The design and applications of high-frequency piezoelectric air transducers are described. Two types of thickness mode air transducers are designed and fabricated using newly synthesized acoustic matching layers with an acoustic impedance as low as 0.3 Mrayls. The insertion losses of these transducers are improved by 32-45 dB compared to that of the transducer without a matching layer. Use of a l-MHz double matching layer transducer with a good RF pulse response for range finding has revealed that the measurement range accuracy is of the order of 0.1 mm. For surface profile and defect measurements of solid objects, a focused transducer with a single matching layer is found suitable due to its small focal spot diameter of 1.3 mm and range accuracy of 0.1 mm. Other applications described here are the analysis of a cloth surface state using the acoustic signals propagating along the cloth surface and passing through the cloth.

A hyperthermia thermometry system using an ultrasound. nonlinear effect caused by superposed pulses wzs developed and a feasibility study to obtain temperature mapping of tissue phantoms and anesthetized pigs heated by an ultrasound applicator was made. The thermometry system consists of a mechanical sector scanner and a main frame with a color monitor. The distribution of the temperature rise is calculated within 1 minute, and displayed on the monitor together with an ultrasound B-mode image. Experimental results show that reasonable temperature rise mapping was obtained in both objects and an agreed to within 2°C with the data obtained by thermocouples located in the phantom.

Noncollinear acoustooptic tunable filters using TeO(2) crystals are described. An anisotropic Bragg diffraction is studied applying simple design expressions to a tilt type in which an acoustic wave is launched a little off the [110] axis. Tuning property, filter bandwidth, angular aperture, required acoustic power, deflection angle, divergenceless configuration, and rapid spectrum scanning have been discussed. These filter properties have been confirmed with measurements using three kinds of filter devices: a basic type, an acoustically enhanced type, and a large angular aperture type. A 5-A bandwidth at 4000 A was obtained by slow scanning. A 32-A separation at 4000 A was observed by a rapid scanning of 0.5 msec throughout the visible region with an extremely low electric drive power.

A new glass, composed of TeO2, was found to be well suited to acousto-optical devices. It exhibits a high figure of merit: Me(p2n6/ρv3) = 23.9×10−18 sec3/g and has very good optical qualities with regard to visible light.

The intensity of the diffracted light in an optically active crystal by anisotropic Bragg diffraction has been observed to depend strongly on the polarization condition of the incident light. The acousto-optic figure of merit for this type of crystal, therefore, should be measured under careful selection of the polarization and geometrical condition of the incident light. The figure of merit Me(p2n6/ρv3) of a TeO2 crystal for the slowest shear sound wave propagation using circularly polarized incident light was found to be 1200 × 10−18 sec3/g at 6328 Å rather than 793 × 10−18 sec3/g, as was previously reported by using arbitrarily polarized light. The previous measurement does not give a correct value of Me, according to the theory given above.