Symbol recognition system particularly for alpha-numeric characters

Claim 2

A symbol recognition system comprising in combination: extraction means for forming a plurality of images of each symbol to be identified; a logic recognition system including first input means for receiving one of said images, coding means for providing a digital code corresponding to the presence of portions of said one image at predetermined locations, decoding means for comparing said code with reference codes and means for detecting ambiguity in said decoding, said first input means comprising a linear array of photodetectors and analoguedigital conversion circuits supplied by said photodetectors and connected to said coding means, said extraction means comprising means for linearly shifting said one image past said array, said coding means comprising means for generating signals representative of the positioning of said one image along said shifting direction and said linear array direction; an analogue recognition system using optical correlation and including second input means for receiving a plurality of said images and analogue means for identifying said images; and control means for making analogue recognition system operative, said control means being operated by said ambiguity detecting means upon detection of ambiguity; said locations corresponding to horizontal and vertical sections determined by secants having perpendicular directions, one direction corresponding to said shift direction considered horizontal, said linear array extending vertically, said coding means comprising circuits of vertical sections and circuits of horizontal sections delivering together said digital code, synchronisation circuits for generating a horizontal positioning signal provided to said analogue means and selection signals provided to horizontal and vertical section circuits, vertical centring circuits for generating a vertical positioning signal provided to said analogue means and selection signals provided to vertical and horizontal section circuits.

Claim 3

A symbol recognition system as claimed in claim 1, wherein each section comprises at least three localisations defining a 3 bits code, two localisations being situated at the ends and the third in the middle of the centered projected symbol along the direction of each section considered, said circuits of vertical section comprising logic circuits for sampling the items of information of possible intersections of the outline of said symbols with said locations taking account of delimited fluctuations of vertical positioning of the median outline and of a fixed positioning of localisations of top and bottom ends, for a standard height of the symbols.

Claim 4

A symbol recognition system as claimed in claim 1 wherein the horizontal section circuits comprise logic circuits supplied by said analogue-digital conversion circuits so as to be associated with the photo-detectors of the linear array, a certain number of end photo-detectors at top and bottom of the array being excluded, each logic circuit generating a digital identification code of a specific horizontal section, said logic circuits supplying a logic selection circuit sampling by means of the vertical centring data only the information of horizontal sections envisaged.

Claim 5

A symbol recognition system as claimed in claim 1, wherein the synchronisation circuits comprise a time base circuit receiving a low frequency clock signal of a frequency proportional to the speed of shift of the projected symbol, a high frequency clock signal, a gate signal corresponding to the horizontal passage of the projected symbol and processing the various control signals of the logic circuits of vertical centring and of horizontal and vertical sections, the said conTrol signals being repeated at the LF period during the recording time defined by the said gate and, at the HF period during the reading time defined during a fraction of the interval separating the end of the said gate from the beginning of the following gate.

Claim 6

A symbol recognition system comprising in combination: extraction means for forming a plurality of images of each symbol to be identified; a logic recognition system including first input means for receiving one of said images, coding means for providing a digital code corresponding to the presence of portions of said one image at predetermined locations, decoding means for comparing said code with reference codes and means for detecting ambiguity in said decoding, said first input means comprising a linear array of photodetectors and analogue-digital conversion circuits supplied by said photodetectors and connected to said coding means, said extraction means comprising means for linearly shifting said one image past said array, said coding means comprising means for generating signals representative of the positioning of said one image along said shifting direction and said linear array direction; an analogue recognition system using optical correlation and including second input means for receiving a plurality of said images and analogue means for identifying said images, said second input means comprising a plurality of optical matched masks respectively corresponding to ambiguity generating symbols, optical integrating means and photodetection means, said extraction means projecting a plurality of images respectively on said masks; and control means for making analogue recognition system operative, said control means being operated by said ambiguity detecting means upon detection of ambiguity, said control means being controlled by said positioning signals; said analogue recognition system constituting a multi-channel optical correlator, each channel comprising a matched mask associated optically with a matrix of photodetectors comprising at least one vertical linear array of photodetectors, the direction of which being perpendicular to said shifting direction, the outputs of said photo-detectors being connected to a spatial selection circuit of at least one photodetector on which is situated the correlation peak, the said selection being produced from a first positioning signal corresponding to the vertical centring, the said selection circuit being connected by a single output to a store circuit, an ambiguity detection signal and a second positioning signal corresponding to the horizontal centering being applied to a selector circuit connected by its output to the said store circuits respectively and delivering a control signal for selecting the store circuits of the ambiguity detection in question at the instant corresponding to the horizontal centring of the optical projection at the input of said analogue device, the store circuits being connected by their output to an analogue OR-circuit selecting in its turn the signal of strongest level from the signals received from the said selected store circuits.

Claim 7

A symbol recognition system comprising in combination: extraction means for forming a plurality of images of each symbol to be identified; a logic recognition system including first input means for receiving one of said images, coding means for providing a digital code corresponding to the presence of portions of said one image at predetermined locations, decoding means for comparing said code with reference codes and means for detecting ambiguity in said decoding, said first input means comprising a linear array of photodetectors and analogue-digital conversion circuits supplied by said photodetectors and connected to said coding means, said extraction means comprising means for linearly shifting said one image past said array, said coding means comprising means for generating signals representative of the positioning of said one image along said shifting direction and said linear array direction; an analogue recognition system using optical correlation and including second input means for receiving a plurality of said images and analogue means for identifying said images, said second input means comprising a plurality of optical matched masks respectively corresponding to ambiguity generating symbols, optical integrating means and photodetection means, said extraction means projecting a plurality of images respectively on said masks; and control means for making analogue recognition system operative, said control means being operated by said ambiguity detecting means upon detection of ambiguity, said control means being controlled by said positioning signals; said analogue recognition system constituting a multi-channel optical correlator, each channel comprising a matched mask associated optically with a matrix of photodetectors comprising at least one vertical linear array of photodetectors, the direction of which being perpendicular to said shifting direction, the outputs of said photo-detectors being connected to a spatial selection circuit of at least one photodetector on which is situated the correlation peak, the said selection being produced from a first positioning signal corresponding to the vertical centring, the said selection circuit being connected by a single output to a store circuit, an ambiguity detection signal and a second positioning signal corresponding to the horizontal centering being applied to a selector circuit connected by its output to the said store circuits respectively and delivering a control signal for selecting the store circuits of the ambiguity detection in question at the instant corresponding to the horizontal centring of the optical projection at the input of said analogue device, the store circuits being connected by their output to an analogue OR-circuit selecting in its turn the signal of strongest level from the signals received from the said selected store circuits.