Patent GB-1358245-A (GB)
Title: Character data handling apparatus
IPC: G06V30/166
Filed: 1972-06-16
Abstract: 1358245 Character recognition systems INTERNATIONAL BUSINESS MACHINES CORP 16 June 1972 [28 June 1971] 28192/72 Heading G4R A character recognition system employs a digital "mask" word in the consolidation of character signals, from the scanner, to a character code word to be fed to a recognition unit. The signals from the scanner are fed to a store and simultaneously signals are derived indicative of the height, width, and vertical position of the character in the field of view. These signals are used to select a required mask word, the word being compared with the character signals to provide the character code. In the embodiment described the character is scanned by a matrix, or a moving column, of light-emitting diode-photoconductor pairs (105, Fig. 1, not shown). Each column scan is divided into 32 elementary areas. The series of 32-bit serial signals pass to a digital filter (200 and Fig. 3, not shown) comprising 4 serially connected shift registers. The output of each register is fed to a logic circuit which controls the state of one cell of one register, the signal at the output of the final register then being noise free. When a counter (250) has detected a certain number of block (character) bits in the outputs of the first 3 registers of the filter, indicating the presence of a character, the character-representing signal from the final register is gated to a character register (119) where it is recirculated. The signal fed to the character register also feeds a profile register (125) which recirculates and accumulates the signal to provide a 32-bit signal containing consecutive black bits whose number equals the height of the character and whose position indicates the vertical position of the character in the field. The number of the black bits is counted (127) to indicate the character height m. To indicate the character width n another counter (129) is advanced by scan-rate clock pulses when the presence of a character has been detected. The width and height counts select one column and two row mask words from a readonly memory (509, Fig. 2, not shown). The words pass to respective recirculating registers (515 and 517, 519). The column register is stepped at scanrate and the row registers at bit-rate. Each time a transition from one bit state to the other is detected in a mask word from a register a corresponding row or column counter is advanced. The column counter selects a column of a matrix (540) of 5 columns and 7 rows of AND gates feeding bi-stables. During the period in which a column is selected, which may be several scan periods, the row counters select successive gates of the column, repeating the selection in each scan period. In synchronism with the selection of the row gates the gates also receive the serial character signals from the character register (119). The outputs of the gates set the bi-stables so that a 35-bit character code is generated. Each bit represents the state of a cell of the 7 x 5 matrix on to which the character has been consolidated, the state of a cell depending upon the state of a number of cells of the m x n matrix into which the scanned character field is notionally divided, and the number of these cells and their position being determined by the mask words. The character code is passed to a recognition unit, not described, which can call for higher level masking if it detects ambiguity.