Image distortion compensation technique and apparatus

Abstract

A method of compensating for distortion within a composite image is disclosed. A biometric surface is sensed with a swipe imager. The images so provided are assembled into a composite image of the biometric surface. The composite image is then adjusted by insertion or deletion of rows therein to result in an image with a different number of rows.

1. A method of compensating for distortion within a composite image comprisingthe steps of :
 sensing a biometric surface with a swipe imager to provide sensed data; 
 forming a composite image from sensed data of the  a biometric surfacefrom the sensed data ; and,  
 adjusting the composite image along a dimension thereof to one of  expand or decrease the composite image size along said dimension by one of  removing composite image elements along a line perpendicular to said dimension within the composite image and  or adding additional  image elements along a line perpendicular to said dimension within the composite image to result in a second composite image with a different number of parallel lines of composite image elements perpendicular to the dimensiontherein .  
 
     
     
       2. A method according to  claim 1  wherein the step of  adjusting the composite image includes the step of  adding rows interspersed at row intervals within the image. 
     
     
       3. A method according to  claim 2  wherein the additional rows are added to compensate for compression of the biometric surface during imagingthereof . 
     
     
       4. A method according to  claim 3  wherein the surface is a fingertip and wherein the compression results from a downward swipe direction of the fingertip. 
     
     
       5. A method according to  claim 4  wherein a row is added to the composite image for every N rows within the composite image. 
     
     
       6. A method according to  claim 5  wherein the rows are added at consistent row intervals. 
     
     
       7. A method according to  claim 6  wherein the row interval is 4. 
     
     
       8. A method according to  claim 6  including the step of  determining a row interval based on an amount of compression within the composite image. 
     
     
       9. A method according to  claim 2  wherein a row is added to the composite image for every N rows within the composite image. 
     
     
       10. A method according to  claim 9  wherein the rows are added at consistent row intervals. 
     
     
       11. A method according to  claim 1  further comprisingthe steps of :
 determining an amount of compression within the composite image;  
 adding lines of image elements within the composite image based on the determined amount of compression; and  
 compensating for image distortion along an axis orthogonal to the dimension.  
 
     
     
       12. A method according to  claim 11  wherein the step of  compensating is performed in dependence upon the determined amount of compression. 
     
     
       13. A method according to  claim 11  comprising the step of  determining a distribution of the compression within the composite image. 
     
     
       14. A method according to  claim 13  wherein the step of  adding is performed in dependence upon the determined distribution of the compression within the composite image and the step of  compensating is performed in dependence upon the determined amount of the compression within the composite image. 
     
     
       15. A method according to  claim 1  further comprising the step of  determining a distribution of compression within the composite image. 
     
     
       16. A method according to  claim 15  wherein the step of  adjusting includes a step of  inserting additional lines of elements within the composite image in dependence upon the determined distribution of the compression within the composite image, the lines perpendicular to the dimension. 
     
     
       17. A method according to  claim 1  wherein the step of  adjusting the composite image includes the step of  removing rows interspersed at row intervals within the composite image. 
     
     
       18. A method according to  claim 17  wherein the rows are removed to compensate for stretching of the biometric surface during imagingthereof . 
     
     
       19. A method according to  claim 18  wherein the surface is a fingertip and wherein the stretching results from an upward swipe direction of the fingertip. 
     
     
       20. A method according to  claim 19  wherein a row is removed from the composite image for every N rows within the composite image. 
     
     
       21. A method according to  claim 20  wherein the rows are removed at consistent row intervals. 
     
     
       22. A method according to  claim 21  including the step of  determining a row interval based on an amount of stretching within the composite image. 
     
     
       23. A method according to  claim 17  wherein a row is removed from the composite image for every N rows within the composite image. 
     
     
       24. A method according to  claim 23  wherein the rows are removed at consistent row intervals. 
     
     
       25. A method according to  claim 1  further comprisingthe steps of :
 determining an amount of stretching;  
 removing lines of image elements from the composite image based on the determined amount of stretching; and  
 compensating for image distortion along an axis orthogonal to the dimension.  
 
     
     
       26. A method according to  claim 25  wherein the step of  compensating is performed in dependence upon the determined amount of stretching. 
     
     
       27. A method according to  claim 25  comprising the step of  determining a distribution of the stretching within the composite image. 
     
     
       28. A method according to  claim 27  wherein the step of  removing is performed in dependence upon the determined distribution of the stretching within the composite image and the step of  compensating is performed in dependence upon the determined amount of the stretching within the composite image. 
     
     
       29. A method according to  claim 16  comprising the step of  determining a distribution of stretching within the composite image. 
     
     
       30. A method according to  claim 29  wherein the step of  adjusting includes a step of  removing lines of composite image elements in dependence upon the determined distribution of the stretching within the composite image, the lines perpendicular to the dimension. 
     
     
       31. A method according to  claim 1  wherein the step of  adjusting comprisesthe steps of :
 determining whether the composite image is stretched or compressed along the dimension;  
 when the composite image is compressed, adjusting the composite image along the dimension to expand the composite image size along said dimension by adding additional  image elements along a line perpendicular to said a  dimension within the composite image to result in the second composite image with a different number of parallel lines of image elements perpendicular to said dimension; and,  
 when the composite image is stretched, adjusting the composite image along the dimension to decrease the composite image size along said dimension by removing image elements along a line perpendicular to said a  dimension within the composite image to result in the second composite image with a different number of parallel lines of image elements perpendicular to said at least one  dimensiontherein .  
 
     
     
       32. A method according to  claim 1  further comprising a step of  determining an amount of one of  compression and  or stretching along the dimension of the composite image and wherein the step of  adjusting of the composite image is performed in order to compensate for a determined amount of the one of  compression and  or stretching along said dimension. 
     
     
       33. A method according to  claim 1  further comprising a step of  determining an amount and distribution of one of  compression and  or stretching along the dimension of the composite image and wherein the step of  adjusting of the composite image is performed in order to compensate for a determined amount and distribution of the one of  compression and  or stretching along said dimension. 
     
     
       34. A swipe contact imager comprising:
 a platen across which a biometric surface is to be passed for imaging thereof;  
 an imaging circuit for sensing a biometric surface passing across the platen and for providing image data relating to portions thereof; and  
 a processor for forming  that forms a composite image from the image data and for adjusting  adjusts the composite image along a dimension thereof to one of  expand or decrease the composite image size along said dimension by one of  removing composite image elements along a line perpendicular to said dimension within the composite image and  or adding additional  image elements along a line perpendicular to said dimension within the composite image to result in a second composite image with a different number of parallel lines of composite image elements perpendicular to the dimensiontherein .  
 
     
     
       35. A storage medium having stored therein data, the data indicative of instructions for performing the steps of  whose contents cause a computing system to perform a method, comprising:
 sensing a biometric surface with a swipe imager to provide sensed data; 
 forming a composite image of the  from sensed data of a biometric surfacefrom the sensed data ; and,  
 adjusting the composite image along a dimension thereof to one of  expand or decrease the composite image size along said  the dimension by one of  removing composite image elements along a line perpendicular to said  the dimension within the composite image and  or adding additional  image elements along a line perpendicular to said  the dimension within the composite image to result in a second composite image with a different number of parallel lines of composite image elements perpendicular to the dimensiontherein .  
 
     
     
       36. A  The storage medium according to  of  claim 35  wherein the data relating to the step of  adjusting the composite image includes data relating to a step of  adding rows interspersed at row intervals within the image. 
     
     
       37. A  The storage medium according to  of  claim 36 wherein the instructions relate to , the method further comprising adding a row to the composite image for every N rows within the composite image. 
     
     
       38. A  The storage medium according to  of  claim 37 wherein the instructions relate to , the method further comprising adding the rows at consistent row intervals. 
     
     
       39. A  The storage medium according to  of  claim 38  wherein the row interval is 4. 
     
     
       40. A  The storage medium according to  of  claim 38 wherein the data relates to instructions for performing the step of , the method further comprising determining a row interval based on an amount of compression within the composite image. 
     
     
       41. A  The storage medium according to  of  claim 35 wherein the data relates to instructions for performing the comprising the step of , the method further comprising:
 determining an amount of compression within the composite image;  
 adding lines of image elements within the composite image based on the determined compression; and  
 compensating for image distortion along an axis orthogonal to the dimension in dependence upon the determined amount of compression.  
 
     
     
       42. A  The storage medium according to  of  claim 41 wherein the data relates to instructions for performing the step of , the method further comprising determining a distribution of the compression within the composite image. 
     
     
       43. A  The storage medium according to  of  claim 42  wherein the data relating to instructions for performing the step of  adding includes data relating to instructions for performing the step of  adding in dependence upon the determined distribution of the compression within the composite image. 
     
     
       44. A  The storage medium according to  of  claim 35 wherein the data relates to instructions for performing the step of , the method further comprising determining a distribution of compression within the composite image. 
     
     
       45. A  The storage medium according to  claim 44  wherein the data relating to instructions for performing the step of  adjusting the composite image includes data relating to instructions for performing the step of  inserting additional lines of elements within the composite image in dependence upon the determined distribution of the compression within the composite image, the lines being perpendicular to the dimension. 
     
     
       46. A  The storage medium according to  of  claim 35  wherein the data relating to instructions for performing the step of  adjusting the composite image includes data relating to instructions for performing the step of  removing rows interspersed at row intervals within the composite image. 
     
     
       47. A  The storage medium according to  of  claim 46 wherein the data relates to instructions for performing the step of , the method further comprising determining a row interval based on an amount of stretching within the composite image. 
     
     
       48. A  The storage medium according to  of  claim 35 wherein the data relates to instructions for performing the steps of , the method further comprising:
 determining an amount of stretching;  
 removing lines of image elements from the composite image based on the determined amount of stretching; and  
 compensating for image distortion along an axis orthogonal to the dimension in dependence upon the determined amount of stretching.  
 
     
     
       49. A  The storage medium according to  of  claim 48  wherein the data relates to instructions for performing the step of , the method further comprising determining a distribution of the stretching within the composite image. 
     
     
       50. A  The storage medium according to  of  claim 49  wherein the data relates to instructions for performing the step of  removing in dependence upon the determined distribution of the stretching within the composite image and the step of  compensating is performed in dependence upon the determined amount of the stretching within the composite image. 
     
     
       51. A  The storage medium according to  of  claim 45  wherein the data relates to instructions for performing the step of , the method further comprising determining a distribution of stretching within the composite image. 
     
     
       52. A  The storage medium according to  of  claim 51  wherein the data relating to instructions for performing the step of  adjusting includes data relating to performing a step of  removing lines of composite image elements in dependence upon the determined distribution of the stretching within the composite image, the lines being perpendicular to the dimension. 
     
     
       53. A  The storage medium according to  of  claim 35  wherein the data relating to instructions for performing the step of  adjusting include instructions relating to performing the steps of  further comprises:
 determining whether the composite image is stretched or compressed along the dimension;  
 when the composite image is compressed, adjusting the composite image along the dimension to expand the composite image size along said  the dimension by adding additional image elements along a line perpendicular to said  the a dimension within the composite image to result in the second composite image with a different number of parallel lines of image elements perpendicular to said  the dimension; and,  
 when the composite image is stretched, adjusting the composite image along the dimension to decrease the composite image size along said  the dimension by removing image elements along a line perpendicular to said  the a dimension within the composite image to result in the second composite image with a different number of parallel lines of image elements perpendicular to said  the at least one dimension therein.  
 
     
     
       54. A  The storage medium according to  of  claim 35  wherein the data relates to instructions for performing the step of  determining an amount of one of  compression and  or stretching along the dimension of the composite image and wherein the instructions relate to  adjusting the composite image is performed in order to  compensate  compensates for a determined amount of the one of  compression and  or stretching along said  or dimension. 
     
     
       55. A  The storage medium according to  of  claim 35  wherein the data relates to instructions for performing the step of  determining an amount and distribution of one of  compression and  or stretching along the dimension of the composite image and wherein the instructions relate to  adjusting the composite image in order to compensate compensates for a determined amount and distribution of the one  of the compression and  or stretching along said  or dimension. 
     
     
       56. A swipe contact imager comprising:
   means for sensing a biometric surface and for providing image data relating to portions thereof; and        means for forming a composite image from the image data and adjusting the composite image along a dimension thereof to expand or decrease the composite image size along said dimension by removing composite image elements along a line perpendicular to said dimension within the composite image or adding image elements along a line perpendicular to said dimension within the composite image to result in a second composite image with a different number of parallel lines of composite image elements perpendicular to the dimension.     
     
     
       57. The swipe contact imager of  claim 34 , further comprising a force measurer configured to measure an amount of force applied to the platen when the biometric surface passes the platen. 
     
     
       58. The swipe contact imager of  claim 57  wherein the processor is configured to adjust the composite image based on the measured amount of force. 
     
     
       59. The swipe contact imager of  claim 57  wherein the force measurer is configured to measure an amount of force applied to the platen in at least two regions, and wherein the processor is configured to adjust the composite image according to the amount of force applied in the at least two regions.