Patent GB-1097782-A (GB)
Title: Pattern recognition apparatus
IPC: G06V30/224
Filed: 1966-03-16
Abstract: 1,097,782. Wagon identification. SPERRY RAND CORPORATION. March 16, 1966 [March 16, 1965], No. 11508/66. Heading B7N. [Also in Division G4] A moving striped pattern is recognisable by means including a striped mask and at least one photo-cell, without the use of an imageforming lens. The pattern is claimed separately. A railway wagon bears a sequence of patterns for identification purposes, comprising a series of patterns representing letters followed by a series of patterns representing numerals, these two series being bracketed by patterns (called " letter symbol " and " figure symbol ") indicating that the enclosed patterns represent letters and numerals respectively. Adjacent patterns are separated by further patterns called " intersymbols ". The intersymbol pattern is a set of vertical stripes but the other patterns each have up to five of six sets of parallel stripes having characteristic orientations to the horizontal (other than vertical). These six standard sets of stripes represent the five bits of the teleprinter code and a parity bit respectively. Horizontal stripes are used for filling in unused portions of the pattern area. As the wagon moves in either direction past a detector, each pattern in turn thereon becomes aligned with seven masks bearing stripes with the seven characteristic orientations respectively. Each mask is backed by a photodetector comprising two bars of photoconductor having the same orientation as the stripes, connected in series and providing a differential output from a common terminal between the bars, one bar being on a peak of the received stripes whenever the other bar is in a valley. Alternatively, each mask may be provided with a plurality of such photodetectors connected in parallel. Referring to Fig. 10, the outputs of the detectors 17 associated with the seven masks are passed through amplifiers 30 which compensate for the effect of variation in wagon speed on detector response, to gain control amplifiers 31 controlled from the vertical stripes (intersymbol) detector. The gain control amplifier 31 outputs are rectified and those not at least half as large as the largest then suppressed 33, 34, the rest being fed to respective Schmitt triggers 35 pulses from which feed integrators 37 feeding respective further Schmitt triggers 38. An output from the latter trigger associated with the intersymbol detector causes the outputs of the triggers 38 associated with the other detectors to be stored in respective shift registers (39, Fig. 9, not shown). When the shift registers storing the teleprinter code bits are full, they are read out to a paper tape punch, in a direction determined by the order in which the letter and figure symbols were detected (Fig. 11, not shown). The first stage of each shift register continually feeds a parity check circuit (Fig. 12, not shown) in which bits arriving together are differently delayed (80) to serialise them, and then counted modulo- 2 in a first flip-flop (82) to set a second flip-flop (84) in the case of parity error, the latter causing a question mark code to be punched in the tape after the contents of the shift registers. The letter symbol has unconventional parity so an AND gate (90) is provided to recognize it and provide an extra pulse to said first flipflop (82). Routing of the wagons may be controlled by the above system.