Showing papers on "Acoustic interferometer published in 1989"
TL;DR: In this paper, a time domain signal processing based on narrow-band filtering of wide-band acoustic wave pulses and cross-corelation is described, which permits to measure both phase and group velocities as a function of frequency.
Abstract: Frequency broadband measurement of the characteristics of acoustic waves propagating in an object is disclosed. A time domain signal processing is described, based on narrow-band filtering of wide-band acoustic wave pulses and cross-corelation which permits to measure both phase and group velocities as a function of frequency.
36 citations
TL;DR: A model relating the velocity shifts of surface acoustic waves (SAW) to the six tensor components of quasistatic stresses makes it possible to define a family of quartz cuts with potentially low stress and temperature sensitivities for oscillator applications.
Abstract: A model is presented, relating the velocity shifts of surface acoustic waves (SAW) to the six tensor components of quasistatic stresses. Stress sensitivity is then defined through six independent coefficients, whatever the origin of the stress (direct external forces, thermoelastic stresses) might be. These coefficients, depending on crystal anisotropy, are computed for different cut angles and propagation directions of quartz crystal, and represented as a contour-line mapping. The determination of SAW quartz cuts compensated for both planar isotropic stresses and first-order temperature effects make it possible to define a family of quartz cuts with potentially low stress and temperature sensitivities for oscillator applications. >
33 citations
03 Oct 1989
TL;DR: In this article, a new lens geometry that can be used with acoustic microscopes to image layered solid structures is proposed, which can efficiently focus the acoustic waves in only one of the Lamb wave modes of the layered solid.
Abstract: A conventional scanning acoustic microscope lens excites all the possible modes of acoustic waves in the solid structure under examination. The excited leaky modes contribute significantly to the high contrast obtained in the images, but because all such modes exist simultaneously, the interpretation of the images is not straightforward. A new lens geometry that can be used with acoustic microscopes to image layered solid structures is proposed. This new lens can efficiently focus the acoustic waves in only one of the Lamb wave modes of the layered solid. The images obtained are easy to interpret, and the subsurface sensitivity is high. >
16 citations
TL;DR: In this paper, a laser-diode interferometer for vibration measurement was constructed using two acoustooptical tunable filters (AOTFS) with slightly different frequencies of the diffracted light.
Abstract: A laser-diode interferometer for vibration measurement was constructed using two acoustooptical tunable filters (AOTFS) with slightly different frequencies of the diffracted light. A sound pressure measurement of a condenser microphone using a combination of a polarization-maintaining fiber and the laser-diode interferometer was demonstrated. The advantages of this interferometer are the ability to use various laser beams in the 0.4-1.2- mu m wavelength region by varying only the acoustic frequency of the OTF, and the ability to use remote measuring equipment for the sound pressure by using a polarization-maintaining fiber. >
10 citations
TL;DR: In this article, a fast neutron chopper produced neutron bursts shorter than the dimensions of the perfect crystal interferometer, and interference experiments became feasible where the beams inside the interferometers were completely separated.
Abstract: A fast neutron chopper produced neutron bursts shorter than the dimensions of the perfect crystal interferometer. Therefore, interference experiments became feasible where the beams inside the interferometer were completely separated. In another experiment, the properties of a four-plate interferometer was tested. Three coupled interferometer loops exist whose net phase shifts determine the intensity modulation behind the interferometer.
10 citations
TL;DR: In this paper, a transient line source, either mechanical or electrical, on the surface of a piezoelectric medium will excite electromagnetic acoustic (EMAC) head waves between quasi-electromagnetic surface disturbances and quasi-acoustic waves.
Abstract: A transient line source, either mechanical or electrical, on the surface of a piezoelectric medium will excite electromagnetic acoustic (EMAC) head waves between quasi‐electromagnetic surface disturbances and quasi‐acoustic waves. EMAC head waves are acoustic in nature, with plane fronts practically parallel to the surface and traveling at acoustic speeds. One such plane wave front is observed experimentally in a thick lead titanate‐zirconate plate in accordance with theory.
7 citations
TL;DR: In this paper, an improved technique for measuring SAW velocity using parallel comb filters is reported, and the measured velocity on the free surface of 36° ST-cut quartz is 3151.9 m/s.
Abstract: An improved technique for measuring SAW velocity using parallel comb filters is reported. The measured velocity on the free surface of 36° ST-cut quartz is 3151.9 m/s. The relative standard deviation of ±57ppm means that this is currently the most precise technique to measure SAW velocity.
5 citations
TL;DR: In this paper, the application of laser-light induced acoustic waves for the determination of sound velocities for pure mode directions in V 2 O 5 single crystals is reported and the longitudinal sound speeds along the crystallographic c and a axes have been measured for the first time and along the b axis has been measured and compared with results of earlier measurements.
5 citations
TL;DR: In this paper, the generation and propagation characteristics of laser-generated acoustic waves in solids were studied using an optical detection technique and a ZnO piezoelectric transducer.
Abstract: Generation and propagation characteristics of picosecond laser-generated acoustic waves in solids were studied using an optical detection technique and a ZnO piezoelectric transducer. The propagation of laser-generated acoustic waves was directional. At the early stage of propagation, the propagation velocity of the wavefront exceeded the sound velocity in solids. The generation and propagation behavior of acoustic waves are very sensitive to the interaction conditions between laser pulses and solid surfaces. The formation and expansion of laser-generated plasmas affect the generation dynamics of acoustic waves.
3 citations
TL;DR: In this paper, the CO2 laser was used as a light source to generate acoustic waves (P, R, and S waves) in an Al sample, and the relationship between the acoustic wave amplitude and the incident laser energy was investigated.
Abstract: The CO2 laser, is for the first time, used as a light source to generate acoustic waves (P, R, and S waves) in an Al sample. The relationship between the acoustic wave amplitude and the incident laser energy is investigated. The spectra of the resonance P and S waves in the Al sample for the frequency range between 1 and 10 MHz are presented. The value of the amplitude ratio between the generated P and S waves is 2.0–3.0.
3 citations
TL;DR: 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.
Abstract: 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. >
01 Jan 1989
TL;DR: In this paper, a waveform generated at the back surface of the solid medium is used to calculate the temperature distribution in the solid Medium. But the waveform is generated at a back surface.
Abstract: TABLE OF CONTENTS-Continued vi Page 4. DISPLACEMENT S O L U T IO N ........................................................................26 Displacement S o lu tion .................................................................... .... . . . 26 5. OBSERVATIONS AND R E SU L T S................................................................... 43 Waveform Generated at the Back Surface of the S o l id ................................43 Physical Interpretation .................................................................... 48 6. C O N C L U S IO N ........................ 57 REFERENCES C I T E D ....................................................... 59 A P P E N D IC E S ........................ 62 Appendix A: Program to calculate the temperature distribution in the solid medium ............................................................................................63 Appendix B: Program to calculate the waveform generated at the back surface of the solid m e d iu m ................................................................. 6 8
TL;DR: In this article, the authors considered the transmission and absorption of plane and spherical acoustic waves in the presence of evaporation and condensation at a flat surface and considered a sound absorbing device as an example.
Abstract: We consider the transmission and absorption of plane and spherical acoustic waves in the presence of evaporation and condensation at a flat surface. A sound absorbing device is considered as an example.