Patent GB-1311671-A (GB)
Title: Apparatus for handling optical information in the form of an optical image
IPC: G06V30/10
Filed: 1969-02-27
Abstract: 1311671 Character recognition NATIONAL RESEARCH DEVELOPMENT CORP 27 May 1970 [27 Feb 1969] 10640/69 Heading G4R Optical information handling apparatus comprises photoelectric means feeding storage means via a plurality of signal channels and gate means, the gate means being opened simultaneously in response to a predetermined signal in a predetermined group of the channels, a propagation logic network prior to the gate means being provided to pass continuous patterns. A character image is moved from right to left across a matrix of photodetectors 10 (in Fig. 6, each column of photodetectors is represented by one of its members) the outputs from which are thresholded in inverters 25 (the two outputs of any inverter shown with two outputs are equal). Each OR gate 18 in a propagation logic network 11 receives inputs from the AND gates 17 associated with the four nearest neighbour positions in the matrix (only two  shown). Each OR 18 in column P also receives the output of the associated inverter, so that when the character reaches column P, signals will propagate in the network 11 so that a 1 signal will appear from each AND 17 corressponding to a photodetector 10 seeing character black which is linked by a continuous chain of nearest neighbour positions also black to a black in column P. The outputs of AND 17 are passed through inhibition logic 12 and gated 28, 29 into flip-flop 27, when the output of any AND 17 in column Q changes to 1, as detected by an OR 31 and differentiator 32. The inibition logic 12 normally passes its inputs unchanged, but when the character reaches column L, signals propagate in the network 12 similarly to network 11 above, ORs 23 and ANDs 21 corresponding in connections to ORs 18 and ANDs 17, a 1 output from an AND 21 inhibiting, via an inverter 24, a corresponding AND 22. Thus the propagation logic 11 passes a single continuous image to the flip-flops 27 and inhibition logic 12 subsequently deletes this image (from the inputs to gates 28, 29). Thus close or overhanging characters are separated for recognition one at a time. The flip-flop 27 control respective lamps to permit recognition by optical incoherent Fourier transform methods as in Specification 1,232,029 (referred to). Alternatively, infra-red radiation devices may replace the lamps to permit chopping by a YIG Faraday effect modulator, or the output may be fed as serial or parallel electric signals to logic or a computer for recognition. Closer spacing of the photodetectors may be used in the portion of the matrix used for character separation than in that used for recognition, or horizontally than vertically, or channels can be joined together. The Fourier comonents of spatial frequencies in particular directions can be obtained by adding outputs lying along particular directions, either modulating each channel output sinusoidally with a respective phase before vector addition, or using potential dividers to obtain sin and cos terms separately then squaring and adding to obtain the amplitude and dividing sin by cos to obtain the phase. The output of each photodetector may be digitized to more than two levels before storing as multi-bit codes in flip-flops and subsequently reconverting to analogue form to give shades of grey. A narrower array of photodetectors (5 or 1 column) may be used, one column feeding a shift register in which the character is reconstituted. A propagation logic network as above may be used to indicate the shape, position and size (the latter from the number of outputs energized) of a cell on a photographic slide. A network is disclosed which delineates the edge of a pattern by inhibiting passage of a given input to its corresponding output if both the immediate neighbour inputs are on. The edge may be followed from a specific point by making passage of a given input also dependent on at least one of the immediate neighbour outputs being on.