Toshio Sannomiya

Accurate measurements of the acoustical physical constants of LiNbO/sub 3/ and LiTaO/sub 3/ single crystals

The acoustical physical constants (elastic constant, piezoelectric constant, dielectric constant, and density) of commercial surface acoustic wave (SAW)-grade LiNbO/sub 3/ and LiTaO/sub 3/ single crystals were determined by measuring the bulk acoustic wave velocities, dielectric constants, and densities of many plate specimens prepared from the ingots. The maximum probable error in each constant was examined by considering the dependence of each constant on the measured acoustic velocities. By comparing the measured values of longitudinal velocities that were not used to determine the constants with the calculated values using the previously mentioned constants, we found that the differences between the measured and calculated values were 1 m/s or less for both LiNbO/sub 3/ and LiTaO/sub 3/ crystals. These results suggest that the acoustical physical constants determined in this paper can give the values of bulk acoustic wave velocities with four significant digits.

Scanning Acoustic Microscope for Quantitative Characterization of Biological Tissues

In the field of medical and biological sciences, an acoustic microscope is being developed as a practical research tool [1–3]. This paper describes a system of reflection-type scanning acoustic microscopy which can measure quantitatively visco-elastic properties of biological tissues on a microscopic scale. This system operates in both amplitude and phase modes with the following two functions; an acoustical imaging function for displaying both amplitude and phase images with high spatial resolution, and a quantitative measurement function for determining both velocity and attenuation at arbitrary points in an imaging area. The operating frequency is variable so that it is possible to make spectroscopic analyses of tissues through acoustic properties. The spatial change of acoustic properties in tissues due to pathological degeneration can be extracted easily by an additional function of false color imaging. Experiments have been performed on dog cardiac infarcted tissue in the frequency range 100 to 200 MHz.

Propagation Properties of Ultrasound in Acoustic Microscopy through a Double-Layered Specimen Consisting of Thin Biological Tissue and Its Holder

In transmission mode SAM, a biological tissue section to be examined is usually mounted on a polyester film holder to compose a double-layered specimen. In this paper, a one dimensional acoustic model for double layers composed of the mounting holder and a tissue section is investigated to discuss the propagation properties through the specimen quantitatively. It has been basically clarified that variations of brightness in the amplitude image correspond to those in acoustic absorption and that variations of brightness in the phase image correspond to those in sound speed in the tissue section.

Acoustic Microscope for Measuring Acoustic Properties by Micro-Defocusing Method

In the literature, much work has been reported on measurement and imaging by acoustic microscopy. In a typical method of quantitative measurements[1], the phase velocity and the propagation attenuation of a leaky surface acoustic wave (LSAW) are determined from the interference period △z and the slope of the V(z)curve, respectively. When the propagation attenuation of a sample is large, sufficient defocused distance necessary for such analysis cannot be attained.

Performance of Scanning Acoustic Microscope Employing Concave Transducers

A scanning acoustic microscope (SAM) has been developed by Quate and Lemons which employs acoustic lenses for focussing ultrasonic waves. Recently, concave film transducers have been proposed instead of acoustic lenses for focussing ultrasonic waves in the SAM system. In this paper, characteristics of ZnO-film concave transducers and their application to a transmission mode SAM as well as a reflection mode SAM are described,. of the SAMs are described including acoustic images observed at the frequences around at 200 MHz. Performances

Scanning Acoustic Microscope with Transducer Swing Along Beam Axis

A transducer swing mechanism is introduced to accomplish a new scanning acoustic microscope system in the interference mode, which is applied to the quantitative measurement of acoustic velocities in thin materials. In this system, the distance between a pair of aligned focusing transducers along the beam axis is varied periodically, as the specimen is synchronously scanned in the X direction. Measurements of acoustic velocities are performed with this system for two kinds of polymer film, polyester and PVF2 films, and a dogs cardiac infarcted tissue at a frequency of 150 MHz.

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 Delta z 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 Delta z. 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 Delta z 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.<<ETX>>

Measurement of bone properties by ultrasound to develop diagnostic equipment

An extracorporeal measurement system is proposed for measurements of bone properties in vivo by introducing a technique of excitation and detection of leaky surface waves developed in acoustic microscopy. Bovine femoral bone was taken as a bone sample, and velocities and attenuations were measured for the longitudinal bulk waves in the range of 2-10 MHz. On the basis of the measured results and published data for bone properties, an ultrasonic measurement system was designed to be operated at a frequency of 1 MHz. With the measurement system, leaky surface skimming compressional waves (LSSCWs) were successfully excited on polished flat surfaces of bones with water coupling, and phase velocities of LSSCWs were measured.<<ETX>>

Scanning Acoustic Microscope/Photoacoustic Microscope Operating on a Unified Software Environment

A scanning acoustic microscope (SAM) and a photoacoustic microscope (PAM) operating on a unified software environment was designed and fabricated. Welded steel plates, in which the welding condition was changed by varying the amount of current and its duration, were used as specimens. SAM and PAM measurements for this specimen were carried out, and the obtained images were compared. This system has the advantage of complementary measurement using both SAM and PAM.

Transmission line method for the measurement of the acoustic nonlinearity parameter in biological liquids at very high frequencies

Nonlinear wave propagation in a system consisting of a liquid specimen held between two SiO2 buffer rods is studied as a new method of determining the acoustic nonlinearity parameter of liquids at very high frequencies. Since the sign of the nonlinearity parameter of SiO2 is opposite that for liquids, the system can be viewed as a transmission line containing regions of both positive and negative nonlinearity. The nonlinear characterization curve is employed in which the second harmonic component output of the receiving transducer is plotted as a function of propagation distance in liquids between the two SiO2 buffer rods. The nonlinearity parameter is determined by measuring the dip position at which the transducer output becomes zero in the curve. Measurements are reported for water and aqueous solutions of dextrose and dextran in the fundamental frequency range 100–200 MHz.