Tsutomu Yano

Range Finding and Surface Characterization Using High-Frequency Air Transducers

The design and applications of high-frequency piezoelec- tric 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 mea- surements 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 propa- gating along the cloth surface and passing through the cloth. air transducers mentioned above. This paper describes the design of these transducers and their applications to range finding, profile measurement of solid objects, and surface state measurement of cloth.

Scan converter for a sector scan type ultrasound imaging system

A scan converter is disclosed for use in a sector scan type ultrasound imaging system in which ultrasound echo signals return from targets along a plurality of radial scan lines distributed in a sector field with a substantially equal tangential angular increment with respect to a reference line. The scan converter comprises a sampling circuit which samples the echo signals at a speed inversely proportional to the cosine of the angle of deflection of the radial scan lines with respect to the reference line so that the sampled points align themselves in lateral lines perpendicular to the reference line. The sampled echo signals are converted into digital echo data and stored in a random access memory in the direction of its columns. The stored data are retrieved serially in the direction of the rows and fed into an interpolator for making interpolations between the successively retrieved echo data. The interpolation data are read into a line memory in succession with the data retrieved from the RAM during each raster scan interval, and then retrieved at a constant rate from preselected storage locations so that the data on the raster scan lines have approximately equal density. The retrieved data from the line memory are converted in analog signals and displayed on a viewing screen.

TeO2 anisotropic Bragg light deflector without midband degeneracy

An advanced acousto‐optic light deflector has been designed using the acoustic shear wave traveling slightly off the [110] axis in TeO2. The midband mode degeneracy reported by Warner et al., which decreases the diffracted light intensity, has been shifted off from the active frequency region. A linearly polarized wave can be used as the incident light instead of the elliptically polarized wave used in the conventional deflector designed by Warner et al. The deflector yields a larger number of resolvable spots due to the broadened bandwidth. Experimentally, with 6328‐A light, a 3‐dB bandwidth of 50 MHz was observed with a diffraction efficiency of 80% and an electric power of 350 mW. The new deflector has a capacity of 500 resolvable spots with a random access time of 10 μsec.

Tellurite Glass: A New Acousto‐Optic Material

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.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.

Ultrasonic diagnostic multiple-sector image display system

In an ultrasonic imaging system echo signals representative of the amplitude of ultrasonic energy returning along a plurality of angularly spaced paths are sampled at a constant speed and stored into a buffer memory. At a speed inversely proportional to the cosine of the angle of said path with respect to a reference line the echo samples are read out of the buffer memory and written into a specified area of a graphic memory at a constant speed in the direction of the rows thereof and at a speed proportional to the tangent of the angle of the path with respect to the reference line in the direction of the columns thereof. At a constant speed echo samples are read out of the graphic memory in the directions of the rows and columns and applied to a monitor to be displayed in a raster scan field.

High-Frequency Ultrasonic Transducer Operating in Air

The design and application of high-frequency piezoelectric air transducers are described. By employing a double layer acoustic matching transformer to a ceramic thickness mode vibrator, an air transducer with low insertion loss (52 dB) and good RF pulse response (9 µs of -20 dB ring-down period) has been developed. Use of the transducer operating at 1 MHz for distance measurement in a range of 0~20 cm has revealed that the range resolution and the measurement accuracy are 1.5 mm and of the order of 0.1 mm, respectively. Other applications described here are the characterization of cloth surfaces and profile measurement of cloths.

Ultrasound pulse reflection mode measurement of nonlinearity parameter B/A and attenuation coefficient

A new method for obtaining depth distribution of the nonlinearity parameter B/A and the frequency‐dependent attenuation coefficient is outlined. In this method, the higher frequency probe pulse wave, superposed coaxially on the lower frequency pump pulse wave, is modulated nonlinearly due to their propagation, and is received as an echo signal. The relationship between these acoustic parameters and the modulation characteristics of the probe pulse wave is derived by the division of the spectra of modulated echo signals with each other. The possibility of canceling out of error factors, such as the frequency‐dependent acoustic reflection coefficient of random scattering medium, in the above division process is discussed. A preliminary evaluation of this method is made by using an experimental system. B/A values are obtained for various kinds of sponge test targets immersed in water, n‐propyl alcohol, isopropyl alcohol, ethylene glycol, or diethylene glycol; and for agar graphite phantom.

Ultrasonic tomographic with alternate image scaling

An ultrasonic tomographic diagnosis apparatus suitable for skin disease displays a first ultrasonic tomographic image (12) of an object of a fairly broad area, wherein sizes in depthwise direction (X in FIG. 1) displayed in an enlarged scale in relation to sizes in a direction (Y in FIG. 1) on the skin surface, and further a second ultrasonic tomographic image (13) of an object wherein sizes in depthwise direction and sizes in the direction on the skin surface are displayed in substantially proportional to actual size relations, for a selected part marked by a marker (14) on the first tomographic image (12). While specific embodiments of the invention have been illustrated and described herein, it is realized that modifications and changes will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all modifications and changes as fall within the true spirit and scope of the invention.

A NEW CRYSTAL Pb5(GeO4)(VO4)2 FOR ACOUSTO‐OPTIC DEVICE APPLICATIONS

A new melt‐grown crystal of apatite type Pb5(GeO4)(VO4)2 has been found to be well suited for acousto‐optic device applications. Acousto‐optic figure of merit is 50.6 × 10−18 sec3/g and acoustic absorption is about 1.2 dB/cm at 200 MHz.

1 MHz Ultrasonic Transducer Operating in Air

Conventional ultrasonic air transducers operating below 100 kHz have been utilized for position sensing in the range of 0.1–10m and provide several unique advantages. A typical application of an ultrasonic air transducer is to the wide range distance measurement of an optically transparent object placed “very close to” up to “relatively far from” the transducer. Additionally the real-time measurement can be done with simple signal processing. However, conventional air transducers have very wide beamwidths and relatively long pulse response characteristics which make it difficult to detect a small and nearby object.