Fresnel zone plates for ultrasonic focussing - made with circular or elliptical grating esp. of methacrylic! polymer

摘要

Fresnel zone plates (acoustic grating) are produced from an acoustically appropriate material, such as polymethacryl, into which a grating defined by specific equations is formed. Pref. the grating is incorporated directly into the electrode of the oscillator. It may then have a rotationally symmetrical focusing zone of concentric rings for perpendicular noise transmission or, as illustrated, an elliptical form of rings for oblique transmission. In thise case the larger axis lies in the plane of transmission. Fresnel zone plates (acoustic gratings) as above amy be used for ultrasonic focusing in various applications in non- destructive testing, medical diagnostics, etc.