System and method for counting ridges in a captured print image

Abstract

A system and method for counting ridges in a captured print image frame is described. A pixel path through the captured print image frame is traversed. A hysteresis band for the pixel path is determined. A number of crossings of the determined hysteresis band is counted while traversing the pixel path. A number of print ridges based on the counted number of hysteresis band crossings is determined.

1 - 34 . (canceled)  
     
     
         35 . A method for counting print ridges in a captured print image frame, comprising the steps of: 
 (1) traversing a pixel path through the captured print image frame;    (2) counting a number of crossings of a first pixel intensity threshold and a second pixel intensity threshold while traversing the pixel path; and    (3) determining a number of print ridges in the captured print image frame based on the counted number of crossing of the first pixel intensity threshold and the second pixel intensity threshold.    
     
     
         36 . The method of  claim 35 , wherein step (3) comprises determining the number of print ridges by dividing the counted number of first pixel intensity threshold and second pixel intensity threshold crossings by two.  
     
     
         37 . The method of  claim 35 , further comprising the step of: 
 (4) determining the first pixel intensity threshold and the second pixel intensity threshold.    
     
     
         38 . The method of  claim 37 , wherein step (4) comprises determining a third pixel intensity threshold based on a first maximum pixel intensity value and a first minimum pixel intensity value in the captured print image frame.  
     
     
         39 . The method of  claim 38 , wherein step (4) further comprises determining a delta value based on the first maximum pixel intensity value and the first minimum pixel intensity value in the captured print image frame.  
     
     
         40 . The method of  claim 39 , wherein step (4) further comprises determining the first pixel intensity threshold as a sum of the third pixel intensity threshold and the delta value.  
     
     
         41 . The method of  claim 39 , wherein step (4) further comprises determining the second pixel intensity threshold as a difference of the third pixel intensity threshold and the delta value.  
     
     
         42 . The method of  claim 35 , further comprising the steps of: 
 (4) traversing a second pixel path across the captured print image frame; and    (5) repeating steps (2) and (3) using the second pixel path.    
     
     
         43 . The method of  claim 35 , further comprising the steps of: 
 (4) storing the number of print ridges; and    (5) evaluating the stored number of print ridges to determine a quality of the captured fingerprint image.    
     
     
         44 . A print scanner system, comprising: 
 an optical system enabled to direct light to an imaging surface of a platen of the optical system;    a camera enabled to capture a print image frame from light reflected by the print surface and directed to the camera by the optical system;    a memory coupled to the camera and enabled to store the captured print image frame; and    a ridge counter coupled to the memory and enabled to traverse a pixel path through the captured print image frame, count a number of crossings of a first pixel intensity threshold and a second pixel intensity threshold while traversing the pixel path, and determine a number of print ridges in the captured print image frame based on the counted number of crossings.    
     
     
         45 . The print scanner system of  claim 44 , wherein the ridge counter is enabled to determine the number of print ridges by dividing the number of crossings by two.  
     
     
         46 . The print scanner system of  claim 44 , wherein the ridge counter is enabled to determine a region of interest in the captured print image frame.  
     
     
         47 . The print scanner system of  claim 44 , wherein the ridge counter is enabled to determine a first pixel intensity threshold and a second pixel intensity threshold.  
     
     
         48 . The print scanner system of  claim 47 , wherein the ridge counter is enabled to determine a third pixel intensity threshold based on a first maximum pixel intensity value and a first minimum pixel intensity value in the captured print image frame.  
     
     
         49 . The print scanner system of  claim 48 , wherein the ridge counter is enabled to determine a delta value based on the first maximum pixel intensity value and first minimum pixel intensity value in the captured print image frame.  
     
     
         50 . The print scanner system of  claim 49 , wherein the ridge counter is enabled to determine the first pixel intensity threshold as a sum of the third pixel intensity threshold and the delta value.  
     
     
         51 . The print scanner system of  claim 49 , wherein the ridge counter is enabled to determine the second pixel intensity threshold as a difference of the third pixel intensity threshold and the delta value.  
     
     
         52 . A ridge counter embodied in software and including control logic for counting print ridges in a captured print image frame, comprising: 
 first control logic means for enabling a processor to traverse a pixel path through the captured print image frame;    second control logic means for enabling a processor to count a number of crossings of a first pixel intensity threshold and a second pixel intensity threshold while traversing the pixel path; and    third control logic means for enabling a processor to determine a number of print ridges in the captured print image frame based on the counted number of first pixel intensity threshold crossings and second pixel intensity threshold crossings.    
     
     
         53 . The ridge counter of  claim 52 , further comprising fourth control logic means for enabling a processor to determine the number of print ridges by dividing the counted number of crossings of the first pixel intensity threshold and the second pixel intensity threshold by two.  
     
     
         54 . The ridge counter of  claim 52 , further comprising fourth control logic means for enabling a processor to determine the first pixel intensity threshold and the second pixel intensity threshold.