Biometric sensing device with isolated piezo ceramic elements

Abstract

The present invention provides an apparatus for sensing biometric information in a finger with piezo ceramic elements. In one embodiment, the apparatus includes an array of discrete piezo ceramic elements and filler. The array of discrete piezo ceramic elements is responsive to acoustic characteristics of parts of the finger. The filler is distributed between the discrete piezo ceramic elements and provides acoustic attenuation and electric isolation between the discrete piezo ceramic elements. A protective layer can receive a ridge pattern of the finger positioned proximate to the array. Air in valleys between ridges of the ridge pattern of the finger acts as an acoustic barrier. A backing layer (air or foam) can also be provided.

What is claimed is:  
     
         1 . An apparatus for sensing biometric information in a finger, comprising: 
 an array of discrete piezo ceramic elements responsive to acoustic characteristics of parts of the finger; and    filler distributed between said discrete piezo ceramic elements, said filler providing acoustic attenuation and electric isolation between said discrete piezo ceramic elements.    
     
     
         2 . The apparatus of  claim 1 , wherein said filler further suppresses shear waves between said discrete piezo ceramic elements and provides mechanical support for said discrete piezo ceramic elements.  
     
     
         3 . The apparatus of  claim 1 , wherein said filler includes microspheres.  
     
     
         4 . The apparatus of  claim 1 , wherein said microspheres include vinyl microspheres.  
     
     
         5 . The apparatus of  claim 1 , wherein said discrete piezo ceramic elements comprises a plurality of discrete columnar piezo ceramic elements, each columnar element having a first end and a second end.  
     
     
         6 . The apparatus of  claim 5 , wherein each first end is electrically coupled to a first grid of conductors and each second end is electrically coupled to a second grid of conductors.  
     
     
         7 . The apparatus of  claim 6 , wherein said first grid of conductors is coupled to a protective layer that can receive a ridge pattern of the finger positioned proximate to said array, wherein air in valleys between ridges of the ridge pattern of the finger acts as an acoustic barrier.  
     
     
         8 . The apparatus of  claim 7 , wherein said second grid of conductors is coupled to a backing layer.  
     
     
         9 . The apparatus of  claim 7 , wherein said second grid of conductors has an air backing, said air backing being acoustically mismatched with said discrete columnar piezo ceramic elements.  
     
     
         10 . The apparatus of  claim 5 , further comprising a protective layer acoustically coupled to said first ends of said elements, wherein said protective layer receives a ridge pattern of the finger positioned proximate to said array such that air in valleys between ridges of the ridge pattern of the finger acts as an acoustic barrier.  
     
     
         11 . The apparatus of  claim 5 , further comprising a backing layer, said backing layer being acoustically mismatched with said discrete columnar piezo ceramic elements.  
     
     
         12 . The apparatus of  claim 11 , wherein said backing layer comprises air.  
     
     
         13 . The apparatus of  claim 11 , wherein said backing layer comprises foam.  
     
     
         14 . The apparatus of  claim 1 , wherein said discrete piezo ceramic elements include lead zirconate titanate.  
     
     
         15 . A biometric sensing apparatus, comprising: 
 a piezoelectric ceramic sensor; and    a processor, coupled said sensor, that receives an input from said sensor and produces an output, wherein said sensor comprises an array of piezoelectric ceramic elements and includes a sonic barrier between each of said elements.    
     
     
         16 . The apparatus of  claim 15 , wherein said sonic barrier is air.  
     
     
         17 . The apparatus of  claim 15 , wherein said sonic barrier is an epoxy containing micro-spheres.  
     
     
         18 . The apparatus of  claim 17 , wherein said micro-spheres are vinyl.  
     
     
         19 . The apparatus of  claim 15 , further comprising: 
 a medium that conducts sonic energy, said medium being coupled to said sensor so that a low sonic energy barrier is formed between said medium and said sensor.    
     
     
         20 . The apparatus of  claim 19 , wherein said medium has an impedance that facilitates conducting sonic energy into tissue.  
     
     
         21 . The apparatus of  claim 20 , wherein said medium is a polymer.  
     
     
         22 . The apparatus of  claim 20 , wherein said medium is urethane.  
     
     
         23 . An apparatus for sensing biometric information in a finger, comprising: 
 an array of discrete piezo ceramic elements responsive to acoustic characteristics of parts of the finger; and    material distributed between said discrete piezo ceramic elements, said material providing acoustic attenuation and electric isolation between said discrete piezo ceramic elements.