AN APPARATUS AND METHOD FOR VERIFYING PERSONAL HANDWRITING

Abstract: The stress wave activity produced during a first generation of a piece of handwriting in an enrollment procedure is put into a store (26). The stress wave activities produced in four subsequent generations of the piece of handwriting, in the enrollment procedure, are used sequentially to produce a weighted average of the stored stress wave activity and the stress wave activity of the subsequent generation of the piece of handwriting, and replaces the stored stress wave activity. The weighted average includes a weighted average of amplitudes and of times of events. The four subsequent generations of the piece of handwriting are resequenced in order of increasing difference from the respective stored stress wave activity. The subsequent generations of the piece of handwriting are again used to sequentially produce weighted averages and replace the stored stress wave activity. The subsequent generations of the piece of handwriting are again resequenced in order of increasing difference from the respective stored stress wave activity. Each of the four subsequent generations of the piece of handwriting are used to produce weighted averages and replace the stored stress wave activity if the difference from the respective stored stress wave activity is less than a predetermined value.

Description: AN APPARATUS AND METHOD FOR VERIFYING PERSONAL HANDWRITING The present invention relates to an apparatus an method for verifying personal handwriting. It is known from British Patent No. 2159998B to detec and store a time varying characteristic, e.g. the stres wave activity produced in a body by a writing instrumen during the generation of a given piece of handwriting. Th time varying characteristic, e.g. the stress wave activity produced by a subsequent generation of the given piece o handwriting is compared with that produced by the store piece of handwriting in order to determine whether th stored and subsequent handwriting pieces have a commo author. In our copending European Patent Application No 90313505.1, filed on 12 December 1990, if it is determine that the subsequent and stored time varying characteristi produced during the generation of the handwriting piece have a common author, a weighted average of the stored tim varying characteristic and the subsequent time varyin characteristic is produced. The stored time varyin characteristic is then replaced by the weighted average o the stored time varying characteristic and the subsequen time varying characteristic produced during the generatio of a piece of handwriting by a common authcr. The weighte average is a weighted average of the magnitudes of the tim varying characteristic between the stored time varyin characteristic and the time distorted subsequent tim varying characteristic and is a weighted average of the tim of events. In this procedure it is necessary that the stored tim varying characteristic is either produced from a singl sample piece of handwriting of the author generated durin an enrollment procedure, or is an average produced from number of sample pieces of handwriting of the autho generated during an enrollment procedure. A problem associated with the production of the store time varying characteristic is that the single sample piec of handwriting of the author, or one or more of the numb of sample pieces of handwriting of the author, is often no a typical piece of handwriting of the author. This is ofte because the author is not relaxed during the enrollmen procedure, or is because the author is not used to writin or for other reasons. If the time varying characteristi produced from the untypical sample of the piece of hand writing, or untypical samples of the piece of handwriting is stored and subsequently compared to the time varyin characteristic produced by an authentic piece of handwritin it is possible that the authentic piece of handwriting wil be determined to be generated by a person other than th author of the stored time varying characteristic, i.e th piece of handwriting will be determined to be a forgery. The present invention seeks to provide a nove apparatus and method for verifying personal handwritin which overcomes the above problem. Accordingly the present invention provides a method o verifying personal handwriting comprising the steps o detecting a time varying characteristic produced by th motion of a writing instrument on a surface of a body durin the generation of a given piece of handwriting, storin random noise or the time varying characteristic produced b the motion of the writing instrument on the surface of th body during a first generation of the piece of handwritin by an author at an enrollment procedure to produce a store time varying characteristic, sequentially producing weighted average of the stored time varying characteristi and the time varying characteristic produced by the motio of the writing instrument on the surface of the body during each one of a plurality of subsequent generations of the piece of handwriting by the author at said enrollment procedure and replacing the stored time varying characteristic with the weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body during the said one of the subsequent generations of the piece of handwriting by the author at th enrollment procedure, sequentially producing a weighte average includes comparing the stored time varyin characteristic and the time varying characteristic produce by the motion of the writing instrument on the surface o the body during each one of the plurality of subsequen generations of the piece of handwriting by the author at th enrollment procedure to give a measure of the difference resequencing the time varying characteristic of each of th plurality of subsequent generations of the piece of hand writing by the author at the enrollment procedure in order increasing difference from the respective stored tim varying characteristic, sequentially producing a weighte average of the stored time varying characteristic and th time varying characteristic produced by the motion of th writing instrument on the surface of the body for each o the resequenced plurality of subsequent generations of th piece of handwriting by the author at the enrollmen procedure and replacing the stored time varyin characteristic with the average of the stored time varyin characteristic and the time varying characteristic produce by the motion of the writing instrument on the surface o the body during said one subsequent generation of the piec of handwriting by the author at the enrollment procedure i the difference is less than a predetermined value to produc an average of the time varying characteristic produced b the motion of the writing instrument on the surface of th body from the subsequent generations of the piece o handwriting by the author at the enrollment procedure. Preferably the method further comprises the step o determining if a predetermined number of the plurality o subsequent generations of the piece of handwriting have difference from the stored time varying characteristic equa to or greater than the predetermined value and aborting th enrollment procedure if the predetermined number is equalle or exceeded. Preferably, after resequencing the time varyin characteristic of the plurality of subsequent generations o the piece of handwriting and before sequentially producin and storing the weighted average of the stored time varyin characteristic and the time varying characteristic produce by the motion of the writing instrument on the surface o the body for each one of the subsequent generations of th handwriting piece if the difference is less than predetermined value, sequentially producing a weighte average of the stored time varying characteristic and th time varying characteristic produced by the motion of th writing instrument on the surface of the body during eac one of the plurality of subsequent generations of the piece of handwriting by the author at said enrollment procedure and replacing the stored time varying characteristic with the weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body during the said one of the subsequent generations of the piece of handwriting by the author at the enrollment procedure, resequencing the time varying characteristic of each of the plurality of subsequent generations of the piece of handwriting by the author at the enrollment procedure in order of increasing difference from the respective stored time varying characteristic. Preferably comparing the stored time varying characteristic with the time varying characteristic produced by the motion of the writing instrument on the surface of the body includes distorting the time varying characteristic in time to obtain a best match with the stored time varying characteristic and storing the value of time distortion required to obtain the best match. Preferably producing a weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body includes distorting the time varying characteristic in time by the values stored to obtain the best match with the stored time varying characteristic, producing weighted average magnitudes of t time varying characteristic between the stored time varyi characteristic and the time distorted time varyi characteristic produced by the motion of the writi instrument on the surface of the body and producing weight average of time of events by displacing the weighted avera magnitudes of the time varying characteristic in ti towards the time varying characteristic produced by t motion of the writing instrument on the surface of the bod Preferably the time varying characteristic is stres wave activity. The time varying characteristic may b capacitance, load, pressure, velocity or acceleration. The present invention also provides an apparatus fo verifying personal handwriting comprising means fo detecting a time varying characteristic produced by th motion of a writing instrument on a surface of a body durin the generation of a given piece of handwriting, means fo storing random noise or the time varying characteristi produced by the motion of the writing instrument on th surface of the body during the first generation of the piec of handwriting by an author at an enrollment procedure t produce a stored time varying characteristic, means fo sequentially producing a weighted average of the stored tim varying characteristic and the time varying characteristi produced by the motion of the writing instrument on th surface of the body during each one of a plurality o subsequent generations of the piece of handwriting by th author at said enrollment procedure anc fcr replacing th stored time varying characteristic with the weighted averag of the stored time varying characteristic and the tim varying characteristic produced by the motion of the writin instrument on the surface of the body during the said one o the subsequent generations of the piece of handwriting b the author at the enrollment procedure, the means fo sequentially producing a weighted average includes means fo comparing the stored time varying characteristic and th time varying characteristic produced by the motion of th writing instrument on the surface of the body during each one of the plurality of subsequent generations of the piece of handwriting by the author at the enrollment procedure to give a measure of the difference, means for resequencing the time varying characteristic of each of the plurality of subsequent generations of the piece of handwriting by the author at the enrollment procedure in order of increasing difference from the respective stored time varying characteristic, second means for sequentially producing a weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body for each of the resequenced plurality of subsequent generations of the piece of handwriting by the author at the enrollment procedure and replacing the stored time varying characteristic with the average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body during said one subsequent generation of the piece of handwriting by the author at the enrollment procedure if the difference is less than a predetermined value to produce an average of the time varying characteristic produced by the motion of the writing instrument on the surface of the body from the subsequent generations of the piece cf handwriting by the author at the enrollment procedure. Preferably the apparatus further comprises means for determining if a predetermined number of the plurality cf subsequent generations of the piece of handwriting have ≥ difference from the stored time varying characteristic equal to or greater than the predetermined value and for aborting the enrollment procedure if the predetermined number is equalled or exceeded. Preferably the apparatus comprises third means for sequentially producing a weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body for each one of the plurality cf subsequent generations of the piece of handwriting by th author at said enrollment procedure resequenced by the mean for resequencing the time varying characteristic of th plurality of subsequent generation of the piece of hand writing and replacing the stored time varying characteristi with the weighted average of the stored time varyin characteristic and the time varying characteristic produce by the motion of the writing instrument on the surface o the body during the said one of the subsequent generation of the piece of handwriting by the author at the enrollmen procedure, second means for resequencing the time varyin characteristic of each of the plurality of subsequen generations of the piece of handwriting by the author at th enrollment procedure in order of increasing difference fro the respective stored time varying characteristic. Preferably the means for comparing the stored tim varying characteristic with the time varying characteristi produced by the motion of the writing instrument on th surface of the body distorts the time varying characteristi in time to obtain a best match with the stored time varyin characteristic and stores the value cf time distortio required to obtain the best match. Preferably the means for producing a weighted averag cf the stored time varying characteristic and the tim varying characteristic produced by the motion cf the writin instrument on the surface of the body is arranged to distor the time varying characteristic in time by the values store to obtain the best match with the stored time varyin characteristic, and is arranged to produce weighted averag magnitudes of the time varying characteristic between th stored time varying characteristic and the time distorte time varying characteristic produced by the motion of th writing instrument on the surface of the body and i arranged to produce a weighted average of time cf events b displacing the weighted average magnitudes of the tim varying characteristic in time towards the time varyin characteristic produced by the motion of the writin instrument on the surface of the body. Preferably the means for detecting the time varyin characteristic is an acoustic emission transducer fo detecting the stress wave activity produced by the motion o the writing instrument on the surface of the body. The means for detecting the time varying characteristi may be a capacitor defined between the writing instrumen and the surface of the body, the time varying characteristi is capacitance. The means for detecting the time varying characteristi may be a load cell for detecting load, or pressure, produce by the motion of the writing instrument on the surface o the body. The present invention will be more fully described b way of example with reference to the accompanying drawings, in which:- Figure 1 is a block diagram of an apparatus i accordance with the present invention. Figure 2 is a flow chart showing the production cf stored time varying characteristic for use in the apparatus shown in figure 1. An apparatus for verifying personal handwriting is shown in Figure 1. An acoustically conductive plate 12 is mounted on isolating blocks 14 in order to acoustically isolate it from the surface upon which it is located. A conventional resonant acoustic emission transducer 16 is acoustically coupled to the plate 12 for the purpose of detecting stress wave activity associated with the plate 12. Such stress wave activity is produced by the generation cf a piece of handwriting on a surface of the plate 12 using a writing instrument 13. A piece of paper or other similarly- surfaced material may be present on the plate 12 to receive the piece of handwriting, or alternatively, the piece of handwriting may be written directly on the plate 12. The writing instrument 13 may be a pen, or a pencil, but other writing instruments may be used. The plate 12 may be steel. The essential requirement is that when the piece cf hand- writing is generated, the friction between them should b sufficient to produce detectable stress waves within th plate 12, and that the plate 12 is acoustically conductive. The transducer 16 detects the stress wave activit within the plate 12 over a narrow band of frequencies aroun the resonant frequency of the transducer 16. The transduce 16 is selected to have a resonant frequency which is wel above audio frequencies so that substantially only stres wave activity produced by the interaction between th writing instrument 13 and the writing surface on the plat 12 is detected by the transducer 16. The transducer 16 converts the detected stress wav activity into an electrical signal. This electrical signa is supplied in series to an amplifier 18, which amplifie the electrical signal and to a root mean square converte 20, which demodulates the electrical signal to an envelop of the stress wave activity associated with the generatio of the piece of handwriting. The bandwidth, dynamic rang and duration of this envelope are suitably limited to thos values which are relevant to and characteristic of th particular piece of handwriting under investigation. The output of the root mean square converter 20 is fe to an analogue to digital converter 22 which produces digitised time record of the stress wave activity produce by the generation of the piece of handwriting. The digitise time record of the stress wave activity is supplied tc processing unit 24. If an author of a piece of handwriting has ne previously used the apparatus, the author is required t enroll onto the apparatus. The enrollment procedure is shew in the form of a flow chart in figure 2. In the enrollmen procedure the author is required to generate the piece c handwriting for a first time. The digitised time reccrd o the stress wave activity produced during the firs generation of the authentic piece of handwriting i supplied to a store 26. The author is then required t produce the piece of handwriting at least a further tw times, preferably a further four times. The digitised tim records of the stress wave activity produced during each o the at least two further generations of the piece of hand writing are used to update the stored digitised time recor in store 26. The processing unit 24 compares the stored digitise time record of the stress wave activity of the firs generation of the piece of handwriting and the digitise time record of the stress wave activity of the secon generation of the piece of handwriting and gives a indication of the degree of conformity between them. Th comparison procedure involves using a dynamic time warpin algorithm which takes a point, or portion, of the store digitised time record of the stress wave activity of th first generation of the piece of handwriting and compares it with the digitised time record of the stress wave activit of the second generation of the piece of handwriting. The digitised time record of the stress wave activity of the second generation of the piece of handwriting is displaced in time relative to the stored digitised time record of the first generation of the piece of handwriting through different time periods, to obtain many better matches, and the best match is selected i.e. the match with least errors. Subsequent points, or portions, of the stored digitised time record of the stress wave activity of the first generation of the piece of handwriting are then compared with the digitised time record of the stress wave activity of the second generation of the piece of handwriting in a similar fashion to obtain best matches. The comparison of a point, or portion, of the stored digitised time record of the stress wave activity of the first generation of the piece of handwriting and the best match of the digitised time record of the stress wave activity of the second generation of the piece of hand¬ writing involves taking a measurement of the difference in amplitude of the stress wave activities and squaring the difference, and taking a measure of the time displacement to obtain the best match. This is a running least square method which gives an indication of the errors between th two digitised time records of the stress wave activity o the first and second generations of the piece of hand¬ writing. The total error for the best match for each point, or portion, of the stored digitised time record of th stress wave activity of the first generation of the piece o handwriting is the sum of the square of the amplitude erro and the time distortion errors. The total error for the bes match of all the points, or portions, of the store digitised time record of the stress wave activity of th first generation of the piece of handwriting is the sum o all the squares of the amplitude errors and all the tim distortion errors. The total error, or difference, betwee the digitised time record of the stress wave activity of th second generation of the piece of handwriting and the store digitised time record of the stress wave activity of th first generation of the piece of handwriting is stored. The processing unit 24 stores the values of tim displacement required to distort the digitised time recor of the stress wave activity of the second generation of th piece of handwriting piece to a best match position with th stored digitised time record of the stress wave activity of the first generation of the piece of handwriting for eac point, or portion, of the stored digitised time record o the stress wave activity of the first generation of th piece of handwriting. The time displacement values ar stored in a back pointer array. The stored digitised time record of the stress wav activity of the first generation of the piece of handwritin is replaced by a weighted average of the stored digitise time record of the stress wave activity of the firs generation of the piece of handwriting and the digitise time record of the stress wave activity of the secon generation of the piece of handwriting. The weighted averag of the two digitised time records includes a weighte average cf the amplitudes and a weighted average of th times of events. In order to produce the weighted average o the stored digitised time record of the stress wave activit of the first generation of the piece of handwriting and th digitised time record of the stress wave activity of th second generation of the piece of handwriting, the tim displacement values stored in the backpointer array ar again used to distort the digitised time record of th stress wave activity of the second generation of the piec of handwriting to the best fit time scale with the stored digitised time record of the stress wave activity of the first generation of the piece of handwriting. The weighted average of each point on the stored digitised time record of the stress wave activity of the first generation of the piece of handwriting and the time warped digitised time record of the stress wave activity of the second generation of the piece of handwriting are then calculated to give a weighted average amplitude of the two digitised time records. The weighted average of times of events is produced by displacing each new stress wave amplitude value in time towards that of the digitised time record of the stress wave activity of the second generation of the piece of hand¬ writing, the time displacement is weighted by the same value as that used for the weighted average of the stress wave amplitudes. This new digitised time record of stress wave activity is stored in the store as a stored first average digitised time record of the stress wave activity of the piece of handwriting and replaces the original stored digitised time record cf the stress wave activity of the first generation of the piece of handwriting. The processing unit 24 compares the stored first average digitised time record of the stress wave activity of the handwriting piece and the digitised time record of the stress wave activity of the third generation of the hand¬ writing piece and gives an indication of the degree of conformity between them. The comparison procedure involves using the dynamic time warping algorithm which takes a point, or portion, of the stored first average digitis time record of the stress wave activity of the handwriti piece and compares it with the digitised time record cf t stress wave activity of the third generation of the han writing piece. The digitised time record of the stress wa activity of the third generation of the handwriting piece displaced in time relative to the stored first avera digitised time record of the stress wave activity of t handwriting piece through different time periods, to obtai many better matches, and the best match is selected i.e. t match with least errors. Subsequent points, or portions, the stored first average digitised time record of the stres wave activity of the handwriting piece are then compar with the digitised time record of the stress wave activit of the third generation of the handwriting piece in similar fashion to obtain best matches. The comparison of a point, or portion, of the stor first average digitised time record of the stress wa activity of the handwriting piece and the best match cf th digitised time record of the stress wave activity of th third generation of the handwriting piece involves taking measurement of the difference in amplitude of the stres wave activities and squaring the difference, and taking measure of the time displacement to obtain the best match This is a running least squares method which gives a indication of the errors between the stored first averag digitised time record of the stress wave activity of t handwriting piece and the digitised time record cf th stress wave activity of the third generation of the hand writing piece. The total error for the best match for eac point, or portion, of the stored first average digitise time record of the stress wave activity of the handwriti piece is the sum of the square of the amplitude error an the time distortion errors. The total error for the bes match of all the points, or portions, of the stored firs average digitised time record of the stress wave activity o the handwriting piece is the sum of all the squares cf t amplitude errors and all the time distortion errors. Th total error, or difference, between the digitised tim record of the stress wave activity of the third generatio of the handwriting piece and the stored first averag digitised time record of the stress wave activity of th handwriting piece is stored. The processing unit 24 stores the values of tim displacement required to distort the digitised time recor of the stress wave activity of the third generation of th handwriting piece to a best match position with the store first average digitised time record of the stress wav activity of the handwriting piece for each point, o portion, of the stored first average digitised time recor of the stress wave activity of the handwriting piece. Th time displacement values are stored in a back pointer array. The stored first average digitised time record of th stress wave activity of the handwriting piece is replaced b a weighted average of the stored first average digitised time record of the stress wave activity of the handwriting piece and the digitised time record of the stress wave activity of the third generation of the handwriting piece. The weighted average of the two digitised time records includes a weighted average of the amplitudes and a weighted average of the times of events. In order to produce the weighted average of the stored first average digitised time record of the stress wave activity of the handwriting piece and the digitised time record of the stress wave activity cf the third generation of the handwriting piece, the time displacement values stored in the backpointer array are again used to distort the digitised time record of the stress wave activity of the third generation of the hand¬ writing piece to the best fit time scale with the stored first average digitised time record of the stress wave activity of the handwriting piece. The weighted average of each point on the stored first average digitised time record of the stress wave activity of the handwriting piece and the time warped digitised time record of the stress wave activity of the third generatio of the piece of handwriting are then calculated to give weighted average amplitude of the two digitised tim records. The weighted average of times of events is produced b displacing each new stress wave amplitude value in tim towards that of the digitised time record of the stress wav activity of the third generation of the handwriting piece, the time displacement is weighted by the same value as tha used for the weighted average of the stress wave amplitudes. This new digitised time record of stress wave activity is stored in the store as a stored second average digitise time record of the stress wave activity of the handwriting piece and replaces the stored first average digitised tim record of the stress wave activity of the handwriting piece. The processing unit 24 compares the stored secon average digitised time record of the stress wave activity of the handwriting piece and the digitised time record of the stress wave activity of the fourth generation of the hand¬ writing piece and gives an indication of the degree of conformity between them. The comparison procedure again involves using the dynamic time warping algorithm. The total error, or difference, between the digitised time record of the stress wave activity of the fourth generation of the handwriting piece and the stored second average digitised time record of the stress wave activity of the handwriting is stored. The processing unit 24 stores the values of time displacement required to distort the digitised time record of the stress wave activity of the fourth generation of the handwriting piece to a best match position with the stored second average digitised time record of the stress wave activity of the handwriting piece for each point, or portion, of the stored second average digitised time record of the stress wave activity of the handwriting piece in a back pointer array. The stored second average digitised time record of th stress wave activity of the handwriting piece is replaced b a weighted average of the stored second average digitise time record of the stress wave activity of the handwritin piece and the digitised time record of the stress wav activity of the fourth generation of the handwriting piece The weighted average of the two digitised time record includes a weighted average of the amplitudes and a weighte average of the times of events and is produced in the sam manner as disclosed above. This new digitised time record o stress wave activity is stored in the store as a store third digitised time record of the stress wave activity o the handwriting piece and replaces the stored second averag digitised time record of the stress wave activity of th handwriting piece. The processing unit 24 compares the stored thir average digitised time record of the stress wave activity o the handwriting piece and the digitised time record of the stress wave activity of the fifth generation of the hand¬ writing piece and gives an indication of the degree of conformity between them. The comparison procedure again uses the dynamic time warping algorithm. The total error, or difference, between the digitised time record of the stress wave activity of the fifth generation of the handwriting piece and the stored third average digitised time record of the stress wave activity of the handwriting piece is stored. The processing unit 24 stores the values of time displacement required to distort the digitised time record of the stress wave activity of the fifth generation of the handwriting piece to a best match position with the stored third average digitised time record of the stress wave activity of the handwriting piece for each point, or portion, of the stored third average digitised time reccrd of the stress wave activity of the handwriting piece in a back pointer array. The stored third average digitised time record of the stress wave activity of the handwriting piece is replaced by a weighted average of the stored third average digitis time record of the stress wave activity of the handwriti piece and the digitised time record of the stress wa activity of the fifth generation of the handwriting piece The weighted average of the two digitised time record includes a weighted average of the amplitudes and a weighte average of the times of events and is produced in the sam manner as disclosed previously. This new digitised tim record of stress wave activity is stored in the store as stored fourth average digitised time record of the stres wave activity of the handwriting piece and replaces th stored third average digitised time record of the stres wave activity of the handwriting piece. It can be seen that the procedure upto now differs fro that disclosed in our European Patent Application No 90313505.1 in that the digitised time records of the stres wave activity for the second, third, fourth and fift generations of the handwriting piece have each been use once to update the stored digitised time record of th stress wave activity produced during the generation of a authentic handwriting piece no matter how great th difference between the stored digitised time record and th digitised time record of the particular handwriting piece. The digitised time records of the stress wave activit for the second, third, fourth and fifth generations of th handwriting piece are resequenced in order of increasin error, or difference, from the particular stored digitise time record of the stress wave activity of the handwritin piece with which it was compared. For example the digitise time record of the stress wave activity of the thir generation of the handwriting piece was compared with th stored first average digitised time record of the stres wave activity of the handwriting piece. Similarly th digitised time record of the stress wave activity of th fifth generation of the handwriting piece was compared wit the stored third average digitised time record of the stres wave activity of the handwriting piece. The processing unit 24 compares the stored fourt average digitised time record of the stress wave activity o the handwriting piece and the digitised time record of th stress wave activity of the one, of the second,third, fourt and fifth generations of the handwriting piece, which ha the least error and gives an indication of the degree o conformity between them using the same method as describe previously. The stored fourth average digitised time record of the stress wave activity of the handwriting piece is replaced by a weighted average of the stored fourth average digitised time record of the stress wave activity of the handwriting piece and the digitised time record of the stress wave activity of the one of the second third,fourth and fifth generations of the handwriting piece which has the least error. The weighted average of the two digitised time records includes a weighted average of the amplitudes and a weighted average of the times of events and is produced in the same manner as disclosed previously. This new digitised time record of stress wave activity is stored in the store as a stored fifth average digitised time record of the stress wave activity of the handwriting piece and replaces the stored fourth average digitised time record of the stress wave activity of the handwriting piece. The processing unit 24 compares the stored fifth average digitised time record of the stress wave activity of the handwriting piece and the digitised time record of the stress wave activity of the one, of the second,third, fourth and fifth generations of the handwriting piece, which has the second lowest error and gives an indication of the degree of conformity between them using the same method as described previously. The stored fifth average digitised time record of the stress wave activity of the handwriting piece is replaced by a weighted average of the stored fifth average digitised time record of the stress wave activity of the handwriting piece and the digitised time record of the stress wave activity of the one of the second third,fourth and fift generations of the handwriting piece which has the secon lowest error. The weighted average of the two digitised tim records includes a weighted average of the amplitudes and weighted average of the times of events and is produced i the same manner as discussed above. This new digitised tim record of stress wave activity is stored in the store as stored sixth average digitised time record of the stres wave activity of the handwriting piece and replaces th stored fifth average digitised time record of the stres wave activity of the handwriting piece. The processing unit 24 compares the stored sixt average digitised time record of the stress wave activity o the handwriting piece and the digitised time record of th stress wave activity of the one, of the second,third, fourt and fifth generations of the handwriting piece, which ha the third lowest error and gives an indication of the degre of conformity between them using the same method a described previously. The stored sixth average digitised time record of th stress wave activity of the handwriting piece is replaced b a weighted average of the stored sixth average digitise time record of the stress wave activity of the handwritin piece and the digitised time record of the stress wav activity of the one of the second third,fourth and fift generations of the handwriting piece which has the thir lowest error. The weighted average of the two digitised tim records includes a weighted average of the amplitudes and weighted average of the times of events and is produced i the same manner as disclosed above. This new digitised tim record of stress wave activity is stored in the store as stored seventh average digitised time record of the stres wave activity of the handwriting piece and replaces th stored sixth average digitised time record of the stres wave activity of the handwriting piece. The processing unit 24 compares the stored sevent average digitised time record of the stress wave activity o the handwriting piece and the digitised time record of th stress wave activity of the one, of the second,third, fourt and fifth generations of the handwriting piece, which ha the greatest error and gives an indication of the degree o conformity between them using the same method as describe previously. The stored seventh average digitised time record of th stress wave activity of the handwriting piece is replaced b a weighted average of the stored seventh average digitise time record of the stress wave activity of the handwritin piece and the digitised time record of the stress wav activity of the one of the second third,fourth and fift generations of the handwriting piece which has the greates error. The weighted average of the two digitised tim records includes a weighted average of the amplitudes and weighted average of the times of events and is produced i the same manner as discussed previously. This new digitise time record of stress wave activity is stored in the stor as a stored eighth average digitised time record of the stress wave activity of the handwriting piece and replaces the stored seventh average digitised time record of the stress wave activity of the handwriting piece. The digitised time records of the stress wave activity fcr the second, third, fourth and fifth generations of the handwriting piece have each been used a second time tc update the stored digitised time record of the stress wave activity produced during the generation of an authentic handwriting piece no matter how great the difference between the stored digitised time record and the digitised time record of the particular handwriting piece. The digitised time records of the stress wave activity for the second, third, fourth and fifth generations of the handwriting piece are again resequenced in order cf increasing error, or difference, from the particular stored digitised time record of the stress wave activity cf the handwriting piece with which it was compared during the second updating of the stored digitised time record. The processing unit 24 compares the stored eight average digitised time record of the stress wave activity o the handwriting piece and the digitised time record of th stress wave activity of the one, of the second,third, fourt and fifth generations of the handwriting piece, which ha the lowest error to give an indication of the degree o conformity between them using the same method as describe previously. If the total error is less than a predetermined valu the digitised time record of the one, of the second, third fourth and fifth generations of the handwriting piece, whic has the lowest error has a good degree of conformity wit the stored eighth average digitised time record of th stress wave activity of the handwriting piece. The stored eighth average digitised time record of th stress wave activity of the handwriting piece is replaced b a weighted average of the stored eighth average digitise time record of the stress wave activity of the handwritin piece and the digitised time record of the stress wav activity of the one of the second third, fourth and fift generations of the handwriting piece which has the lowes error if the total error is less than the predetermine value. A new digitised time record of stress wave activit is stored in the store as a stored ninth average digitise time record of the stress wave activity of the handwritin piece and replaces the stored eighth average digitised tim record of the stress wave activity of the handwriting piece If the total error is equal to or greater than th predetermined value the digitised time record cf tne one o the second, third, fourth and fifth generations of th handwriting piece, which has the lowest error is net i conformity with the stored eighth average digitised tim record of the stress wave activity of the handwriting piece The stored eighth average digitised time record of th stress wave activity of the handwriting piece is not update by the digitised time record of the stress wave activity c the one of the second, third, fourth and fifth generation of the handwriting piece which has the lowest error if th total error is equal to or greater than the predetermine value. The processing unit 24 compares either the store eighth or ninth average digitised time record of the stres wave activity of the handwriting piece and the digitise time record of the stress wave activity of the one, of th second,third, fourth and fifth generations of the hand writing piece, which has the second lowest error and give an indication of the degree of conformity between them usin the same method as described previously. If the total error is less than a predetermined valu the digitised time record of the one, of the second, third, fourth and fifth generations of the handwriting piece, whic has the second lowest error has a good degree of conformit with the stored eighth or ninth average digitised time record of the stress wave activity of the handwriting piece. The stored eighth or ninth average digitised time record of the stress wave activity of the handwriting piece is replaced by a weighted average of the stored eighth or ninth average digitised time record of the stress wave activity of the handwriting piece and the digitised time record cf the stress wave activity of the one of the second third,fourth and fifth generations of the handwriting piece which has the second lowest error if the total error is less than the predetermined value. A new digitised time record of stress wave activity is stored in the store as a stored ninth or tenth average digitised time record cf the stress wave activity of the handwriting piece and replaces the stored eighth or ninth average digitised time record of the stress wave activity of the handwriting piece. If the total error is equal to or greater than the predetermined value the digitised time record of the one of the second, third, fourth and fifth generations of the handwriting piece, which has the second lowest error is net in conformity with the stored eighth or ninth average digitised time record of the stress wave activity cf the handwriting piece. The stored eighth or ninth average digitised tim record of the stress wave activity of the handwriting piec is not updated by the digitised time record of the stres wave activity of the one of the second, third, fourth an fifth generations of the handwriting piece which has th second lowest error if the total error is equal to o greater than the predetermined value. The processing unit 24 compares either the store eighth, ninth or tenth average digitised time record of th stress wave activity of the handwriting piece and th digitised time record of the stress wave activity of th one, of the second,third, fourth and fifth generations o the handwriting piece, which has the third lowest error an gives an indication of the degree of conformity between thei using the same method as described previously. If the total error is less than a predetermined valu the digitised time record of the one, of the second, third, fourth and fifth generations of the handwriting piece, whic has the third lowest error has a good degree of conformit with the stored eighth, ninth or tenth average digitise time record of the stress wave activity of the handwritin piece. The stored eighth, ninth or tenth average digitise time record cf the stress wave activity of the handwritin piece is replaced by a weighted average of the store eighth, ninth or tenth average digitised time record of th stress wave activity of the handwriting piece and tn digitised time record of the stress wave activity of the on of the second third,fourth and fifth generations of th handwriting piece which has the third lowest error if th total error is less than the predetermined value. A ne digitised time record of stress wave activity is stored i the store as a stored ninth, tenth or eleventh averag digitised time record of the stress wave activity of th handwriting piece and replaces the stored eighth, ninth c tenth average digitised time record of the stress wav activity of the handwriting piece. If the total error is equal to or greater than th predetermined value the digitised time record of the one c the second, third, fourth and fifth generations of th handwriting piece, which has the third lowest error is no in conformity with the stored eighth, ninth or tenth averag digitised time record of the stress wave activity of th handwriting piece. The stored eighth, ninth, tenth or eleventh averag digitised time record of the stress wave activity of the handwriting piece is not updated by the digitised time record of the stress wave activity of the one of the second, third, fourth and fifth generations of the handwriting piece which has the third lowest error if the total error is equal to or greater than the predetermined value. The processing unit 24 compares either the stored eighth, ninth, tenth or eleventh average digitised time record of the stress wave activity of the handwriting piece and the digitised time record of the stress wave activity cf the one, of the second,third, fourth and fifth generations of the handwriting piece, which has the greatest error and gives an indication of the degree of conformity between them using the same method as described previously. If the total error is less than a predetermined value the digitised time record of the one, of the second, third, fourth and fifth generations of the handwriting piece, which has the greatest error has a good degree of conformity with the stored eighth, ninth, tenth or eleventh average digitised time record of the stress wave activity of the handwriting piece. The stored eighth, ninth, tenth or eleventh average digitised time record of the stress wave activity of the handwriting piece is replaced by a weighted average of the stored eighth, ninth, tenth or eleventh average digitised time record of the stress wave activity of the handwriting piece and the digitised time record of the stress wave activity of the one of the second third,fourth and fifth generations of the handwriting piece which has the greatest error if the total error is less than the predetermined value. A new digitised time record of stress wave activity is stored in the store as a stored ninth, tenth, eleventh or twelfth average digitised time record of the stress wave activity of the handwriting piece and replaces the stored eighth, ninth, tenth or eleventh average digitised time record of the stress wave activity of the handwriting piece. If the total error is equal to or greater than the predetermined value the digitised time record of the one of the second, third, fourth and fifth generations of the handwriting piece, which has the greatest error is not in conformity with the stored eighth, ninth, tenth or eleventh average digitised time record of the stress wave activity of the handwriting piece. The stored eighth, ninth, tenth or eleventh average digitised time record of the stress wave activity of the handwriting piece is not updated by the digitised time record of the stress wave activity of the one of the second, third, fourth and fifth generations of the handwriting piece which has the greatest error if the total error is equal to or greater than the predetermined value. The digitised time records of the stress wave activity for the second, third, fourth and fifth generations cf the handwriting piece are each used a third time to update tne stored digitised time record of the stress wave activity produced during the generation of an authentic handwriting piece if the difference between the stored digitised time record and the digitised time record cf the particular handwriting piece is less than the predetermined value. If any two of the second, third, fourth and fifth generations of the handwriting piece result have digitised time records of stress wave activity which have differences from the stored digitised time record greater than the predetermined value, the enrollment procedure is aborted and the whole procedure is repeated. The final stored digitised time record of the stress wave activity cf the handwriting piece is a better average of the digitised time records o the several generations of the handwriting piece. Any poor or untypical, samples of the generation of the handwritin piece made during the enrollment procedure are rejected whe the stored digitised time record is updated a third time b the digitised time records of each of the handwriting piece. When the digitised time record of the stress wav activity of a subsequent authentic generation of the piec of handwriting is compared with the final stored digitise time record, produced during the enrollment procedure, th subsequent authentic generation of the handwriting piece is not determined to be a forgery. Alternatively if an author of a handwriting piece has not previously used the apparatus, the author is required to enroll onto the apparatus. In the enrollment procedure random noise is supplied to a store 26. The author is required to produce a handwriting piece at least two times, preferably four times. The digitised time records of the stress wave activity produced during each of the at least two generations of the handwriting piece are used to update the stored digitised time record in store 26. The same procedure of comparing the digitised time records of the stress wave activity of each generation of the handwriting piece sequentially with the stored digitised time record is followed as discussed before. A suitable weighting factor used during the procedure is four times the stored digitised time record to one times the digitised time record being compared to the stored digitised time record. Although the description has referred to the use of stress wave activity as the time varying characteristic, other suitable time varying characteristics may be used. One example is the use of a load cell to detect the force, load or pressure applied on the writing instrument, or body, during the generation of the piece of handwriting. A further example is the use of a capacitor to detect the capacitance defined between the writing instrument and the surface cf the body. Other suitable time varying characteristic derived from the dynamics of the production of a piece c handwriting are position, velocity and acceleration.

Claims: Claims : - 1. A method of verifying personal handwriting comprisin the steps of detecting a time varying characteristi produced by the motion of a writing instrument on a surfac of a body during the generation of a given piece of hand writing, storing random noise or the time varyin characteristic produced by the motion of the writin instrument on the surface of the body during a firs generation of the piece of handwriting by an author at a enrollment procedure to produce a stored time varyin characteristic, sequentially producing a weighted average cf the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body during each one of a plurality of subsequent generations of the piece of hand¬ writing by the author at said enrollment procedure and replacing the stored time varying characteristic with the weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body during the said one of the subsequent generations of the piece of handwriting by the author at the enrollment procedure, sequentially producing a weighted average includes comparing the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body during each one of the plurality of subsequent generations of the piece of hand¬ writing by the author at the enrollment procedure to give a measure of the difference, resequencing the time varying characteristic of each of the plurality of subsequent generations of the piece of handwriting by the author at the enrollment procedure in order of increasing difference frcr. the respective stored time varying characteristic, sequentially producing a weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body for each of the resequenced plurality cf subsequent generations of the piece of handwriting by th author at the enrollment procedure and replacing the stored time varying characteristic with the average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body during said one subsequent generation of the piece of handwriting by the author at the enrollment procedure if the difference is less than a predetermined value to produce a better average of the time varying characteristic produced by the motion of the writing instrument on the surface of the body from the subsequent generations of the piece of handwriting by the author at the enrollment procedure. 2. A method as claimed in claim 1 further comprising the step of determining if a predetermined number of the plurality of subsequent generations of the piece of hand¬ writing have a difference from the stored time varying characteristic equal to or greater than the predetermined value and aborting the enrollment procedure if the pre¬ determined number is equalled or exceeded. 3. A method as claimed in claim 1 in which, after resequencing the time varying characteristic of the plurality of subsequent generations of the piece of hand¬ writing and before sequentially producing and storing the weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body for each one of the subsequent generations of the handwriting piece if the difference is less than a predetermined value, sequentially producing a weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body during each one of the plurality of subsequent generations of the piece of handwriting by the author at said enrollment procedure and replacing the stored time varying characteristic with the weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body during the said one of the subsequent generations of the piece of handwriting by the author at the enrollment procedure, resequencing the tim varying characteristic of each of the plurality of subsequent generations of the piece of handwriting by the author at the enrollment procedure in order of increasing difference from the respective stored time varying characteristic. 4. A method as claimed in claim 1 in which the comparing of the stored time varying characteristic with the time varying characteristic produced by the motion of the writing instrument on the surface of the body includes distorting the time varying characteristic in time to obtain a best match with the stored time varying characteristic and storing the value of time distortion required to obtain the best match. 5. A method as claimed in claim 4 in which producing a weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body includes distorting the time varying characteristic in time by the values stored to obtain the best match with the stored time varying characteristic, producing weighted average magnitudes of the time varying characteristic between the stored time varying characteristic and the time distorted time varying characteristic produced by the motion of the writing instrument on the surface of the body and producing weighted average of time of events by displacing the weighted average magnitudes of the time varying characteristic in time towards the time varying characteristic produced by the motion of the writing instrument on the surface of the body. 6. A method as claimed in claim 1 in which the time varying characteristic is stress wave activity. 7. A method as claimed in claim 1 in which the time varying characteristic is capacitance. 8. A method as claimed in claim 1 in which the tim varying characteristic is load or pressure. 9. A method as claimed in claim 1 in which the tim varying characteristic is velocity. 10. A method as claimed in claim 1 in which the varyin characteristic is acceleration. 11. An apparatus (10) for verifying personal handwritin comprising means (16) for detecting a time varyin characteristic produced by the motion of a writin instrument (13) on a surface of a body (12) during th generation of a given piece of handwriting, means (26) fo storing random noise or the time varying characteristi produced by the motion of the writing instrument (13) on th surf ce of the body (12) during the first generation of th piece of handwriting by an author at an enrollment procedur to produce a stored time varying characteristic, means (24 for sequentially producing a weighted average of the store time varying characteristic and the time varyin characteristic produced by the motion of the writin instrument on the surface of the body during each one of plurality of subsequent generations of the piece o handwriting by the author at said enrollment procedure an for replacing the stored time varying characteristic wit the weighted average of the stored time varyin characteristic and the time varying characteristic produce by the motion of the writing instrument on the surface o the body during the said one of the subsequent generation of the piece of handwriting by the author at the enrollmen procedure, characterised in that the means (24) fo sequentially producing a weighted average includes means fo comparing the stored time varying characteristic and th time varying characteristic produced by the motion of th writing instrument on the surface of the body during eac one of the plurality of subsequent generations of the piec of handwriting by the author at the enrollment procedure t give a measure of the difference, means (24) fo resequencing the time varying characteristic of each of th plurality of subsequent generations of the piece of handwriting by the author at the enrollment procedure in order of increasing difference from the respective stored time varying characteristic, second means (24) for sequentially producing a weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body for each of the resequenced plurality of subsequent generations of the piece of handwriting by the author at the enrollment procedure and replacing the stored time varying characteristic with the average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body during said one subsequent generation of the piece of handwriting by the author at the enrollment procedure if the difference is less than a predetermined value to produce an average of the time varying characteristic produced by the motion of the writing instrument on the surface of the body from the subsequent generations of the piece of handwriting by the author at the enrollment procedure. 12. An apparatus as claimed in claim 11 further comprising means (24) for determining if a predetermined number of the plurality of subsequent generations of the piece of hand¬ writing have a difference from the stored time varying characteristic equal to or greater than the predetermined value and for aborting the enrollment procedure if the predetermined number is equalled or exceeded. 13. An apparatus as claimed in claim 11 in which the apparatus comprises third means (24) for sequentially producing a weighted average of the stored time varying characteristic and the time varying characteristic produced by the motion of the writing instrument on the surface of the body for each one of the plurality of subsequent generations of the piece of handwriting by the author at said enrollment procedure resequenced by the means for resequencing the time varying characteristic of the plurality of subsequent generation of the piece of hand writing and replacing the stored time varying characteristi with the weighted average of the stored time varyin characteristic and the time varying characteristic produce by the motion of the writing instrument on the surface o the body during the said one of the subsequent generation of the piece of handwriting by the author at the enrollmen procedure, second means (24) for resequencing the tim varying characteristic of each of the plurality o subsequent generations of the piece of handwriting by th author at the enrollment procedure in order of increasin difference from the respective stored time varyin characteristic. 14. An apparatus as claimed in claim 11 in which the mean (24) for comparing the stored time varying characteristi with the time varying characteristic produced by the motio of the writing instrument on the surface of the bod distorts the time varying characteristic in time to obtain best match with the stored time varying characteristic an stores the value of time distortion required to obtain th best match. 15. An apparatus as claimed in claim 14 in which the mean (24) for producing a weighted average of the stored tim varying characteristic and the time varying characteristi produced by the motion of the writing instrument on th surface of the body is arranged to distort the time varyin characteristic in time by the values stored to obtain th best match with the stored time varying characteristic, an is arranged to produce weighted average magnitudes of th time varying characteristic between the stored time varyin characteristic and the time distorted time varyin characteristic produced by the motion of the writin instrument on the surface of the body and is arranged t produce a weighted average of time of events by displacin the weighted average magnitudes of the time varyin characteristic in time towards the time varying characteristic produced by the motion of the writing instrument on the surface of the body. 16. An apparatus as claimed in claim 11 in which the means (16) for detecting the time varying characteristic is an acoustic emission transducer for detecting the stress wave activity produced by the motion of the writing instrument (13) on the surface of the body (12). 17. An apparatus as claimed in claim 11 in which the means for detecting the time varying characteristic is a capacitor defined between the writing instrument and the surface of the body, the time varying characteristic is capacitance. 18. An apparatus as claimed in claim 11 in which the means for detecting the time varying characteristic is a load cell for detecting load, or pressure, produced by the motion of the writing instrument on the surface of the body. 19. An apparatus as claimed in claim 16 in which the means (16) for detecting the stress wave activity comprises a resonant acoustic emission transducer.

Inventors: WEBSTER JOHN RICHARD, WEBSTER, JOHN, RICHARD
Applicants: ROLLS ROYCE PLC, ROLLS-ROYCE PLC
Application year: 1992
Main classification: G07C9
IPC codes: A61B5, G06K9, G06T7, G07C9