EP0042953A2 — Bar code candidate select circuit

Claim 1

Independent Claim 395 words

Bar code candidate select circuit for use with a scanner capable of generating a train of square wave pulses indicative of bar coded indicia on a surface being scanned and of generating a framing signal for a label having C characters where each character consists of N successive pulses, characterized in that it comprises: a pulse width counter for measuring the width of each pulse in the train as a function of the number of constant frequency pulses occurring between the leading and trailing edge of the pulse; an accumulator circuit connected to the output of said pulse width counter for generating a stream of basic unit signals, each of said signals having a value proportional to the combined duration of N successive pulses beginning at a different pulse in the train; a subtractor circuit having first and second inputs from said accumulator circuit for subtracting a second basic unit signal from a first, contiguous non-overlapping basic unit signal, said subtractor circuit having an absolute difference output and a carry output, the carry output having a first value when the first basic unit signal is greater than the second basic unit signal and a second value when the second basic unit signal is greater than the first basic unit signal; a comparator circuit having inputs from said subtractor circuit and said accumulator circuit for determining whether predetermined relationships exist between two non-sequential basic unit signals representing contiguous, non-overlapping characters, said comparator circuit further including: a first comparator for generating a first type of output signal only when the absolute difference output is less than a first predetermined fraction of one of the compared basic unit signals, a second comparator for generating a first type of output signal only when the absolute difference is less than a second predetermined fraction of the first of the compared basic unit signals, and a third comparator for generating a first type of output signal only when the absolute difference is greater than the second predetermined fraction of the second of the compared basic unit signals; means for storing the signals generated by said comparator circuit during the examination of (N x C) successive basic unit signals; and means for logically combining selected outputs from said storage means to produce a framing signal when a first type of output signal appears concurrently at the selected outputs from said storage means.

Claim 2

Dependent Claim 395 words

Bar code candidate select circuit for use with a scanner capable of generating a train of square wave pulses indicative of bar coded indicia on a surface being scanned and of generating a framing signal for a label having C characters where each character consists of N successive pulses, characterized in that it comprises: a pulse width counter for measuring the width of each pulse in the train as a function of the number of constant frequency pulses occurring between the leading and trailing edge of the pulse; an accumulator circuit connected to the output of said pulse width counter for generating a stream of basic unit signals, each of said signals having a value proportional to the combined duration of N successive pulses beginning at a different pulse in the train; a subtractor circuit having first and second inputs from said accumulator circuit for subtracting a second basic unit signal from a first, contiguous non-overlapping basic unit signal, said subtractor circuit having an absolute difference output and a carry output, the carry output having a first value when the first basic unit signal is greater than the second basic unit signal and a second value when the second basic unit signal is greater than the first basic unit signal; a comparator circuit having inputs from said subtractor circuit and said accumulator circuit for determining whether predetermined relationships exist between two non-sequential basic unit signals representing contiguous, non-overlapping characters, said comparator circuit further including: a first comparator for generating a first type of output signal only when the absolute difference output is less than a first predetermined fraction of one of the compared basic unit signals, a second comparator for generating a first type of output signal only when the absolute difference is less than a second predetermined fraction of the first of the compared basic unit signals, and a third comparator for generating a first type of output signal only when the absolute difference is greater than the second predetermined fraction of the second of the compared basic unit signals; means for storing the signals generated by said comparator circuit during the examination of (N x C) successive basic unit signals; and means for logically combining selected outputs from said storage means to produce a framing signal when a first type of output signal appears concurrently at the selected outputs from said storage means.

Claim 3

Dependent Claim 198 words

Circuit according to claim 1 characterized in that it further includes: means for providing a scan direction signal in phase with the signals generated by the scanner; an overflow latch connected to the accumulator circuit for indicating that the basic value of a given character exceeds an allowable limit; a first set of coincidence elements connected to said scan direction means, said overflow latch and said subtractor circuit for prociding a first margin character indicating signal if the scan direction signal has a first value while the first comparator produces a first output signal or while the carry output has a first value or while the overflow latch indicates that the first of the compared basic unit signals exceeds the allowable limit; and a second set of coincidence elements connected to said scan direction means, said overflow latch and said subtractor circuit for providing a second margin character indicating signal if the scan direction signal has a second value while the third comparator produces the first output or while the carry output has a second value of while the overflow latch indicates that the second of the compared basic unit signals has a value exceeding the allowable limit.

Claim 4

Dependent Claim 71 words

Circuit according to claim 2, characterized in that it further includes a center character testing circuit having inputs from scan direction means, said first comparator circuit, said third comparator circuit and from the carry output of said substractor circuit, said center character testing circuit producing either a first output signal indicating the existence of an apparent center character or a second output signal indicating the absence of an apparent center character.

Claim 5

Dependent Claim 104 words

Circuit according to claim 3, characterized in that said center character testing circuit further comprises: a first coincidence element for producing a first type of output signal when the scan direction means, the first comparator, the third comparator and the carry output each provides a first level of input signal; a second coincidence element for producing a first type of output signal when the scan direction means, the first comparator means, the third comparator and the carry output concurrently provide input signals having a second level; and an OR gate for combining the outputs from said first coincidence element and said second coincidence element.

Claim 6

Independent Claim 247 words

A method of detecting a label candidate in the train of square wave pulses indicative of bar coded indicia on a surface being scanned where the label includes C characters, each consisting of N successive pulses, said method being characterized by the steps of: generating a stream of basic unit signals, each having a value proportional to the combined duration of N-successive pulses beginning at a different pulse in the train; subtracting a first basic unit signal from a second basic unit signal representing the contiguous non-overlapping basic unit signal to provide an absolute difference value and a carry value; comparing the absolute difference value with a first predetermined fraction of one of the compared signals to generate a first level of output signal when the absolute difference value is the lesser; comparing the absolute difference value with a second predetermined fraction of the first of the compared signals to generate a first level of output signal when the absolute difference value is the lesser; and comparing the absolute difference value with the second predetermined fraction of the second of the compared signals to generate the first level of output signal when the absolute difference value is the greater; storing the signals generated as a result of each of the comparisons during the examination of N x C successive basic unit signals; and logically combining selected ones of the stored signals to produce a label candidate signal when all of the selected signals have the first level.

Claim 7

Independent Claim 247 words

A method of detecting a label candidate in the train of square wave pulses indicative of bar coded indicia on a surface being scanned where the label includes C characters, each consisting of N successive pulses, said method being characterized by the steps of: generating a stream of basic unit signals, each having a value proportional to the combined duration of N-successive pulses beginning at a different pulse in the train; subtracting a first basic unit signal from a second basic unit signal representing the contiguous non-overlapping basic unit signal to provide an absolute difference value and a carry value; comparing the absolute difference value with a first predetermined fraction of one of the compared signals to generate a first level of output signal when the absolute difference value is the lesser; comparing the absolute difference value with a second predetermined fraction of the first of the compared signals to generate a first level of output signal when the absolute difference value is the lesser; and comparing the absolute difference value with the second predetermined fraction of the second of the compared signals to generate the first level of output signal when the absolute difference value is the greater; storing the signals generated as a result of each of the comparisons during the examination of N x C successive basic unit signals; and logically combining selected ones of the stored signals to produce a label candidate signal when all of the selected signals have the first level.

Claim 8

Dependent Claim 209 words

Bar code candidate select circuit for use with a scanner capable of generating a train of square wave pulses indicative of bar-coded indicia on a surface being scanned of generating a framing signal for identifying the location of pulses in the train potentially representing a label having a plurality of data characters delimited by a margin character and a center character, each of said characters consisting of N successive square wave pulses, characterized in that it comprises: means connected to the scanner for generating a series of overlapping, N-pulse basic unit signals, each of which has a value representative of the accumulated width of N successive square wave pulses, successive ones of said basic unit signals being generated from the start of successive square wave pulses; data stream separating means connected to said basic unit signal generating means for presenting a pair of basic unit signals simultaneously on a pair of outputs, said pair of basic unit signals representing potential contiguous but non-overlapping N-pulse characters; and comparator means connected to said data stream separating means for comparing the relative values of the basic unit signals in each presented pair to determine whether the relative values fall within predetermined limits indicative of possible combinations of datan margin and center characters.

Claim 9

Dependent Claim 209 words

Bar code candidate select circuit for use with a scanner capable of generating a train of square wave pulses indicative of bar-coded indicia on a surface being scanned of generating a framing signal for identifying the location of pulses in the train potentially representing a label having a plurality of data characters delimited by a margin character and a center character, each of said characters consisting of N successive square wave pulses, characterized in that it comprises: means connected to the scanner for generating a series of overlapping, N-pulse basic unit signals, each of which has a value representative of the accumulated width of N successive square wave pulses, successive ones of said basic unit signals being generated from the start of successive square wave pulses; data stream separating means connected to said basic unit signal generating means for presenting a pair of basic unit signals simultaneously on a pair of outputs, said pair of basic unit signals representing potential contiguous but non-overlapping N-pulse characters; and comparator means connected to said data stream separating means for comparing the relative values of the basic unit signals in each presented pair to determine whether the relative values fall within predetermined limits indicative of possible combinations of datan margin and center characters.

Claim 10

Dependent Claim 241 words

Circuit according to claim 6, characterized in that said comparator means further comprises: means for generating a signal representing the absolute difference of the values of the presented pair of basic unit signals; a first comparator device connected to said data stream separating means and to said absolute difference signal generating means for determining whether the magnitude of a predetermined fraction of one of the presented basic unit signals is greater or less than the absolute difference signal, the output of said first comparator means being indicative of the presence or absence of adjacent potential data characters; a second comparator device connected to said data stream separating means and to said absolute difference signal generating means for determining whether the magnitude of a predetermined fraction of the first of the presented basic unit signals is greater or less than the absolute difference signal, the output of said second comparator means being indicative of the presence of absence of a pair of adjacent potential margin and data characters; and a third comparator device connected to said data stream separating means and to said absolute difference signal generating means for determining whether the magnitude of the absolute difference signal is greater or less than the magnitude of a predetermined fraction of the second of the presented basic unit signals, the output of said third comparator means being indicative of the presence or absence of a pair of adjacent potential data and margin characters.

Claim 11

Dependent Claim 35 words

Circuit according to claim 7 characterized in that said comparator means further includes logic means connected to said second and third comparator means for testing for the presence of potential, adjacent center and data characters.

Claim 12

Dependent Claim 81 words

Circuit according to claim 8 characterized in that it further includes: storage means for storing a plurality of outputs from said comparator means, said storage means having separate storage devices for storing the separate outputs representing tests for potential margin-data character pairs, data-data character pairs and data-center character pairs; and means for logically combining outputs from said separate storage devices to detect the presence of outputs representative of a plurality of potential data characters delimited by potential margin and center characters.

Bar code candidate select circuit

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