Method for determining a reference autograph character string on the basis of a set of sample autograph character strings from the same writer

Claim 1

A method for determining at least one reference autograph character string as a reference set based on a sample set of sample autograph character strings from a same writer, comprising the steps of: through a writing by hand of a predetermined text, producing at least three sample character strings by a same writer for formation of the sample set; during the production of the sample character strings using a stylus, recording and retaining characteristic dynamic parameters describing motion of the stylus; on the basis of the dynamic parameters, and in dependence on whether the stylus is pressed against a writing surface or not, decomposing each sample character string into at least a first and a second partial character string in the form of a first and a second stroke; normalizing the dynamic parameters of all the character strings; determining and retaining differences in the dynamic parameters between a respective sample character string and all sample character strings from the sample set not as yet taken into account in the determination for each dynamic parameter as a parameter deviation; carrying out the determining and retaining of the differences in the dynamic parameters strokewise such that strokes are compared via dynamic programming; determining that sample character string as said at least one reference character string for the reference set which comprises a smallest parameter deviation from all other sample character strings with respect to all dynamic parameters; during calculation of minimal distance between respective strokes, a combination of at least two normalized dynamic parameters is chosen, of which a first describes at least stylus position in dependence on time, so that strokewise a verification measure is obtained indicating similarity of the sample character string to the other sample character string; and wherein for the reference set REF={REF 1 , . . . , REF n } a form matrix of the form: ##EQU8## and a motion matrix of the form: ##EQU9## are formed for all REF i with REF j , i,j=1 . . . n with ##EQU10## as well as ##EQU11## for I=2 . . . I(K), j=2 . . . J(K) as a calculating rule for a verification measure within a stroke k, k=1 . . . K, and ##EQU12## for I=2 . . . I(K), j=2 . . . J(K) as a calculating rule for a verification measure at stroke borders with: ##EQU13## from which a following minimum is further formed: MIN,index!=min (sum((Form.*Form).*(Bewegung.*Bewegung))) where ".*" denotes element-element multiplication whereby the reference signature occurs: Ref={O index }.

Claim 2

A method for determining at least one reference autograph character string as a reference set based on a sample set of sample autograph character strings from a same writer, comprising the steps of: through a writing by hand of a predetermined text, producing at least three sample character strings by a same writer for formation of the sample set; during the production of the sample character strings using a stylus, recording and retaining characteristic dynamic parameters describing motion of the stylus; on the basis of the dynamic parameters, and in dependence on whether the stylus is pressed against a writing surface or not, decomposing each sample character string into at least a first and a second partial character string in the form of a first and a second stroke; normalizing the dynamic parameters of all the character strings; determining and retaining differences in the dynamic parameters between a respective sample character string and all sample character strings from the sample set not as yet taken into account in the determination for each dynamic parameter as a parameter deviation; carrying out the determining and retaining of the differences in the dynamic parameters strokewise such that strokes are compared via dynamic programming; determining that sample character string as said at least one reference character string for the reference set which comprises a smallest parameter deviation from all other sample character strings with respect to all dynamic parameters; during calculation of minimal distance between respective strokes, a combination of at least two normalized dynamic parameters is chosen, of which a first describes at least stylus position in dependence on time, so that strokewise a verification measure is obtained indicating similarity of the sample character string to the other sample character string; and wherein for the reference set REF={REF 1 , . . . , REF n } a form matrix of the form: ##EQU8## and a motion matrix of the form: ##EQU9## are formed for all REF i with REF j , i,j=1 . . . n with ##EQU10## as well as ##EQU11## for I=2 . . . I(K), j=2 . . . J(K) as a calculating rule for a verification measure within a stroke k, k=1 . . . K, and ##EQU12## for I=2 . . . I(K), j=2 . . . J(K) as a calculating rule for a verification measure at stroke borders with: ##EQU13## from which a following minimum is further formed: MIN,index!=min (sum((Form.*Form).*(Bewegung.*Bewegung))) where ".*" denotes element-element multiplication whereby the reference signature occurs: Ref={O index }.