Patent GB-1480066-A (GB)
Title: Apparatus for recognising handwriting
IPC: G06V10/75
Filed: 1974-08-09
Abstract: 1480066 Character recognition systems NATIONAL RESEARCH DEVELOPMENT CORP 9 Aug 1974 [6 July 1973] 32225/73 Heading G4R An arrangement for recognizing a sample of drawn signs or of handwriting, e.g. a signature, includes means for generating feature signals from the sample, each feature signal being representative of a different feature of the sample. The term "feature" precludes point to point variations which, taken singly, do not characterize a particular writer. The feature signals are compared with reference signals representing corresponding features of a known writer. One of the features is the sum of the times of occurrence of an event in the sample, relative to a time datum in the sample, divided by a number proportional to the time taken to form the sample. Alternatively, or in addition, one of the features is the sum of positions of occurrence of an event, relative to a spatial datum, divided by a number proportional to the size of the sample. The event may be, as appropriate, the making or loss of contact of the stylus with the writing surface, or turning points in the horizontal and vertical directions. In one embodiment the sample is written with a stylus on a unit which generates signals representing the instantaneous x, y co-ordinates of the stylus on the writing surface and from which one or both of the features defined above may be obtained. Other features are also obtained from the signals. For example the signals are digitized at successive instants and at each insstant the difference between the present x coordinate and that at the preceding instant is determined: the sequence of x increments -so derived is a first feature signal. Each x increment counts down a register preset to a reference feature value representing the total distance travelled in the x direction when a reference sample was presented by a known writer. A second feature signal representing the y increments is derived similarly and counts down a register preset to a corresponding reference feature value to act as a comparator. Further feature signals are derived representing the time for which the stylus contacted the writing surface, the time taken to write the sample (which may differ from the contact time because the stylus may be lifted during writing) and the number of times the stylus was lifted. The largest x increment represents the maximum x velocity and is gated to a register as a sixth feature signal when the sample is completed. The values remaining in the registers when the sample is completed are weighted and added, and if the sum is sufficiently small the writer is assumed to be the same as he who wrote the reference sample. The registers are preset, prior to writing the sample, by the writer keying in a personal code which reads from a store the corresponding set of reference feature values and a set of signals which control the weighting of the values remaining after counting down. These values may be used during a training mode to set up reference feature values in the store. They may also be used to modify the values in the store each time the arangement is used, in order to compensate for long term changes in the way in which the writer writes the sample. Various other features which can be used are referred to. In another arrangement, instead of counting down registers, each feature signal is compared directly with the corresponding reference feature. In another, the number of features falling within corresponding predetermined ranges is determined. The various operations may be performed by a suitably programmed digital computer.