Patent GB-1214373-A (GB)
Title: Improvements in or relating to character reading systems
Inventor: SHEPARD DAVID H
IPC: G06V10/12
Filed: 1968-03-06
Abstract: 1,214,373. Character recognition. COGNITRONICS CORP. 6 March, 1968 [20 March, 1967], No. 10951/68. Heading G4R. In a character reading system comprising a central station having means for character analysis, which is coupled to a remote station having means for generating signals corresponding to data scanned from a document, means at the remote station produce clock pulses at scan positions uniformly spaced along the scanning path and means controlled by the clock pulses develop binary pulses in accordance with the amount of radiation reflected from the document to direct to the central station data signals corresponding to the binary pulses. The document 26, Fig. 4, is inserted into a guide channel and carried by a drum 20 which is rotated in discrete steps by a stepping motor 22, Fig. 5. A pressure pad 32 is provided with an aperture exposing a transverse portion of the document to scanning by a beam 42 reflected by a mirror 44 from a light source 46, e.g. an electric arc or a laser. The mirrors 44 are arranged around the circumference of a rotating disc 50 driven by a synchronous motor and are disposed at equal angles with respect to their neighbours.. Each time the beam is swept across the document 26 the drum 20 is stationary and between sweeps the drum is rotated a small angular increment by the motor 22. The light reflected from the document is detected by a photo-cell 94 and the resulting signal is supplied to an amplifier 102, Fig. 5, producing a binary output depending upon whether the signal is above or below a predetermined threshold value which is fed to a control circuit 104. A half-silvered mirror 114 reflects the main beam 42 so that a beam 42a scans a strip 110 carrying uniformly spaced vertical markings 112 and the light reflected by the strip is detected by a photo-cell 108. The resulting clock pulses are supplied via an amplifier 106 to the control circuit 104 to gate the signal input, the gated binary pulses then being fed into a shift register in the circuit 104 where the transitions between "black" and "white" are detected and used to control a counter 120 operated by the clock pulses. The counter 20 produces permutation code signals indicating the number of consecutive scan samples of the same character (white or black) which are transferred to a buffer store 122 supplying via transmission line 124 the central station 126. As described, 384 clock pulses are produced during each scan and at the end of a scan the circuit 104 produces a pulse to step the motor 22. The last sample may be arranged by circuit 104 to be a "black" bit to indicate to the central station that the scan is complete. Should the buffer 122 become filled a signal is sent via line 130 to the control circuit 104 which stops the counter and holds the count already developed by the counter, interrupts the stepping signal so that the drum 20 remains in position for a rescan of the same path, and counts 384 clock pulses subsequent to the signal on line 130. When the count reaches 384 the counter 12 is activated, the motor 22 stepped and the coding and transmission is resumed.