GB1428264A - Ultrasonic delay line - Google Patents

Abstract

1428264 Ultrasonic delay lines MITSUMI ELECTRIC CO Ltd 6 April 1973 [6 April 1972] 16606/73 Heading H3U Delay lines are provided in which at least one beam reflecting mirror surface D 1 , Fig. 2, D 1 , D 5 , Fig. 22, has an elliptical, or D 2 , Fig. 13, plane bounded by elliptical, profile, acting to refocus spread components 5a, 5b of an ultrasonic wave from input transducer 2 on to the output transducer 2<SP>1</SP> without changing their transit time compared with the main beam. A single input/ output transducer may be used. The foci of the ellipse are positioned either at the centre points of transducers when regarded as point sources, or at virtual images of same in plane reflecting surfaces of the delay line, Fig. 2; Figs. 1,3-9 (not shown), or at intermediate points of the beam path at which the beam refocuses, there being 2, 3, or 4, elliptical profiled surfaces in the delay line, Fig. 22; Figs. 19-21, 23-26 (not shown). When the transducers are regarded as sources distributed over their areas, with spreading in the regions 5c#5a, 5d#5b, Fig. 13, a plane portion d p reflects the non- spreading part of the beam, elliptical portions d a , db, having as foci, either the edges a 0 , b 0 , a 0 <SP>1</SP>, b 0 <SP>1</SP> of the transducers, or virtual images of same in plane reflecting surfaces of the delay line, refocusing the spreading parts of the beam back on to the output transducer, see also Figs. 10- 12, 14-18 (not shown). The surface which would otherwise support the output transducer may act to reflect the beam back to the input transducer, a single transducer delay line with doubled delay time thus being produced. The delay medium is elinvar, ceramic, or glass and is 0À5-5 acoustic wavelengths thick, the transducers being adhesively bound thereto and polarized parallel to the major surfaces. The eccentricity of the elliptical profile surfaces depends on the precise delay time required, the latter being the same for non-spread, and spread and refocused, parts of the beam.