Comparison

Abstract

A method of simulating the effect of distortion on a representation of a marker, such as a fingerprint is provided. The method is useful for generating data for use in various processes concerned with fingerprints and particularly avoids the need to manually generate and collect such data. The method includes obtaining a plurality of representations from an individual, the representations being subject to different distortions relative to one another. A function, such as a thin plate spline function, is then used to describe the effects of the different distortions on the plurality of representations obtained. This generic model of the effects of distortion can then be used to generate distortions for a further representation from an individual, preferably another individual. The simulated distorted representations can be used in a variety of ways.

1 . A method of simulating the effect of distortion on a representation of a marker, the method including 
 obtaining a plurality of representations from an individual, the representations being subject to different distortions relative to one another;    describing the effect of the different distortions on the plurality of representations using a function;    taking a further representation from an individual and preferably another individual, applying the function to that representation to generate one or more simulated distorted representations.    
     
     
         2 . A method according to  claim 1  in which the function is or includes a non-linear function.  
     
     
         3 . A method according to  claim 2  in which the function is a non-linear transformation.  
     
     
         4 . A method according to  claim 1  in which the function is or includes one or more matrices.  
     
     
         5 . A method according to  claim 1  in which the function is defined, at least in part, by a comparison of a pair of the representations having different distortions.  
     
     
         6 . A method according to  claim 5  in which the comparison considers the position of one or more minutiae in each of the representations and/or considers the position of one or more points on one or more ridges.  
     
     
         7 . A method according to  claim 1  in which the function is defined, at least in part, by a thin plate spline approach.  
     
     
         8 . A method according to  claim 1  in which the plurality of representations are obtained from the individual under controlled conditions.  
     
     
         9 . A method according to  claim 8  in which the conditions are controlled in terms of the finger used and/or substrate used and/or pressure used and/or extent of distortion used.  
     
     
         10 . A method according to  claim 1  in which one or more repeats of each representation are obtained.  
     
     
         11 . A method according to  claim 1  in which a plurality of representations are obtained from a plurality of individuals.  
     
     
         12 . A method according to  claim 1  in which the method is applied to a plurality of different individuals to provide a plurality of functions.  
     
     
         13 . A method according to  claim 12  in which the two or more of the functions are combined to give a composite function.  
     
     
         14 . A method according to  claim 12  in which two or more of the functions are combined to give a general description of distortion.  
     
     
         15 . A method according to  claim 12  in which the plurality of functions and/or composite function are used to generate one or more simulated distorted representations from a further representation.  
     
     
         16 . A method according to  claim 1  in which the function is applied to a further representation to generate one or more simulated distorted representations from a further representation.  
     
     
         17 . A method according to  claim 16  in which the further representation to which the function is applied being an undistorted representation.  
     
     
         18 . A method according to  claim 16  in which the representation to which the function is applied is from a different individual to the individual or individuals that the distorted representations are obtained from.  
     
     
         19 . A method according to  claim 16  in which a plurality of simulated distorted representations are obtained from each representation.  
     
     
         20 . A method according to  claim 16  in which the function is used to generate one or more simulated distorted representations for a plurality of individuals, with the same function being used in for each individual.  
     
     
         21 . A method according to  claim 16  in which the simulated distorted representations are supplied to a data set.  
     
     
         22 . A method according to  claim 21  in which the data set is used in a comparison method in which a representation being compared is considered against within finger variability and/or between finger variability.  
     
     
         23 . A method according to  claim 21  in which the data set is used to form a probability distribution.  
     
     
         24 . A method according to  claim 23  in which a probability distribution relates to the distance between different representations of the same marker and/or in which a probability distribution relates to the distance between different representations of different markers.  
     
     
         25 . A method according to  claim 1  in which the method is repeated for one or more different types and/or directions of distortion.  
     
     
         26 . A method according to  claim 1  in which the distortion arises from one or more of the following factors: the particular finger from which the representation arises, the particular hand from which the representation arises, the gender of the person from whom the representation arises, the profession of the person from whom the representation arises, the height of the person from whom the representation arises, the size of the person from whom the representation arises, the weight of the person from whom the representation arises, the age of the person from whom the representation arises, the type of the substrate on which the representation arose, the material of the substrate on which the representation arose, the shape of the substrate on which the representation arose.  
     
     
         27 . A method of forming a data set including distorted representations of a marker, the method including 
 obtaining a plurality of representations from an individual, the representations being subject to different distortions relative to one another;    describing the effect of the different distortions on the plurality of representations using a function;    taking a further representation from an individual, preferably another individual, applying the function to that representation to generate one or more simulated distorted representations;    adding the one or more simulated distorted representations to a data set.