Decoding method and system for ETAB bar code

Claim 1

A decoding process for decoding graphical bar coded information, coded such that three relative distances between consecutive similar transitions, from mark to space and space to mark are used to characterize the binary coded data 0 and 1 in such a manner that one distance is used to code one binary value and two distances, i.e., a long distance and a short distance are used to code the other binary value, said process involving the following operations for decoding the (i+1) th coded bit: measuring the distance between graphic edges characterizing said (i+1) th bit; comparing the measured distance to a first or to a second predetermined threshold level depending whether the number of decoded binary one bits up to and including the i th bit was even or odd; selecting the value of the (i+1) th bit based on the result of this comparison; and, updating at least one of the threshold values based on the last bit value selected.

Claim 6

A system for dynamically decoding ETAB bar coded information using one bit distance for coding one of the binary bit values and two distances for coding the other, said system including: input means; scanning means connected to said input means for scanning the bar coded information and for generating an analog time varying signal representative of the mark to space and space to mark transitions; measuring means connected to said scanning means for sequentially determining from said time varying signal the measures of the distances between consecutive similar transitions; decoding means connected to said measuring means for decoding the (i+1) th bit contained in said ETAB bar coded information, said decoding means including: threshold means for setting a first and a second threshold levels; first comparing means connected to said measuring means and to said threshold means, for comparing the distance between two consecutive similar transitions relative to said (i+1) th bit, to said first threshold whenever the number of decoded bits of said one of the binary bit values was even up to and including the i th bit; second comparing means connected to said measuring means and to said threshold means, for comparing the distance between two consecutive similar transitions relative to said (i+1) th bit to said second threshold whenever the number of decoded bits of said one of the binary bit values was odd up to and including the i th bit; first discriminating means connected to said first comparing means for discriminating between the binary value coded with one distance and one of the binary values coded with two distances, depending upon the output of said first comparing means for characterizing said (i+1) th bit; second discriminating means connected to said second comparing means for discriminating between the binary value coded with one distance and the other one of the binary values coded with two distances, depending upon the output of said second comparing means for characterizing said (i+1) th bit; and, updating means for updating at least one of said dynamic threshold levels in accordance with the distance characterizing the (i+1) th bit.

Claim 7

A system for dynamically decoding ETAB bar coded information using one bit distance for coding one of the binary bit values and two distances for coding the other, said system including: input means; scanning means connected to said input means for scanning the bar coded information and for generating an analog time varying signal representative of the mark to space and space to mark transitions; measuring means connected to said scanning means for sequentially determining from said time varying signal the measures of the distances between consecutive similar transitions; decoding means connected to said measuring means for decoding the (i+1) th bit contained in said ETAB bar coded information, said decoding means including: threshold means for setting a first and a second threshold levels; first comparing means connected to said measuring means and to said threshold means, for comparing the distance between two consecutive similar transitions relative to said (i+1) th bit, to said first threshold whenever the number of decoded bits of said one of the binary bit values was even up to and including the i th bit; second comparing means connected to said measuring means and to said threshold means, for comparing the distance between two consecutive similar transitions relative to said (i+1) th bit to said second threshold whenever the number of decoded bits of said one of the binary bit values was odd up to and including the i th bit; first discriminating means connected to said first comparing means for discriminating between the binary value coded with one distance and one of the binary values coded with two distances, depending upon the output of said first comparing means for characterizing said (i+1) th bit; second discriminating means connected to said second comparing means for discriminating between the binary value coded with one distance and the other one of the binary values coded with two distances, depending upon the output of said second comparing means for characterizing said (i+1) th bit; and, updating means for updating at least one of said dynamic threshold levels in accordance with the distance characterizing the (i+1) th bit.