Patent GB-1179144-A (GB)
Title: Print Reading System.
Inventor: HAMRICK JAMES GILMER
IPC: G06K9/74
Filed: 1967-10-30
Abstract: 1,179,144. Character recognition. RAPHAEL SCANDATA CORP. 30 Oct., 1967, No. 49120/67. Heading G4R. In a character recognition system for reading a printed document, the document is scanned and images of the characters are sequentially projected to a recognition zone for matching against standard characters on a member which also includes code means for identifying each character and for indicating its set-width, a match being detected by photo-sensitive means to enable photo-sensitive means to read the code means and determine the identity and setwidth of the matching standard character, the scanning, means being advanced in accordance with the determined set-width, halting of the advance being inhibited if no image of a character is present at the recognition zone. A printed page to be read, recorded on microfilm, is projected by microfilm reader 10 (Fig. 4c) via a tiltable mirror 20 (for selecting a line) and a rotatable hexagonal mirror 30 (for selecting a character) on to a track of standard characters on a rotating drum 40 for mask .matching. Other tracks of the drum 40 hold, adjacent each standard character, a binary code identifying it and a spacing code specifying its set-width. When a manual start-button 5 (Fig. 4c) is pressed, solenoid 12 advances the microfilm to the first page to be read, motor 22 is driven in reverse to tilt mirror 20 to its highest position, line counter 80 (Fig. 4c) is reset, motor 22 is driven forward until a photo-cell 63 (Fig. 4a) preceded by a lens 6 which condenses a line of print into a narrow band indicates that the first line to be read is in position, ratchet release solenoid 37 is energized via switch 39 to permit motor 31 to rotate hexagonal mirror 30 until a corner of the hexagon opens switch 39 so that the start of the line is selected, and a ring-counter 90 (Fig. 4b) and a line length counter 100 are reset. A switch 43 (Fig. 4c), actuated at the beginning of each drum revolution, sets flip-flop 110 (Fig. 4a) to enable circuit 112, fed by photo-cell 60 behind the standard character drum track, to detect a match when it occurs. Ratchet release solenoid 37 is energized from flip-flop 7 to permit hexagonal mirror 30 to rotate until photo-cell 62 detects the first character of the line when solenoid 37 is de-energized. If a match is not found during a given drum revolution, a pulse from a switch 44 actuated by the drum 40 is allowed to energize solenoid 37 to advance the hexagonal mirror 30 by one increment and a match is looked for on the next drum revolution - In this way horizontal mispositioning of the character is compensated for. Detection of a match by. photo-cell 60 and circuit 112 (a) switches off flip-flop. 110 to prevent further matches (e.g. an 0 would "match" the standard Q-to prevent errors the more complicated of similar characters come later on the drum 40), (b) enables gates 70a-77a (Fig. 4a) to gate the binary code identifying the character, from photo-cells 70-77 sensing drum 40, to output recorder/display 99, (c) enables gates 64a-68a to gate the spacing code, sensed from drum 40 by photo-cells 64-68, to flip-flop 64b-68b, (d) permits ring-counter 90 to be incremented by oscillator 93 until it equals the spacing code as decoded at 69, equality being detected by gates G1-G18. Equality, besides stopping the counting, turns on flip-flop 7 to energize solenoid 37 to permit hexagonal mirror 30 to rotate to bring the next character into position. Switch 34 produces a pulse for each increment of rotation, these pulses decrementing ring counter 90. When counter 90 reaches zero, rotation is stopped provided a character is now in position as indicated by photo-cell 62. If not, rotation continues until a character has been reached, A counter 115 (Fig. 4b) counts the number of drum revolutions used with a given character and if it reaches 4, i.e. without match, an alarm light 2c (Fig. 4a) is lit, flip-flop 110 is reset and automatic operation ceases. The operator enters the unrecognizable character (which is projected on to a screen together with adjacent characters for his benefit) at a keyboard 130 (Fig. 4a). It is compared at 132 with successive binary codes from the drum 40, identifying the successive standard characters, read by photo-cells 70-77. On equality, the code read is gated 70a-77a to the output recorder/display 99, the failure counter 115 is reset, the spacing code is gated 64a-68a to the flip-flops 64b-68b for use as before and normal automatic operation recommences. However, the spacing code will not be quite right since the system will have overshot the centre of the unrecognized character. Accordingly, manual lever 26 (Fig. 4c) is used to centre the character just entered by rotating the mirror 20. At all times, the increments of rotation of the hexagonal mirror 30, as represented by pulses from switch 34, are counted by line length counter 100 and when a count preset on manual dials 101-103 is reached the system proceeds to the next line, lever 26 being reset by spring 29 on withdrawing of brake 28a, and the line counter 80 is incremented. When the count in the latter reaches a value preset on manual dials 81, 82, the system proceeds to the next page. A switch 27 (at mirror 20) can also cause advance to the next page. The threshold in the match circuit 112 is adjusted in accordance with the total light from the unknown character, as detected by photo-cell 61. A space code and an end of line code are recorded at 99 at the appropriate times. A manual switch 136 (Fig. 4b) is provided to enable manual insertion of new matter. The drum 40 may be removable and may have. a plurality of fonts ,on. different tracks, one track being selected. The projected image could be split to allow a plurality of characters to. be recognized concurrently using respective tracks on the drum.