Patent GB-1356417-A (GB)
Title: Pattern recognition system
IPC: G06V30/224
Filed: 1971-09-21
Abstract: 1356417 Character recognition systems COMPAGNIE INTERNATIONALE POUR L'INFORMATIQUE 21 Sept 1971 [25 Sept 1970] 44058/71 Heading G4R A character recognition system employs a digital unit which either identifies the character or identifies a family of characters which includes the scanned character. During a second scan the character is projected on to masks representing the characters in the families, and the outputs of detectors associated with the masks are selected in accordance with the familyidentifying signal, if any, from the digital unit in order to identify the character from the others in the specified family. The system uses characters of particular shape, e.g. OCRA, scanned horizontally by a vertical column of photo-sensors feeding the digital unit. The circuit samples the output of the sensors, providing 3-bit signals representative of the presence or absence of part of the character at 3 positions in each of two horizontal and one vertical sections, H1, H2 and V1, Fig. 2. During a first scan the character image is moved over the column of photosensors, the cell outputs being converted to binary form. The binary signals pass to "vertical" and "horizontal" channels which respectively provide the 3-bit signals representing vertical and horizontal sections of the character. The signals also pass to a circuit (34, 35) which determines the vertical off-centring of the image, and to a circuit (30-35) which provides timing signals. The timing circuit is also fed with clock pulses generated by the apparatus which moves the image over the photosensors, and with relatively high frequency clock pulses. The circuit delivers three horizontal gating signals (FH1-FH3) for sampling the binary signals at instants corresponding to the three positions in the horizontal sections, and a vertical gating signal for sampling the signals corresponding to the vertical section. The vertical channel, Figs. 5, 6 (not shown), includes a register which, under control of the vertical gating signal, stores the outputs of the photosensors as they sense the required vertical slice. The signals stored are shifted in the register by the vertical off-centring signal to bring the bottom of the character to the bottom of the register. The signals in predetermined cells of the register are then processed to provide the vertical section 3-bit signal. The horizontal channel, Figs. 8, 9 (not shown), includes a number of circuits, each fed with the output of a corresponding photosensor and with the horizontal gating signals. Each circuit provides a 3-bit signal to a register, the signal depending on the output of the photosensor during a number of adjacent L.F. clock periods in each gating period. The signals in the register are shifted under control of the vertical centring signal and appropriate cells are read out to provide two horizontal section 3-bit signals. The horizontal and vertical 3-bit signals are fed to a recognition unit and, if possible, the character is identified. If this is not possible the family in which it lies is identified. During the second scan period (in which the next character to be recognized is being scanned by the column of cells associated with the digital unit) the character is projected on to each of a number of masks representing the characters in the families. Each mask is viewed by a line of photosensors. The vertical offcentring signal from the digital unit controls the selection of the output of one of the photosensors in each line. Those of the outputs which correspond to masks of the family indicated by the family signal are passed to stores which store the values of these outputs at the instant that the horizontal centre of the character image is passing over the masks. The highest valued of the stored signals is determined to identify the character.