Optical wavelength-selectivity in optical switches using waveguide-type collinear acoustooptic interaction is studied from the viewpoint of the sidelobe suppression. It is found that the sidelobe level can be reduced from -9.3 dB to -20 dB by weighting the coupling coefficient over the interaction region. A method to realize the sidelobe suppression by means of modifying the surface acoustic wave (SAW) waveguide is proposed and theoretically analyzed to design the SAW waveguide. A sidelobe suppression at -20 dB is realized with a SAW waveguide of a dense-flint glass strip whose width and thickness are varied accordingly in the ranges of 700-26μm, and 0.4-1.0μm, respectively, on a Y-X LiNbO3 substrate.
The broadband supercontinuum (SC) with high coherence enables to realize the accurate optical frequency standard. We generate the SC from 1200 nm to 2200 nm using the polarization maintaining highly nonlinear dispersion shifted fiber (PM-HNL-DSF). It is expected that coherence can be complicated because of the fluctuations in the input pulse. We measure coherence as a function of wavelength across the SC spectrum by using the interferometer. The interference fringes can be observed and degree of coherence is calculated with their peak value of them. In case of the short fiber, degree of coherence is independently of the input power. On the other hand, in case of the long fiber, degree of coherence degrades and the spectral fine structure arises as the input power increases. We also analyze the coherence of SC with numerical simulations using the nonlinear Schrödinger equation and numerical results are similar to the experimental ones. The spectral fine structure which is the results of the cross-phase modulation (XPM) can affect coherence degradation because it is very sensitive to the fluctuations in the input pulse.
Stoichiometric LiNbO3 thick films on a z-cut LiNbO3 substrate were grown by using a sol-gel method improved by the addition of a large amount of protective colloid such as polyvinyl alcohol to the precursor solution. This method has been expanded to grow Ti-doped LiNbO3 waveguide films and low propagation loss and efficient electro-optic effect for these films have been made clear using a Mach-Zehnder interferometer. The magnitude of Pockels effect in the waveguide structure has been compared with that of a z-cut congruent LiNbO3 substrate and the similar results have been confirmed. The superiority of this epitaxial layer to the previous one that enables us to fabricate with easy processing and low cost is also discussed.
The host-guest thin film using nonlinear optical material was fabricated by the spin coat method on the bottom face of a right-angled prism dropped down the solution of tershari-Butyl Vanadyl-phthalocyanine ((t-Bu)nVOPc) and PMMA. To improve the nonlinear optical characteristics, the host-guest thin film was treated with organic gas. Optical bistable characteristics were evaluated by using the optical quasi-waveguide prepared with host-guest thin film after and before organic gas treatment. After and before organic gas treatment, optical bistable characteristics were observed by changing the incident angles of laser beam to prism. Optical bistable characteristics after organic gas treatment were compared with before treatment. After treatment, optical bistable behavior is more sensitive than that before treatment. Moreover, the organic gas treating time dependences of optical bistability were investigated by using the measuring equipment of optical bistability.
In our country, the handicapped and the elderly people in bed increase rapidly. In the bedridden person’s daily life, there may be limitations in the physical movement and the means of mutual communication. For the support of their comfortable daily lives, therefore, the development of human interface equipment becomes an important task. The equipment of this kind is being already developed by means of laser beam, eye-tracking, breathing motion and myo-electric signals, while the attachment and handling are normally not so easy. In this study, paying attention to finger motion, we have developed human interface equipment easily attached to the body, which enables one to measure the finger flexure and extension for mutual communication. The state of finger flexure and extension is identified by a threshold level analysis from the 3D-locus data for the finger movement, which can be measured through the infrared rays from the LED markers attached to a glove with the previously developed prototype system. We then have confirmed from an experiment that nearly 100% recognition for the finger movement can be achieved.
For electromagnetic compatibility, broadband antenna is important for measurements of fast pulse transient electromagnetic phenomena and broadband characteristics due to noises and high frequency interferences. We analyzed the characteristics of a semicircle type bow-tie antenna with various slots using the FDTD method. It was shown from the simulation results that the shape and the position of slot influenced greatly broadband characteristics of antenna. We confirmed that a semicircle type bow-tie antenna with a triangle slot was effective for broadband antenna.
Biological hazards due to radio-frequency (RF) waves result mainly from the temperature rise in tissue. It should be, therefore, clarified to what extent the RF waves of portable telephones increase the temperature-rise in human brain that includes the central part governing the body-temperature regulation function. In this paper, we calculated both the specific absorption rate (SAR) and the resultant temperature-rise for 900 MHz and 2 GHz portable telephones using the finite-difference time-domain (FDTD) method for three typical use positions, i.e., the vertical position, cheek position and tilt position. As a result, we found that there was an increase for median and 1% value of the cumulative distribution of temperature-rise in children’s brains for any use positions of the portable telephones compared to that in the adult’s brain, and also that the increasing trend in children’s brains for temperature-rise is identical to the temperature-rise trend in children’s hypothalamus. In addition, we found that the ten-gram averaged peak SAR among the adult and children heads had the same trend as that of the 0.1% value of the relatively cumulative distribution of temperature-rise, which shows that the ten-gram averaged peak SAR reflects only the localized temperature-rise in the brain surface.
In archiving video for surveillance, frame-based coding has been used and it makes storage size large because the whole image is stored even if there is no object in the image. On the other hand, object-based coding has the capability to make storage size small, because it distinguishes between the foreground and the background regions of the image, and stores only foreground objects such as people. This paper describes object-based coding by pixel state analysis. In our method, pixel state analysis detects the foreground objects and background regions in video frames. Furthermore, it distinguishes foreground object pixels as stationary or transient pixels. For stationary pixels, it is possible to restore the color intensity by refering to the same pixel location in the last frame. Therefore, our method makes the storage size smaller. Additionally, the transient pixels of foreground objects are compressed using LZH codec. Since LZH codec uses lossless compression, the object region can be compressed with lesser loss in image quality. We have evaluated our method over 9 test sequences and obtained an improvement of 15% in compression ratio and better quality for the moving parts of the object region compared to MPEG-4.
We propose a method for separating speeches using two spectrograms. First, two spectrograms are generated from voices recorded with a pair of microphones. The onsets and the offsets of the frequency components are extracted as the features using image processing techniques. Then the correspondences of the features between the spectrograms are determined and the intermicrophone time differences are calculated. Each of frequency components with the common onset/offset occurrences and time difference are grouped together as originating one of the speech signals. A set of band-pass filters are generated corresponding to each group of frequency components. Finally, each of the separated speech signals is extracted by applying the set of band-pass filters to the voice signal recorded by a microphone. Experiments were conducted with the mixture of a male speech sound and a female speech sound consisting of Japanese vowel and contain consonant. The evaluation results demonstrated that the separation was done reasonably well with the proposed method.
In this paper we propose a new automatic identification system. In our system, a user’s face is captured by a camera in order to identify him/her. By using an illumination difference image which is made of light coming from the right and left sides, our system can distinguish between a real person and a photograph. We describe an algorithm that detects whether the object facing the camera is planar(in the case of a photograph) or not(in the case of a real person). We propose a new technique for performing person-photograph distinction by using the surface direction image features.
This paper describes a new method for on-line recognition of handwritten mathematical formulas using distances among strokes in symbol segmentation process. Segmentation methods optimizing the results of symbol recognition over whole formulas are often applied before structural analysis of handwritten mathematical formulas. Though improvements on symbol segmentation using geometrical features of strokes are reported in related previous works, they are not sufficient for recognizing handwritten mathematical formulas without restrictions such as input order. To remove the restrictions, we employ a correction value for symbol segmentation derived from a confidence value of stroke combination. This confidence value is calculated by counting up a pair of distances between strokes on a lot of actual handwritings of mathematical formulas in the learning phase. The experimental result shows effectiveness of a correction value based on a confidence value of stroke combination for symbol segmentation. The proposed method reduced 40% of segmentation errors in comparison with the previous method. More improvements will be realized to make use of detailed information of strokes and mathematical structure for symbol segmentation.
The zero assignment is significant one among remarkable control synthesis problems. For example, this problem can be formulated as the model matching problem which attains the desired input-output characteristic or the improvement of transient response of closed loop system. In discrete-time systems, poles and zeros can be assigned by state feedback law using 2-delay input control. However, in continuous-time systems, it is well known that zeros cannot be assigned by the state feedback control law. Taking into account this situation, in this paper, a design method which can assign zeros of control system by the state feedback using a dual observer is proposed. It is noted that the number of control inputs is increased by the number of assignable zeros in the dual observer synthesis. Following this procedure in the state feedback control synthesis through the increased control channel, zero assignment can be attained.
This paper describes a non-contact current measurement in small electric parts by using a non-contact thermometer. When the small electric parts are used in a small machine or device, it is difficult for a conventional current sensor to measure current in the small electric parts. Assuming that the temperature rise of the parts is proportional to the power consumption, the temperature rise and the resistance of the parts are used to obtain the current through the electric parts. In our experiment, the relationship between the current, temperature rise and power consumption is clarified. The power consumption is proportional to the temperature rise and the current is in proportion to the square root of the temperature rise. The method how to measure the current without contact is explained.
Simulation studies were carried out about a group of self-autonomous mobile robots collaborating in collection cleaning-up tasks. The robots are endowed with two kinds of human-like personalities; positivity and tenderness. Dependent on the rank of positivity, decision is made on which one of robots nearby should avoid collision and which one of robots heading for the same small baggage should carry one. As for large baggage which can be carried only by two collaborating robots, tenderness plays an essential role. In the first series of simulation, the initial configuration of 4 robots, 4 small baggage, and 2 large baggage were fixed. The cleaning-up tasks were carried out for all combinations of personalities, 625 cases in total. In the second series, 8 robots performed the task. 5 voluntarily cases were chosen to carry out 100 simulations for each case, by changing the configuration of baggage. From the results of the simulation, it was found that the heterogeneous group performs the task more effectively than the homogeneous group. It seems that diversity in personality is good for survival. In addition to the performance index of task execution time, satisfaction index is introduced to evaluate the degree of satisfaction of the group, too.
In general, mathematical subjects are used for programming education in universities. In this case, many students lose the interest in the programming because the students have the preconception that is difficult to program by using the mathematical expressions. Especially beginners of the programming are a tendency to lose the interest. Therefore it is pointed out to use the subjects which do not need mathematical knowledge as much as possible. In this paper the authors have tried to make animation that are generated by programs instead of the mathematical subjects in a beginners’ programming class using C language used in a wide-ranging field. The authors discuss about improvements of the interest of students for programming by the try that is to make animation by programs in a programming class and refer to its effects.
In this paper, we propose a new keyword extraction method for generation a user profile using collected papers without using a large corpus. We assume that a user’s interest exists in papers. Our method can extract keywords that can express user’s interest in papers that user’s interest exit. Our method can be used for enhancing the paper collection and sharing system, MiDoc. In MiDoc, user profiles are automatically constructed by using the method. We conducted several experiments to show how effectively our method can extract keywords that represent user’s interests. In the experiment, our method was compared with the exsiting methods. The results lead to the conclusion that the method can effectively extract keywords that represent user’s interests. In this paper, We define user profile is keywords that express user’s interest.
We studied the evaluation for the intensity of stress of students in lesson using heart rate variability. Heart rate of many students were measured simultaneously by developed portable measurement systems. Heart rate variability data suggests that many students have more stress in normal dictation lesson then video lesson using difficult subject.
In-line Fresnel electron holography has a possibility to be a phase retrieval technique of an isolated object with high precision, though a defocused conjugate image is superposed to a reconstructed image and modulates phase information of the object. In this study, we improved a phase image with the procedure of a sequential inference, by removing the conjugate image.