Patent ID: 6142948
Filing Date: 2000-11-07
Classification: A61B

Abstract:
A vibration displacement detecting system comprising:a piezoelectric substrate having an upper- and a lower end surfaces being parallel to each other, said lower end surface being in contact with a matter;an input interdigital transducer having an arch-shape and formed on said upper end surface of said piezoelectric substrate, the thickness of said piezoelectric substrate being smaller than an interdigital periodicity of said input interdigital transducer;an output interdigital transducer having an arch-shape and formed on said upper end surface of said piezoelectric substrate, said input- and output interdigital transducers making a pair with a concentric center;a signal analyzing unit connected between said input- and output interdigital transducers; anda monitor connected with said signal analyzing unit,said piezoelectric substrate, and said input- and output interdigital transducers forming a detecting assembly,said input interdigital transducerreceiving an input electric signal with a frequency approximately corresponding to said interdigital periodicity,exciting a leaky elastic wave in said piezoelectric substrate,causing a mode conversion from said leaky elastic wave, having the wavelength approximately equivalent to said interdigital periodicity, to a longitudinal wave in said matter, making a thing located inside said matter reflect said longitudinal wave back,said output interdigital transducerdetecting a reflected longitudinal wave as a delayed electric signal with a frequency approximately corresponding to said interdigital periodicity,said signal analyzing unit sensing a vibration displacement generated by said thing in terms of a change in said delayed electric signal, andsaid monitor displaying said vibration displacement.