Patent ID: 6340347
Filing Date: 2002-01-22
Classification: A61B

Abstract:
A vibration displacement sensing device comprising:a piezoelectric substrate having two end surfaces; an input interdigital transducer; a first output interdigital transducer; a second output interdigital transducer, all said input-, said first output-, and said second output interdigital transducers being formed on one end surface of said piezoelectric substrate; and a signal analyzer, said piezoelectric substrate, said input interdigital transducer, said first- and second output interdigital transducers forming a sensing assembly, said input interdigital transducer receiving an input electric signal, exciting an elastic wave, composed of a leaky- and a non-leaky components, in said piezoelectric substrate, radiating said leaky component of said elastic wave in the form of a longitudinal wave toward a first material located inside a second material which has an acoustic impedance different from that of said first material and is in contact with the other end surface of said piezoelectric substrate, and making said first material reflect said longitudinal wave back, said first output interdigital transducer detecting a reflected longitudinal wave as a first delayed electric signal, said second output interdigital transducer detecting said non-leaky component of said elastic wave as a second delayed electric signal, said signal analyzer sensing a vibration displacement caused by said first material from a difference between said first- and second delayed electric signals.