EP0164012A1 — Apparatus and method for reading a two-dimensiona…

Claim 1

Independent Claim 236 words

Apparatus for reading a two-dimensional bar code having bars located nominally at a predetermined pitch comprising means (3, 20) for scanning said bar code (2) with a plurality of spaced apart scan lines, means (3, 20) for generating for each scan line a sequence of elements of image data, recognition means (6) for recognising said bar code from said sequences of elements of image data, and transferring means (5) for selectively transferring said sequences of elements of image data to said recognition means, characterised in that said transferring means (5) comprises indicator generating means (21, 22, 23, 24, 25, 26, 30, 31, 32, 33, 34) for generating for each of said sequences of elements of image data an indicator representing the likelihood that said sequence represents the scanning of a portion of a bar, profile vector constructing means (28) for constructing a plurality of profile vectors from selected ones of said indicators, comparison means (35) for determining for each profile vector which of the sequences of elements of image data, the indicators of which are used to construct said profile vector, represent the scanning of a portion of a bar and which of said sequences represent the scanning of a space between adjacent bars, means (35) for selectively transferring to said recognition means only those sequences of elements of image data which represent the scanning of a portion of a bar and disregarding all other sequences.

Claim 2

Dependent Claim 236 words

Apparatus for reading a two-dimensional bar code having bars located nominally at a predetermined pitch comprising means (3, 20) for scanning said bar code (2) with a plurality of spaced apart scan lines, means (3, 20) for generating for each scan line a sequence of elements of image data, recognition means (6) for recognising said bar code from said sequences of elements of image data, and transferring means (5) for selectively transferring said sequences of elements of image data to said recognition means, characterised in that said transferring means (5) comprises indicator generating means (21, 22, 23, 24, 25, 26, 30, 31, 32, 33, 34) for generating for each of said sequences of elements of image data an indicator representing the likelihood that said sequence represents the scanning of a portion of a bar, profile vector constructing means (28) for constructing a plurality of profile vectors from selected ones of said indicators, comparison means (35) for determining for each profile vector which of the sequences of elements of image data, the indicators of which are used to construct said profile vector, represent the scanning of a portion of a bar and which of said sequences represent the scanning of a space between adjacent bars, means (35) for selectively transferring to said recognition means only those sequences of elements of image data which represent the scanning of a portion of a bar and disregarding all other sequences.

Claim 3

Dependent Claim 95 words

Apparatus according to Claim 1 characterised in that said indicator generating means comprises means (21) for counting the number of elements of image data of a first state in each sequence of elements of image data, means (22, 23, 24, 30, 31, 32, 33, 34) for comparing the element count for each sequence with predetermined criteria to determine whether the sequence of elements of image data is likely to represent the scanning of a bar or the scanning of a space between adjacent bars, and for generating an indicator as a result of said comparison.

Claim 4

Dependent Claim 87 words

Apparatus according to Claim 2 characterised in that said means for comparing the element count for each sequence with predetermined criteria comprises first discriminatory test means (22) for determining whether a sequence comprises primarily elements of a first state, second discriminatory test means (23) for determining whether a sequence comprises primarily elements of a second state, and third discriminatory test means (30) for determining whether a sequence not satisfying said first or said second discriminatory test means comprises primarily elements of said first or said second state.

Claim 5

Dependent Claim 36 words

Apparatus according to Claim 4 characterised in that said third discriminatory test means (30) comprises means for comparing the element count of each sequence of elements with the element count of a previous sequence of elements.

Claim 6

Dependent Claim 20 words

Apparatus according to any one of the preceding claims characterised in that each of said indicators has a binary value.

Claim 7

Dependent Claim 66 words

Apparatus according to any one of the preceding claims characterised in that said profile vector constructing means (28) comprises means for selecting sets of indicators, each set representing a respective set of scan lines expected to scan a bar, the space between said bar and the adjacent bar, and the adjacent bar, and means for constructing a profile vector from each of said sets of indicators.

Claim 8

Dependent Claim 116 words

Apparatus according to any one of the preceding claims characterised in that said comparison means (35) comprises a storage device storing a plurality of profile vectors together with decisions related to each stored profile vector, means for comparing each constructed profile vector with said stored profile vectors to identify for each constructed profile vector a corresponding stored profile vector, and means for utilising the decisions relating to the corresponding stored profile vector to determine which of the sequences of elements of image data, the indicators of which are used to construct said constructed profile vector, represent the scanning of a portion of a bar and which sequences represent the scanning of a space between adjacent bars.

Claim 9

Dependent Claim 16 words

Apparatus according to Claim 7 characterised in that said storage device comprises a programmed logic array.

Claim 10

Dependent Claim 38 words

Apparatus according to any one of the preceding claims characterised in that said means (3, 20) for scanning said bar code comprises means for scanning the bar code in a direction parallel to the bar code longitudinal axis.

Claim 11

Dependent Claim 37 words

Apparatus according to any one of the preceding claims characterised in that said means (3, 20) for scanning said bar code comprises means for scanning the bar code in increments that are sub-multiples of the bar pitch.

Claim 12

Independent Claim 174 words

A method of reading a two-dimensional bar code having bars located nominally at a predetermined pitch comprising: scanning the bar code with a plurality of spaced apart scan lines, generating for each scan line a sequence of elements of image data, and selectively transferring said sequences of elements of image data to recognition means, characterised by generating for each of said sequences of elements of image data an indicator representing the likelihood that said sequence represents the scanning of a portion of a bar, constructing a plurality of profile vectors from selected ones of said indicators, determining for each profile vector which of the sequences of elements of image data, the indicators of which are used to construct said profile vector, represent the scanning of a portion of a bar and which of said sequences represent the scanning of a space between adjacent bars, and selectively transferring to said recognition means only those sequences of elements of image data which represent the scanning of a portion of a bar and disregarding all other sequences.

Claim 13

Independent Claim 174 words

A method of reading a two-dimensional bar code having bars located nominally at a predetermined pitch comprising: scanning the bar code with a plurality of spaced apart scan lines, generating for each scan line a sequence of elements of image data, and selectively transferring said sequences of elements of image data to recognition means, characterised by generating for each of said sequences of elements of image data an indicator representing the likelihood that said sequence represents the scanning of a portion of a bar, constructing a plurality of profile vectors from selected ones of said indicators, determining for each profile vector which of the sequences of elements of image data, the indicators of which are used to construct said profile vector, represent the scanning of a portion of a bar and which of said sequences represent the scanning of a space between adjacent bars, and selectively transferring to said recognition means only those sequences of elements of image data which represent the scanning of a portion of a bar and disregarding all other sequences.

Claim 14

Dependent Claim 76 words

A method according to Claim 11 characterised by counting the number of elements of image data of a first state in each sequence of elements of image data, comparing the element count for each sequence with predetermined criteria to determine whether each sequence of elements of image data is likely to represent the scanning of a bar or the scanning of a space between adjacent bars, and generating an indicator as a result of said comparison.

Claim 15

Dependent Claim 74 words

A method according to Claim 12 characterised in that said comparison operation comprises a first discriminatory test for determining whether a sequence comprises primarily elements of a first state; a second discriminatory test for determining whether a sequence comprises primarily elements of a second state; and a third discriminatory test for determining whether a sequence not satisfying said first or said second discriminatory test comprises primarily elements of said first or said second state.

Claim 16

Dependent Claim 33 words

A method according to Claim 13 characterised in that said third discriminatory test comprises comparing the element count of each sequence of elements with the element count of a previous sequence of elements.

Claim 17

Independent Claim 67 words

A method according to any one of the preceding claims 11, 12, 13 or 14 characterised in that said profile vector construction operation comprises selecting sets of indicators, each set representing a respective set of scan lines expected to scan a bar, the space between said bar and the adjacent bar, and the adjacent bar, and constructing a profile vector from each of said sets of indicators.

Claim 18

Dependent Claim 113 words

Apparatus according to any one of the preceding claims 11, 12, 13, 14 or 15 characterised in that said determining operation comprises storing a plurality of profile vectors together with decisions related to each stored profile vector, comparing each constructed profile vector with said stored profile vectors to determine for each constructed profile vector a corresponding stored profile vector, and utilising the decisions relating to the corresponding stored profile vector to determine which of the sequences of elements of image data, the indicators of which are used to construct said profile vector, represent the scanning of a portion of a bar and which sequences represent the scanning of a space between adjacent bars.

Apparatus and method for reading a two-dimensional bar code

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