Transcutaneous measurement and spectrum analysis of heart wallvibrations

For the noninvasive diagnosis of heart disease based on the acoustic and elastic characteristics of the heart muscle, it is necessary to transcutaneously measure small vibration signals, including components with an amplitude of less than 100 μm, from various parts of the heart wall continuously for periods of more than several heartbeats in a wide frequency range up to 1 kHz. Such measurement, however, has not been realized by any ultrasonic diagnostic methods or systems to date. By introducing the constraint least-square approach, this paper proposes a new method for accurately tracking the movement of the heart wall based on both the phase and magnitude of the demodulated signal to determine the instantaneous position of the object so that the vibration velocity of the moving object can be accurately estimated. By this method, small vibrations of the heart wall with small amplitudes less than 100 μm on the motion resulting from a heartbeat with large amplitude of 10 mm can be successfully detected with sufficient reproducibility in the frequency range up to several hundred Hertz continuously for periods of about 10 heartbeats. The resultant small vibration is analyzed not only in the time domain, but also in the frequency domain. As confirmed by the preliminary experiments herein reported, the new method offers potential for research in acoustical diagnosis of heart disease     

An acoustic micrometer and its application to layer thickness measurements

The principle and system of the acoustic micrometer are described. Its basic performance, with respect to the stability, accuracy, spatial resolution, and temperature dependence, is also discussed. Gold layers electroplated on substrates of 42% Ni-Fe alloy were taken as test specimens in the present study. The measurable range of the thickness for gold layers covered from 1 to 20 mum when a frequency range of 10-200 MHz was used. Stability and accuracy were achieved to within +/-0.2% and +/-1%, respectively.     

Excitation of plate waves in thickness measurements of layers deposited on thin plates

Layer thickness measurements with an acoustic micrometer using pseudo-Sezawa waves in which ultrasonic waves are obliquely applied to a layered surface of a specimen have been proposed. A case in which the plate thickness of the specimen is so thin that it cannot be regarded as a half space is studied. A number of modes of plate waves are then excited in addition to pseudo-Sezawa waves. The plate waves, giving rise to the appearance of extra dips in the power spectrum of reflected waves, cause difficulties in the measurements. To prevent the excitation of plate waves, it is proposed that a mask of a sound-insulating material with a slit aperture should be placed on the layered surface of the specimen. Experiments and theoretical calculations, using lead frames of LSI chips as typical test specimens with thin substrates, were performed to demonstrate the effectiveness of the present method in preventing the excitation of plate waves.     

Microdefocusing method for measuring acoustic properties using acoustic microscope

Many papers have been reporting on measuring acoustic properties of materials by acoustic microscopy. In a conventional method of V (z) curve analysis, the phase velocity and the propagation attenuation of a leaky surface acoustic wave (LSAW) are determined from the interference period Deltaz and the slope of the V(z) curve, respectively. For this method it is necessary to measure the V(z) curve for a period several times as long as the interference period Deltaz. Therefore, it is difficult to measure the acoustic properties of a sample with high resolution by the method. In order to overcome these problems, a method called the microdefocusing method is proposed. The method determines the acoustic properties of a sample by analyzing V (z) values measured in the microdefocusing region within an interference period Deltaz near a focal plane. An ultrasonic transducer called the butterfly transducer is proposed to be applied to this microdefocusing method and a digital signal processing procedure is developed to analyze the output of the ultrasonic transducer. Basic experiments are performed to confirm the principles of the new method.     

Multimode interference mechanism in V(z) curves obtained by acoustic line-focus beam

The multimode interference mechanism in the acoustic material signatures of V(z) curves, which generally deforms the dip intervals and the shape, is investigated theoretically and experimentally for the acoustic line-focus beam. It is shown, taking a (111)-Si substrate as an example, that V(z) curves associated with multiple leaky waves are represented as a superposition of elemental V(z) curves with different characteristic dip intervals corresponding to the respective velocities of the leaky waves.     

Leaky SAW velocity on water/silicon boundary measured by acoustic line-focus beam

Propagation characteristics of leaky SAWs at the boundary of water/silicon are investigated by the nonscanning reflection acoustic microscope using a line-focus beam. Experiments are performed for typical crystalline planes of silicon such as (111), (110), (001) and slightly inclined (111). These results obtained by the line-focus beam are compared to the experimental results obtained by the conventional point-focus beam.     

Propagation characteristics of leaky SAWs on water/LiNbO3 boundary measured by acoustic microscope with line-focus beam

A nonscanning reflection acoustic microscope with a line-focus beam is applied to investigate propagation characteristics of leaky SAWs on water/LiNbO3 boundary. Experiments are performed for both cases without and with an Al-film shorting plane at the boundary of water/Y-cut-LiNbO3. The effect of water `loading? on LiNbO3 is successfully detected.     

Characteristics of vertical earth potential difference signals

A modified measurement method to observe the electric earth potential difference is proposed in order to reduce the unnecessary signals induced by artificial and natural earth current sources. With this method, the potential difference is measured as the voltage between two electrodes that are buried in different vertical positions beneath the ground. We evaluated this method at four sites under different measurement conditions and we discuss the characteristic features of the three types of observed signals: (1) Horizontal earth potential difference signals appear according to the current induced by variations in geomagnetic fields. Vertical signals, however, do not appear because there is no induced vertical current. (2) After heavy rainfall the characteristic quasi-periodic pulse train signal occasionally appears. However, no such signal can be found in the horizontal direction. (3) Pulse signals appear with exactly the same period that could be expected to be caused by artificial current sources from structures and buildings. Consequently, in order to use this vertical observation method effectively, we should choose a location where the ground surface is as level as possible and which is as far as possible from current source points. © 1998 Scripta Technica, Electr Eng Jpn, 123(1): 23–31, 1998     

New approach to developing LC materials for IDS driving on reflective displays

As usage time for portable electronic terminals increases, associated problems regarding such extended use (e.g., battery holding times and eyestrain) are highlighted. Within the domain of power saving, we previously developed an idling stop (IDS) driving that avoids unnecessary refresh. Moreover, for reducing eyestrain to the highest extent possible, we calculated a luminance change in IDS driving that is not perceived as flickering by humans, via the use of a temporal modulation transfer function. According to the results of such calculations, a liquid crystal mixture that suppresses luminance changes perceived by humans was hence constructed. With the combined use of the liquid crystal mixture and a c‐axis‐aligned crystal oxide semiconductor with low off‐state leakage current, a display could be developed wherein leakage current in IDS driving could be significantly reduced, along with enjoyed benefits of prolonged refresh intervals and power savings. The subject display is very eye‐friendly, with less flickering than comparable technologies.     

Characteristics and applications of metal tape

To manufacture low noise and high output tape, we have to choose excellent particles and also make its surface as smooth as possible. We developed a metal tape with higher output and higher S/N compared with those of conventional oxide tape by introducing new technologies of higher packing density and mirror surface finishing. This metal tape realized higher recording density which could be used in 8 mm Video, electronic still camera ("MAVICA"), magnetic contact printing system and various digital recording systems. This paper describes characteristics and applications of the metal tape.