Acoustic sensing through a barrier

Abstract

The invention provides embodiments of an apparatus and for improved, higher quality and higher resolution acoustic impedance scanning of an object through a barrier. Such acoustic impedance scanning can be employed to obtain biometric information of a person via fingerprint pattern.

What is claimed: 
     
         1 . An apparatus for acoustically scanning a target, comprising:
 a barrier having an acoustic impedance property value and having a first side and a second side that each face in substantially opposing directions; and   an acoustic sensor having an acoustic impedance property value that matches or proximately matches said acoustic impedance value of said barrier, said acoustic sensor having a first transmitting side through which acoustic energy is transmitted away from said acoustic sensor, wherein   said first transmitting side of said acoustic sensor is positioned so that it abuts said first side of said barrier, and positioned so that said acoustic sensor is configured to transmit said acoustic energy through said barrier and towards a target abutting said second side of said barrier, and   said acoustic energy is transmitted at a frequency exceeding a resonant frequency for said acoustic sensor that would otherwise be in effect if said acoustic sensor was instead being operated in direct physical contact with said target.   
     
     
         2 . The apparatus of  claim 1 , wherein said acoustic impedance property value of said acoustic sensor proximately matches that of said barrier by having an amount of acoustic impedance that is no more than two percent different from said acoustic impedance value of said barrier. 
     
     
         3 . The apparatus of  claim 1 , wherein said acoustic impedance property value of said acoustic sensor proximately matches that of said barrier by having an amount of acoustic impedance that is no more than five percent different from said acoustic impedance value of said barrier. 
     
     
         4 . The apparatus of  claim 1 , wherein said acoustic impedance property value of said acoustic sensor proximately matches that of said barrier by having an amount of acoustic impedance that is no more than ten percent different from said acoustic impedance value of said barrier. 
     
     
         5 . The apparatus of  claim 1 , wherein said acoustic sensor includes an acoustic energy transmitter, which has a rear side that abuts a backing material having a substantially lower acoustic impedance property value relative to that of said barrier. 
     
     
         6 . The apparatus of  claim 5 , wherein said substantially lower acoustic impedance property value is no more than ten percent of said acoustic sensor. 
     
     
         7 . The apparatus of  claim 5 , wherein said substantially lower acoustic impedance property value is no more than two percent of said acoustic sensor. 
     
     
         8 . The apparatus of  claim 5 , wherein said backing material is air. 
     
     
         9 . The apparatus of  claim 1 , wherein said acoustic energy is transmitted at a frequency of at least 10 Mhz. 
     
     
         10 . The apparatus of  claim 1 , wherein said acoustic energy is transmitted at a frequency of at least 18 Mhz. 
     
     
         11 . The apparatus of  claim 1 , wherein said acoustic sensor is configured to measure acoustic impedance of said target within a measurement time window while simultaneously transmitting acoustic energy, wherein said measurement time window initiates following an initial transmission of acoustic energy from said acoustic sensor, and terminates no later than upon an occurrence of two round trip travel times. 
     
     
         12 . The apparatus of  claim 11 , wherein each round trip travel time is an amount of time required for said acoustic energy to transmit from said acoustic sensor to said target and to reflect from said target and arrive back to said acoustic sensor. 
     
     
         13 . A system for acoustically scanning a target, comprising:
 a barrier having an acoustic impedance property value and having a first side and a second side that each face in substantially opposing directions; and   an acoustic sensor having an acoustic impedance property value that matches or proximately matches said acoustic impedance value of said barrier, said acoustic sensor having a first transmitting side through which acoustic energy is transmitted away from said acoustic sensor, wherein   said first transmitting side of said acoustic sensor is positioned so that it abuts said first side of said barrier, and positioned so that said acoustic sensor is configured to transmit said acoustic energy through said barrier and towards a target abutting said second side of said barrier; and   said acoustic energy is transmitted at a frequency exceeding a resonant frequency for said acoustic sensor that would otherwise be in effect if said acoustic sensor was instead being operated in direct physical contact with said target; and   a backing material in contact with a second side of said acoustic sensor.   
     
     
         14 . The system of  claim 13 , wherein said acoustic sensor is configured to measure acoustic impedance of said target within a measurement time window while simultaneously transmitting acoustic energy, wherein said measurement time window initiates following an initial transmission of acoustic energy from said acoustic sensor, and terminates no later than upon an occurrence of two round trip travel times. 
     
     
         15 . The system of  claim 14 , wherein each round trip travel time is an amount of time required for said acoustic energy to transmit from said acoustic sensor to said target and to reflect from said target and arrive back to said acoustic sensor. 
     
     
         16 . The system of  claim 14 , wherein said measurement time window instead initiates after an occurrence of one said round trip travel time after said initial transmission of acoustic energy from said acoustic sensor. 
     
     
         17 . A method for acoustically scanning a target, comprising:
 providing a barrier having an acoustic impedance property value and having a first side and a second side that each face in substantially opposing directions;   positioning an acoustic sensor comprising a matrix of vibrating piezo electric pillars driven by an electrical signal having a first transmitting side through which acoustic energy is transmitted away from the acoustic sensor, wherein said acoustic sensor is positioned such that it abuts said first side of said barrier, and an acoustic impedance property value of said acoustic sensor matches or proximately matches said acoustic impedance value of said barrier; and   transmitting said acoustic energy from said acoustic sensor through said barrier and towards a target abutting said second side of said barrier, wherein said acoustic energy is transmitted at a frequency exceeding a resonant frequency for said acoustic sensor that would otherwise be in effect if said acoustic sensor was instead being operated in direct physical contact with said target.   
     
     
         18 . The method of  claim 17 , wherein said acoustic impedance property value of said acoustic sensor proximately matches that of said barrier by having an amount of acoustic impedance that is no more than two percent different from said acoustic impedance value of said barrier. 
     
     
         19 . The method of  claim 17 , wherein said acoustic sensor is configured to measure acoustic impedance of said target within a measurement time window while simultaneously transmitting acoustic energy, wherein said measurement time window initiates following an initial transmission of acoustic energy from said acoustic sensor, and terminates no later than upon an occurrence of two round trip travel times. 
     
     
         20 . The method of  claim 19 , wherein each round trip travel time is an amount of time required for said acoustic energy to transmit from said acoustic sensor to said target and to reflect from said target and arrive back to said acoustic sensor.