Method and apparatus for capturing information in drawing or writing
First Claim
1. A method of verifying a signature comprising the steps of:
- using modeling means to generate a representation of a signature from data representing a finite state machine previously derived from a plurality of genuine signatures; and
comparing the generated signature with a trial signature to be verified in rejecting or accepting the trial signature.
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Abstract
A signature to be verified is written on an area which carries horizontal and vertical lines using a pen. As the lines are crossed signals representative of the vertical and horizontal components of the pen tip velocity and whether the tip is in contact with the area are passed to a computer. A hidden Markov model derived from vertical and horizontal velocities and a "contact" signal occurring as a number of authentic signatures are written is stored by the computer. A forward pass of the Baum-Welch algorithm is used to calculate the probability that the vertical and horizontal components of the pen tip and the contacts between pen tip and the writing area could have been produced from the hidden Markov model. This probability is used to decide whether the signature is authentic. The hidden Markov model stored by the computer is derived from an initial model based on pen tip velocities and contacts occurring in an authentic signature, and re-estimation carried out using forward and backward passes of the Baum-Welch algorithm and velocities and contacts from further authentic signatures.
100 Citations
27 Claims
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1. A method of verifying a signature comprising the steps of:
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using modeling means to generate a representation of a signature from data representing a finite state machine previously derived from a plurality of genuine signatures; and comparing the generated signature with a trial signature to be verified in rejecting or accepting the trial signature.
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2. Apparatus for use in signature verification comprising:
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modeling means for storing data defining the states of a finite state machine model of a signature; and means for generating a display of a representation of the signature from at least some of the stored data; whereby a signature to be verified can be compared with said representation.
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3. A method of generating a representation of a signature comprising the steps of:
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retrieving a series of values from stored data representing a finite state machine derived by modeling means from examples of the signature written using a writing instrument with a tip, each value being at least one of a number of values defining states of the finite state machine, and the values in the series being retrieved from the stored data and representing successive states of the finite state machine; and generating a series of visible points and/or lines in a representation of the signature from the series of values. - View Dependent Claims (4, 5, 6, 7)
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8. Apparatus for generating a representation of a signature comprising:
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modeling means for retrieving a series of previously stored values from data representing a finite state machine, each value being at least one of a number of values defining states of the finite state machine, and the values in the series being retrieved from said data and representing successive states of the finite state machine; and means for generating a series of visible points and/or lines as a representation of the signature from the series of values.
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9. A method of automatic signature verification comprising, for each signatory, the steps of:
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using modeling means for deriving and storing finite state machine data representing a finite state machine particular to the signatures of a specific signatory based on corresponding measurements of a plurality of signatures from the specific signatory written on a writing surface carrying parallel lines, the measurements of each signature comprising discrete velocities of the tip of a writing instrument used to write the said plurality of signatures determined from the rate at which the said lines are crossed by said tip, each state of the finite state machine being defined at least partially by a mean tip velocity component particular to that state; and verifying signatures by comparing the finite state machine data with data from signatures alleged to be written by the signatory. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. Apparatus for signature verification comprising:
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velocity-measuring means for determining the velocity of the tip of a writing instrument used to write signatures on a writing surface carrying parallel lines by determining the rate at which the said lines are crossed by the said tip; modeling means for deriving and storing sets of data representing a respective finite state machine for the signature of each person whose signature is to be recognized by the apparatus, each set of data being based on measurements on a plurality of signatures from one said person written on a writing surface carrying parallel lines and the measurements of each signature comprising discrete velocities of the tip of a writing instrument used to write the said plurality of signatures as determined by the said velocity measuring means, and each state of each finite state machine being defined at least partially by a mean tip velocity component particular to that state; and means for verifying signatures based on the sets of stored data. - View Dependent Claims (21, 22)
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23. A method of modeling a signature comprising the steps of:
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obtaining corresponding measurements from a plurality of signatures from one signatory written on a writing surface carrying parallel lines, the measurements on each signature comprising discrete velocities of the tip of a writing instrument used to write the said plurality of signatures determined from the rate at which said parallel lines are crossed; and using modeling means to define data representing a finite state machine particular to that signatory based on the measurements obtained, each state of the finite state machine being defined at least partially by a mean tip velocity component particular to that state.
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24. Apparatus for deriving a finite state machine modelling a signature comprising:
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velocity-measuring means for determining the velocity of the tip of a writing instrument used to write signatures on a writing surface carrying parallel lines by determining the rate at which the said lines are crossed by said tip; and modeling means for deriving and storing data representing a finite state machine particular to one signatory based on corresponding discrete velocity measurements obtained using the velocity-measuring means from a plurality of signatures from that signatory, each state of the finite state machine being defined at least partially by a mean tip velocity component particular to that state.
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25. A method of verifying a signature comprising the steps of:
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obtaining measurements from a signature to be verified written on a writing surface carrying parallel lines, the measurements comprising discrete velocities of the tip of a writing instrument used to write the signature determined from the rate at which said parallel lines are crossed; determining the probability that the said measurements could have been generated by a finite state machine represented by stored data derived by modeling means from at least one genuine signature, each state of the finite state machine being defined at least partially by a mean tip velocity component particular to that state; and accepting or rejecting the signature on the basis of the probability determined.
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26. Apparatus for verifying a signature comprising:
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means for obtaining measurements from a trial signature to be verified written on a writing surface carrying parallel lines, the measurements comprising discrete velocities of the tip of a writing instrument used to write the signature determined from the rate at which said parallel lines are crossed; means for determining the probability that said measurements could have been generated by a finite state machine represented by stored data derived by modeling means from at least one genuine signature, each state of the finite state machine being defined at least partially by a mean tip velocity component particular to that state; and means for accepting or rejecting the signature on the basis of the probability determined. - View Dependent Claims (27)
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Specification