EP0436072A2
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EP
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Method of decoding bar code symbols from partial scans
Assignee: Symbol Technologies LLC
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Filing: 1990-09-17
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Granted: —
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Expires: 2010-09-17
Abstract
Abstract A method for decoding bar code symbols in which a bar code reader and associated components scan a bar code symbol produce a representation of the symbol, and attempt to decode that representation in order to produce a character message. The method consists of the steps of storing a first representation of the bar code symbol corresponding to a first scan path through a first portion of said symbol smaller than the entire symbol, and storing a second representation of the bar code symbol corresponding to a second scan path through the symbol. The method then processes said representations in the event a successful decode has not taken place by utilizing the signal from a first scan with the signal from a subsequent scan to determine whether the information from successive scans can be concatenated to form a combined signal. The process is repeated with different subsequent scans until successful decoding of the combined signal.
Inventors
- 👤 Theodosios Pavlidis
- 👤 Joseph Cai
- 👤 Frederick Schuessler
- 👤 Jiali Diane Chen
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 10:59
CPC Classifications
G; G06; G06K; G06K7/00; G06K7/10; G06K7/14; G06K7/1404; G06K7/146; G06K7/1491; G06K7/01; G06K7/016; G06K7/0166
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
143 words
A method for decoding a bar code symbol composed of an ordered sequence of characters, each character including a plurality of individual elements of different light reflectivity: (a) scanning said symbol along a first scanning path and storing a representation of said characters from the scan to form a first sequence; (b) scanning said symbol along another path different from the preceding scanning path and storing a representation of the subsequent sequence of characters from such scan to form a second sequence; (c) processing said first sequence and said second sequence by identifying a sequence of characters in the trailing position of one of said sequences with a sequence of characters in a starting position of the other of said second sequences to form a new first sequence; and (d) repeating steps (b) and (c) until all characters in said symbol are stored.
Claim 2
Dependent Claim
27 words
A method as defined in claim 1, wherein said elements extend in parallel on a surface so as to form a linear pattern of bars and spaces.
Claim 3
Dependent Claim
37 words
A method as defined in claim 1, wherein said sequence of characters include a unique start character as the first character and a unique stop character as the last character, as considered in the direction of scanning.
Claim 4
Dependent Claim
26 words
A method as defined in claim 1, wherein said step of scanning comprises directing a laser beam in a scan pattern of mutually parallel scan lines.
Claim 5
Independent Claim
153 words
A method for decoding a symbol composed of an ordered sequence of characters, each character including a plurality of individual elements of different light reflectivity with a set of predetermined patterns of elements representing valid characters, while all other patterns represent invalid characters, comprising the steps of: (a) scanning said symbol along a first scanning path and storing a representation of said characters from the scan to form a first sequence; (b) scanning said symbol along another scanning path different from the preceding scanning path and storing a representation of the subsequent sequence of characters from such scan to form a subsequent sequence; (c) processing said first sequence and said subsequent sequences by joining characters in said first sequence with valid characters in said subsequent sequence to form a combined sequence; and (d) repeating steps (b) through (c) until all characters in said combined sequence are valid characters and represent the entire symbol.
Claim 6
Independent Claim
182 words
A method for reading indicia having portions of different light reflectivity such as bar code symbols by a scanner comprising the steps of: (a) scanning a target containing a bar code symbol; (b) detecting at least a portion of light of variable intensity reflected off the target with a sensor and generating an electrical signal corresponding to data represented by the symbol; (c) processing said electrical signal to determine whether the reflected light of variable intensity is indicative of the presence of a predetermined indicia pattern such as a bar code symbol and to terminate said scanning upon the successful decoding thereof; (d) further processing said electrical signal in the event a successful decode has not taken place by utilizing the signal from a first scan with the signal from a subsequent scan to determine whether the information from successive scans can be concatenated to form a combined signal and indicative of a presence of a predetermined indicia pattern such as a bar code symbol; and (e) repeating step (d) with a different subsequent scan until successful decoding of said combined signal.
Claim 7
Dependent Claim
36 words
A method as defined in claim 6, wherein said step of scanning comprises directing a laser beam in a scan pattern of mutually parallel scan lines, and said step of scanning is terminated upon successful decoding.
Claim 8
Dependent Claim
48 words
A method as defined in claim 6, further comprising the step of storing said electric signals in a memory array by addressing the rows and columns of said memory array in a sequence of addresses that represents a linear traversal of the field of view corresponding to scanning.
Claim 9
Dependent Claim
44 words
A method as defined in claim 8 wherein the scanner is contained in a hand-held unit which includes a manually-activated trigger, and the method further includes the step of manually activating said trigger by the user to initiate said step of scanning said target.
Claim 10
Independent Claim
108 words
A method of decoding a bar code symbol that may contain distortion, said symbol including a sequence of characters, each character including a plurality of individual elements of different light reflectivity, with a set of predetermined patterns of elements representing legitimate characters, while all other patterns represent illegitimate characters, comprising the steps of: (a) storing a first representation of said bar code symbol derived from scanning through said bar code symbol; (b) storing a second representation of said bar code symbol derived from scanning through only a portion of said bar code symbol; and (c) improving said first representation using said second representation to form an improved representation.
Claim 11
Dependent Claim
49 words
The method of claim 10 wherein said step of improving said first representation comprises the steps of: (a) replacing at least one element of a distorted character of said first representation with at least one element of a corresponding character of said second representation to form said improved representation.
Claim 12
Dependent Claim
19 words
The method of claim 11 wherein said step of replacing results in said improved representation containing only legitimate characters.
Claim 13
Dependent Claim
65 words
The method of claim 11 further comprising, if the entire bar code symbol is not decodable using said improved representation, the step of: (a) attempting to improve, by element replacement, said improved representation using a third representation of said bar code symbol derived from scanning through at least a portion of said bar code symbol using said improved representation to form a further improved representation.
Claim 14
Dependent Claim
36 words
The method of claim 13 further comprising, if said step of attempting to improve said second representation was successful, the step of: (a) attempting to decode the entire bar code symbol using said further improved representation.
Claim 15
Dependent Claim
152 words
In a method for decoding bar code symbols in which a bar code reader and associated components scan a bar code symbol having a succession of linear elements of different light reflectivity, produce a representation of the symbol and attempt to decode the representation of the symbol in order to produce a legitimate character message containing legitimate characters which are decodable, all non-decodable characters being illegitimate, the improvement comprising the steps of: (a) storing a first representation of the bar code symbol corresponding to a first scan path through a first portion of said symbol smaller than the entire symbol; (b) storing a second representation of said bar code symbol corresponding to a second scan path through said symbol; and (c) replacing at least one element of an illegitimate character of said first representation with at least one element of a corresponding character of said second representation to form an improved representation.
Claim 16
Dependent Claim
19 words
The improved method as defined in claim 15, wherein said second scan path is smaller than the entire symbol.
Claim 17
Dependent Claim
36 words
The improved method as defined in claim 15, further comprising the step of utilizing representations from scans through a subsequent scan path through at least a portion of said symbol to form a further improved representation.
Claim 18
Dependent Claim
31 words
The improved method 17 further comprising the steps of repeatedly redefining said improved representation and said further improved representation until either the decode is successful or no further scans are available.
Claim 19
Dependent Claim
446 words
In a method for decoding bar code symbols in which a bar code reader and associated components using a flying spot beam scans a bar code symbol having a succession of linear elements of different light reflectivity, produce a representation of the symbol and attempt to decode the representation of the symbol in order to produce a legitimate character message containing legitimate characters which are decodable, all non-decodable characters being illegitimate, the improvement comprising the steps of: (a) storing a first representation of the bar code symbol corresponding to a first scan path through a first portion of said symbol smaller than the entire symbol, said representation including information measuring the elapsed time between (i) a reference time that has a fixed relationship to the time of the start of said scan and (ii) the moment at which a predetermined bar or space of the bar code symbol, such as the first bar of its start or stop character, was crossed by the laser spot, such elapsed time to be referred to below as t₁; (b) storing a second representation of the bar code symbol corresponding to a second scan path of said symbol , said representation including information measuring the elapsed time between (i) a reference time that has a fixed relationship to the time of the start of said scan and (ii) the moment at which a bar or space, recognizably the same as the bar or space used in the first scan, was crossed by the laser spot, such elapsed time to be referred to below as t₂; (c) calculating the difference between t₁ and t₂ defined as t₃, to represent the relative motion between the scanner and the bar code symbol; (d) using the second stored representation, measuring the elapsed time between the reference time related to the start of the second scan and the time that the laser spot beam crosses the last decodable character during the second scan so that a string of decodable characters is defined, the length of said string being smaller than the length of the bar code symbol, said elapsed time being defined as t₄; (e) adding t₃ and t₄, computed a time t₅, which, for the next scan to be acquired, represents the elapsed time between the reference time from the start of the third scan and the time that the laser spot will begin to cross the same sequence of characters in the substring used in the second scan; (f) using t₃ as the reference time to locate and decode the stored representation of a new character in the next scan, so that the stored representations can be combined to form an improved representation.
Claim 20
Dependent Claim
36 words
The improved method as defined in claim 19, further comprising the step of utilizing representations from scans through a subsequent scan path through at least a portion of said symbol to form a further improved representation.
Claim 21
Dependent Claim
35 words
The improved method as defined in claim 19 further comprising the steps of repeatedly redefining said improved representation and said further improved representation until either the decode is successful or no further scans are available.
References Cited (Backward Citations)
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