Method and apparatus for bar code reading and decoding
First Claim
1. A method for decoding a bar code pattern, said method comprising the steps of:
- scanning said bar code pattern to produce an electrical output waveform representation of reflective variations occurring during said scanning;
converting said electrical output waveform to a sequence of binary signals representative of bar and space widths in said bar code pattern so as to produce a width signal sequence representing, in alternating fashion, the bar and space widths present in said bar code pattern;
converting said width signal sequence to a gap signal sequence; and
comparing portions of said gap signal sequence with predetermined gap sequence patterns to determine a symbol represented by said bar code pattern.
1 Assignment
0 Petitions
Accused Products
Abstract
A method and apparatus reliably and robustly decode single width bar codes that may be placed on a variety of materials. The decoding is independent of whether or not the bar code represents dark bars on a light background or light bars on a dark background. The decoder may be implemented either in hardware or as part of a program in a stored program general purpose computer. The signal processing approach taken generates gap sequence information from width sequence information to match predetermined gap sequence patterns. The method and apparatus of the present invention are also particularly amenable to independent creation of the gap sequences from three different techniques which are independent and which thus add robustness to the system. Lastly, the decoding method of the present invention takes advantage of a preprocessing function to remove any certain forms of noise that may be present in the scanned data.
67 Citations
12 Claims
-
1. A method for decoding a bar code pattern, said method comprising the steps of:
-
scanning said bar code pattern to produce an electrical output waveform representation of reflective variations occurring during said scanning; converting said electrical output waveform to a sequence of binary signals representative of bar and space widths in said bar code pattern so as to produce a width signal sequence representing, in alternating fashion, the bar and space widths present in said bar code pattern; converting said width signal sequence to a gap signal sequence; and comparing portions of said gap signal sequence with predetermined gap sequence patterns to determine a symbol represented by said bar code pattern. - View Dependent Claims (2, 3, 4)
-
-
5. A method for decoding a bar code pattern having a check sum symbol, said method comprising the steps of:
a.) 1. scanning said bar code pattern to produce an electrical output waveform representative of reflective variations occurring during said scanning;
-
6. converting said electrical output waveform to a sequence of binary signals representative of bar and space widths in said bar code pattern so as to produce a width signal sequence representing, in an alternating fashion, bar and space widths present in said bar code pattern;
-
3. converting said width signal sequence to a gap signal sequence; 4. comparing said gap signal sequence with predetermined gap sequence patterns to produce a symbol sequence including said check sum symbol; b.) determining if said check sum symbol is correct and repeating steps a.) 1 through a.) 4 for a specified number of times if said check sum symbol is incorrect; and c.) indicating a decoded symbol pattern or that an uncorrectable error has occurred. - View Dependent Claims (9)
-
-
7. A method for decoding a bar code pattern, said method comprising the steps of:
a.) 1. scanning said bar code pattern to produce an electrical output waveform representative of reflective variations occurring during said scanning;
-
8. converting said electrical output waveform to a sequence of binary signals representative of bar and space widths in said bar code pattern so as to produce a width signal sequence representing, in an alternating fashion, bar and space widths present in said bar code pattern;
-
3. converting said width signal sequence to a gap signal sequence; and 4. comparing said gap signal sequence with predetermined gap sequence patterns to produce a symbol sequence; b.) repeating steps a.) 1 through a.) 2 for a specified number of times; and c.) indicating a decoded symbol pattern or that an uncorrectable error has occurred based on the results from said repeated steps a.) 1 through a.) 4. - View Dependent Claims (12)
-
-
10. A method for decoding a bar code pattern, said method comprising the steps of:
a.) 1. scanning said bar code pattern to produce an electrical output waveform representative of reflective variations occurring during said scanning;
-
11. converting said electrical output waveform to a sequence of binary signals representative of bar and space widths in said bar code pattern so as to produce a width signal sequence representing, in alternating fashion, the bar and space widths present in said bar code pattern;
-
3. converting said width signal sequence to produce a gap signal sequence based upon values selected from the group consisting of center-to-center width sequence values, leading edge-to-leading edge sequence and trailing edge-to-trailing edge sequence values; and 4. comparing said gap signal sequence with predetermined gap sequence patterns to produce a symbol sequence; and b.) repeating the steps a.) 1 through a.) 4 for a specified number of times to produce a plurality of gap signal sequences; and c.) indicating a decoded symbol pattern or that an uncorrectable error has occurred based on the results from said repetition.
-
Specification