within a range of 50 nm at a bandwidth of 0.5-0.6 nm. A simulated result shows that the loss of this demultiplexer is smaller than that of a conventional demultiplexer     

Preparation of a transparent alumina film doped with CdS and its nonlinear optical properties

We have examined the preparation of transparent alumina film and CdS-doped alumina film prepared by the sol-gel process using aqueous sol starting from AlCl₃. The resulting alumina films obtained by sol-gel transformation are transparent in the visible and near infrared up to 1000 °C. Homogeneous solution of alumina sol and Cd(CH₃COO)₂ was converted into gel film by dehydration. Then, on exposure to H₂S stream at 250–600 °C, a CdS-doped film was obtained. It shows relatively sharp blue-shifted visible absorption that is attributed to size quantization effect. Large nonlinear absorption and refractive index have been obtained, because high concentration of CdS particles can be achieved by using this method.     

Resonance acoustoelasticity measurement of stress in thin plates

A computer-driven, swept-frequency measurement technique is developed on the basis of resonance birefringence acoustoelasticity to evaluate the stresses in thin plates. The resonance frequency depends on the thickness and the elastic wave velocity; they change with stress because of the Poisson effect and the acoustoelastic effect. The resonance frequency is obtained from the spectral response curve in the electric impedance of the piezoelectric transducer. The frequency displacement induced by acoustically coupling the transducer can be minimized by employing the resonance peak closest to the transducer fundamental frequency. To illustrate the method, the residual stress is measured in butt-welded aluminum alloy plates and is compared with the results of conventional methods.     

Tunable light source using a liquid-crystal Fabry-Perot interferometer

A tunable light source with a liquid-crystal Fabry-Perot interferometer (LC-FPI) tuning element that emits a laser beam with a tuning range of 41 nm has been constructed. Incorporating a multiple quantum well (MQW) laser diode with a phase control (PC) section enables the selection of almost all external modes. Stable single-mode emission is obtained for the region, except where the slope of the lasing wavelength versus applied voltage to the liquid crystal is quite large.<>     

Novel photonic switch arrays consisting of vertically integrated multiple-quantum-well reflection modulators and phototransistors: excitation absorptive reflection switch

The authors report a novel photonic switch array, the exciton absorptive reflection switch (EARS), which operates as an optical three-terminal switch with a high contrast ratio and optical gain. The device consists of vertically integrated GaAs/AlGaAs multiple-quantum-well modulators and GaAs heterojunction phototransistors, which are optically isolated and electrically connected in series with distributed Bragg reflectors. 8*8 arrays of EARS with a contrast ratio of more than 20 dB and a high optical gain were demonstrated.<>     

Switchable-logic photonic switch array monolithically integratingMSMs, FETs, and MQW modulators

As a two-dimensional parallel digital processing device, we describe a switchable-logic photonic switch array that monolithically integrates metal-semiconductor-metal (MSM) photodetectors, field-effect-transistor (FET) amplifiers, and multiple-quantum-well (MQW) modulators. All-optical positive and negative logic operations are demonstrated with controllable thresholds and a 3-dB bandwidth of 300 MHz. In this device, the logic mode is switched by changing the bias voltage polarity of the MSM photodetector     

Vector Potentials in Simply Structured Spaces

The results obtained in a previous paper are extended from bounded to unbounded spaces. To do so, a new term, simply structured, is introduced. The result is as follows. In a simply structured space, whether it is bounded or unbounded, a piecewise smooth divergence-free vector function of position is the curl of another vector function of position called a vector potential. With this extension, it becomes clear why one can claim the existence of magnetic vector potentials. Magnetic induction is piecewise smooth and divergence-free in a simply structured space called the universe. Seven examples are presented to facilitate the understanding of the present discussion. They are about the electric and magnetic fields in infinite straight coaxial cables and the electric field in modified Euclidean spaces.     

High bit rate and programmable multiwavelength generator based onRaman soliton effect in DSF

A wavelength tunable multiwavelength pulse source with clock rate tunability is described. A tuning range of 32 nm and multiwavelength generation were achieved at a 10 GHz clock rate and a quasi-320 GHz OTDM signal. The device consists of a programmable PLC multiplexer and employs amplitude-to-wavelength conversion based on the Raman soliton effect     

Silicon quantum dot superlattice solar cell structure including silicon nanocrystals in a photogeneration layer

The solar cell structure of n-type poly-silicon/5-nm-diameter silicon nanocrystals embedded in an amorphous silicon oxycarbide matrix (30 layers)/p-type hydrogenated amorphous silicon/Al electrode was fabricated on a quartz substrate. An open-circuit voltage and a fill factor of 518 mV and 0.51 in the solar cell were obtained, respectively. The absorption edge of the solar cell was 1.49 eV, which corresponds to the optical bandgap of the silicon nanocrystal materials, suggesting that it is possible to fabricate the solar cells with silicon nanocrystal materials, whose bandgaps are wider than that of crystalline silicon.

PACS

85.35.Be; 84.60.Jt; 78.67.Bf