Silicon rubber surfaces for biometric print TIR prisms

Abstract

Molded silicone rubber sheets with optical quality surfaces and methods for making the same. The silicone rubber sheets are made by molding liquid silicone rubber in a mold. In embodiments, the mold forms parallel optical quality flat surfaces. In one embodiment, a stiffening plastic is molded in the middle of the silicone rubber sheet between the parallel optical quality flat surfaces. In another embodiment, the mold forms one optical quality flat surface while the surface parallel to the optical quality flat surface is bonded to a prism.

What is claimed is:  
     
         1 . A silicone rubber sheet, comprising: 
 at least one layer of silicone rubber compound; and    at least one optical quality surface attached to said at least one silicone rubber compound, wherein said at least one optical quality surface is molded to said at least one layer of silicone rubber compound.    
     
     
         2 . The silicone rubber sheet of  claim 1 , wherein said at least one layer of silicone rubber compound is comprised of one of liquid silicone and liquid silicone diluted with a silicone thinner.  
     
     
         3 . The silicone rubber sheet of  claim 1 , wherein said at least one layer of silicone rubber compound is integrally molded to a surface of a device.  
     
     
         4 . The silicone rubber sheet of  claim 3 , wherein said device is a TIR (Total Internal Reflection) prism.  
     
     
         5 . The silicone rubber sheet of  claim 2 , wherein said silicone rubber compound comprised of liquid silicone diluted with a silicone thinner is diluted 10-40 percent.  
     
     
         6 . The silicone rubber sheet of  claim 1 , wherein said at least one layer silicone rubber compound includes a TIR platen surface that is of optical quality.  
     
     
         7 . The silicone rubber sheet of  claim 1 , wherein said at least one layer of silicone rubber compound has an embedded layer of a stiff plastic approximately midway of said at least one layer of silicone rubber compound.  
     
     
         8 . A method for making a silicone rubber sheet, comprising the steps of: 
 (1) preparing a liquid silicone compound;    (2) out gassing said liquid silicone compound;    (3) pouring said liquid silicone compound into one or more cavity molds; and    (4) curing said liquid silicone compound to generate said silicone rubber sheet.    
     
     
         9 . The method of  claim 8 , further comprising the step of removing said silicone rubber sheet from said mold.  
     
     
         10 . The method of  claim 9 , further comprising the step of cutting said silicone rubber sheet to defined dimensions for a defined application.  
     
     
         11 . The method of  claim 8 , wherein step (1) comprises the steps of: 
 (a) coating a surface of a prism with a binder; and    (b) curing the binder, wherein said silicone rubber sheet will be integrally molded to the prism after step (4) is completed.    
     
     
         12 . The method of  claim 11 , wherein step (a) further comprises the step of coating said binder with a silicone sealer.  
     
     
         13 . The method of  claim 8 , wherein step (1) comprises the steps of: 
 (a) applying a binder to a stiffening material;    (b) curing said stiffening material;    (c) placing said stiffening material in a tension device between said one or more cavity molds; and    (d) tensioning said stiffening material.    
     
     
         14 . The method of  claim 8 , wherein step (1) comprises the step of diluting liquid silicone with a silicone thinner solution.  
     
     
         15 . A total internal reflective (TIR) platen for a biometric imaging device, comprising: 
 a silicone rubber compound; and    a first and second optical quality molded surface, wherein said first optical quality molded surface provides for a TIR platen surface and said second optical quality molded surface for making optical contact with a prism.    
     
     
         16 . The TIR platen of  claim 15 , wherein said silicone rubber compound is integrally molded to said prism.  
     
     
         17 . The TIR platen of  claim 15 , wherein said silicone rubber compound includes a stiff plastic material in the middle of said silicone rubber compound.