METHOD FOR READING BARCODES IN ABSENCE OF LOCATION-INDICATING TAGS
First Claim
12. A sensing device for recovering a waveform representing a linear bar code, said sensing device comprising:
- a two-dimensional image sensor for capturing a plurality of partial two-dimensional images of said bar code during movement of said sensing device relative to said bar code; and
a processor configured for;
determining, from at least one of the images, a direction substantially perpendicular to the bars of the bar code;
determining, substantially along the direction, a waveform fragment corresponding to each captured image;
determining an alignment between each pair of successive waveform fragments; and
recovering, from the aligned waveform fragments, the waveform,wherein said method is configured to perform said steps only in the absence of a location-indicating tag in a field of view of the image sensor,
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Abstract
A method of recovering a waveform representing a linear bar code, the method including the steps of: moving a sensing device relative to the barcode, said sensing device having a two-dimensional image sensor; capturing, using the image sensor, a plurality of two-dimensional partial images of said bar code during said movement; determining, from at least one of the images, a direction substantially perpendicular to the bars of the bar code; determining, substantially along the direction, a waveform fragment corresponding to each captured image; determining an alignment between each pair of successive waveform fragments; and recovering, from the aligned waveform fragments, the waveform. The method is performed only in the absence of a location-indicating tag in a field of view of the image sensor.
14 Citations
20 Claims
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12. A sensing device for recovering a waveform representing a linear bar code, said sensing device comprising:
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a two-dimensional image sensor for capturing a plurality of partial two-dimensional images of said bar code during movement of said sensing device relative to said bar code; and a processor configured for; determining, from at least one of the images, a direction substantially perpendicular to the bars of the bar code; determining, substantially along the direction, a waveform fragment corresponding to each captured image; determining an alignment between each pair of successive waveform fragments; and recovering, from the aligned waveform fragments, the waveform, wherein said method is configured to perform said steps only in the absence of a location-indicating tag in a field of view of the image sensor, - View Dependent Claims (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 20)
wherein said method is performed only in the absence of a location-indicating tag in a field of view of the image sensor.
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2. The method of claim 1, wherein a field of view of the image sensor is smaller than the length of the bar code.
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3. The method of claim 1, wherein each partial two-dimensional image of said bar code contains a plurality of bars.
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4. The method of claim 1, further comprising the step of:
determining a product code by decoding the waveform.
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5. The method claim 1, further comprising the step of:
low-pass filtering the captured images in a direction substantially parallel to the bars.
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6. The method of claim 1, wherein the alignment between each pair of successive waveform fragments is determined by performing one or more normalized cross-correlations between each pair.
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7. The method of claim 1, wherein the waveform is recovered from the aligned waveform fragments by appending each fragment to a previous fragment, and skipping a region overlapping with said previous fragment.
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8. The method of claim 1, wherein the waveform is recovered from the aligned waveform fragments by:
determining an average value for a plurality of sample values of the waveform, said sample values being contained in portions of the waveform contained in overlapping waveform fragments.
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9. The method of claim 8, wherein the average value is a weighted average, whereby sample values captured from a centre portion of each image have a higher weight than sample values captured from an edge portion of each image.
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10. The method of claim 9, wherein the sample values for each image are weighted in accordance with a Gaussian window for said image.
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11. The method of claim 1, wherein the waveform is recovered from the aligned waveform fragments by:
aligning a current waveform fragment with a partially-constructed waveform constructed using all waveform fragments up to the current fragment.
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13. The sensing device of claim 12, wherein a field of view of the image sensor is smaller than the length of the bar code.
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14. The sensing device of claim 12, wherein a field of view of the image sensor is sufficiently large for capturing an image of a plurality of bars.
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15. The sensing device of claim 12, wherein the processor is further configured for:
determining the alignment between each pair of successive waveform fragments by performing one or more normalized cross-correlations between each pair.
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16. The sensing device of claim 12, wherein the processor is further configured for:
determining an average value for a plurality of sample values of the waveform, said sample values being contained in portions of the waveform contained in overlapping waveform fragments.
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20. The sensing device of claim 1, wherein said image sensor has a field of view sufficiently large for capturing an image of a whole location-indicating tag disposed on a surface, and said processor is further configured for determining a position of the sensing device relative to the surface using the imaged tag when said location-indicating tag is contained in a field of view of the image sensor.
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15-1. The sensing device of claim 12 further comprising:
communication means for communicating the waveform to a computer system.
Specification