Omnidirectional bar code reader with method and apparatus for detecting and scanning a bar code symbol
First Claim
1. In a bar code reader, a method for detecting the location of a bar code symbol comprising:
- capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image;
approximately a derivative of a first scan line in a given area of said stored two dimensional image;
approximately a derivative of a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image;
multiplying said derivative of said first scan line and said derivative of said second scan line respectively to obtain a product of said derivative of said first scan line and said derivative of said second scan line respectively;
accumulating a sum of the respective products of said derivative of said first scan line and said derivative of said second scan line to provide a location score signal for said stored two dimensional image, wherein said location score signal represents the relative likelihood that said given area of said stored two dimensional image contains a bar code image; and
scanning said captured image stored in said memory, responsive to said location score signal indicating that said stored two dimensional image contains a bar code image, in said given area to scan said bar code symbol.
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Accused Products
Abstract
A bar code reader includes an optical system for storing a two dimensional image in memory, which stored two dimensional image contains a bar code symbol. A method and apparatus is disclosed for detecting the location of said bar code image by computing the accumulated sum of the products of the derivatives of respective first and second scan lines as a location score for the image under consideration. The higher the location score, the higher the probability that the area under consideration contains a bar code image. Also, a method and apparatus is disclosed for determining the fine orientation of a located bar code image by the cross-correlation of interpolated scan line data. The bar code image is filtered by shifting interpolated scan line data in accordance with the detected peak of the cross-correlation and combining the shifted scan line data.
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Citations
58 Claims
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1. In a bar code reader, a method for detecting the location of a bar code symbol comprising:
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capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; approximately a derivative of a first scan line in a given area of said stored two dimensional image; approximately a derivative of a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; multiplying said derivative of said first scan line and said derivative of said second scan line respectively to obtain a product of said derivative of said first scan line and said derivative of said second scan line respectively; accumulating a sum of the respective products of said derivative of said first scan line and said derivative of said second scan line to provide a location score signal for said stored two dimensional image, wherein said location score signal represents the relative likelihood that said given area of said stored two dimensional image contains a bar code image; and scanning said captured image stored in said memory, responsive to said location score signal indicating that said stored two dimensional image contains a bar code image, in said given area to scan said bar code symbol. - View Dependent Claims (2, 3, 4, 5)
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6. In a bar code reader, a method for determining the orientation of a bar code symbol comprising:
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capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; interpolating a first scan line in a given area of said stored two dimensional image; interpolating a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; calculating a cross-correlation function of said interpolated first scan line data and said interpolated second scan line data; detecting a peak of said cross-correlation function of said first and second interpolated scan line data, wherein the position of said peak of said cross-correlation function of said interpolated first and second scan line data corresponds to the orientation of said bar code image; and scanning said captured image stored in said memory responsive to said detected peak of said cross-correlation function, along a line having substantially said orientation to scan said bar code symbol. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. In a bar code reader, a method for detecting a bar code symbol comprising:
capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; locating an area within the field of view of said stored two dimensional image likely to contain a bar code image, said locating step comprising; approximately a derivative of a first scan line in a given area of said stored two dimensional image; approximating a derivative of a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; multiplying said derivative of said first scan line and said approximate derivative of said second scan line respectively to obtain a product of said derivative of said first scan line and said derivative of said second scan line respectively; and accumulating a sum of the respective products of said derivatives of said first scan line and said derivative of said second scan line to provide a location score for said stored two dimensional image, wherein said location score signal represents the likelihood that said given area of said stored two dimensional image contains a bar code image; examining the image within said located area of said stored two dimensional image to determine the orientation of said bar code image, said step of examining the image within said located area of said stored two dimensional image comprising; interpolating a first scan line in said located area of said stored two dimensional image; interpolating a second scan line substantially parallel to said first scan line in said located area of said stored two dimensional image; calculating a cross-correlation function of said interpolated first scan line data and said interpolated second scan line data; and detecting a peak of said cross-correlation function of said first and second interpolated scan line data, wherein the position of said peak of said cross-correlation function of said interpolated first and second scan line data corresponds to the orientation of said bar code image; and scanning said captured image stored in said memory, responsive to said location score signal indicating that said stored two dimensional image contains a bar code image, in said given area along a line having substantially said orientation to scan said bar code symbol.
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18. In a bar code reader, an apparatus for detecting the location of a bar code symbol comprising:
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means for capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; means for approximating a derivative of a first scan line in a given area of said stored two dimensional image; means for approximating a derivative of a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; means for multiplying said derivative of said first scan line and said derivative of said second scan line respectively to obtain a product of said derivative of said first scan line and said derivative of said second scan line respectively; means for accumulating a sum of the respective products of said derivative of said first scan line and said derivative of said second scan line to provide a location score signal for said stored two dimensional image, wherein said location score represents the relative likelihood that said given area of said stored two dimensional image contains a bar code image; and means for scanning said captured image stored in said memory, responsive to said location score signal indicating that said stored two dimensional image contains a bar code image, in said given area to scan said bar code symbol. - View Dependent Claims (19, 20, 21, 22)
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23. In a bar code reader, an apparatus for determining the orientation of a bar code symbol comprising:
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means for capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; means for interpolating a first scan line in a given area of said stored two dimensional image; means for interpolating a second scan line substantially parallel to said first scan line in said given area of said stored two dimension image; means for calculating a cross-correlation function of said interpolated first scan line data and said interpolated second scan line data; means for detecting a peak of said cross-correlation function of said first and second interpolated scan line data, wherein the position of said peak of said cross-correlation function of said interpolated first and second scan line data corresponds to the orientation of said bar code image; and means for scanning said captured image stored in said memory, responsive to said detected peak of said cross-correlation function, along a line having substantially said orientation to scan said bar code symbol. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. In a bar code reader, an apparatus for detecting a bar code symbol comprising:
means for capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; means for locating an area within the field of view of said stored two dimensional image likely to contain a bar code image, said locating means comprising; means for approximating a derivative of a first scan line in a given area of said stored two dimensional image; means for approximating a derivative of a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; means for multiplying said derivative of said first scan line and said derivative of said second scan line respectively to obtain a product of said derivative of said first scan line and said derivative of said second scan line respectively; and means for accumulating a sum of the respective products of said derivative of said first scan line and said derivative of said second scan line to provide a location score signal for said stored two dimensional image, wherein said location score signal represents the likelihood that said given area of said stored two dimensional image contains a bar code image; means for examining the image within said located area of said stored two dimensional image to determine the orientation of said bar code image, said means for examining the image within said located area of said stored two dimensional image comprising; means for interpolating a first scan line in said located area of said stored two dimensional image; means for interpolating a second scan line substantially parallel to said first scan line in said located area of said stored two dimensional image; means for calculating a cross-correlation function of said interpolated first scan line and said interpolated second scan line; and means for detecting a peak of said cross-correlation function of said first and second interpolated scan line, wherein the position of said peak of said cross-correlation function of said interpolated first and second scan line corresponds to the orientation of said bar code image; and means for scanning said captured image stored in said memory, responsive to said location score signal indicating that said stored two dimensional image contains a bar code image, in said given area along a lone having substantially said orientation to scan said bar code symbol.
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35. In a bar code reader, a method for determining the orientation of a bar code symbol comprising:
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capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; selecting a first scan line in a given area of said stored two dimensional image; selecting a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; calculating a cross-correlation function of said selected first scan line and said selected second scan line; and detecting a peak of said cross-correlation function of said first and second selected scan line, wherein the position of said peak of said cross-correlation function of said selected first and second scan lines corresponds to the orientation of said bar code image; and scanning said captured image stored in said memory, responsive to said detected peak of said cross-correlation function, along a line having substantially said orientation to scan said bar code symbol. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
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46. In a bar code reader, an apparatus for determining the orientation of a bar code symbol comprising:
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means for capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; means for selecting a first scan line in a given area of said stored two dimensional image; means for selecting a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; means for calculating a cross-correlation function of said selected first scan line and said selected second scan line; means for detecting a peak of said cross-correlation function of said first and second selected scan lines, wherein the position of said peak of said cross-correlation function of said selected first and second scan lines corresponds to the orientation of said bar code image; and means for scanning said captured image stored in said memory, responsive to said detected peak of said cross-correlation function, along a line having substantially said orientation to scan said bar code symbol. - View Dependent Claims (47, 48, 49, 50, 51, 52, 53, 54, 55, 56)
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57. In a bar code reader, a method for detecting a bar code symbol comprising:
capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; locating an area within the field of view of said stored two dimensional image likely to contain a bar code image, said locating step comprising; approximating a derivative of a first scan line in a given area of said stored two dimensional image; approximating a derivative of a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; multiplying said derivative of said first scan line and said approximate derivative of said second scan line respectively to obtain a product of said derivative of said first scan line and said derivative of said second scan line respectively; and accumulating a sum of the respective products of said derivative of said first scan line and said derivative of said second scan line to provide a location score signal for said stored two dimensional image, wherein said location score signal represents the likelihood that said given area of said stored two dimensional image contains a bar code image; examining the image within said located area of said stored two dimensional image to determine the orientation of said bar code image, said step of examining the image within said located area of said stored two dimensional image comprising; selecting a first scan line in said located area of said stored two dimensional image; selected a second scan line substantially parallel to said first scan line in said located area of said stored two dimensional image; calculating a cross-correlation function of said selected first scan line and said selected second scan line; and detecting a peak of said cross-correlation function of said first and second selected scan lines, wherein the position of said peak of said cross-correlation function of said selected first and second scan lines corresponds to the orientation of said bar code image; and scanning said captured image stored in said memory, responsive to said location score signal indicating that said stored two dimensional image contains a bar code image, in said given area along a line having substantially said orientation to scan said bar code symbol.
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58. In a bar code reader, an apparatus for detecting a bar code symbol comprising:
means for capturing a two dimensional image for storage in a memory, said stored two dimensional image containing an image of a bar code symbol anywhere within the field of view of said stored two dimensional image; means for locating an area within the field of view of said stored two dimensional image likely to contain a bar code image, said locating means comprising; means for approximating a derivative of a first scan line in a given area of said stored two dimensional image; means for approximating a derivative of a second scan line substantially parallel to said first scan line in said given area of said stored two dimensional image; means for multiplying said derivative of said first scan line and said derivative of said second scan line respectively to obtain a product of said derivative of said first scan line and said derivative of said second scan line respectively; and means for accumulating a sum of the respective products of said derivative of said first scan line and said derivative of said second scan line to provide a location score signal for said stored two dimensional image, wherein said location score signal represents the likelihood that said given area of said stored two dimensional image contains a bar code image; means for examining the image within said located area of said stored two dimensional image to determine the orientation of said bar code image, said means for examining the image within said located area of said stored two dimensional image comprising; means for selecting a first scan line in said located area of said stored two dimensional image; means for selecting a second scan line substantially parallel to said first scan line in said located area of said stored tow dimensional image; means for calculating a cross-correlation function of said selected first scan line and said selected second scan line; and means for detecting a peak of said cross-correlation function of said first and second selected scan lines, wherein the position of said peak of said cross-correlation function of said selected first and second scan lines corresponds to the orientation of said bar code image; and means for scanning said captured image stored in said memory, responsive to said located score signal indicating that said stored two dimensional image contains a bar code image, in said given area along a line having substantially said orientation to scan said bar code symbol.
Specification