https://publications-cnrc.canada.ca/eng/view/object/?id=bc0e0683-5b32-4da4-acaa-1370639b1db3
Focussing of Ultrasonic Waves in Air Using Micromachined Fresnel Zone-Plate - NRC Publications...
Focussing of Ultrasonic Waves in Air Using Micromachined Fresnel Zone-Plate
fresnel zone plateultrasonic wavesin airfocussingusing