Patent GB-1040294-A (GB)
Title: Improvements in or relating to electronic systems and arrangements for recognising printed characters
Inventor: PARKS JOHN RONALD
IPC: G06V30/10
Filed: 1962-05-01
Abstract: 1,040,294. Automatic character reading- NATIONAL RESEARCH DEVELOPMENT CORPORATION. July 31, 1963 [May 1, 1962], No. 16693/62. Heading G4R. In a character reading apparatus the character is scanned in a master and signals relating to predetermined positions in different scans are compared to determine whether certain shape elements are present. In Fig. 1 (not shown), the character is cut at x1-r6 by three scans S1 S2, S3. If the signals x1and x3 are delayed to coincide with x5, the combination of these signals may indicate a curved shape element. Similarly, points x2, x4 and x6 are all present when there is an oblique line. The signals may be combined by multiplying them together. The scanning master may consist of three groups of scans interleaved. The delay devices to be used for delaying the signals may be cables 20, Fig. 6 (not shown), each comprising a delay winding 21 round a ferrite core 22 and covered by dielectric layer 23 and capacitive layer 24 consisting of parallel wires. The pick-off winding 14 slides on the outer plastic layer and is covered by a metal screen 18. The winding 14 may be adjusted to any desired point. The signals may be multiplied by deriving logarithm signals which are added and applied to an antilogarithm circuit. The logarithm circuit, Fig. 10 (not shown), may consist of a series of amplifiers A1-An of equal gain except for the last which whose gain depends on the number of stages. The output of each stage is limited to value E and all except the last are added at 25, the last being subtracted. As the input signal increases the stages saturate so that the rate of increase becomes progressively less. The output of unit 25 approximates to the logarithm of the input. The system of Fig. 11 (not shown), uses a C.R.T. to scan the character, the vertical scan being driven by oscillator 33 which also drives the horizontal scan through counters 36, 37 dividing by 3 and 20 respectively. A flying-spot is focused on the paper 32 and reflected light received in photo-cell 40. The photo-cell output passes via clamp 42 and the logarithmic amplifier 43 to delay DL1 whose delay time corresponds to one vertical scan. The same signal passes via a one-scan delay 44 and gate 45 to delay DL2 and via a further one-scan delay 46 and gate 47 to delay DL3. The gates 45, 47 are opened by the stage outputs of ring counter 36 to select the scan groups giving the signals which are to be combined. The outputs from the tappings on the delay lines are combined in block 48 by adding and applying the sum to an antilog circuit. In an alternative arrangement the delay units may be serially arranged with gates interposed to make the scan group connection. The adders are resistor networks and the antilog circuit consists of a transistor designed to give an exponential response. Shape element signals are integrated and stored to provide signals for the recognition circuit. The light reflected from the character may be integrated in a sphere 50, Fig. 15 (not shown), having a lens 31 to pass and focus the scanning beam from the C.R.T. 30 and an opening for the photomultiplier tube 40. The light applied to the paper may be stabilized by a feed-back control arrangement. In a further alternative the signals from the sensing device are clipped to form black and white binary signals which are sampled in delay devices or shift-registers and combined by gating. A camera tube may replace the flying- spot scanner.