Patent GB-1334542-A (GB)
Title: Character reading techniques
IPC: G06V30/12
Filed: 1970-11-13
Abstract: 1334542 Character recognition COGNITRONICS CORP 13 Nov 1970 [14 Nov 1969] 54248/70 Heading G4R In a method of machine reading of a document, pre-printed control indicia on the document control processing of the document. A document (e.g. employee's time sheet) has pre-printed on it an identification number (at the top left), field codes usually preceding or above respective fields (and each consisting of a distinctive mark followed by one or more decimal digits), and format indicia such as boxes in which data characters can be inserted -(these indicia being of a colour invisible to the scanner, e.g. red if a red laser is used). At each of a plurality of remote stations, a document can be advanced stepwise around a drum so that lines of characters can be scanned by a laser beam and rotating mirror drum in a horizontal raster, with a photo-electric detector feeding a thresholder via an amplifier having normalizing feedback. The thresholder output is converted to black-white pulses by a clocked flip-flop and gates to a coder which codes the signals as the distances between successive white-black transitions. The code groups are transmitted to a central station and stored on a drum. A decoder scan converter deals with the signals from the different remote stations on a time-shared basis and decodes them to reconstitute the characters in a core matrix store which is read-out to simulate a vertical raster scan of the characters. The characters are recognized and their identities stored. In the case of the identification number, the number of digits is counted as a check and the sum of the digits is checked to see if it is a multiple of ten (the last digit of the number is redundant for this purpose). If a check fails, the number is displayed on a C.R.T. with an arrow to indicate error and the operator may actuate a " kill " button to cause a signal to be sent back to the remote station to eject the document from the scanner and light a lamp. If there is no error, the digits of the number are decoded to provide signals, some of which are coded and sent to the remote station, to indicate: type of programme to be carried out by the central station, vertical distance to first field to be read (to control high-speed skipping movement of the document), initial horizontal scan zone (to control the gate at the output of the clocked flipflop, see above, to blank off the unrequired portions of each scan), type of characters viz. numeric or alphanumeric and font (to control recognition), fixed or variable length output, output to be stored or sent to customer immediately by remote transmission for storage on magnetic or paper tape, customer telephone number, and job or application represented by the document. The field codes are used to indicate fixed or variable length field, field is checking number, maximum or minimum field length, add subtract or compare field with accumulator, new horizontal scan zone begin or end position, only control codes present in line and in succeeding lines until countermanded from present horizontal position until a 0 code is reached in the line, skip (in scanner) defined distance after current line, skip rest of document, next digit is check digit for all control codes in the line, and benchmark for skew compensation. As appropriate, coded signals representing operations are sent to the remote station, as with the identification number, and in either case these signals are inserted into a register under control of clock signals incorporated in the code bits, and decoded. Signals can be sent similarly (a) to alter the threshold level in response to more than a preselected number of characters in the line not being recognized, in accordance with whether the characters are too light or too heavy as determined by the recognition circuitry, (b) to drive the document in reverse to permit re-scan of the line, (c) to inhibit document feed. Skew-compensation is by comparing the horizontal positions of the benchmark and a corresponding other control digit on the form and if out of tolerance a horizontal offset is provided for characters at the central station to correct their position relative to their respective field codes. An " error " signal at the central station can be sent to the remote station by blanking off the clock signals normally present in the transmission path, their absence causing document ejection and lighting of an alarm lamp. Actuation of the " kill " button (see above) may have its effect in the same way.