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Showing papers on "Acoustic interferometer published in 1992"


Journal ArticleDOI
TL;DR: In this article, a noncontact all-optical method for surface photoacoustics is described, where the surface acoustic waves (SAWs) were excited employing a KrF laser and detected with a Michelson interferometer using a 633nm HeNe laser.
Abstract: A noncontact all‐optical method for surface photoacoustics is described. The surface acoustic waves (SAWs) were excited employing a KrF laser and detected with a Michelson interferometer using a 633‐nm HeNe laser. Due to an active stabilization scheme developed for the interferometer a surface displacement of 0.2 A could be detected. The materials investigated included pure materials such as polycrystalline aluminum, and crystalline silicon; films of gold, silver, aluminum, iron, and nickel on fused silica; and a‐Si:H on Si(100). In the case of pure materials the shape of the acoustic pulse and the phase velocity were determined. The dispersion of the SAW phase velocity observed for the film systems was used to extract information on the film thickness, density, and transverse and longitudinal sound velocity. Models for the theoretical treatment of film systems and the calculation of dispersion curves are presented.

182 citations


Journal ArticleDOI
TL;DR: In this article, a separation process based on the acoustic radiation force created in stationary fields produced by a forced coincidence excitation at ultrasonic frequencies of fluid-filled pipes has been developed.
Abstract: A separation process based on the acoustic radiation force created in stationary fields produced by a forced coincidence excitation at ultrasonic frequencies of fluid‐filled pipes has been developed. The efficacy of this method for the collection and manipulation of fine secondary phases in flowing suspensions will be compared to equivalent operations in stationary fields generated in acoustic interferometer chambers operated without coincidence effects. The basis for the axial translation of the phases concentrated at the pressure nodes to either end of the cell as a result of an applied periodic sweep in the driving frequency will be examined.

50 citations



PatentDOI
TL;DR: In this paper, an apparatus for treating a patient with acoustic waves has a source of acoustic waves and an X-ray locating system, which includes an Xray radiator and a radiation detector, mounted opposite each other on a C-arm.
Abstract: An apparatus for treating a patient with acoustic waves has a source of acoustic waves and an X-ray locating system, which includes an X-ray radiator and a radiation detector, which are mounted opposite each other on a C-arm. The C-arm is adjustable along its outer circumference around its central axis. The source of acoustic waves is adjustable along the inner circumference of the C-arm such that the acoustic axis of the acoustic wave source constantly intersects the central axis of the C-arm.

25 citations



Journal ArticleDOI
TL;DR: In this paper, an optical method for generating and detecting periodic surface acoustic waves is described, where the periodic source is created by splitting the beam from a Nd:YAG laser and recombining the beams at a sample surface to form an interference pattern.
Abstract: An optical method for generating and detecting periodic surface acoustic waves is described. The periodic source is created by splitting the beam from a Nd:YAG laser and recombining the beams at a sample surface to form an interference pattern. The periodic surface waves launched from the source are detected optically using either a modified Michelson interferometer or by laser probe beam deflection. In both cases the detection spot is smaller than the ultrasonic wavelength. Rayleigh waves in the 1–20 MHz frequency range can readily be generated and detected on thick aluminium samples (plate thickness greater than the wavelength). It is also possible to generate narrowband Lamb waves in plates which are thin compared to the wavelength, experimental and theoretical waveforms are presented for this case.

15 citations


Book ChapterDOI
01 Jan 1992
TL;DR: In this article, the authors proposed a non-destructive evaluation (NDE) method of materials in circumstances where liquid or gel coupler can not be used and the main limitation of this technique is its low sensitivity compared with the standard piezoelectric transducer method.
Abstract: Laser ultrasonics is expected to provide a nondestructive evaluation (NDE) method of materials in circumstances where liquid or gel coupler can not be used[1-6]. However, the main limitation of this technique is its low sensitivity compared with the standard piezoelectric transducer method. One of this reason is the low amplitude of acoustic waves that can be generated without damage. If one uses high peak power laser to generate strong acoustic waves, ablation damage of the surface is resulted [2] as illustrated in Fig.1 (a). Even in the thermoelastic regime, photodissociation may be introduced in polymers by repeated laser irradiation [3].

10 citations


Patent
20 Aug 1992
TL;DR: An acoustic wave generator has a shockwave source contained in a housing with a volume between the source and the location at which the acoustic waves exit the generator which is divided into two sub-volumes, each filled with acoustic propagation medium as mentioned in this paper.
Abstract: An acoustic wave generator has a shockwave source contained in a housing with a volume between the shockwave source and the location at which the acoustic waves exit the generator which is divided into two sub-volumes, each filled with acoustic propagation medium. The location at which the acoustic waves exit the generator is in the form of a deformable cushion which permits the generator to conform to the surface of a subject to be irradiated with the acoustic waves. The liquid propagation medium in both sub-volumes is circulatable, with the amount of liquid propagation medium in the sub-volume forming the cushion being variable.

10 citations


Journal ArticleDOI
TL;DR: In this article, the sound velocity of 78 commercial plastics have been measured at a frequency of 2 MHz in the room temperature for evaluation of transducer window materials and the results indicated that some types of polymethyl pentene, ethylene-vinyl acetate and polyetherblockamide are similar to human body in acoustic impedance.
Abstract: The sound velocity of 78 commercial plastics have been measured at a frequency of 2 MHz in the room temperature for evaluation of transducer window materials. The acoustic impedance of these materials are derived from the measured values of the sound velocity in addition to the density. The results obtained suggest that some types of polymethyl pentene, ethylene-vinyl acetate and polyetherblockamide are similar to human body in acoustic impedance. By using these materials an excellent acoustic transducer window in an ultrasonic diagnostic instrument is indicated.

9 citations


ReportDOI
01 Sep 1992
TL;DR: In this article, the authors compared two acoustic impedance measurement techniques, a wave decomposition method and an inverse eigenvalue method, which inverts the functional form of impedance tube eigenvalues.
Abstract: : This report describes an investigation that compares two acoustic impedance measurement techniques. The first is a wave decomposition method that breaks the wave energy into reflected and incident components and then calculates acoustic impedance. The second is an inverse eigenvalue method that inverts the functional form of impedance tube eigenvalues and then calculates acoustic impedance. An experiment comparing the measured acoustic impedance from both methods results in similar values.

5 citations



Journal ArticleDOI
TL;DR: In this article, the effect of the acoustic wave on the index of refraction was discussed and it was shown that the energy of acoustic wave is negligible compared with the increase of internal energy produced by the optical pumping.

Proceedings ArticleDOI
20 Oct 1992
TL;DR: In this article, an instrument for measurement of ultrasonic displacement has been developed by modifying a scanning-tunneling microscope probe, which can be used for measurements of high-frequency surface displacement in applications requiring better lateral resolution than optical probes can provide.
Abstract: An instrument for measurement of ultrasonic displacement has been developed by modifying a scanning-tunneling-microscope probe. It can be used for measurement of high-frequency surface displacement in applications requiring better lateral resolution than optical probes can provide. The application of the instrument to the characterization of surface acoustic waves is described. >

Book ChapterDOI
01 Jan 1992
TL;DR: In this article, it is shown that disturbances in shock and expansion tubes can be modelled as lateral acoustic waves and the ratio of sound speed across the driver-test gas interface is shown to govern the quantity of noise in the test gas.
Abstract: It is shown that disturbances in shock and expansion tubes can be modelled as lateral acoustic waves. The ratio of sound speed across the driver-test gas interface is shown to govern the quantity of noise in the test gas. Frequency “focusing” which is fundamental to centred unsteady expansions is discussed and displayed in centreline pitot pressure measurements.

Journal ArticleDOI
TL;DR: In this paper, simultaneous acoustic impedance measurements of transverse and longitudinal sound at 61 MHz and pressures of 15.6, 10.5, and 8.0 bar were reported.
Abstract: We report on simultaneous acoustic impedance measurements of transverse and longitudinal sound at 61 MHz and pressures of 15.6, 10.5, and 8.0 bar.

Proceedings ArticleDOI
01 Mar 1992
TL;DR: In this article, an algorithm based on the application of transmission line theory to the propagation of both acoustic and electromagnetic waves in isotropic media having arbitrary velocity and impedance profiles is presented to calculate the space evolution of the reflection coefficient.
Abstract: An algorithm based on the application of transmission line theory to the propagation of both acoustic and electromagnetic waves in isotropic media having arbitrary velocity and impedance profiles is presented to calculate the space evolution of the reflection coefficient. Several cases will be presented to demonstrate the validity of the algorithm.

Patent
28 Jan 1992
TL;DR: In this paper, the authors aim to ensure optimum and efficient application of the high-power sound pulses and the acoustic power emitted by the transducer by using the reflected sound waves as a measure of the emitted acoustic power.
Abstract: The aim is for the acoustic power emitted by the shock wave transducer (2) and the sound pressure determined hereby to be controlled or regulated in the focus (3) in order to be able to ensure optimum and efficient application of the shock waves and high-power sound pulses. For this purpose, the sound waves (6) emitted by the transducer (2) are deflected at least partially in the direction towards the transducer (2), the electric voltage induced at the transducer (2) by the reflected sound waves serving as a measure of the emitted acoustic power.

Journal ArticleDOI
TL;DR: In this article, it has been observed that the surface acoustic wave intensity required to produce maximum acoustic emission count decreases with increasing cell thickness and the changes occurring in the liquid crystal when subjected to surface acoustic waves were studied using a polarising microscope and the results were explained on the basis of this visual observation.

Journal ArticleDOI
TL;DR: In this paper, a five-channel splitter of a new type is discussed, in which normal optical modes of monochromatic light interact simultaneously with two acoustic waves, which differ in frequency.
Abstract: A five-channel splitter of a new type is discussed. In this splitter, normal optical modes of monochromatic light interact simultaneously with two acoustic waves. These two waves are orthogonal with respect to each other and differ in frequency. Experiments reveal a splitting at transverse sound frequencies of 20.1, 16, and 13.5 MHz at light wavelengths of 488, 514, and 633 nm, respectively, in a TeO2 single crystal.