GB1427519A - Method and apparatus for pattern recognition - Google Patents

Abstract

1427519 Pattern recognition systems NATIONAL RESEARCH DEVELOPMENT CORP 2 May 1973 [4 May 1972] 20858/72 Heading G4R The system employs a read-only store comprising an array of fusible resistors. During a training mode the store is set up by fusing certain resistors when each of a number of training patterns is applied to the store. During a recognition mode the training pattern most closely resembling an applied pattern to be recognized is indicated. The arrangement shown in Fig. 1 has a photosensor array 10 which scans a character, fingerprint, or other pattern. The photosensor outputs are normalized at 12, for example by subtracting the mean of the maximum and minimum outputs from each output, to compensate for contract variations. Amplifiers 14 receive the output of normalizer 12, and each amplifier i provides an output r+2V/3 on lead a i and an output r-2V/3 on lead b i , or vice versa, dependent upon the sign of the input to the amplifier. Voltage V is the fusing voltage of the resistors forming read-only store 16, and r is a reference voltage. All the amplifier output leads are connected via fusible resistors to all the output leads c1-c n and d1-d n of the store. The number n is the number of training pattern to be applied. During the training mode a sequence of training signal patterns corresponding to reference patterns is applied to the store inputs a1-a100, b1-b100, and, for each training pattern, the corresponding pair of output leads, e.g. c1, d1, is connected to r+2V/3 and r-2V/3 respectively. As a result certain of the resistors associated with the output leads are fused away. In the recognition mode the output leads c and d are connected as shown to differential amplifiers g1-g n . When an unknown pattern is scanned by the photosensors the signals from amplifiers g pass to circuit 18 which determines which of the amplifiers is providing the greatest output. A signal appears on the corresponding lead k1-k n and indicates the training pattern most clearly resembling the unknown pattern. If none of the outputs of amplifiers 9 is greater than a reference voltage applied to terminal 23 a signal appears at kt to indicate lack of recognition.